COMPOSTING

A LITERATURE STUDY

MAY 1990

Environment
Environnement

Ontario Jim Bradley, Minister/ministre

ISBN 0-7729-7125-0
PIBS 988

COMPOSTING

A LITERATURE STUDY

1989

Report prepared by:

M.M. Dillon Limited and

Cal Recovery Systems Incorporated

MAY 1990

Copyright: Queen's Printer for Ontario, 1990

This publication may be reproduced for non-commercial purposes

with appropriate attribution.

DISCLAIMER

This report was prepared for the Ontario Ministry of the
Environment as part of a ministry-funded project. The views and
ideas expressed in this report are those of the author and do not
necessarily reflect the views and policies of the Ministry of the
Environment, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.

TABLE OF CONTENTS

1.0 INTRODUCTION 1-1

1.1 Introduction 1-1

1.2 Background 1-1

1.3 Compost Quality 1-1

1.4 References 1-2

2.0 GENERIC COMPOSTING INFORMATION 2-1

2.1 Definitions of Key Terminology and Nomenclature 2-1

2.2 Description of Generic Composting Technologies 2-3

2.2.1 Turned Windrow 2-4

2.2.2 Static Pile (Forced Aeration) 2-5

2.2.3 In- Vessel 2-5

2.2.4 Hybrid Composting 2-7

2.3 Generic Operating and Control Parameters 2-7

2.3.1 Time Requirements 2-7

2.3.2 Temperature Requirements 2-8

2.3.3 Moisture Requirements 2-8

2.3.4 Oxygen Requirements 2-12

2.3.5 Nutritional Requirements 2-12

2.3.6 Particle Size 2-13

2.3.7 Mixing Requirements 2-14

2.3.8 Hydrogen Ion Level (pH) 2-14

2.4 Approaches to Municipal, Commercial/Industrial,

and Agricultural Composting 2-14

2.4.1 Municipal Wet/Dry Systems 2-15

2.4.2 Variations on the Wet/Dry System 2-17

2.4.3 Post Collection Separation 2-18

2.4.4 Home Composting 2-21

2.4.5 Co-Composting 2-23

2.5 References 2-24

i

TABLE OF CONTENTS

3.0 DOCUMENTATION OF EXISTING COMPOST TECHNOLOGIES 3-1

3.1 Introduction 3-1

3.2 Internationally Available Technologies 3-1

3.2.1 Turned Windrow 3-2

3.2.2 Static Pile 3-4

3.2.3 In-Vessel 3-6

3.2.4 Hybrid 3-20

3.3 Canadian Technology 3-22

3.3.1 Channel System 3-22

3.4 Economics of Composting 3-23

3.5 Marketing 3-27

3.5.1 Characteristics and Uses 3-27

3.5.2 Marketability 3-32

3.5.3 Developing Markets 3-39

3.6 References 3-44

3.6.1 Technologies 3-44

3.6.2 Economics of Composting 3-46

3.6.3 Marketing Compost Products 3-47

4.0 EVALUATION OF REPRESENTATIVE NORTH AMERICAN FACILITIES 4-1

4.1 Operating and Proposed Composting Facilities in Canada 4-1

4.1.1 Municipal Programs 4-1

4.1.2 Private Sector Composting Initiatives in Ontario 4-3

4.2 United States 4-3

4.2.1 Introduction 4-3

4.2.2 Sewage Sludge 4-4

4.2.3 Municipal Solid Waste 4-8

4.2.5 Yard and Garden Debris 4-12

TABLE OF CONTENTS

4.2.6 General Summary and Conclusions 4~16

4.3 References 4"17

5.0 EVALUATION OF REPRESENTATIVE INTERNATIONAL FACILITIES . 5-1

5.1 Introduction 5-1

5.2 Federal Republic of Germany 5-1

5.3 France • 5-3

5.4 Italy 5-5

5.5 Japan 5-5

5.6 South America 5-8

5.7 Soviet Union 5-8

5.8 Switzerland 5-9

5.9 United Kingdom 5-10

5.10 References 5-10

6.0 DOCUMENTATION OF POLICIES, REGULATIONS,

STANDARDS AND/OR GUIDELINES 6-1

6.1 Compost Quality and Standards/End Use Regulation 6-1

6.1.1 North America 6-4

6.1.2 International 6-8

6.2 Compost Facility Siting and Approvals 6-15

6.3 Health and Safety Requirement 6-17

6.4 Hazardous Waste Handling, Storage, and Disposal 6-19

6.5 References 6-20

7.0 OTHER EMERGING TECHNOLOGIES 7-1

7.1 Irradiation of Sewage Sludge for Composting 7-1

7.1.1 Introduction 7-1

7.1.2 Sludge Irradiation Experience and Regulation 7-1

7.1.3 Effects of Irradiation on Pathogens 7-2

TABLE OF CONTENTS

7.1.4 Summary 7-3

7.2 References 7-4

8.0 ALTERNATIVES TO COMPOSTING 8-1

8.1 Introduction 8-1

8.1.1 Animal Feed 8-1

8.1.2 Biogas Production 8-1

8.1.3 Landfarming 8-2

8.2 References 8-4

9.0 CONCLUSION 9-1

APPENDIX A LITERATURE SEARCH

APPENDIX B PARTIAL LIST OF VENDORS AND FACILITIES

EXECUTIVE SUMMARY

Composting is a process used since antiquity to convert organic waste materials, both vegetable
and animal, to a rich, humus-like soil amendment used in agriculture. Composting is an aerobic
decomposition process in which organic matter is naturally oxidized to simple chemical
compounds with the accompanying release of heat, water vapour, and carbon dioxide. The heat
release also causes the destruction of harmful pathogens and weed seeds in the compost.
Successful composting depends primarily on adequate temperature and mositure control, oxygen
supply and nutrients to feed the microbial populations.

Potential raw materials for composting include the compostable fraction of municipal solid waste,
yard, garden and grass leaf wastes, agricultural crop residues and animal manures, food processing
wastes, forest products and paper production wastes and other biodegradable wastes from industry
and other sectors of society. The primary objective of composting is to recover and recycle a
valuable resource in an economic and environmentally acceptable manner.

The literature has been surveyed to provide this state-of-the-art report on composting science,
operational practices and compost production systems around the world. The report provides
definitions of key terminology and nomenclature and a description of generic composting
technologies. The process technologies are grouped in four categories: turned windrow, static
pile, in-yessel and finally, hybrid systems which contain combinations of the first three. This
section is followed by a description of generic operating and control parameters in compost
production.

A discussion of solid waste collection systems and waste storage is followed by a discussion of
the advantages of household source separation and collection procedures such as the wet/dry
system and the separate collection of yard and garden wastes, food wastes and co-composting.
The advantages of both pre-collection separation and post-collection separation are examined.
Means of post-collection separation of components in the solid waste stream are discussed
including screening, air classification, and size reduction.

The section on home composting describes the biological principles involved such as the lower
volumetric limit for effective pathogenic kill, odour control, aeration and environmental constraints
to avoid nuisance complaints.

The economics of composting are discussed and comparative cost information on selected North
American compost faculties is provided. Marketing of the compost is a factor limiting
widespread utilization of this waste reduction process. Data on North American and international
composts, their chemistry, typical uses and typical markets are listed. Many approaches to
compost market development have been tried with varying degrees of success. The key elements
of a marketing program and the need for public education on the uses of compost is reviewed.

A discussion of existing compost technologies follows and many of the established manufacturers
and suppliers and their proprietary composting production systems are reviewed. Representative
North American facilities are evaluated. Representative international facilities are also evaluated
in some detail. Useful lessons can be learned from the study of many of these facilities and the
implementation of national policies on composting. Legislation, regulations, standards and
guidelines in various North American and European jurisdictions are reviewed.

The future potential for implementing municipal solid waste programs in North America appears
to be bright. Obstacles that must be removed before the future potential is attained are discussed.
The composting of yard and garden wastes is a high-profile public and municipal concern.
Collection strategies to take advantage of the availability of this organic resource and their
respective operating systems are reviewed.

Each section of the study is followed by a comprehensive bibliography that should be useful to
the composting practitioner in Ontario.

1.0 INTRODUCTION

1.1 Introduction

The Ontario Ministry of the Environment (MOE) is in the process of developing guidelines and
standards for large scale compost production, quality control, end use applications and facility
siting. These guidelines will help to ensure that compost can be produced and used without
adversely affecting human and animal health, food production and the natural environment.

In order for the MOE to develop these guidelines, an up-to-date overview on state-of-the-art
composting is required. Existing government and industry regulations and standards that relate
either directly or indirectly to composting, in Ontario and other jurisdictions, have been
outlined in this study. A worldwide literature review of existing and emerging composting
technologies has been documented as well.

1.2 Background

Interest in composting has increased dramatically in recent years. Rising public concern about
incineration and landfilling has led to a renewed interest in other waste disposal methods; one
of which is composting.

In recent times, attention has been given to using nature's self-cleaning and self-renewal
processes to deal with the growing volumes of refuse generated by modern society. Most
modem cities now have sewage treatment plants which employ nature's processes to convert
organic materials into a sludge that is separated from water, which then is clean enough to
return to our rivers and streams.

Until recently, landfills seemed to be the appropriate and least expensive way for communities
to deposit their solid waste. Now, however, that method is less acceptable and nature's
composting process is being used more and more to deal with the quantities of refuse generated
daily in modem communities. A significant portion of the municipal solid waste (MSW)
stream is compostable and therefore composting has the potential to divert a large proportion of
material from the more traditional disposal methods, landfill and incineration (EFW). It is
important that the compost produced be of the highest quality so that if used in agriculture, it
will not adversely affect human and animal health, food production and the natural
environment. Composting faculties must be designed and operated to minimize nuisance and
impacts on public health and the natural environment.

To handle these large volumes of municipal waste, the process of decomposition has to be
speeded up. The microorganisms in the waste are given an environment which allows them to
grow rapidly and work at peak efficiency in breaking down the waste. To do this, the
microorganisms need air, water and nutrients.

1.3 Compost Quality

In an attempt to standardize compost specifications, and encourage improvements in MSW
compost quality, an international committee of recognized experts has recently defined
composting (the process) and compost (the product) as follows [1]:

1-2

• Composting - A controlled biooxidative process that:

involves a heterogeneous organic substrate in the solid state;

evolves by passing through a thermophyllic stage and a temporary release of
phytotoxin; and

tends to the production of carbon dioxide, water, minerals and stabilized organic
matter (compost).

• Compost - The stabilized and sanitized product of composting which is beneficial to
plant growth. It has undergone an initial rapid stage of decomposition and is in the
process of humification (stabilization stage).

These definitions are useful in that they serve as a baseline in determining compost quality
specifications.

First order requirements include stabilization of the organic material, that is, biological
degradation and mineralization of the more rapidly oxidized, low molecular weight organic
constituents. This accomplished, the odour production potential of the compost is minimized.
In addition, sanitation, the destruction of human pathogens, is simultaneously achieved,
primarily due to the heat production achieved during the early, most rapid, stages of the
composting process. Weed seeds are also killed in the process. (See Figure 2-2.)

Composting should be characterized as a two part process. The first stage primarily involves
microbial degradation or breakdown of the lower molecular weight organics, leading to initial
stabilization and sanitation of the product. In the second phase, degradation or biooxidation of
organic material continues to take place, albeit at a lower rate and primarily involving higher
molecular weight organics. However, there is a shift during this period to synthetic activity as
well, primarily resulting in the formation of increasing quantities of humus in the compost.

Inclusion of contaminants, heavy metals and hazardous organic materials greatly reduces
compost quality, applicability and marketability. The input of these materials is reduced by not
composting solid wastes from industrial sources, using well trained picking line operators, not
shredding wastes prior to composting, and careful screening and final air separation. Public
education and the institution or voluntary source separation programs such as wet/dry systems
also have a significant effect in reducing hazardous contaminants in compost.

The quality of the compost will directly affect its end use. High quality composts may find
end uses in horticulture and landscaping. Poor quality composts may only be suitable as
landfill cover and reforestation.

1.4 References

[1] F. Zucconi and M. de Bertoldi. BioCvcle. 56 pp. (May-June 1987).

2.0 GENERIC COMPOSTING INFORMATION

Composting has long been recognized as a means of solid waste management. Since early
history, composting has been used to process various organic wastes into a humus-like material
suitable for use as a soil amendment. Scientific studies of operating parameters for the
compost process were begun in the early 1940s. Nevertheless, for purposes of clarity and
completeness, some "generic" information on composting (including definitions of key
terminology and descriptions of processing, operating and control parameters, and approaches)
is provided in this section.

2.1 Definitions of Key Terminology and Nomenclature

This section begins by defining three terms that are basic to all discussions concerned with
municipal solid waste (MSW). The three terms are "garbage," and "rubbish," and "refuse." In
the terminology used in the professional literature during the past forty years, the designation
"garbage" has been restricted to food preparation (kitchen) wastes and to highly putrescible
wastes in general. All other components of residential municipal solid waste (including
beverage containers, paper, scrap metal, and a variety of other components) bore the collective
label of "rubbish." These two elements (garbage and rubbish) collectively were referred to as
"refuse."

This simplistic division of municipal solid waste into garbage and rubbish does pose the
difficulty of how to classify yard wastes. In the early classification, green (herbaceous)
material usually was classified as garbage and dry or woody material, as rubbish. Currently,
these materials are collectively referred to as "yard and garden debris."

With the increasing popularity of solid waste as a subject matter in the popular literature, has
come a softening of the distinctions between the terms garbage, rubbish, and refuse. A trend
has developed to use the terms garbage and refuse synonymously. Also with this trend has
come the use of the term "wet fraction" to refer to garbage as defined above.

"Composting" has been given many definitions in the literature. The following engineering
version is appropriate for composting as a waste treatment option and has been fairly widely
accepted [1-3]:

"Composting is the biological decomposition of wastes of plant or animal origin
under controlled circumstances to a condition sufficiently stable for
nuisance-free storage and for safe use in land application."

The definition sufficiently distinguishes composting as it occurs in nature from the restrictive
sense of a waste treatment option. Key terms in the definition are: 1) biological
decomposition; 2) under controlled conditions; and 3) sufficiently stable. Inclusion of the term
biological decomposition implies that composting as a waste treatment option is for the most
part restricted to organic wastes. Under special conditions, however, some microorganisms can
attack materials not of living origin. The specification, under controlled conditions,
distinguishes engineered composting from the simple decomposition that takes place in an open
dump or in a feedlot. The third term, sufficiently stable, is an important requirement to any
compost operation. For a compost product to be innocuous with respect to environmental
impact and effect on plant growth, it must be sufficiently stable. The requirement also
provides a basis for comparing one compost system with another.

2-2

Other key terminology of importance in the discussion and understanding of composting are
provided below.

Aeration

Aerobic

Anaerobic

Biological
Decomposition

Bulking Agent
C/N

Co-composting
Compost

Curing

Heavy Metals

Humus
In-vessel

Leachate

Limiting Factor

Mesophyllic

Microorganisms
Residuals

Sludge

Stability

Static Pile

The process of exposing composting material to oxygen.
A process or condition occurring in the presence of oxygen.
A process or condition occurring in the absence of oxygen.

The process of breaking down organic materials through the use of
microorganisms into component parts or basic elements.

Material used to add volume to composting feedstocks, aids in aeration.

The ratio of carbon to nitrogen.

Composting of two or more waste streams simultaneously.

Relatively stable humus-like material resulting from the composting
process.

The stage during which materials that are more resistant to breakdown
are stabilized; also known as maturation.

Elements including cadmium, mercury, lead and chromium which may
be found in the waste stream.

Organic materials resulting from decay of plant or animal matter.

A method of composting in which the compost is mechanically mixed
and aerated in a container.

Liquid formed by water percolating through a mass of solid waste or
compost and extracting dissolved or suspended materials from the mass.

The parameter in lowest supply that limits growth and activity of the
organisms under consideration.

Term popularly applied to mesophiles, i.e., organisms that grow at
moderate temperatures. The mesophyllic temperature range usually is
considered as being between 8° and 50°C.

Microscopically small living organisms that metabolize waste materials.

Materials removed from the feedstock to the composting process or from
the finished compost. Residuals may require landfill disposal.

A semi-liquid residue remaining from the treatment of municipal and
industrial water and wastewater.

The state at which the composted materiral can be stored without
causing a nuisance or can be applied to the soil without causing
problems.

A windrow composting method in which aeration is accomplished either
by forcing or drawing air through the composting mass by way of ducts
generally installed at the base of the pile.

2-3

Thermophyllic Term applied to thermophiles, i.e., organisms that grow at high

temperatures. Thermophyllic temperatures are usually higher than 50 C.

Windrow An elongated pile of material.

Yard and Garden

Debris Leaves, grass clippings, primings, etc. discarded from yards and gardens.

2.2 Description of Generic Composting Technologies

The technology of composting involves three major steps: 1) preparation of the raw material
or substrate; 2) the compost process itself; and 3) grading of the final product. This section
deals with the second step, the compost process itself. Process technologies can be grouped
under four categories:

• turned windrow;

• static pile (forced aeration);

• in-vessel; and

• hybrid (a combination of the above elements).

In reality, the fourth category is an artifice to accommodate the many miscellaneous
combinations of the first three.

Each system basically expresses a particular approach to accomplishing aeration of the
composting mass. (Exceptions are the very few systems mat call for an anaerobic phase before
or after the aerobic phase.) Of course, supplying aeration is not the sole objective of system
design. Other objectives are providing environmental and operational conditions that approach
the optimum for the active microbial populations.

Because a prime objective of each technology is that of accomplishing aeration, the
descriptions of the technologies are preceded here with a discussion of methods of aeration:
agitation, injection, and a combination of the two.

Agitation can be done by turning, tumbling, and stirring. The term "turning" refers to the
successive tearing down and reconstruction of a windrow. Turning exposes the composting
material to air and renews the supply of 02 in the interstices in the windrow. Tumbling
involves cascading the composting material so as to expose the particle surfaces to ambient air.
It may be accomplished by passing the composting material through a rotating cylinder
equipped with internal vanes. Tumbling also may be done by dropping the composting
material from a conveyor belt installed on a frame that moves on rails placed at the bottom of
a rectangular tank (bin). The belt scoops up and then drops the composting material. Stirring
is done by passing a plow-like device or an auger through the composting material.

Air injection (forced aeration) is perhaps the least expensive of the aeration methods. As the
name indicates, it is accomplished by forcing or drawing air through the composting mass.
Injection often is used in combination with agitation. Individual in-vessel compost systems
may depend entirely on agitation or injection, or may use them in combination.

As mentioned earlier, the compost technologies have been grouped under four categories:
turned windrow static pile, in-vessel, and hybrid. The first two categories (turned windrow and
static pile) are both classified as "open" systems inasmuch as they are not contained within a
structure. The classification, however, does not exclude enclosing the operation in a shelter or
building. Open systems more commonly are termed windrow systems. The term "windrow"
simply means "an elongated pile" and can apply equally to windrows mat are aerated by way
of turning and to those that are subjected to forced aeration.

24

The third compost technology listed above (in-vessel) can be categorized as an "enclosed"
system because the compost is mechanically mixed and aerated in a structure. To conserve on
capitalization, maintenance, and operational costs, many in-vessel systems call for the initial
stage of the compost process to take place in a reactor and all succeeding stages in windrows.
Such combinations may be loosely termed "hybrid" systems. In practice, almost all in-vessel
designs can be classified as hybrids. Typical retention periods of composting material in the
reactor are not sufficiently long to permit adequate stabilization and, consequently, further
treatment outside the confines of the reactor generally is needed.

2.2.1 Turned Windrow

As stated earlier, turning is the term applied to the tearing down and reconstruction of the
windrows of material being composted. Although turning can be done manually (i.e., with a
pitchfork), mechanically (i.e., with a front-end loader) or both, manual turning is impractical
under modem conditions and with volumes larger than one or two cubic meters. Front-end
loaders, bulldozers or comparable machines are suitable only for small-scale operations because
of capacity and quality of turning limitations. There are several types of large-scale turning
equipment on the market. They differ among themselves with respect to effectiveness and
durability. According to their promotional literature, many of the large mechanical turners can
process as much as 900 tonnes/hour of waste. Although essential for most sewage sludge and
MSW compost operations, large-scale turning equipment probably would be beyond the finan-
cial resources of most yard waste compost projects.

The ideal turning pattern is one in which the outside layer of the original windrow becomes the
interior of the rebuilt windrow. At a rninimum, care should be taken that at least at some time
during the compost cycle, every panicle of material is in the interior of the pile. Less than
ideal turning patterns can be compensated for by increasing the frequency of turning.

In practice, frequency of turning is a compromise between oxygen demand and economic and
technological feasibilities. Nature of the waste and its structural strength and moisture content
are important determinants. Other factors are pathogen kill, uniformity of decomposition, and
the desired rate of composting. For example, increasing the frequency of turning can decrease
the residence time to 1 to 2 months as compared to the 6 to 12 months that would be required
at a turning frequency of only once a month. Less frequent turning is preferable for operations
involving a waste with a low moisture content or one consisting of structurally firm particles.

The turned windrow approach calls for stacking the material to be composted into a pile that
has the shape of a windrow with a more-or-less triangular cross-section. The cross-sectional
shape can be changed to fit special conditions. If the pile is turned by machine, the
configuration is the one imparted by the machine.

Although ideally, the windrow should be from 1.5 to 1.8 m (5 to 6 feet) in height, the practical
height will be a function of the type of turning machine. Optimum height is a function of the
tendency of the material to compact under its own weight.

Width of windrow is determined by convenience, expediency, and type of turning equipment
Width is not critical because the oxygenation by diffusion supplies very little of the oxyger
needed in the composting mass. Usually, the width is from 2.4 to 4.5 m (8 to 15 feet).

Windrow length should befit the operation and site configuration. To set up a semi-continuous
system, each day's input of raw waste is added to one end of the windrow or, for large-scale
operations, by placing each day's input into a new windrow. Basically, continuity comes from
adding fresh material to one end of the windrow and removing composted material from the
other end.

Aside from the usual array of factors, area requirement depends upon the capacity and working
space requirements of the type of turning equipment utilized.

2-5

2.2.2 Static Pile fForced Aeration)

Essentially, the static Dile approach calls either for forcing (injecting) air into the composting
mass, or conversely, for drawing air through the composting mass. The composting material
may or may not also be turned. The system involves the following steps: 1) mixing of the
raw waste with a bulking agent (if required); 2) construction of the windrow; 3) onset and
completion of the compost process; 4) screening of the bulking agent from the composted
mixture (if required); 5) curing; and 6) storage.

Construction of a static pile windrow is begun by laying a grid of perforated pipe on the
compost pad. The grid is connected to a fan. The grid is covered with a layer of bulking
agent or finished compost. The material to be composted is then stacked on the covered grid.
The substrate is topped with a 30 cm (1 foot) layer of finished compost. If desired, the
windrows may be sheltered from the elements.

Because the optimum rate of aeration depends upon several site and material-specific factors, it
should be determined experimentally for each operation. Typical air flow rates for static pile
windrows are between 120 and 170 m3/h.

The static method is not applicable under all conditions or to all types of materials. Chances
are that the static pile method may not be effective with wastes characterized by one or more
of the following: 1) a large particle size; 2) a large and varied particle size distribution; 3) a
tendency to clump; or 4) a high moisture content. It is best suited to materials that are
relatively uniform in particle size and whose particle size does not exceed 3.8 to 5 cm (1.5 to
2 in.) in any direction. Granular materials are best. Inappropriate size distributions for the
bulking agent or inaccurate ratios of bulking agent to waste tend to constrict the air flow. The
outcome is that areas of relatively slow degradation and foul odours (anaerobic pockets) are
formed.

Probably the static pile approach would be successful with mixtures of dewatered food waste or
lawn clippings bulked with the chopped woody fraction of yard debris, straw, or dry leaves.
Forced aeration is very useful for composting yard waste. Since the static pile approach is
most effective with wastes that are granular and relatively homogeneous, it has had its most
widespread application in sewage sludge composting.

2.2.3 In-Vessel

The objective in the design of in-vessel systems should be to provide the best environmental
conditions, particularly, aeration, temperature, and moisture. Unfortunately, the design of most
in-vessel systems falls shon of that objective. Almost all in-vessel systems use forced aeration
in combination with stirring, tumbling, or both.

In-vessel systems can be classified into the two broad groups: 1) rotating drum; and 2) tank
(horizontal and vertical).

2.2.3.1 Rotating Drum

The rotating horizontal drum is one of the earliest in-vessel systems to rely upon tumbling as
the primary mode of aeration. The tumbling material in the drum is exposed to air which is
continuously renewed with air forced into the drum interior through a series of nozzles installed
in the drum wall. In most versions, the drum is a long, slightly inclined cylinder about 2.7 m
(9 feet) in diameter. The drum is rotated at a few (less than 10) revolutions per minute (rpm).
According to the promotional literature, the retention periods in the drum may range from 1 to
6 days. Because the degree of stability attainable in such a brief time is insufficient, the
material must be further composted over an additional period, which usually is on the order of
1 to 3 months. This period serves as the maturation (curing) stage. The common procedure is
to set up a two-stage process flow in which the first stage is a rotating drum and the second is
a windrow (either turned or static pile).

2-6

High capital, operational, and maintenance costs restrict the horizontal drum approach to
large-scale applications, such as composting municipal refuse and co-composting.

2.2.3.2 Horizontal Tank

Rectangular

An in-vessel system that has much in its favour, involves the use of a long rectangular,
horizontal tank and incorporates a combination of rumbling and forced aeration. Tumbling is
accomplished by periodically passing a travelling endless belt through the composting material.
In addition to the tumbling, air is forced through the perforated bottom of the tank and into the
composting mass in the tank.

In the operation, suitably prepared waste is placed in the tank. At the end of a 6- to 12-day
retention period, the material is removed from the tank and is windrowed over a period of one
to two months. Although somewhat expensive for composting yard wastes, this system
probably would be well suited for MSW, sewage sludge, mixtures of MSW and sludge, and
properly bulked high-moisture food wastes. Times involved (in tank plus required windrowing)
range from one to two months.

Cylindrical

Another version of the horizontal tank is a circular tank that relies upon a combination of
forced aeration and stirring. The tank is equipped with a set of hollow augers perforated at
their edges and supported by a bridge attached to a central pivoting structure. The bridge with
its set of augers is slowly rotated, as also are the augers. Air forced through the perforations is
distributed into the composting material. Retention time varies. If it is less than three weeks
or so, the discharged material must be windrowed until stability is reached.

2.2.3.3 Vertical Tank

As the term indicates, this version of in-vessel systems consists of vertically-oriented tanks (i.e.,
silos) which rely upon forced aeration and stirring. A problem that besets such systems is the
difficulty in sufficiently aerating the upper layers of the composting material without unduly
cooling the lower layers.

One such system involves the use of three completely enclosed vessels. A special feature of
this version' is a rotating screw device installed at the bottom of the vessel for discharging the
compost. One of the three tanks serves as a storage container for carbonaceous material
intended for use as a bulking agent and for correcting the C/N. The composting process takes
place in the second and third vessels - the "bioreactor" and the "cure reactor." Air is fed
continuously into the bottom of the bioreactor, with positive control maintained by pulling air
off the top. Composted material from the bioreactor is transferred into a cure reactor, in which
further stabilization takes place. Air is fed continuously into the cure reactor to maintain
aerobic conditions and to remove moisture due to evaporative cooling. Since the retention
period in the bioreactor is on the order of two weeks, the normal daily operating sequence
begins with the bioreactor outfeed discharging approximately 1/14 of the contents into a
conveyor. The conveyor transports the material to the top of the cure reactor. At the same
time, the outfeed device in the cure reactor is started and final compost product is discharged.
Retention time in the cure reactor is about 20 days. Problems frequently encountered in the
operation of the units are: 1) a tendency of the material "to bridge" over the discharge screw;
2) failure of the rotating screw; and 3) excessive condensation on the upper layer of the
bioreactor. The system originally was designed for sewage sludge and manure composting. Up
until now, most of the experience has been with sewage sludge. The extent of the experience
with municipal refuse has been limited to one or two installations in western Europe.

2-7

2.2.4 Hybrid Composting

The broad category, "Hybrid Composting," was discussed in the introductory paragraphs of
Section 2.2, and in the subsection on in-vessel composting. Hence, no further discussion on
the subject is had at this time other than to point out that almost all in-vessel systems are
potential candidates for hybridization.

2.3 Generic Operating and Control Parameters

This section is introduced by a brief explanation of the biology of the compost process so as to
facilitate the description of the operating and control parameters.

In practice, composting takes place in two stages. The transition from the first to the second is
gradual and uninterrupted. The first stage is the active stage in which biological activity is
proceeding at its highest rate. Heat generation is such that in the absence of heat dissipation,
the temperature of the mass soon reaches 60 to 70° C. In this stage, readily biodegradable
material is decomposed to less readily degradable intermediates. With the disappearance of the
readily available nutrients, the temperature of the mass drops because of a slowing of microbial
activity. This second stage is known as the curing (maturation) stage. It ends when the
residue reaches the required degree of stability. Hence, an important consideration in the
evaluation of a compost systems is the fact that the compost process is finished only upon the
completion of the curing stage.

Composting is essentially a microbial process in its early stages. However, as the process
continues, microscopic protozoa, macroflora and macrofauna (specifically the macroin vertebrae)
may appear. Among the latter, earthworms (e.g. Lumbricus terestri's. L rubellus. Eisenia
foetida) periodically nave attracted attention due to claims made by some individuals, who
attributed certain useful properties to the worms.

Usually, the microflora active in composting are present in the material to be composted.
Consequently, no inoculums are required. In the unlikely event that it might be beneficial,
mass inoculation can be done by recirculating some end product or bv introducing a massive
dose (about 10% of the mass) of microorganisms specifically cultured for the purpose. The
general experience has been that no other additives (enzymes, hormones) are needed [4,5].

Because microbes are the essential agents in composting, factors that affect their growth and
activity simultaneously determine rate and extent of composting. These factors constitute the
operating and control parameters. Among the more important factors are time, temperature,
moisture, nutrition content, oxygen, and mixing.

2.3.1 Time Requirements

With respect to the overall compost process, the parameter of time should be an interval
sufficiently long to permit the process to reach its desired goal. Therefore, the compost process
is sufficiently complete as soon as the composting mass has been stabilized such that: 1) it
can be stored without causing nuisances; and 2) it has reached a stage of maturity at which it
is not inhibitory to plant growth. At present, several sets of standards and methods are being
developed and proposed for measuring stability of the finished compost. Among the measures
receiving attention are the carbon-to-nitrogen (C/N) ratio, and seed germination and growth
tests.

With reference to a stage of the process, the interval should be long enough to permit activities
peculiar to that stage to reach a satisfactory conclusion. For example, by the end of the initial
stage, the necessary microbial populations should have: 1) begun the logarithmic rate of
growth phase; and 2) become sufficiently active to cause the temperature of the pile to begin a
sharp ascent to thermophyllic levels. By the end of the active stage, microbial activity should
have begun to slow and temperature to plateau immediately prior to a gradual drop. By that
time, the readily decomposed components should have !>een convened to intermediates suitable

2-8

for eventual breakdown in the curing stage. The curing interval is particularly important
because it must be long enough for the composting material to have reached the final level of
stability.

When used in reference to a continuous culture, the interval is the time the average particle is
in the reactor or in the body of the composting windrow. The term applied to the interval may
be any one of the following three: retention time, detention time, or residence time. The
terms are used interchangeably. It should be noted that the terms are applicable to any
continuous system, whether it be an in-vessel system, a turned windrow, or a static pile.

One sampling of time ranges is given in Table 2-1. The times are total times, i.e., they include
lag, active, and full curing stage.

2.3.2 Temperature Requirements

With the exception of some in-vessel systems, little is done about temperature unless a
significant aberration is observed. The underlying reason for the laissez-faire approach is the
self-heating characteristic typical of an actively composting mass. Because of this
characteristic, unless something intervenes, the initially mesophyllic (ambient) temperatures of a
composting mass rapidly are replaced by thermophylhc temperatures. This rapid rise is a mark
of the active stage of composting. Eventually, as microbial activity diminishes, the temperature
returns to mesophyllic levels during the curing stage. A typical temperature curve is presented
in Figure 2-1.

Temperature approaches a limiting factor in the composting process when it exceeds 60°C.
Temperatures greater than 60°C tend to inhibit bacterial activity. Methods of lowering an
unfavourably high temperature depend upon the type of system being used. However, the
usual method is to increase the rate and extent of aeration.

Too slow a rise of temperature, or complete absence of a temperature rise, in an adequately
insulated composting mass is an indication of inhibited microbial proliferation and activity due
to some operational or environmental imbalance or inadequacy (e.g., aeration, nutrition,
moisture). The attainment and maintenance of thermophylhc temperatures for a time period is
a requirement, mostly with respect to weed and pathogen control. Recommended temperatures
for inactivation of plant pathogens and weed seeds are presented graphically in Figure 2-2.

2.3.3 Moisture Requirements

The role of moisture in the composting process begins with the microbes involved in the
process and extends to and includes the moisture required for rendering nutrient chemicals
available to the microbes and for transporting other substances. With respect to the microbes,
it is an essential part of their assimilatory, metabolic, and reproductive mechanisms. Its
importance is emphasized by the fact that all activity ceases when the moisture content drops to
about 8% or lower. Accordingly, the closer that minimum is approached, the slower will be
bacterial activity. In practice, it is advisable to keep the moisture level at a minimum of about
48%, but the actual permissible range is between 45% and 55%[2].

With respect to maximum permissible moisture content, if it were not for certain physical,
technological, and practical constraints, the ideal moisture content would closely approach
100%. Indeed, the wastes treated by way of the conventional aerobic oxidation systems used
in wastewater treatment are in this category. However, as far as composting in the accepted
sense of the term is concerned, certain factors necessitate a significant lowering of the
maximum permissible moisture content. The most important of these factors is the oxygen
requirement and means of meeting the requirement.

Maximum permissible moisture content and oxygen are closely interrelated in compost practice.
Regardless of method of composting, the 0, supply to the individual microbes must come from
the air contained in the interstices between panicles of wastes and from the ambient air. As
the moisture content increases, more air is displaced from the interstices and, hence, less 02 is

2-9

TABLE 2-1
Examples of Composting Times* [2]

Type of Waste Time (weeks)

Yard and park debris (including grass clippings) 4 to 8

Leaves (separately collected) - C/N adjusted 4 to 8

- C/N not adjusted 24 to 52

MSW - with or without sewage sludge 8 to 24
(preprocessed - including size reduction)

Sewage sludge (suitably bulked) 6 to 10

Animal manure and associated wastes 6 to 18

Assorted food processing wastes 6 to 18
(appropriately preprocessed or bulked)

These composting times are to the same stability criterion.

2-10

FIGURE 2-1
Typical Temperature Curve [2]

20 30

TIME (DAYS

40

50

2-11

FIGURE 2-2
Plant Pathogens: Sterilization Temperatures* [21]

GC

100

90

80

70

60

50

40

few resistant weed seeds
resistant plant viruses

most weed seeds

H

all plant pathogenic bacteria
most plant viruses

— soil insects

— most plant pathogenic fungi

— most plant pathogenic bacteria, worms, slugs

— gladiolus becomes yellow; fusarium oxysporum
— Botrytis grey mould

— Rhizoctonia solani

— nematodes

— water moulds

Using external heat for 30 minutes under moist conditions.

2-12

available. As a result, the maximum permissible moisture content is that level at which
sufficient air remains in the interstices to assure an adequate supply of oxygen, but above
which oxygen becomes limiting. The level depends upon the extent to which individual
particles maintain their original shapes after being wettened or compressed.

The inadequate structural strength of material such as cannery wastes, sewage sludge, and fresh
manure, can be compensated by the addition of a bulking material. A bulking material is one
that maintains its original shape upon being mixed with an amorphous waste. Examples of
bulking materials are wood shavings and chips, straw, dry leaves, and corn stalks. Mixtures
that have mostly paper (e.g., sewage sludge bulked with refuse) have an upper permissible
moisture content of only 55% to 65%. (Incidentally, the maximum permissible moisture
content for municipal refuse is on the order of 55%.) On the other hand, the permissible
moisture content for manure mixed with hay, straw, wood shavings, or comparable bedding can
be as high as 70% to 75% (2,3]. The relation between aeration and moisture content is further
discussed in the section that follows.

2.3.4 Oxygen Requirements

Although in the 1940s and 1950s, anaerobic composting was regarded as a serious alternative
to aerobic composting, modern composting strives to be essentially aerobic for many good
reasons. Among the reasons are the assumed greater efficiency, reliability, and tolerance of
shock conditions (e.g., sudden brief and drastic changes in environmental conditions), and the
generation of fewer objectionable odours and other nuisances.

As is mentioned in the section on technology, aeration is accomplished through agitation
(turning, tumbling, stirring), by forcing or drawing air through the composting mass, or through
a combination of agitation and forced aeration. A variety of aeration rates is suggested in the
literature. Among them are the following two: 1) 562 to 623 mVair ton volatile matter/day
[6]; and 2) 263 to 306 mmVgram volatile solids/hr [7]. The rate at which sufficient oxygen to
maintain aerobiosis is supplied is a function of the nature and structure of the waste. Thus, the
amount of oxygen required with a combination of easily decomposed waste and a large and
very active microbial population would be much greater than would be required with a
refractory waste and a small microbial population. Production of foul odours is a qualitative
indication of insufficient aeration. Another excellent indicator is an unduly slow temperature
rise in the active stage or an unexpected drop in temperature in later stages. Indicators less
readily apparent, but more quantitative, are an unexplained slowing of rate of breakdown of
organic matter, slowing of rate of oxygen consumption and carbon dioxide generation, and
absence of expected physical changes in the composting mass.

In practice, the aeration rate should be determined by experimenting with the waste to be
composted. If aeration is by turning, frequency of turning is the operational point of interest.
With forced aeration, it is in terms of rate and volume of throughput air. Economic factors
may force compromises in both areas. It is possible that composting could be accelerated by
adding pure 02 to the input air stream. However, the gain probably would not justify the
sharply increased monetary expenditure.

2.3.5 Nutritional Requirements

For microbes, the macronutrients are carbon (C), nitrogen (N), phosphorus (P), and potassium
(K). Among the micronutrients are cobalt (Co), manganese (Mn), magnesium (Mg), and
copper (Cu). Calcium (Ca) falls between the macro and the micronutrients. Its principal role
is as a buffer (resist changes in pH). Ideally, the waste should contain all necessary macro-
and micronutrients. In practice, nitrogen probably would be the only nutrient that would need
to be added. The occasion for adding nitrogen would be to bring an unfavourably high C/N
ratio down to a more suitable level.

2-13

To be of use to the microbes, nutrients must be in a form that can be assimilated by them, i.e.,
is chemically available to them. Chemical availability to microbes is strictly a function of their
enzymatic makeups or ability to synthesize enzymes as needed. Certain groups of microbes
have the enzymatic complex or potential with which they can attack, degrade, and utilize the
intact organic matter present in a freshly generated waste. Others can use as a source of
nutrients only the intermediates that result from this attack, degradation, or utilization. The
significance of this latter fact is that composting of a waste becomes the sum total of the
collective activities of a dynamic succession of different groups of microorganisms in which
one group serves as a precursor for succeeding groups.

Organic materials differ in their degree of resistance to microbial attack, in that some are
readily broken down whereas others are resistant even when exposed to the required enzymatic
complex. Moreover, breakdown of resistant materials advances slowly even under optimum
environmental conditions. Examples of resistant substances are lignin (wood) and chitin
(feathers, shellfish exoskeletons). Although readily available to many fungi, cellulose-C (in
wood, straw, pith) is resistant to most microbes. Nitrogen is readily available when it is in the
proteinaceous, peptide, or amino acid form. The small amounts of nitrogen in lignin and chitin
are released too slowly for practical composting. Sugars and starches are readily decomposed,
and fats are less so.

Experience has shown that with the exception of carbon and nitrogen, most organic wastes
contain nutrients in the amounts and ratios required for composting [2,3]. Although less
important than actual concentrations, ratios of certain nutrients to one another do exert an effect
on microbial growth and activity. The most important of such ratios is the C/N ratio. The
ideal ratio is about 20 to 25 parts of carbon to 1 of nitrogen (20/1 to 25/1). The composting
process becomes increasingly slower as the C/N rises above this range. At high C/N ratios,
microbes begin to immobilize nitrogen at the expense of microbial action. At C/N ratios lower
than this range, nitrogen begins to be lost from the composting material as ammonium-N. A
C/N ratio can be lowered by adding a nitrogenous waste (e.g., grass clippings, green vegetation,
non-ruminant animal manure). Adding a carbonaceous waste such as hay, dry leaves, or
chopped twigs, will raise a low C/N ratio of a waste such as sewage sludge.

2.3.6 Particle Size

With some justification, particle size could be validly regarded as a form of physical
availability. In point-of-fact, it constitutes a limiting element in the expression of chemical
availability. The justification for this claim arises from the role of enzymatic action in
determining chemical availability. Because of that role, the larger the ratio of surface area of a
particle to its mass, the greater is its exposure to enzymatic action, and hence, the more rapid
becomes the rate of microbial activity and breakdown.

In theory, the smaller the panicle size, the more rapid is the rate of microbial attack. There is,
however, a minimum size ("minimum permissible particle size") below which maintenance of
the porosity in the composting mass necessary for sufficient aeration becomes very difficult.
With a rigid or not readily compacted material (e.g., fibrous materials, wood chips), the
optimum size is from 5 to about 7.5 cm (2-3 in.). At the other extreme, the minimum particle
size of the greater part of fresh green plant material (e.g., food wastes, fruits, lawn clippings),
should be no less than 5 cm (2 in.). Depending upon the decomposability of the material, the
maximum size can be as large as 15 cm (6 inches).

2-14

2.3.7 Mixing Requirements

To fully appreciate the importance of mixing and its functions in composting, it is necessary to
keep in mind that for practical purposes, the microbes are not mobile. Therefore, the only
environment encountered by each microbe is the exceedingly thin aqueous film by which it is
surrounded. This film contains a mixture of: 1) dissolved nutrients; 2) nutrients in the
cohoidal state; 3) gases of atmospheric origin; 4) gases from metabolic processes; and 5)
breakdown products released by the microbe. These breakdown products may be inhibitory or
even toxic to the organism that synthesizes it. At the least they displace substances useful to
the microbe, or they may bring about adverse changes in the immediate environment such as
lowering the pH level. In short, the film is the sole source of nutrients and gases for the
microbe and simultaneously is the repository for all of its products, both beneficial and
inhibitory. Consequently, to ensure maximum, or at least adequate microbial activity, it is
necessary to periodically renovate the immediate environments of all active microbes. The
only way of doing this is by periodic mixing. Thoroughness and sufficient frequency of
mixing constitute limiting factors.

With respect to composting, an outstanding benefit of mixing is its promotion of uniformity of
decomposition. For pathogen control, it ensures the exposure, at one time or another, of all
composting material to conditions lethal to pathogens. For aerobic composting, it renews the
oxygen supply in the interstices between particles and removes accumulated carbon dioxide.
An ancillary benefit is the promotion of loss of excess moisture. Of course, if moisture is
limiting, this drying effect may be a disadvantage.

2.3.8 Hydrogen Ion Level (pH)

Usually, the pH level drops to about 5.0 as soon as composting conditions have been
established. This initial drop is soon followed by a gradual rise that continues until a level of
8.5 is reached. Because of this sequence, buffering by adding lime (CaCOH)^ is not necessary.
In fact, the addition of lime may lead to excessive loss of ammonia (NH3-N). An exception
might be in the composting of fruit wastes. With such wastes, the initial drop may be to 4.5.
Liming, however, improves the physical condition (e.g., porosity, texture) of the composting
wastes.

2.4 Approaches to Municipal, Commercial/Industrial,
and Agricultural Composting

The basic principles and technologies described earlier can be applied to municipal,
commercial/industrial, and agricultural composting operations. Major differences in composting
these types of waste are the adaptations that are needed to compensate for the particular
characteristics of the waste serving as substrate. Examples of such characteristics would be
structure, lack of some macronutrient, or handling in general. Thus, these adaptations are
mostly those made to accommodate the particular waste to the compost process.

The major sources of most compostable commercial/industrial residues are from the food
processing, meat packing, and rendering industries. Each of these wastes varies in structure,
nutrient content, etc. as do residues from agriculture and municipal solid wastes. A description
of the adaptations and of variations between adaptations related to each of these wastes would
be a major undertaking. Therefore, the remainder of this section deals mainly with the
collection and storage of MSW, as composting is impacted.

Regarding municipal solid wastes, not all components are suitable as a substrate for the
composting process. Moreover, the presence of the unsuitable components is both a liability in
the composting process and also detracts from the utility or attractiveness of the compost
product. Consequently, the compost process becomes more efficient and the quality of the

2-15

product improves to the extent that these components are eliminated from the MSW.
Separation of non-compostable components from the compostable components in MSW can
take place before or after the MSW is collected. If separation takes place before collection, it
is termed "source separation," and, if after collection, "post-collection separation." In short,
freedom from non-compostables is a function of the manner in which MSW is treated at the
point of generation, in storage, and in collection. (It should be noted that the advantages of
source separation vs. post collection separation and the procedures involved, apply to all
recyclable resources in the MSW.)

As is true in sewage sludge composting in general, the system usually proposed and applied in
co-composting is the static pile. The present trend is towards enclosing the static piles in a
shelter in order exert some control over the release of emissions into the environment. Another
trend is towards in-vessel composting. The advantages and disadvantages of the two
approaches as discussed previously also prevail in co-composting.

2.4.1 Municipal Wet/Dry Systems

2.4.1.1 Definitions and Classifications

The terms "wet" and "dry" refer respectively to the garbage (wet) and rubbish (dry)
components of the waste scream. Until the late 1970s, the heading of this section would have
been Separate Collection, because the only form of source separation was that of refuse into
garbage and rubbish. Thus, the separate collection of that day may be regarded as a rud-
imentary form of modem source separation.

2.4.1.2 Types of Storage and Collection Systems

Storage and collection are interdependent in that extent and type of separation in storage
directly influences collection with regard to equipment and mode.

If no separation is done by the waste generators, all waste stream components are stored in
single containers (combined storage), and hence are collected as such (combined collection).
The combined refuse is then transported to a central site, where selected components may or
may not be separated. Separation of this combined refuse constitutes post-collection separation.

In source separation, waste components are separated by the householder, and storage is
adapted to maintain this separation. Various home storage containers designed to maintain
separation are on the market and have been described in the literature [8]. The separated
components can be collected simultaneously and kept separate by using a compartmentalized
collection vehicle specifically designed for mis function [9]. The separated components can
also be collected separately. The frequency of collection must be suited to the nature of the
particular components and the rate at which they are accumulated. Each approach
(simultaneous collection and separated collection) has its particular advantages and
disadvantages. Separation continues to be maintained at the treatment and disposal site.
Among the many advantages of source separation are a greater freedom from contaminants,
particularly heavy metals, as is indicated by the data in Table 2-2.

2-16

TABLE 2-2

Effect of Source Separation on the Heavy Metal Content
of Various MSW Composts (Netherlands)

Type of

Compost

(Pre-Processing Method)

Element
(ppm)

A

B

C

D

Cadmium

7

1.8

1.0

0.5-

0.8

Chromium

180

40

30

50-

60

Copper

600

100

50

26 -

■ 37

Lead

800

420

160

41 ■

■ 67

Nickel

110

25

10

9 -

14

Zinc

1,700

520

230

140-

■ 210

A Raw MSW composted in windrows without any pre-processing. After composting (12

months), product is screened and inerts removed. [10]

B MSW shredded and mechanically processed to remove non-compostable material (i.e.,

glass, metals, plastics, etc.). Organic fraction composted. [10]

C Source Separation - Metals and other inorganic materials collected separately from

organics. Organics composted. [10]

D Vegetable, fruit and yard wastes - Collected and composted separately from inorganics

and paper.[ll]

2-17

2.4.1.3 Wet (Garbage) Collection

The nature of garbage is such that the separate collection of the material is subject to many
serious environmental and hygienic constraints that begin with its storage and continue through
collection. In addition to being particularly odoriferous and unsightly, garbage attracts vectors
and rodents. The strong attraction is due to the fact that it is a highly accessible and excellent
source of nutrients for the pests, and also can serve as a shelter for rodents. Consequently, it
is essential that garbage be isolated from the environment as completely as is possible. This
isolation must begin with storage, continue through collection, and not end until treatment or
disposal has been completed.

The storage container for garbage should be durable and easily cleaned. Most importantly, it
must be have a close-fitting lid that is not easily displaced. The storage container and its
contents should be protected from disturbance by domestic animals (dogs, cats) and be
accessible only to the garbage collector.

As with storage, the collection of garbage should be such that exposure is minimal. Ideally,
the collection vehicle should either be designed for garbage collection or it should be carefully
adapted to that function. In particular, it should be water-tight and should be cleaned at the
end of each run. Careful isolation and control must be continued during storage at the disposal
site and throughout the subsequent disposal process.

Because garbage is so highly putrescible, ideally collection should be on a daily basis.
Duration of storage at the disposal site prior to treatment or disposal should be minimal.

2.4.2 Variations on the Wet/Dry System

Variations on the wet/dry system range in extent from minor adjustments made to
accommodate specific situations, to major changes that are discussed in the remainder of this
section.

2.4.2.1 Recycling Centres

This variation calls for the generator to transport all or some of his or her separated recyclable
wastes to a recycling centre. Items not transported to the centre are kept at the generation site
and are collected later. An adaptation of this variation would be for the generator to transfer
all recyclable wastes to strategically placed municipal collection bins for later transfer to a
centre. This latter adaptation is being increasingly adopted in Europe. Yet another approach is
for the householder to transport certain components of his or her wastes to a recycling centre,
and leave the remaining components to be picked up by the collection vehicle.

The advantage of making the generator responsible for transporting some or all of the
recyclable wastes is that it relieves the community of the responsibility and expense associated
with it. On the other hand, its success is dependent upon the cooperation of householders.

2.4.2.2 Separate Collection of Yard and Garden Debris

This variation calls for the separate collection of yard wastes as a part of a municipal
composting program. The term "yard and garden debris" is broad in that it includes not only
wastes generated by householders, but also landscaping wastes (e.g., lawn clippings, leaves,
herbaceous plants) generated at office complexes, in parks, on other municipal properties, etc..
The approach has gained a tremendous amount of popularity in the U.S., particularly in the
Northeast.

2-18

2.4.2.3 Separate Collection of Yard and Food Wastes

This involves the collection of combined yard debris and food preparation wastes. Each of the
two wastes, although separately stored, are later combined, either in the collection vehicle or at
the treatment site. This variation might be loosely considered as being a version of
co-composting, i.e., of yard wastes and food wastes. The practice is attracting favorable
attention in Europe and Canada.

2.4.2.4 Co-Composting Yard and Food Wastes

The addition of food wastes to yard wastes not only broadens and intensifies constraints
already on yard waste composting, it also adds constraints to counteract the undesirable
environmental and hygienic impacts due to food wastes. These impacts were named and
discussed in the section on wet garbage. Odour emission can be taken as an example. The
odours associated with the normal storage and composting of yard wastes do not constitute a
problem. On the other hand, the odour of raw garbage is objectionable to most individuals,
and the objectionable nature persists until the material has been stabilized. Measures to be
taken to comply with the constraints were also described earlier.

With respect to co-composting food wastes and yard wastes, probably the best approach would
be to store and collect the two wastes separately. This is important because the storage and
collection requirements for food wastes differ drastically from those for yard wastes. These
reflect the wide difference between the physical and molecular natures of the wastes and their
degradability, as well as between continuity of generation and volumes involved. Resorting to
separate storage and collection postpones the time when the constraints peculiar to food wastes
must be applied to the combined debris. Obviously, the task of ensuring proper isolation of the
combined mass from the environment becomes more complex and onerous when the two
wastes are finally combined for composting, e.g., stacked into windrows or introduced into the
compost reactor.

The addition of food wastes to yard wastes does npi lower the quality and utility of the
compost product. In fact, in terms of quality, the product may be structurally and chemically
enhanced, especially if the yard wastes had a sizeable concentration of woody material.

In summary, in terms of the compost process per se, the addition of food wastes to yard waste
probably would have a beneficial effect. However, this benefit is not obtained without cost.

2.4.3 Post Collection Separation

Combined storage and combined collection continued to be the approach commonly followed
until the 1980s. At that time, the interest in resource recovery resumed its current rate of
expansion.

A basic step in the preparation of the raw material involves the separation of the compostable
from the non-compostable fraction. For yard and food wastes collected separately from MSW,
this step would involve manual sorting. For MSW, the ideal in terms of achieving highest effi-
ciency for segregation would be to carry out the primary separation at the household level
(pre-collection separation).

Post-collection separation is for the most part done mechanically, although some manual sorting
may be employed. Mechanical separation is accomplished in a series of unit processes. Chief
among these unit processes are size reduction, screening, air classification, and magnetic sep-
aration. Basic principles and technologies are described in considerable detail in the literature
[3,15,16].

2-19

2.4.3.1 Size Reduction

Of the many types of size reduction equipment the two most commonly used for MSW are the
hammermill and the grinder, with the hammermill being the more common of the two. Basic
types of hammermills are the vertical-shaft and the horizontal-shaft. The operating principles
for both types are quite similar. With a vertical mill, particle size can be controlled by
changing the spacing between hammers and housing; whereas with a horizontal hammermill, it
is accomplished by means of grate bars.

The most commonly used type of grinder is the ring grinder. The ring grinder basically differs
from the vertical hammermill in that the grinder has grinding wheels rather than hammers. The
refuse is ground by the action between several free-floating grinding wheels and a series of
fixed bars protruding from the shell of the machine. Particle size is controlled by adjusting the
spacing between grinding wheels and a choke ring. No grate bars are used.

For particular applications, optimization of the performance of the size reduction process can be
directed to one or more of the following: feedrate, size distribution, wear, and power
consumption. Certain interrelationships, and particularly their bearing on cost, should be kept
in mind when optimizing the process. For example, optimization directed at particle size has a
major effect on the overall cost of the size reduction operation. The reason is that energy
consumption and equipment wear-and-tear increase in direct proportion to extent of reduction in
particle size [17,18]. Thus, specific energy consumption (net energy [kWh]/tonne size reduced)
increases sharply at characteristic particle sizes smaller than 0.75 cm (0.3 inches); whereas it is
relatively modest at particle sizes larger than 2.5 cm (1 inch) [18]. ("Characteristic particle
size" refers to the size of the screen openings through which 63.2% of the particles can be
passed.)

As with energy consumption, wear-and-tear of the hammers increases sharply with reduction in
characteristic particle size distribution. Hammer wear becomes especially high as the
characteristic particle size drops below 0.75 cm (0.3 inches).

2.4.3.2 Air Classification

Basically, separation is accomplished in an air classifier through the interaction between a
moving air stream and the material introduced within a column. Refuse components
characterized by a large drag-to-weight ratio tend to be suspended in the air stream. They
constitute the air-classified light fraction. Particles that have a small drag-to-weight ratio (e.g.,
metals, glass, fines) tend to settle. Not surprisingly, they make up the air-classified heavy
fraction.

Existing air classifier designs can be broadly classified into vertical, horizontal, and inclined.
The air stream moves vertically through the classifier column in the vertical version. Vertical
classifiers differ among themselves; some may be provided with baffles (zig-zags).

The air classifier split can be expressed as the ratio of the light fraction to the heavy fraction.
The split is influenced by several variables, namely, air-to-solids -ratio, column velocity, refuse
moisture content, particle size distribution, and column loading. Generally, the present opinion
is that overall performance improves until the column loading factor approaches 7 Mg/hr/m2
(0.7 ton/hr/ft2). Loadings higher than this do not further enhance performance. On the other
hand, separation is not significantly improved by lowering column loading to less than
5 MgThr/m2 (0.5 ton/hr/ft2) [19].

2-20

2.4.3.3 Screening

Panicles may be effectively separated into two or more size groups by the use of a screen. In
such a separation, the size group having a minimum particle size larger than that of the screen
openings stays on the screen and is known as the oversized fraction. The second size group
passes through the openings and is known as the undersize fraction.

A list of important screening parameters would include screening efficiency, residence time,
bed depth, critical frequency, screen capacity, screen loading, length-to-diameter ratio (trommel
screens), and screen performance. Efficiency relates to the ratio of undersize material actually
removed by the screen to the total amount of that material in the feed material. Therefore, it
constitutes a measure of the degree of separation of materials based on particle size. Efficiency
attained in a given situation is a function of the physical properties of the input material,
degree of agitation imparted to the material while on the screen surface, depth of the material
on screen surface (bed depth), and residence time on the screening device.

The surface area of the screen should be large enough to allow a sufficiently long residence
time (average length of time on a screening surface or inside a trommel screen), and yet permit
the depth of the bed of refuse on the screen to be sufficiently thin. Meeting this twofold re-
quirement necessitates a very large surface area when high-volume materials such as paper and
plastics are major components of the feed material.

Types of Screens

Screens may be classified into two broad groups: flat-bed screens and cylindrical screens.
Among the principal types of flat bed screens are vibrating, reciprocating, and gyrating. The
only type of cylindrical screen is the trommel. The types most commonly found in the waste
processing industry are the vibratory flat bed screen, the disc screen, and the trommel screen.
Whereas experience with flat bed screens has been less than successful, that with the trommel
screen has been quite successful in terms of effectiveness and efficiency [15].

• Flat Bed Screens

The vibrating flat bed screen is used in waste processing for separating fine particles.
The vibratory motion of the screen enhances its efficiency by: 1) increasing the
number of particles that come in contact with its surface; 2) reducing the incidence of
entrapment of small particles; and 3) prolonging residence time. A limiting factor on
efficiency is the depth of the material on the screen surface. Permissible depth varies
with length of residence time.

The reciprocating screen is a type of vibrating screen. Its action is a rocking motion,
end-to-end, in which the screen is on an incline and the housing is on springs. A
disadvantage of the reciprocating screen is the frequency of spillage. Moreover, the
significant screen wear associated with the vibration can lead to other problems.

The gyrating screen, another version of the vibrating screen, pivots at one end of its
housing. Chances for spillage from a gyrating screen are lower because the particles
never leave the screen surface.

The disc screen is a third version of the vibrating flat bed screen. It consists of a
series of discs attached to small-diameter shafts in parallel configuration. The discs
from each alternating cylinder complement each other. As the cylinders rotate, objects
of small size pass through the length of the screen.

2-21

• Cylindrical Screens

The trommel screen is a rotary cylindrical screen, the screening surface of which may
be either a wire mesh or a perforated plate. In some operations, incoming waste is
passed through a trommel before being size reduced (pre-trommeling). In others, the
trommel screen is used after the waste has been size reduced (post-trommeling). Some
operations have both pre- and post-trommeling [20].

Extensive usage has shown the trommel screen to be a particularly efficient device for
screening waste. Its efficiency comes from the tumbling to which it subjects
throughput material. Because it combines a high degree of screening efficiency with a
minimum of screening surface, rumbling is very effective for screening municipal solid
waste The general experience has been that with respect to screening municipal solid
waste, trammeling surpasses all flat bed screens.

The size of a trommel screen's openings can be arranged such as to direct particular
municipal waste components either into the oversize fraction or into the undersize
fraction. If the component size distribution of refuse is known, the effect of a given
screen mesh on the final size distribution of each component after screening can be
determined.

Four important design and screen performance parameters specifically applicable to trommels
are critical frequency, screen loading, length-to-diameter ratio, and angular velocity. Critical
frequency is that frequency of rotation at which material in the trommel is held by centrifugal
force against the screening surface through an entire revolution. With respect to screen
loading, screening efficiency remains fairly constant until an overload condition is approached.
Typical length-to-diameter ratios for raw refuse and the screened air-classified light fraction
range from 2:1 to 5:1. Angular velocity determines particle motion and associated velocity of
material along the axis of the screen. The relation varies with screen geometry and inclination.

2.4.4 Home Composting

2.4.4.1 Specific Biological Principles

The basic biology of home composting is the same as that described earlier. However, the
manifestations and corresponding responses in terms of procedure with home composting may
differ somewhat from those appropriate for other composting applications. For example, in
home composting, the heat retention capacity (self-insulation) of the composting mass has a
much greater influence on the rise of temperature level in the interior of the composting mass
than it has in larger-scale operations. The smaller the mass, the lower is the self-insulation
capacity. Thus, for temperatures to reach levels lethal to human, livestock, and plant
pathogens, the volume of the composting material must at a minimum be approximately 1 m3
(3.3 ft3) The volume would be slightly less with a less porous mass and more with a very
porous mass, especially if the mass is exposed to high winds. The lethal temperature for plant
pathogens and weed seeds is on the order of 70°C (see Figure 2-2). Lethal temperatures for
most human and animal pathogens are in the range of 50 to 65°C, with the exception of the
more resistant forms (e.g., spores, conidia, ova) which can require temperatures in the range of
70 to 80°C for inactivation. Consequently, failure to reach lethal levels could lead to a
reinfection of ornamentals and food plants if the householder were to return the compost
product to the garden.

2-22

2.4.4.2 Methods and Equipment

Because the usual site of a home composting operation is in a residential area, the generation
of objectionable odours in the composting mass must be carefully avoided. Because
objectionable odours almost invariably are generated as a result of the onset of anaerobiosis in
the pile, the best preventive as well as remedial measure is adequate aeration. Needed aeration
is most simply attained by increasing the turning frequency. An added advantage of increasing
the turning frequency is the acceleration of composting rate. For example, with a substrate
consisting mostly of herbaceous plant debris (i.e., little or no shrubbery), required retention
time to produce a fully composted product may be as brief as 12 days at a turning frequency
of one turning every other day (a total of three turnings), and as long as 30 days with turning
as once per week. If frequent turning is infeasible, then an odour problem may be alleviated
by covering the material with a thin layer of soil or of fully matured compost.
Equipment is largely a matter of the personal preference. For the compost enthusiast, it can
border on the elaborate, e.g. a chipper for brush, a grinder for herbaceous debris, and even a
prefabricated "reactor."

Unless the composting is done in a rural setting, an open pile is to be avoided and a bin
should be used. The bin may be constructed of concrete, wood, or even of hardware cloth.
Floor dimensions should be at least 1 x 1 m (3.3 x 3.3 feet). The height can be from 1 to 2 m
(3.3 to 6.6 feet). The bin should be constructed such that one side can be removed to provide
easy access to the composting mass. If hardware cloth is used, the mesh size should be 6 mm
(0.25 inches), and the wire should be of heavy gauge. Obviously, the cloth should be attached
to a sturdy frame. An advantage in the use of hardware cloth is that all surfaces of the com-
posting mass are exposed to air. Disadvantages are: 1) the same exposure becomes a
detriment in the event of a fly problem; 2) durability does not match that of concrete or wood;
and 3) there is little protection against heat loss.

A double bin (adjacent bins sharing one common wall) has certain advantages. For example,
one bin could serve as the reactor, while material for a second run could be accumulating in
the second bin. To meet local health regulations, the exposed surface of the composting
material should be covered with a fly-proof screen.

A five-tined pitchfork is an excellent tool for turning the material, because it facilitates the
desired fluffing of the material. Manipulation of a conventional manure fork is awkward.
Turning by way of a shovel would be more difficult and less effective than with a fork.

2.4.4.3 Constraints

An important constraint on home composting pertains to the substrate. For example, the use of
meat wastes as a substrate constituent in home composting is conducive to the development of
nuisance problems. Not only does the meat become malodorous, it is a strong attractant for
vectors and rodents. Although it is true that these problems disappear as the compost process
advances, an appreciable time intervenes. Many health regulatory agencies have rules against
the use of meat waste as a substrate. If it is nevertheless used, strong countermeasures should
be taken.

Another constraint regards siting the compost bin. The location on one's property should not
be where it would interfere with a neighbour's enjoyment of his property. In other words, it
should be some distance from property boundaries.

Other constraints pertain to convenience and feasibility. One such constraint comes from
spatial requirements that for the most part limit home composting to single-family residences.
Even with single-family residences, dedicating any space to composting may not be possible.
Granted that space is available, proper conduct of a home composting operation demands a
considerable dedication on the part of the homeowner, and must compete with other demands

2-23

for time. After all, whether or not the operation becomes a source of nuisances and even of
health problems is a function of the dedication had by the operator.

2.4.5 Co-Composting

Co-composting may be broadly defined as "composting a mixture consisting of two or more
types of wastes." Examples of such mixtures are manures and crop residues, manures and
MSW, industrial food processing waste and MSW, and MSW and sewage sludge. Because the
reference in the modem literature usually is to the MSW/sewage sludge mixture,
"co-composting" is used in that sense in this section, unless otherwise specified.

In common with other forms of composting discussed in the preceding sections, co-composting
is not a recent development. In fact, in almost all of the early attempts at demonstration and
full-scale application of MSW composting, the usual procedure was to add sewage sludge in
some form to the MSW. The purpose of the addition was not so much to treat the sludge, as
it was to supply needed moisture and to enrich the MSW with nitrogen and phosphorus.
Although the practice of co-composting in the U.S. gradually waned during the 1970s, it
continued unabated in western Europe. In fact, the loss of interest in the U.S. was not
confined to co-composting; it also applied to MSW composting. It was not until after the
phenomenal surge of sewage sludge composting in the early 1980s, that interest in MSW
composting began to revive. The revival was triggered mainly by the possibility of MSW
serving as a bulking agent in sewage sludge composting. Not to be overlooked, however, is
another recent development that has intensified the revival, an increasing consideration of
composting of MSW as an alternative to incineration.

The generic biology and parameters of co-composting are identical with those for composting
in general. Adaptations in technology are those made in response to the sludge fraction of the
mixture. For the most pan the adaptations relate to developing procedures for thoroughly
mixing the sludge and MSW without promoting clumping and other phenomena that lead to
significant loss of porosity. Equipment for accomplishing such mixing is appearing on the
market.

The need for adaptations in technology arises from the shortcomings of MSW as a bulking
agent. These shortcomings are traceable to the high paper content of typical MSW. As is
common knowledge, the "structural strength" of paper drops with rise in moisture content.
Consequently, the tendency of a mixture of sludge and paper is to compact. (The significance
of structural strength with regard to moisture content and aeration was discussed earlier.)
Moreover, the morphology of shredded paper particulates is not conducive to pore formation,
i.e., interstices are flattened in shape and their volumes are small. Furthermore, paper fibers
have a tendency to mat, and this tendency intensifies with increase in moisture content. A
disadvantage as a bulking agent, but a distinct advantage as a microbial substrate, is the
susceptibility of the cellulose fraction of paper to microbial attack and subsequent assimilation
of the carbon thus released. However, the loss of bulking agent is more than counterbalanced
by the destruction of a sizeable portion of the MSW output.

One of the more serious problems confronting co-composting of sewage sludge and MSW is
the serious constraints made on the use and also on the disposal of the co-compost product.
Problems and constraints that apply to sewage sludge compost and to MSW compost also apply
to the co-compost product. Underlying these constraints are the heavy metal and toxic or
otherwise hazardous organics contributed to the product by the sewage sludge fraction of the
mixture. In Europe, the contribution is great enough to sharply restrict usage of the
co-compost product. Concentrations of toxic substance in sewage sludge and MSW could be
considerably reduced through the imposition of strict standards on effluents discharged by
industry and communities into the community waste streams. With respect to MSW, careful
control of household hazardous wastes would be a distinct advance.

2-24

In 1980, the Ontario Ministry of Agriculture and Food (OMAF) and the Ontario Ministry of
the Environment (MOE) agreed to conduct research on the utilization of composted materials
on agricultural land [21].

A five year study was conducted to investigate the effects of composted sewage sludge from
Windsor and composted paper waste from Toronto on the growth and yield of com grown in
two soil types. The composts were applied only once at rates of 55, 111, 165 and 220 tonnes
per hectare. The organic matter level in the clay loam soil increased with increasing amounts
of compost applied. Organic matter levels increased on the sandy loam soil when the Toronto
compost was applied. Levels increased using the Windsor compost only at the 220 t/ha
loading.

The soil phosphorous (?) levels increased with increasing rates of the Windsor compost on
both soil types. The Toronto compost increased P levels only in the clay loam soil. The
potassium and magnesium levels remained the same in both soils.

Com growth and yield was unaffected with one exception. The com showed marked
phytotoxicity and lower yields in the year that the uncured composted paper waste was applied
to the clay loam soil.

The compost had no effect on the heavy metal levels of the com leaf and grain. Levels of
copper and nickel in the soil were slightly increased by the compost additions.

2.5 References

[1] Golueke, C.G., Composting. Rodale Press, Inc., 110 pp., 1972.

[2] Golueke, C.G., Biological Reclamation of Solid Wastes. Rodale Press, Inc., 249 pp.,
1977.

[3] Diaz, L.F., G.M. Savage, and C.G. Golueke, Resource Recovery frpm Municipal Splid
Wastes. Vol. II. Final Processing. CRC Press, Boca Raton, Florida, 178 pp.,
1982.

[4] Golueke, C.G. and L.F. Diaz, "Starters -- Inoculums and Enzymes," BioCycle
30_(4):553-557 (April 1989).

[5] Golueke, C.G., "A Critical Evaluation of Inoculums", Applied Microbiology. 2:45-53
(1954).

[6] Shulze, K.F., "Rate of Oxygen Consumption and Respiratory Quotients During the
Aerobic Decomposition of Synthetic Garbage", Compost Science. 1:36 (Summer
1960).

[7] Lossin, R.D., "Compost Studies: Pan HI, Measurement of Chemical Oxygen Demand
of Compost", Compost Science. 12 (March/April 1971).

[8] Glenn, J., "The Transition of Home Storage Containers," BioCvcle. 3_0(6):45-51 (June
1989).

[9] "Collection Vehicles Hit the Road," BioCvcle. 2fl(6):37-39 (June 1989).

[10] Oosthoek, J. and J.P.N. Smit, "Future of Composting in the Netherlands, BioCycle.
28(6):37-39 (July 1987).

2-25

[11] Lustenhouwer, H.W.A., F.A. Reijenga, and H.C. van Weenen, "Source Separation and
Collection of Household Compostables," BioCvcle. 28(6):33-36 (July 1987).

[12] Diaz, L.F., G.M. Savage, and C.G. Golueke, Resource Recovery from Municipal Solid
Wastes. Vol. I. Primary Processing. CRC Press, Boca Raton, Florida, 166 pp.,
1982.

[13] Savage, G.M., J.C. Glaub, and L.F. Diaz, Unit Operations Models for Solid Waste
Processing. Pollution Technology Review No. 133, Noves Publications, 214 pp.,
1986.

[14] Processing Equipment for Resource Recovery Systems. Vol. HI -- Field Test Evaluation
of Shredders. Final Report prepared by Cal Recovery Systems, Inc. for U.S.
EPA, Report No. 600/2-80-001, 1980.

[15] Savage, G.M., J.C. Glaub, D.J. Lafrenz, and L.F. Diaz, Engineering Design Manual for
Solid Waste Size Reduction Equipment. U.S. EPA Report No.
EPA-600/SB-82-C, 1982.

[16] Savage, G.M., L.F. Diaz, and G.J. Trezek, "Performance Characteristics of Air
Classifiers in Resource Recovery Processing", Proceedings of Ninth National
ASME Waste Processing Conference. May 1980.

[17] Land Treatment of Hazardous Wastes. Ed. J.F. Parr, P.B. Marsh, J.M. Kla, Noyes Data
Corporation, 422 pp., 1983.

[18] Comprehensive Studies of Solid Waste Management. SERL Report No. 69-1, Sanitary
Engineering Research Laboratory, University of California, Berkeley, 245 pp.,
1969.

[19] Comprehensive Studies of Solid Waste Management. SERL Report No. 72-3. Sanitary
Engineering Research Laboratory, University of California, Berkeley, 166 pp.,
1972.

[20] Decomposition of Toxic and Nontoxic Organic Compounds in Soils. Ed. Mr. M.R.
Overcash, Ann Arbor Science Publishers, Inc/Butterworth Group, 455 pp ,
1981.

[21] Dalzell, H.W., A.J. Briddlestone, K.R. Gray and K. Thurairajan, Soil Management:
Compost Production and Use in Tropical and Subtropical Environments. FAO
Soils Bulletin 56, Rome, 1987.

[22] Baldwin, C.S., C. Nanni and M.A. Nuttall, Compost Utilization and Com Production in
Southwestern Ontario. Ministry of Agriculture and Food Ontario Report, 1989.

3.0 DOCUMENTATION OF EXISTING COMPOST TECHNOLOGIES

3.1 Introduction

A generic description of the composting process, types of processing technologies, operating
and control parameters, and applications was the focus of Section 2. In this section, the
emphasis turns from a general textbook-type description of the process to a presentation of
information on existing composting practices. Descriptions of various composting systems are
presented to demonstrate the technologies being practised. The remainder of the section is
devoted to a discussion of the economic and marketing aspects of composting.

It is important to mention at this time that much of the information presented in the following
sections was extracted from promotional literature developed by the system vendors and,
therefore, may be somewhat biased. All of the costs in this section are in Canadian dollars.

3.2 Internationally Available Technologies

As discussed in Section 2, compost technologies can be broadly divided into four groups:
turned windrow, static pile, in-vessel, and hybrid (which is a combination of technologies). In
the sections that follow, descriptions are provided for compost systems that fall into each of
these categories. Appendix B provides a partial list of vendors and facilities. The systems
described are representative of those currently on the market. The following systems are
discussed:

Turned windrow

Static pile

In-vessel

Hybrid

Agripost, Inc.

Ecological Technologies (ECOTECH), Inc.
Environmental Recovery Systems, Inc.
Compost Management Associates Ltd.

Buhler-Miag, Inc.

Daneco

WPF Corporation

American Bio Tech, Inc.

American Recovery Corporation

Ashbrook-Simon-Hartley

Bedminster Bioconversion Corp.: The Eweson Process

Compost Systems Company (Paygro and Dynatherm)

Ebara Environmental Corp.

Fairfield Service Company

International Process Systems

OTVD Group Energies

PURAC Engineering, Inc.

Recomp

Royer Industries

Taulman Composting Systems

Califomia-Co-Composting Systems
Harbert/Triga International, Inc.
Waste Processing Corporation (Dano)

3-2

3.2.1 Turned Windrow

3.2.1.1 Agripost

The Agripost system was originally developed and implemented over 30 years ago. The two
projects in the 1950s included one in McKeesport, Pennsylvania and the other on the island of
Jamaica. Today the system is being marketed by Agripost Inc. in Pompano Beach, Florida.
The company is in the process of building an 725 tonne/day MSW processing facility to pro-
cess pan of the waste generated in Dade County, Florida. Final testing of the plant is expected
to be completed by November of 1989. Initially, the facility is expected to produce
representative end-products for testing and for marketing.

Feedstocks

The Agripost process treats mixed municipal solid waste. Agripost's description of its system
indicates that it is capable of treating 100% of the incoming waste stream [1-4].

Description of Operation

All of the processing and composting is conducted inside of buildings. According to the
vendor, the system works as follows: waste is discharged on the tipping floor, non-processible
materials are removed, and the remainder of the waste is conveyed into two stages of size
reduction. The ground waste is inoculated with a bacterial enzyme to expedite the
decomposition process. The inoculated material is transported to an adjacent building and
formed into windrows for composting. The piles are turned periodically depending upon
temperature and moisture content. The active bacteria in the pile is capable of degrading all
organic materials. Heat produced by this action creates an oxidizing effect on metals, plastics,
and other hard "inorganic" constituents. After four weeks of active composting, the material is
conveyed to a tertiary stage of size reduction. After shredding, the compost is screened. The
oversize items are returned to the composting process. The undersize is ready for marketing.
The company claims that the inorganics are broken down into an oxide form and become part
of the fertilizer [1-4].

Agripost offers to either own and operate a facility, or to sell the plant to the customer. The
company will not, however, turn over the actual operation. Agripost requires that provisions be
made to operate the plants, maintain ownership of the product, and maintain the responsibility
for distributing the compost.

3.2.1.2 Ecological Technologies

Ecological Technologies, Inc, (Ecotech), was founded approximately two years ago. Ecotech is
one of the few vendors that has an operating MSW compost facility in the United States. The
plant is located in Sumter County, Florida. The facility began operating in the summer of
1988. Ecotech has the exclusive license to market the process developed by U.S. Waste
Recovery Systems. The technology is known as the "BDX Process."

Feedstocks

The plant operating in Sumter County currently processes about 100 tons of mixed municipal
solid waste per day.

3-3

Description of Operation

The processing system can be described as follows: MSW is discharged on the tipping floor.
Oversize and hazardous materials are removed from the feedstock. The remainder of the
refuse is conveyed into a flail mill. The mill tears open bags and other containers. The
milled refuse is then conveyed past a magnetic belt for removal of ferrous metals. After
magnetic separation, the material is handsorted to remove aluminum, glass, paper, plastic, and
cardboard. After hand sorting, the material is conveyed into a shredder. The shredder size
reduces the material to particles 2.5 to 5 cm in size. It is reported that the hand sorting
operation and the magnetic separation recover a minimum of 25% of the recyclable materials.

The shredded material is loaded onto small dump trucks and transported to the composting
pad. The composition of the composting feedstock is between 50% and 75% paper and
vegetative waste, and about 25% plastic, metals, wood, etc. The refuse feed is formed into
windrows and aerated mechanically. The compost turner is equipped with nozzles for
maintaining the proper moisture content and adding a proprietary formula of enzymes and
bacteria. The inoculum is added for the purpose of accelerating waste decomposition.

After the material is composted, it is air classified and screened. The screen is an auger type
with graduated 2 to 2.5 cm openings. Ecotech has been considering the use of a trommel
screen for final processing. Residuals from the process are estimated at about 5% to 10% of
the incoming waste stream [5-7].

Markets

The County has a number of interested potential end-users such as local citrus growers and
nurseries. The County is, however, waiting to start actual marketing activities until tests on
the end-product are completed. In other projects, Ecotech expects to explore the potential of
using the compost for horticultural and agricultural uses. Other markets under consideration
include international export markets and reclamation of marginal lands [5-7].

Economics

It has been estimated that the capital cost of the facility in Sumter County, Florida was on the
order of $4.1 million. Ecotech contributed $1.8 million and the County the remainder. It has
been reported that the tipping fee at the facility is U.S. $20.75/tonne [7].

3.2.1.3 Environmental Recovery Systems

Environmental Recovery Systems (ERS) was established in 1986. ERS is planning an MSW
facility in New Milford, Connecticut [8]. The system for the New Milford facility was
designed by ERS and evaluated by Morrison-Knudsen Engineers, Inc. The project team for
the facility includes ERS, MK- Environmental Services (for design and construction
management), and CH2M-HU1 (for environmental and permitting support).

Feedstocks

The facility planned for New Milford is designed to recover over 90% of the municipal solid
waste stream [8].

3-4

Description of Operation

The processing facility functions as follows. Municipal solid waste is discharged onto the
tipping floor where sorters open bags and remove unacceptable items. Non-processible
materials are sent to the landfill for disposal. The waste is pushed into a conveyor belt and
transported to a trommel screen. The trommel separates the waste into two fractions. The fine
waste fraction (primarily organic maner such as leaves, grass, and food, as well as some din) is
conveyed over a magnetic head pulley to remove ferrous metals. The remainder is transported
to the composting area. The oversize fraction from the trommel is conveyed to a sorting room.
In the sorting room workers remove recyclable items. The rest of the oversize material is
shredded and screened.

The smaller panicles are taken to the composting area. The large paper fraction is removed
and baled. The feedstock to the composting process is placed in windrows, which are
mechanically fluffed and aerated. After a period of 28 days, the compost is sampled and tested
in a laboratory. Once specifications are met, based on local regulations, the compost is placed
in curing/storage piles.

The process is designed to produce compost and to recover corrugated cardboard, paper
products, ferrous metals, plastics, glass, aluminum, and other non-ferrous metals. ERS's
informational proposal [8] indicates that the process requires no incineration and no landfill.
The average size of an ERS system would be 635 tonnes/day [8-9].

3.2.1.4 Compost Management Associates Ltd.

Compost Management Associates Ltd. of Toronto and Organic Recycling Inc. of New York,
draw on more than 12 years of direct experience in the hands-on management of composting
sites. Compost Management plans and sets up the composting program, provides ongoing
training for site staff and supervises all critical operations. The municipality provides the land,
equipment and equipment operators.

Feedstocks

Compost Management have experience in composting agricultural waste and leaves, and have
integrated other organic materials such as grass clippings, mixed yard wastes, chipped brush
and residential food waste.

Description of Operation

Compost Management ensures that the municipality retains complete control of the composting
operation while providing experience and technical expertise. Site design and management are
flexible to accommodate local conditions, climate, management objectives and seasonal
equipment availability.

3.2.2 Static Pile

3.2.2.1 Buhler-Miag

Buhler-Miag is a subsidiary of Buhler Brothers Ltd. of Uzwil, Switzerland. Buhler-Miag
primarily is an equipment manufacturer having a Canadian office in Toronto, Ontario. The
company has designed and provided equipment for about 100 processing plants throughout the
world. The plants range in capacity from approximately 36 to 2,700 tonnes of waste per day.
Until recently, Buhler's resource recovery system was marketed in the United States by Reuter,
Inc. of Minnesota. In November 1988, its agreement with Reuter ended. Shortly thereafter,
Buhler entered into an agreement with Wheelabrator Technologies, Inc. of Danvers,

3-5

Massachusetts, in which Wheelabrator is made the distributor of Buhler-Miag's front -end solid
waste processing, recycling, and composting systems in the United States.

Representatives from Wheelabrator indicate that the systems will either be: 1) integrated into
its new waste-to-energy projects; 2) installed in some existing facilities; or 3) sold separately
for centralized processing facilities. Initially, the composting component of the Buhler system
will be used by Wheelabrator as part of its integrated "Recycle First" program

Feedstocks

Capacities for the Buhler-Miag system range from about 45 to 635 tonnes/day of municipal
solid waste. Initially, the composting components of the Buhler system will be used by
Wheelabrator for leaves and yard waste.

Description of Operation

The processing line includes handsorting, magnetic separation, air classification, size reduction,
and screening. The material is composted in aerated windrows. Additional aeration is
accomplished by means of a windrow turning machine. After composting, the material is
conveyed to a processing area where it is run through additional size reduction and fine
screening. The screening process is designed to remove plastic, paper and woodchips. The
refined compost then goes to a ballistic separator and a magnetic belt for the removal of glass
particles, stones, and ferrous metals. The finished compost can be ground once more
depending upon the specifications for the particular end uses [10-12].

To date, there is no Buhler-Miag MSW composting system operating in North America.

3.2.2.2 Daneco

Daneco is an Italian corporation which has ten commercial-scale MSW composting projects
overseas. Six facilities currently are under operation and three are at various stages of
construction. The capacities of these facilities range from about 54 to 600 tonnes of MSW per
day. In the U.S. Daneco has been selected to implement a 154 tonnes/day MSW composting
plant in Southold, New York, pre-qualified for a 180 tonnes/day composting facility in
Hennepin County, Minnesota, and is one of two finalists to build a 435 tonnes/day material
recovery and composting plant in San Diego, California [13].

Feedstocks

The Daneco system is designed to process mixed municipal solid waste. Sewage sludge can be
added to the MSW feedstock prior to composting. The Daneco system can be used for
composting facilities in the range of 45 to over 900 tonnes/day.

Description of Operation

A typical design for a Daneco facility is as follows. Waste delivered by collection vehicles is
discharged on the floor of a receiving area. Non-processible wastes are identified and removed.
Processible waste is conveyed into a shredder. After size reduction, the material is conveyed
past a magnetic belt for the recovery of ferrous metals and into a trommel screen. The
trommel separates the stream into two fractions. The oversize fraction is taken to the residue
storage area. The undersize is taken to a secondary trommel screen for additional processing.
The secondary trommel recovers an oversize fraction that is relatively free of high density
materials and an undersize fraction that contains both organic matter and inerts. The undersize
is transported to a wet system for removal of the inert matter. After separation of the inert
matter, the organic fraction is mixed with the oversize fraction. The entire mixture is
transported to the composting area.

3-6

At the composting area, the feedstock is formed into windrows. The windrows are aerated by
means of air distribution channels located in the floor. After the composting process is
completed, the material is cured. Prior to marketing, the finished compost is processed through
a lump shredder and a screen for refining. The overall system can be modified to also produce
a refuse-derived fuel, either fluff or densified. The inert matter recovered from the wet
separator can be, after magnetically removing the ferrous metals, used as an aggregate for
construction activities [5].

Daneco has a North American subsidiary, Daneco Inc., in New York City.

3.2.2.3 WPF

The company offers a system that is totally under cover. The company is in the process of
building two processing facilities, one with a capacity of 180 tonnes/day and the other,
680 tonnes/day. The facilities are scheduled to begin operation at the beginning of 1990 [14].

Feedstocks

The two facilities being built by WPF will process mixed municipal solid waste. After
recyclable materials are recovered, sewage sludge can be added to produce a co-compost
product. The capacity of the system ranges from 45 to 1,100 tonnes per day [15].

Description of Operation

According to information provided by WPF, the system consists of a series of modules for the
recovery of recyclable materials and compost. In the process, the waste is deposited in the
tipping area. Oversize items, tires, and other materials are removed on the tipping floor.
Non-processible materials are also removed and taken to a landfill. The compostable material
is processed through two stages of size reduction. A magnetic belt removes the ferrous metals.
Finally, the shredded material goes through a flail/homogenizer.

The MSW feed can be mixed with sludge and then put into windrows. The windrows are
aerated by means of vents placed on the floor. In addition to forced aeration, the windrows are
turned every three days by means of a windrow turning machine.

The composting system can recover up to 95% of the incoming waste stream. The active
composting process is claimed to require 17 days. After composting, the material is processed
through a flail mill for additional size reduction and then through a 0.64 cm trommel screen.
Other unit processes such as air classification can be added as required. The compost is then
allowed to mature for a period of 45 days in an aerated, covered area [14-15].

3.2.3 In-Vessel

3.2.3.1 American Bio Tech

Feedstocks

Materials treated by this technology include dewatered sludge solids and an amendment
(sawdust). Proportional amounts of dewatered sludge, amendment, and recycled compost are
mixed to the targeted content of 35% dry solids [16].

3-7

Description of Operation

A conveyor moves the feedstock mixture to the reactor train. This mixture is deposited on top
of the bioreactor, but only after the following operations are completed: 1) one layer of
finished compost is removed from the bottom of the curing cell and either stored for shipping
and sale, or recycled as needed; and 2) a layer of mixture is removed from the bottom of the
bioreactor and is transferred to the top of the cure reactors, making room for a fresh mixture of
dewatered sludge and amendment on top of the bioreactor [16].

The movement of material through the system is accomplished by a large take-out screw which
traverses the entire length of the bottom of the bio and cure reactors. Approximately 61 cm. of
product is removed each pass. Loading and unloading functions can be carried out on a
continuous basis without process interruption. According to the vendor, this reduces the
occurrence of anaerobic, odorous conditions [16].

Aeration is accomplished through the use of an air manifold coupled to vertical lances
positioned throughout the compost mass. The manifold system is positioned near the top of
the containment structure. Every other manifold is designed to alternately deliver air to or
evacuate air through the lances, thus creating a shortened horizontal airflow path between the
rows of lances.

The purpose of the reduced air path is a lower pressure drop and subsequently, lower energy
consumption. The low pressure allows the use of industrial fans instead of high pressure
positive displacement blowers. In addition, according to the vendor, the shortened air path
decreases the possibility of the air short-circuiting and causing anaerobic pockets within the
composting mass.

Each lance utilizes an internal air profile insert and partitions to assure an even, controllable
airflow profile over its entire length. The design is intended to compensate for increased
density in the lower section of the reactor. The air profile insert is field changeable to allow
modifications to the airflow profile [16].

The process is controlled by varying airflow rates which adjust temperature to attain the
maximum biological rates, stabilization, and drying within the bioreactors and cure reactors.
The control system provides trend information to facility operators, thereby allowing control of
airflow rates to be based on trend rather than point changes in the measurements. Reactor
temperatures are recorded for this purpose. Airflow rates are shown on an indicator meter next
to each blower and in the instrument control room where they are recorded. Temperature
probes are installed in each reactor for continuous monitoring of reactor temperature profiles.
Automatic operation of on/off loading sequences are activated by operator control buttons [16].

Quality Control Parameters

The ABT process provides 14-day bioreaction and curing stages, both taking place in fully
enclosed, odour controlled structures. The reactors are totally enclosed and designed to
maintain' a negative pressure. The negative pressure serves two purposes: to reduce the
amount of moisture and odours within the building enclosure and to ensure all odours arc con-
tained. All exhaust air from the reactor building considered to be odorous is treated by a
multi-stage odour control system consisting of: 1) heat exchanger for condensing particulates;
2) wet scrubber for condensation and odour particles; 3) two-stage chemical reactor tower, and
4) adequate retention time for chemical reaction [16].

Problems with high noise levels from fans arc kept to minimal levels by the following two
design measures: 1) the process air fans are housed in a separate mid-mezzanine level within
the reactor building; and 2) they are low horsepower centrifugal fans [16].

3-8

Promotional literature from American Bio Tech states that the finished compost is pathogen
free upon discharge from the cure reactors, free from objectionable odour, and has a pH
ranging between 6 and 8 [16].

Marketing

Markets considered most likely for the final compost product are the ornamental and
horticultural industries, as well as various public agencies responsible for restoration of public
lands [16].

3.2.3.2 American Recovery Corporation

American Recovery Corporation (ARC) is a joint venture between Potomac Capital Investment
Corp. (a wholly-owned subsidiary of Potomac Electric Company of Washington, DC) and
Sorain Cecchini Recovery, Inc. Sorain Cecchini is an American affiliate of Sorain Cecchini of
Rome, Italy [17]. The technology developed by Sorain has been available for 25 years. The
company has a number of operating plants overseas that include a MSW composting
component. The front-end processing line is also being marketed as part of a combustion
process (mass bum or RDF).

Description of Operation

In the processing line, trommel screens are used to segregate the organic fraction. The
remainder of the waste stream then goes through a number of unit processes including size
reduction and air classification. According to ARC, this results in the production of a number
of recyclable feedstocks. The system includes equipment designed to remove polyethylene film
from the waste stream. The film serves as feedstock for the production of waste bags. Hand
sorting is used primarily for cardboard and aluminum [18].

ARC is in the process of building a pilot in-vessel composting facility in Santa Barbara,
California. The system could be used by municipalities to conduct composting trials of their
yard waste and organic residues [19].

ARC will initially concentrate on using the composting component of its system for source
separated leaves and yard debris. It is expected that the amount of residuals after composting
and recycling will be on the order of 25% by volume.

3.2.3.3 Ashbrook-Simon-Hartley

This Houston-based company sells a tunnel reactor in-vessel composting system. It has
operational sludge composting facilities in Newburg, Oregon and in Hamilton, Ohio, as well as
a mobile sludge unit in Oceanside, California. The company also has a facility under
construction in Hickory, North Carolina and one in the design stage in Camden County, New
Jersey. The company has two plants operating in Germany, both privately owned and with a
processing capacity of 365 to 455 tonnes/day [20].

Description of Operation

The pre-processing line is designed to pull out paper, glass, metals, and plastics, but because
the system does not have a screw or auger inside, it can handle inorganics. The material
coming out of the reactor would be ground and screened. The company strongly encourages
integrating recycling programs with the composting operation, and also emphasizes that the
actual pre- and post-processing line should always be tailored to a community's needs [5].

The length of the composting process is 10 days in the vessel and several weeks of curing.
The residuals after composting is about 20% [5].

3-9

3.2.3.4 Bedminster Bioconversion Corp.: The Eweson Process
Feedstocks

The Eweson digester processes a mixture of solid waste and sewage sludge in approximately
the ratio that the population of a typical municipality produces them The digester can process
sewage sludge either in the raw or digested form, and at solids contents ranging from 4% to
air-dried. In other words, the process can take sewage sludge at any stage in its treatment in a
wastewater treatment plant [21].

Description of Operation

The company strongly encourages community recycling programs, but is capable of designing a
system to son out recyclables prior to composting [5]. Bedminster s processing fane spnar to
composting includes hand-sorting and magnetic separation. Marketable inorganic materials
such as ferrous metals, aluminum, PET and HDPE plastics are removed [21].

The Eweson Digester is divided into three compartments and rotated by means of an
electrically driven bullgear. Air is circulated through it at controlled rates in a flow direction
counter to the material flow.

Only large metal objects are removed before the refuse is dumped into the receiving hopper.
The remaining waste is fed into the first compartment by means of a hydraulic ram. Sewage
sludge is added to bring the moisture content up to about 50% and to bring the
carbon-to-nitrogen ratio to 35:1 or less.

Internal projections in the digestor break up the rubbish bags and other large fbjef du^g the
tumbling action, exposing more surface area to the bacterial action. The aim is to attain as
high a temperature as possible in the first compartment to soften the incoming material. This
™ achieved by: 1) the bacterial action; and 2) the circulating air, high in moisture and carbon
dioxide, that has already been heated in passing through the second and third stages. The
carbonic acid from the carbon dioxide dissolves non-water-soluble microbial nutrients in the
waste. Temperatures up to 71° are reached in Compartment 1.

After one to two days, 85% of the material in the first compartment is transferred to
Compartment 2. The remaining 15% serves as an inoculum for the next batch. In
Compartment 2, the waste continues to decompose at a high rate, with thermophilic bacterial
action This compartment is also initially charged with a special inoculum. After one to two
days, the waste is transferred to Compartment 3, again leaving about 15% behind to serve as
inoculum

In Compartment 3, the bacterial activity is less intense and the incoming circulating air has the
lowest moisture and carbon dioxide content. A certain amount of drying occurs. The retention
time in Compartment 3 is also one to two days [21].

The size of the system ranges from 45 to 270 tonnes/day. Bedminster's target-markets for the
system are municipal entities with populations of 10,000 to 100,000 [5].

In order to significantly reduce pathogens, the solid waste is maintained at irrinimum operating
conditions of 40°C for five days. For four hours during this period, the temperature exceeds
55°C [20] To further reduce pathogens, the solid waste is maintained at operating conditions
above 55°C within the vessel and in a dynamic aerated phase for a period of time long enough
to comply with PFRP (Processes to Further Reduce Pathogens) requirements [21].

3-10

According to the vendor, the Bedminster's Eweson system has the ability to dilute
concentrations of heavy metals which exist in sewage sludge. When liquid sludge is used (in
contrast to dewatered sewage sludge), the solids in the sewage sludge are one-tenth or less the
volume of the total volume of sewage sludge and solid waste processed. As a result of micro-
bial activity in the digester, the solids in the sewage sludge, including the heavy metals
contained in the mixture, are dispersed. This dispersion reduces the concentration of metals to
approximately one-tenth of their input amounts [21].

In a municipal situation where toxic metals in sewage sludge are a potential problem,
dewatered sewage sludge would not be used in the Eweson system. Rather, sewage sludge
would be delivered to the Bedminster plant at a solids content between 5% and 10% [21].

Markets

Compost markets that the company is developing include horticulture, agriculture, silviculture,
sod farms, and home garden use [5].

Environmental Impact

Potential negative environmental impacts are discussed by the vendor as follows:

Air: The only air-bom effluents are carbon dioxide and water vapour.

Water: None.

Noise: Low noise levels from electrical motors.

Odour: No odours other than those emanating from the solid waste while it resides on

the tipping floor. Sewage sludge is kept in closed tanks.

Visual/

Aesthetic: Tipping and curing areas under roof; overall appearance of the plant similar to
that of any modem manufacturing facility.

Other: "Tailings" from the plant would be free of putrescible material and therefore

incapable of creating leachate in a landfill.

3.2.3.5 Compost Systems Company

The Compost Systems Company (CSC) operates three different types of in-vessel composting
systems. The company refers to them as Enclosed Dynamic Composting, or EDC, systems:

1. Paygro, a horizontal bin-type system

2. Dynatherm, a horizontal plug-flow reactor

3. Fairfield, a circular digester (sold by CSC for sludge only, with Fairfield marketing the
system for MSW composting)

The following pages present information regarding Paygro and Dynatherm. Information
regarding the Fairfield system is described under the heading of the Fairfield Service Company.

3-11

Paygro

Dewatered sludge, finished compost, and small amounts of fresh bulking agent (e.g. bark,
sawdust, tree trimmings, wood chips, etc.) are mixed in appropriate quantities to achieve a feed
mixture of at least 40% dry solids. An automatic mixing system discharges the mixture onto
the central conveyor for loading of the reactors [22].

Material moves via conveyors to either of two parallel reactors. The reactors are 6.1 m wide
and can range in length from 61 to 305 m. Operating depth is normally 2.9 m, but can be
increased up to 3.8 m for extremely large installations, or when land area is limited.

Composting material is normally retained in the reactor for a period of 14 days (longer for
extremely cold climates), during which time it is remixed and repositioned at least two times.
Remixing of the reactor contents assures that all material is exposed to sufficiently high
temperatures to destroy pathogens; this remixing also improves porosity of the composting mix.
Air is supplied to the reactors by a series of fans positioned along the reactor walls. The fans
are designed to either force air upwards or downwards through the reactor contents. An
automatic control system regulates both the quantity and direction of air from temperature
sensing devices located in the reactors.

Material is removed from the reactor and either relocated in the tanks or discharged as finished
compost (55% to 70% dry solids) to storage prior to sale or recycling as the primary bulking
agent [23].

In accordance with the U.S. EPA requirements for pathogen control, the compost mass meets
or exceeds a temperature of 55°C for a minimum of three days. The control system can
provide precise control of the air throughout the reactor contents to guarantee that the
requirements are met. Mixing and turning the contents of the reactor further ensures that all
finished compost has been exposed to proper temperatures. Laboratory analyses and
temperature profiles have demonstrated the system's capability to meet EPA's requirements [24].

Dynatherm

Dewatered sludge (generally 15% to 35% dry solids) is mixed with small amounts of fresh
amendment (e.g. bark, sawdust, wood chips, tree trimmings, etc.) and appropriate amounts of
recycled compost to achieve a feed mixture of at least 40% dry solids. This mixture is then
conveyed to the Dynatherm reactor where it is retained and aerated for a period of 14 days or
more [24]. The reactors are rectangular in shape and can be manufactured from steel or
concrete depending upon size and location.

For a single module system, the material is remixed during the recycling step. For a dual or
multiple module system, an intermediate mixer is provided to ensure optimum porosity of the
material entering the next module. Upon completion of the aeration cycle, the compost is
discharged from the final reactor and either recycled as a principal component of the mix or
discharged as finished compost.

Air is supplied to each module by two low pressure fans, each providing air to a distinct zone
within the module. An automatic control system regulates the amount of air to each zone
through temperature feedback from the composting mass. Off-gas from the system is
discharged through fans in the roof of each module. The off-gas can be vented, as required, to
an odour control system designed for the specific facility.

Steel reactor modules can be factory assembled and shipped on a standard low-bed truck.
Depending on the size of the installation, from one to ten modules can be combined either
end-to-end or by stacking one on top of another. Separate control and discharge modules are
connected to the reactor modules to complete the installation.

3-12

The heart of the Dynatherm system is a moving floor, which provides non-compacting and
reliable transfer of the composting mass from the feed to the discharge end of each module.
The floor consists of a number of parallel sliding members, or planks, separated only by
narrow aeration headers. Every third plank is attached to a single hydraulic cylinder and
moves independently from the other planks. Each third of the floor planks is retracted in
sequence with the overbearing load being held in position by the greater friction of the
stationary planks. After all the planks have been retracted, they move forward simultaneously
in the direction of discharge, carrying the overbearing load with them. The sequence is then
reinitiated to move the load in a step-wise fashion toward the discharge end [24].

3.2.3.6 Ebara Environmental Corp.

Ebara Environmental Corp., a Japanese company, has three operating MSW composting plants,
two in Japan and one in New Zealand, as well as other projects in various stages of
development [5].

Feedstocks

The composting feedstock consists of about 80% of the incoming waste stream, consists
primarily of garbage, paper, wood and earthware. Ebara requires its clients to also have in
place a hazardous waste collection program, and will not accept bulky refuse, e.g., carpet,
bicycles, and such materials as gas cylinders and fluorescent lights at the composting facility.
Sludge can be used as a moisture adjustment for the compostable materials of the MSW stream
[51.

Description of Operation

Ebara has developed compost processing equipment called a Selective Pulverizing Classifier
(SPC). The SPC consists of a rotary screen drum and scrapers that turn in response to the
rotary drum. MSW is pulverized and classified by utilizing a difference in strength or fragility
of material in the MSW. This machine has four steps of pretreatment: separation, pulverizing,
screening, and moisture adjustment. A magnetic separator is used with the SPC on the front
end of the system prior to composting.

Ebara's composting phase uses the Round-Trip Paddling Fermentor, a horizontal composting bin
with a special paddle type rotator. The literature says the bin provides stirring, mixing, transfer
and aeration of the composting mass. The company's post-processing equipment is known as
its refining system. When needed, an Electro-Static Separator Compost Refiner is used. This
is a sorting machine that utilizes the difference in electric conductivity to remove fine glass,
plastics, etc. from the compost. When used together, says Ebara, the compost has a foreign
matter content of less than 1% [5].

The level of residuals after composting that need to be landfilled is about 20%. The length of
the composting process is 10 days in the vessel and 20 days in curing piles. The minimum
size of the system is one ton/day; the maximum capacity is 900 tonnes/day.

3.2.3.7 Fairfield Service Company

Feedstocks

The Fairfield system is designed to handle a mix of municipal solid waste, commercial solid
waste, and dewatered sewage sludge (dewatered to approximately 20% dry solids) [25]. The
company's technology is currently in operation at die Delaware Reclamation Plant in New
Castle, Delaware. The company does not own projects it builds, although it will operate diem,
as is the case in Delaware [5].

3-13

Because source separation is considered more effective than mechanical separation, Fairfield
strongly encourages communities to implement recycling programs. Communities are also
required to implement a hazardous waste collection program [5].

Operating Description

A conveyor carries waste materials to a picking area, where non-processible materials are
removed manually. A hammermill shreds the remaining material into a coarse gnnd. The
classifier removes metal and glass for salvage. Combustible material such as wood, plastics
and rags are used as auxiliary fuel for product dryer. A pulper provides final gnnd and adds
moisture to the organics (including paper) before digestion.

The homogenized mixture is conveyed (through an enclosed chute) into enclosed composting
digestors The Fairfield digestor is a circular vessel convened with a dome. Aerator augers
are suspended from a bridge that travels around the top of the digester wall. Integral units of
the bridge include: 1) drive machinery to rotate the bridge; 2) machinery for the multiple
aerator augers; and 3) a conveyor which transports incoming matenal from an overhead center
hopper to the place where it enters the digester near the wall. The matenal is aerated and
moved toward the center discharge by the action of the multiple augers. A conveyor at the
bottom of the digester removes digested material. Air is forced into the digester by a motor
driven blower and distributed throughout the material by pipes [26].

A self-generated temperature of approximately 66°C is produced and maintained by the
metabolism of the aerobic-thermophyllic microorganisms. The speed of the augers, the rate of
rotation of the carriage assembly and the amount of air introduced into the digester are
controllable to obtain optimum temperature and correct retention time of matenal in the
digester [26].

The retention time is 5 to 7 days. The composted product is fed into a hopper which
discharges the material uniformly at variable rates. The drying system consists of a
humus-buming incinerator, with an auxiliary oil-fired burner, providing heat to a honzontal
rotary dryer. Air to dry the humus product is drawn by an induced draft fan through the dryer
via a cyclone and venturi scrubber.

Compost discharged from the digesters can be further processed by drying, screening or
peptizing it into products for marketing such as bedding for poultry producers, and as an
ingredient in lawn fenilizer and soil mixes [25].

The amount of residuals requiring landfill is 15%. The minimum size of the Fairfield system
is 45 tonnes/day. There is no maximum capacity [5].

Quality Control Parameters

Efficient pathogen destruction is achieved by maintaining sufficiently high temperatures to
ensure pasteurization [25]. The Fairfield digester meets the requirements of the U.S. EPA that
the composting material be maintained within a vessel at operating conditions of 55°C or
greater for not less than three days [27].

Marketing

The primary market that Fairfield is developing for the compost is in horticulture [5].

3-14

3.2.3.8 International Process Systems

Feedstocks

Existing IPS facilities in Connecticut have successfully composted a wide variety of wastes:
mushroom farm waste, juice mill pomace and sludge, food processing waste, fermentation
waste, agricultural waste, leaves and chipped brush, municipal sewage sludge [28]. Materials
used as bulking agents include sawdust, recycled compost, shredded leaves, wood chips from
waste brush or clean construction wood waste, and shredded paper [29].

Description pf Operation

The entire operation takes place in a weatherproof building. Incoming waste is mixed with
bulking agents and loaded into the space at the front of the bay. Days later the finished
compost is removed at the other end of the bay.

A mixer/agitator machine works the compost every day, starting at the back end by removing
the finished compost and moving towards the front, mixing, agitating, and moving the material
3.7 m down the bay every day, thus creating space for a new load of waste. Each bay can
handle up to 10.7 m3 waste per day [28].

Compost remains in the bays for a minimum of 18 days, assuming the compost is moved
through the bays by operation of the agitator once a day, 7 days per week. The retention time
can be increased or reduced. The actual solids retention in the composting system is also
dependent on the degree to which compost is recycled as a bulking agent. IPS claims that,
through the use of recycled compost, a product is obtained which eliminates the need for
further curing [29].

Temperature and ventilation controls are used to maintain aerobic conditions and optimum
temperatures during the composting process. A series of blowers are mounted at intervals
along the sides of the outer bays. They are controlled by timers or by an automatic feedback
system for forced aeration. The airflow is upward from the bottom of the bay via a system of
perforated pipes. Each blower is independently controlled allowing precise temperature
management during each stage of the process [29].

Dry, stable compost is discharged into a storage area at the end of the bays. The IPS system
is modular; the basic module is a horizontal bay, 1.8 m wide by 1.8 m high and 67 m long.
As many as four bays can be placed side by side and served by a single mixer/agitator. When
greater capacity is needed, additional bays can be added without disturbing ongoing operations
[28].

Key Characteristics for Biofilter

International Process Systems recommends the use of a biofilter for odour control. Several
materials and soils can be used in the construction of biofilters. The quality of the medium is
important in the performance of the filter.

The following are the key characteristics given by International Process Systems for biofilter
media [29]:

ph 6-8

Moisture content (%) 10-40

Porosity (% air-filled) 30-60
Organic matter content (%) 5-30

3-15

3.2.3.9 OTVD

OTVD, a French company, markets an MSW processing system that includes a patented
composting technology known as Siloda. The minimum size of the OTVD system is 45
tonnes/day; there is no maximum [5].

Feedstocks

The feedstock consists of municipal solid waste, sewage sludge, and a "relatively dry organic
substrate" such as sawdust, wood chips, or ground bark. Dry amendment is needed to obtain a
porous mixture with an acceptable degree of moisture and the proper C/N ratio [30].

Description of Operations

Pre-processing of the waste includes magnetic separation, air classification, shredding, and
passage of the material through a rotating screen sized at 2.5 to 7.6 cm.

In the Siloda process, fermentation takes place in parallel silos installed in a roofed shed. The
silos are open at both ends to admit a horizontal paddle wheel. The paddle wheel travels on
rails on top of the walls separating the silos. The number of silos is variable and depends on
the quantity and quality of the product to be treated each day.

The product is regularly turned over by the paddle wheel, the blades of which slice the
compost from the bottom upwards and drop it into an Archimedean screw housed in the centre
of the paddle wheel. This screw flings the product into an adjacent silo and in doing so
aerates the product and equalizes fermentation. The wheel is transported from one silo to the
next The air required for composting is injected via piping installed in the bottom of the silos
[30].

The compost remains in the vessel for 10 to 15 days, gradually being moved throughout the
system by the paddle wheel. The material is then cured for 60 days in a curing yard. After
the composting phase, the material is screened to a size of 0.6 to 1.9 cm. The back end of the
system also includes pulverization and air classification. About 50% to 70% of the incoming
waste stream is composted [30].

Marketing

Marketing is done by another subsidiary of OTVD's parent company [5]. Primary markets for
the end product have been mushroom growers, vineyards, farms, greenhouses, and landscapes
[31].

3.2.3.10 PUR AC In-Vessel Composting Systems

The in-vessel composting system which PURAC offers today is the fourth generation in its line
of composting technologies.

Feedstocks

Feed to the system is partially dewatered sludge (18% to 35% solids from a belt press, vacuum
filter, centrifuge or other similar device). Dewatered sludge is mixed with recycled compost
and a carbonaceous additive to provide proper porosity, moisture content, and C/N.

3-16

Description of Operation

Generation 3 consisted of a closed, cylindrical vertical composting tank with a new air exhaust
system. The purpose of the change was to locate the exhaust air nozzles on the vertical pipes
approximately 1 m down in the material. In doing so, the process air is exhausted at the
warmest level where the air has the maximum content of moisture. This condition provides for
a more efficient withdrawal of water. Air flow as well as the necessary amount of
carbonaceous material used are reduced. Another advantage with the Generation 3 concept is
that the exhaust air flow is larger than the amount of air supplied at the bottom. The dif-
ference is made up by fresh air drawn from the top through the layer of new material. This
material has a very high oxygen demand, which can be satisfied through this additional airflow
from the top The process is designed to start quicker, which saves time or reactor volume
[32].

In addition to employing this improved air exhaust system, PURAC's new Generation 4 system
utilizes a rectangular rather than a cylindrical vessel. PURAC maintains that its new
rectangular vessel eliminates many of the problems associated with cylindrical. The mixing
screw for a cylindrical vessel must be located in the centre of the vessel, where it is affected
by corrosion and wear 24 hours a day and is impossible to inspect, maintain or replace without
emptying the reactor. The process of emptying the cylindrical reactor, inspecting or replacing
the screw, and recharging and re-establishing the biological process takes six to eight weeks.
Since inspections should take place every year, PURAC determined that this was not acceptable
[33].

The Generation 4 rectangular reactor circumvents such problems through the use of a travelling
parascrew. Only the screw comes in contact with the material, and only at the time when it
passes through the material, a period limited to 40 hours per week. In the Generation 4
reactor, "the driving unit and gears are located outside the reactor and can easily be inspected
and maintained even during operation. When the screw is not in operation it is outside the
corrosive compost in the reactor and stored in the ventilated 'garage' at the end of the reactor.
Thus the corrosion is minimized." [32].

Other advantages to the rectangular reactor and travelling screw which PURAC cites include:
1) expandability of the rectangular reactor, 2) avoidance of anaerobic zones; 3) flexibility in
sizing the reactor; and 4) improved material loading and distribution [32].

PURAC offers this further description of the Generation 4 system: "The rectangular vessel is
built up by modules having a length of approximately five meters. Between these modules
there are partition walls. These are limited in height and enable the infeed as well as outfeed
device to pass above and below. The vessel can be built to virtually any size. To increase the
size, the length of the vessel is extended with additional standardized modules. The same
standardized infeed and outfeed devices are used. This means that a rectangular reactor is
divided into a number of separate compartments. These can literally be operated separately but
are served by the same infeed and outfeed devices. The internal walls make it possible to
empty sections of the vessel." [33].

Following processing, the compost can be cured either within the original reactor vessel, in a
separate curing reactor, or on an aerated outdoor or indoor surface. If an open curing method
is used, the curing floor area is covered by a layer of special porous asphalt over a layer of
sand where perforated air supply pipes of plastic are situated. The air passes from the pipes
through the sand and asphalt layers [32].

3-17

3.2.3.11 Recomp, Inc.

Recomp is licensed by Bedminster Bioconversion to market the Eweson digester in some
western states. The company also is one of the few vendors with an operating MSW
composting facility, a 50 ton/day co-composting project in St. Cloud, Minnesota. The facility
began operating under Recomp's ownership in April 1988.

Feedstocks

The substrate to the co-composting operations is about 65% MSW and 25% sludge, with a
solids content of about 5%. The MSW feedstock consists primarily of food waste, paper,
glass, yard waste and some plastic, non-ferrous metal, and textiles [5].

Description of Operation

The incoming waste stream goes through a pre-sorting process on the tipping floor, then goes
though a bag splitter and into a trommel screen that separates the light and heavy fraction.
The recyclable materials are removed manually by hand sorting. The remaining material
(except for ferrous that is extracted by magnetic separation) is mixed with sludge and is loaded
into the digester. According to Recomp, the MSW is not shredded prior to composting. The
rotating action of the digester as well as a device inside accelerates breakdown of materials.

The material remains in the digester for four to five days, and then is transferred to curing
piles for 14 to 21 days. About 65% of the incoming waste stream actually enters the
composting system. The material passes through a 3.8 cm. trommel screen when it exits the
digester. The screen removes most of the plastic, aluminum, and bi-metal cans that are not
removed manually. After the material is cured, it is passed through a 1.9 cm screen. A 1 cm.
screen is available if a finer product is needed. The quantity of residuals that need to be
landfilled after composting is 30%.

The minimum size of the system is 45 tonnes/day; the maximum capacity is 365 tonnes/day
[5].

Marketing

"In addition to Christmas tree farms, Recomp plans to sell the product for use in public
works/highway applications, forest nurseries, and planter mix manufacturing. The current price
for the compost is $2.3 1/m3 unscreened, and $7.69/m3 screened [5].

3.2.3.12 Royer Industries, Inc.

Royer's involvement in the composting industry previously was primarily as a supplier of
screens and shredders to sewage sludge and leaf composting facilities. Recently, however, the
company expanded its line to include the Enclosed Dynamic Composting System it had
developed for processing sludge, MSW, and other organic wastes Royer will be supplying its
system to the co-composting faculty under design in Brooksville, Florida. The equipment will
be used for the compost curing phase [5].

Feedstocks

Feedstocks to the Royer Industries composting systems are dewatercd sludge, MSW, other
organic wastes, and bulking agent (sawdust) [5,34].

3-18

Description of Operation

Composting is conducted in parallel 2.4 m wide troughs. Starting at the unloading end of the
first trough, the compost turner moves through the trough contents, mixing, breaking up, and
turning the material and moving it forward about 3 m. Each operating day, de watered sludge
and bulking agent are placed in the loading end. When the turner reaches the loading end, the
new material is thoroughly mixed and moved into the aeration zone. After the turner
completes its cycle in one trough, it moves onto the automatic transfer dolly, which positions it
at the next trough to repeat the cycle. The Royer compost turner will mix four troughs of
composting material in an 8-hr day. The turning and transfer cycles are totally automatic, so
the operator is free to load and unload material and to perform routine maintenance.

The length of the troughs will depend upon the planned work schedule and the required
composting period. The system can be designed to operate on a 5, 6, or 7-day per week
schedule. At least 14 days are required to produce a compost product, which should then be
cured in a separate pile. If the composting process is extended to 21 days, the curing period
can be eliminated. Assuming a 5-day work week, the material will be turned 10 times in
14 days, requiring troughs 33.5 m long [34].

During the composting process, positive aeration is achieved by a series of blowers, which
force air into the mixture through a network of perforated pipe. An automatic control system,
operated by temperature probes and timers, turns the blowers on and off to maintain proper
composting temperatures. Chan recorders plot the temperature measured by sensors built into
the walls of the troughs [34].

Surge loads can be processed by making a second pass in a day, or by adding a nonscheduled
work day. Composting time can be extended without the addition of new material. To
compensate for variations in moisture content, operators can adjust the quantity of bulking
agent added to the mix. The system's total capacity can be increased by adding troughs [34].

3.2.3.13 Taulman Composting Systems

Feedstocks

Feed to the system is partially dewatered sludge (18% to 35% solids) from a belt press,
vacuum filter, centrifuge or other similar device. Dewatered sludge is mixed with recycled
compost and a carbonaceous additive to provide proper bed porosity, moisture content, and
C/N. Sawdust, barkchips, shredded newsprint, rice hulls, peanut hulls, milled straw, bagasse,
ground leaves, other yard waste, and corncobs have all been used successfully as carbonaceous
additives in the systems [35].

Description of Operations

The compost system consists of a completely enclosed, mechanical composting reactor and a
separate enclosed product curing reactor. The enclosed reactors make it possible to control
composting temperature and aerobic conditions within a close tolerance, thereby ensuring a
stable final product. The system is designed to completely eliminate odour [35].

The feed is introduced into the top of the vessel and composted for a period of approximately
14 days in the enclosed bio-reactor in a plug-flow, continuous regime. Air is fed continuously
into the bottom of each reactor, with positive control maintained by removing air uniformly
from the top of the reactor. Proper composting temperatures are maintained in the bio-reactor
to effect pathogen kill and organic solids stabilization.

3-19

Temperature of the composting sludge, and the carbon dioxide or oxygen content of the off-gas
stream are monitored continuously and sent to a microprocessor to control the quantity of air
fed to the bio-reactor. Integration of these control functions allows complete control over the
composting conditions.

A temperature profile through the vessel shows higher temperatures near the top, and somewhat
lower temperatures in the centre and bottom. This temperature variance, together with
differences in oxygen content from top to bottom, results in different zones of microorganisms
being established throughout the height of the vessel. Each zone has a specific function, such
as virus inactivation, weed-seed destruction, pathogenic organism kill, and organic material
conversion to humus. Since this is a plug-flow reactor, all sludge must travel through each of
the zones. The compost is not mixed so that the different zones are kept intact.

The composted material from the bio-reactor is transferred into the top of a 20-day cure reactor
where stabilization of the organic material is completed. Air is fed into the cure reactor to
assure aerobic conditions and to remove moisture via evaporative cooling.

The normal daily operating sequence begins with the bio-reactor outfeed device discharging
approximately 1/14 of the contents of the bio-reactor into the conveyors leading to the top of
the cure reactor. The cure reactor outfeed device is simultaneously started and final compost
product discharged. This operation requires about 2 hours.

Dewatered sludge cake, recycled compost, and carbonaceous material are combined and
transported to the top of the bio-reactor where mixing takes place. The mixed material is then
charged into the top of the bio-reactor. This operation also requires about 2 hours.

The final product from the cure reactor is a pathogen free humus-like compost product suitable
for use as a high quality soil conditioner. Taulman reports the following characteristics as
typical of the final product [35]:

Moisture, % 50-60

Nitrogen, % 1.0-1.7

Phosphorous, %P205 0.8-3.3

Potassium, % 0.1-0.4

Bulk density, kg/m3 300-500

Volume reduction, % 25-35

Water absorption capacity, % 40-70
Humic acid content, %

(based on total organic solids) 2.0-5.0

Pathogen destruction Complete

Economics

According to Taulman, the total present worth cost (capital and operating) of the Taulman
system is about the same as that of a well designed windrow or static pile facility. If a cover
is required for die windrow or static pile, the Taulman system should be less costly. It will be
less costly than incineration and heat drying.

The power requirement is low for the Taulman system. The only continuously operating
machinery are the blowers which supply air to the reactors. One man for one-half shift is
generally required to charge one bio- reactor and one cure reactor daily. The system requires
no operator anention during the other two shifts each day.

3-20

3.2.4 Hybrid

3.2.4.1 California Co-Composting Systems

Founded in 1982, CCSI is the licensee in 13 western states for the Voest-Alpine composting
equipment from Linz, Austria. Voest Alpine has 12 plants operating in Europe. CCSI
facilities range in size from 725 to 900 tonnes/day [5].

Feedstocks

Sewage sludge and MSW are fed to the system at a ratio of 1 to 4 [5]. The client is required
to implement a hazardous waste collection from households and businesses.

Description of Operation

The Voest-Alpine composting system includes a rotating drum and aerated windrows. The
processing line prior to composting consists of hand sorting, magnetic separation, air
classification, shredding, and screening to 8 mm. The post-processing line includes screening
to a particle size of 8 mm, air classification, and magnetic separation.

Material is composted in the vessel for 28 days, followed by four to six months of curing in
windrows. Between 60% and 80% of the incoming waste is actually composted. The amount
of residuals will vary from 8% to 23%, depending upon the end product market [5].

3.2.4.2 Harbcn/Triga

Harbert/Triga has an operational sewage sludge composting plant in Saint Palais, France. The
company also builds and operates plants which process both MSW and sewage sludge.

MSW/Sludge Co-Composting

Most of the waste processing is done at the front end of the system and includes:
hand-sorting, magnetic separation, air classification, shredding, grinding, and use of a vibrating
screen. Most of the compostable materials are separated out in one step; further processing is
used to recover recyclables. After composting, the material passes through a magnetic
separator and is screened. The compost remains in the fermentation tower for seven days, and
then is cured in windrows. The length of the curing time depends on the end use. Between
20% and 25% of the incoming waste stream is composted. Feedstocks include yard waste,
food waste, and sewage sludge if designed into the process. The amount of residuals that need
to be landfilled after composting ranges from 45% to 80%, depending on the end use. The
facility size ranges from 9 to 554 tonnes/day. Markets for the final compost include vineyards,
fruit tree growers, plant nurseries, and soil amendment for public works projects [5].

Sludge Composting

The following information is based upon Harbert/Triga 's sewage composting plant in Saint
Palais, France.

Wet sludge is mixed with a bulking material (usually a combination of sawdust and pulverized
pine bark). Mixing is monitored to produce an appropriate mixture with a water content of
65% [36].

The mixture of sludge and sawdust is poured into one of the four 65 m3 cells of the two

fermentation towers. A non-stop air flow rate is sucked through the mixture, the temperature

of which rises rapidly to over 70°C. Air is finally scrubbed in a lime solution before being
released into the atmosphere.

3-21

In completely filled cells, one thira of the content is taken out every day to be poured back on
top of the cell. After 10 to 12 days, the fresh compost is removed to be piled onto the
covered curing yard. Curing compost piles are turned with a front loader every two weeks in
order to maintain an appropriate oxygen content and temperature.

After two months, the compost is ready to be sold. Material from Harbert/Triga state that the
compost has the following characteristics and nutrient contents [36]:

Water content 45 to 50%

Organic material 85%
(related to dried material)

Nitrogen 2.0%

Phosphorous 1.5%

Potassium 0.2%

Element:; such as borium, copper, zinc, etc. can also be found.

It has been observed that total losses of the incoming mixture (sludge plus sawdust) are within
the 40% range [36].

3.2.4.3 Waste Processing Corporation — the DANO System

Over 200 plants worldwide utilize the DANO composting system [37]. Existing DANO
composting plants range in size from 45 to 900 tonnes/day [5,38]. In addition to Waste
Processing Corporation, Riedel Waste Disposal Systems, Inc. also is licensed to market the
DANO composting technology.

Feedstocks

DANO plants process municipal solid waste. The compostable fraction of MSW (primarily
newspaper, corrugated, mixed waste paper, yard and food wastes) is the feedstock to the
composting system. Sludge can be added to the MSW prior to being loaded in the drum
[5.38].

Description of Operation

MSW is tipped onto a concrete floor or pit in an enclosed receiving station. Recyclable items
are removed and placed in bins for transport. MSW is then placed in a large, slowly rotating
drum. This drum is about 3.6 m in diameter and 24.5 m in length. The drum rotates at 1 to
3 rpm. The drum is designed to quickly pulverize and homogenize the waste material. Air
and water are added to the waste to hasten the process. After 4 to 12 hours in the drum, the
waste is removed and screened to son out the oversized items. Alternatively, such items may
be screened out earlier, on the tipping room floor. A double screen located inside die drum
may be used to separate the refuse into three separate fractions. Coarse and medium fractions
are then available for magnetic and hand separation of recyclables.

Waste material is carried by conveyor from the drum to either windrows or aerated static piles.
Active composting for both methods is about 21 days, with approximately 6 weeks for curing.

The amount of residual material to be landfilled after composting is 20% by volume, or 30%
by weight, and varies according to end use.

3-22

3.3 Canadian Technology

A small number of Ontario municipalities have been approached by the larger U.S. and
European solid waste processing equipment manufacturers with offers to install large, turnkey
recycling and composting facilities owned and operated by and for the benefit of the equipment
vendor. This recent manifestation of interest in the Ontario market stems from two important
public announcements. The first concerns a new government policy objective to divert from
landfill 50 percent of the municipal solid waste stream by the year 2000. The second concerns
the Greater Toronto Area (GTA) Regional Governments' decision to work together to resolve
their waste disposal crisis. Later in 1989, they intend to issue a request for proposal (RFP) for
the disposal of all of the GTA municipal solid waste estimated to exceed 3 million tonnes
annually. The sheer volume of waste to be diverted and available for recycling and
composting has captured the attention of the many vendors and entrepreneurs.

In Ontario, the legislation requires that major projects of this type must undergo rigorous
environmental assessment and scrutiny by the public and the regulators. To avoid this costly
and time consuming process, new recycling and composting planning in Ontario to date has
resulted in designs that limit the plant waste production capacity to less than 200 tonnes/day.
Approval of these facilities under provision of the Environmental Protection Act are less
tedious and less costly since extended public hearings are avoided. The relatively small daily
capacity of current projects has also allowed consulting engineering firms in Ontario with
expertise in recycling and composting to dominate the Ontario scene. With the exception of
existing static pile composting operations, all new Ontario facilities on the drawing boards
appear to fit in the hybrid design category.

3.3.1 Channel System

The advantage claimed in Canada for the channel system is that a high rate of primary
composting can be achieved in the channels thereby greatly reducing the time to complete the
process and reducing the land area required for the facility. The channel system is non-
proprietory.

The channel walls are normally constructed side-by-side and are 4 m wide, about 40 m long
and 2 m high. A compost mixing device travels along the top of the channels to mix the
compost and propel it along the channel towards the discharge end. (See Royer Industries Inc.
who use a similar system.)

The blended raw materials are introduced at the loading end of the channel. During the
retention time, usually ten days, several important activities take place. Aeration of the
compost is provided through the diffusion bed which consists of a network of perforated pipes
underlying a uniform thickness of crushed stone. While the oxidation of organic matter is a
continuing process, the introduction of air is programmed to satisfy the biomass demand for
oxygen and cooling.

The mixing device operates once daily along each channel to provide several important
functions. The flailing teeth of the mixer breaks up colonized microorganisms and fungi and
uniformly distributes them through the mixed biomass to further encourage rapid
decomposition. The flail also mechanically breaks up the particles in the biomass to provide
greater surface area and promotes contact with the organisms present. The mixing action
releases water vapour and gases generated in the biomass while fresh air is introduced to
provide cooling and aeration. The mixer transports the biomass toward the unloading end of
the composting channel. With each daily pass of the mixing machine, the entire contents of
each composting channel is displaced by about 3 m in the opposite direction away from the
direction of the moving mixing machine.

3-23

3.4 Economics of Composting

The waste management literature contains descriptions of dozens of operating composting
facilities However, little information is available concerning the economics of building and
operating those facilities. Tables 3-1, 3-2, and 3-3 present a summary of capital and operations
and maintenance (O&M) costs reported for operating sludge, yard waste, and MSW composting
facilities, respectively. The reported O&M costs for sludge composting facilities ranges from
$40 to $537 per dry tonne, with the highest unit operating costs reported for the smallest
facilities.

For yard waste composting, much less economic information has been reported. Reported
O&M costs range from approximately $5.2 to $65 per tonne of yard waste. Tipping fees
reported for MSW composting facilities, both operational and proposed, range from about $26
to $91 per tonne of MSW.

The reported capital and O&M costs vary over a considerable range due to several factors such
as facility size and technology employed. Since the costs were not reported on a constant
dollar basis, general price inflation also has an influence on the range.

But, other factors make an economic comparison of operating facilities and composting
technologies very difficult. For example, local factors such as climate, labour, and equipment
are highly variable. Moreover, accounting practices vary since composting projects are
frequently public sector operations added to existing wastewater or solid waste operations.
Cost items such as land, labour, and equipment needed for composting operations may be
shared with other existing operations such that the costs attributed to composting reflect
estimated incremental costs rather than actual market values. For instance, some of the capital
costs for sludge composting systems on Table 3-1 include equipment for sludge dewatering.
Others do not. Some, but not all, include the cost of land. To complicate matters, the
definition of operations and maintenance costs are not precisely consistent. In summary, since
the accounting rules used to allocate the costs (and revenues) of public sector composting
systems are in many cases arbitrary, the reported results are not always comparable.

A more comparable way to describe the economics of composting is to develop and apply a
consistent set of assumptions to a hypothetical or proposed situation, and project the costs of
various technical or project size alternatives. A few examples of this approach to economic
analyses appear in the literature. The East Bay Municipal Utility District [22] projected, for
example, that alternative expansions to its existing pilot-scale sludge composting program
would have annual costs of $129 to $172 per dry tonne of sludge with certain assumptions for
the landfilling of reject materials and compost revenues. The five alternatives include several
combinations of technologies.

Similar studies have been performed to project the costs and benefits (avoided disposal and
product sales revenue) of various MSW composting and co-composting technologies and
project sizes for specific municipalities [23]. It is important to recognize, however, that the
utility of these studies is limited to the locale in which the governing assumptions apply.

3-24

TABLE 3-1
Summary of Reported Costs for Sewage Sludge Composting Facilities

Facility

Size

(tonne/day dry)

Capital
Cost ($)*

O & M Cost
($/dry tonne)*

Reference

Swampscott, MA
Old Town, ME

.3
.3

52.000
325,000

548

527

20
20

Durham, NH

0.9

775.000

101

20

Clayton, GA
Bangor, ME
Morgantown, NC
Occoquan, VA

1.3
1.9

2.9
3.3

NA

17,800

127,500

1,750,000

376
40
98
59

8
20
20
20

S. Portland, ME

3.5

2,934,000

204

20

Sarasota, FL

3.9

NA

493

8

Middleton, NE

4.1

5,000,000

219

20

W. Warwick, RI

4.5

NA

49

20

Merrimack, NH

7.3

216,400

132

20

Hampton Roads. VA

9.0

3,000,000

242

15

Cape May, NJ
Sussex Co, NJ

10.0
11.0

NA
3,530,000

279

NA

8
6

Windsor, Canada

22.0

940,000

71

20

Camdon, NJ

22.0

1,880,000

169

19

Akron, OH

23.0

NA

175

8

Portland, OR

24.0

NA

149

8

Plartsburgh, NY
Columbus, OH

25.0
36.0

NA
7,776,000

129
194

8
15

Blue Plains, DC

62.0

5,820,000

225

20

Montgomery Co, MD
Philadelphia, PA

80.0
118.0

20,715,000
1,760,000

276
249

15
20

NA - not available

* All costs have been convened to Canadian dollars.

3-25

TABLE 3-2
Summary of Reported Costs for Yard Waste Composting Facilities

Facility

Size

(tonne/yr)

Capital
Cost ($)*

O & M Cost
($/tonne of
yard waste)*

Total Com-
post Cost
($/tonne)*

Reference

Westfield, NJ

14

NA

11.5/m3
(64.83)'

37.36/m3
(52.5)2

14

Woodbury, MN

105

NA

19.41

75.3

14

East Tawas, MI

125

NA

< 13

25.9

14

Omaha, NB

455

NA

4.7

57.6

14

Seattle, WA

3,266

NA

29.2

45.9

14

Morris Co., NY

6,800

774,000

45.1

NA

12

Montgomery, Co., MD

4,000

NA

23.9

131.8

14

Monterey, NJ

NA

NA

8.8

NA

1

San Mateo Co., CA

37,000

NA

5.74/m3
(32.24)'

8.68/m3
(25.2)2

21

Notes:

1. Assuming a yard waste density of 178 kg/m3.

2. Assuming a compost density of 713 kg/m3.
NA = not available.

* All costs have been convened to Canadian dollars.

3-26

TABLE 3-3
Summary of Reported Costs for MSW Composting Facilities

Facility

Size
(tonne/yr)

Capital
Cost ($)*

O&M
Cost ($)*

Tipping Fee
($/tonne)*

Reference

Fillmore Co., MN

16-22

1,310,000

NA

44-50

3

Swift County, MN**

22

1,400,000

266,000

76

13

St. Cloud, MN

14,000

NA

NA

50

21

Cairo, Egypt

44,000

770,000

NA

22

16

Portland, OR**

200,000

13,100,000

5,000,000

44

4

Dade County, FL**

275,000

25,000,000

NA

26

11

Portage, WI

NA

NA

NA

39

21

NA = not available

* All costs have been converted to Canadian dollars.

** Proposed

3-27

With regard to MSW and yard waste composting, there does not appear to be any reported
information indicating significant economy-of-scale in the sizing of facilities for the production
of these materials. The O&M costs reported for sludge composting do, however, seem to
indicate some economy-of-scale for that material. Regarding the reported economics of
operating existing facilities, several of the referenced reports do mention that production costs
increase markedly when facilities are used at less-than-capacity.

3.5 Marketing

Marketing plays an important role in the ultimate effectiveness of any program to compost
wastes, whether the wastes be MSW, sewage sludge, yard debris, or another organic material.

The primary objective of securing a market is that of finding an end-use for the finished
product. The compost process itself results in a significant amount of volume reduction.
Consequently, if the finished product were simply disposed of, a certain amount of landfill
space would nevertheless be conserved. In fact, there are those that believe that volume
reduction is reason enough to implement a compost program [1]. However, the value of any
program to compost wastes is greatly increased when an end-use for the product is secured -
the quantities of waste requiring landfill are reduced further, and a beneficial use for the
product is found [2],

A secondary objective, and one that is not always realized, is to provide revenue from the sale
of the compost. Twenty-five years ago, the driving force behind composting was the hope of
selling the finished product at a profit. The difficulties today in siting and developing landfills,
combined with an interest in conserving resources, has reduced the profit motive in composting
to one of secondary importance [3]. Nevertheless, any revenues obtained from selling the
compost product would, obviously, serve to offset the cost of processing.

3.5.1 Characteristics and Uses

3.5.1.1 Characteristics

The utility of compost as a soil amendment has long been recognized. The most beneficial
characteristic of compost is its high organic content. Compost also contains certain nutrients
that can be helpful in plant production. Selected characteristics of various types of composts
are presented in Table 3-4. These characteristics include: moisture content, organic matter,
C/N ratio, pH, nitrogen, phosphorus, and potassium.

3-28

TABLE 34
Characteristics of Various Composts

Moisture Orgenics C/N
Content (X) (X dry wt')

Nitrogen Phosphorus Potassium
(X dry wt) (X dry wt) (X dry wt)

BARK

Japan [4]

0.8O0

1.70

0.500

MANURE

Japan [4]

1.700

3.20

1.900

HSU

France [5]

36-40

30-33

18-19

7.50-7.70

France [6]

33-40

45-53

7.50-8.00

1.0-1.2

France [7]

40-42

30-35

19-20

7.50

France [8]

1.100

0.60

0.600

Italy [9]

41.39

24.50

0.960

0.68

1.010

Japan [4]

2.100

2.00

1.400

Oman [10]

35.90

55.00

19.00

6.63

1.300

0.40

0.600

Spain [11]

43.96

31.98

7.02

0.860

0.74

0.510

Spain [11]

69.43

24.15

7.16

1.330

0.83

0.950

Spain [11]

58.20

18.80

7.10

1.660

1.06

0.780

U.S. (Minnesota)

[2]

46.90

6.80

1.080

0.35

0.760

HSU/PIG HANURES

Italy [9]

25.01

16.60

0.830

0.55

0.560

PAPERS

U.S. (New York) [12]

8.10

1.730

0.94

1.250

SLUDGE

Japan [4]

2.300

4.00

0.400

U.S. (Oregon) [2]

58.96

4.74

1.810

1.79

24.050

SLUDGE/BARK

Italy [13]

55.00

50.00

12.50

6.90

2.200

0.45

0.400

SLUDGE/VINEYARD WASTE

Italy [13]

55.00

48.00

12.20

6.50

2.000

0.69

1.400

SPENT MUSHROOM

Netherlands [14]

60.90

20.30

0.700

0.78

0.960

YARD DEBRIS

U.S. (Minnesota)

[15]

7.60

0.075

0.02

0.027

U.S. (Oregon) [2]

48.90

64.50

6.70

0.630

0.14

0.620

U.S. (Oregon) [2]

48.50

67.30

7.10

0.900

0.16

0.720

3-29

Because of the organic matter in compost, it can positively affect soil in a number of ways
[2,4,16-21]:

Physical properties of soil

Chemical properties of soil

Biological properties of soil

Crop yields

improves soil texture

increases water retention capacity

improves aeration capacity

improves structural stability

resistance to wind and water erosion

stabilizes soil temperatures

increases nutrient content

turns mineral substances in soil
into forms available to plants

regulates mineral input, particularly
nitrogenous compounds

serves as buffer in making minerals
available to plants

source of micronutrients

affects the development of fauna and microflora

renders plants less vulnerable to
attack by parasites

promotes faster root development of plants

can produce higher yields

inhibits weed growth

3.5.1.2 Uses

A professional marketing firm has identified 22 major end uses for compost [22]. In addition
to its beneficial properties as a soil conditioner, compost can be used as a mulch (to aid water
retention and inhibit weed growth), as a top dressing (to improve appearance and inhibit weed
gTOwth), and for landfill cover [23].

Due to the beneficial characteristics of compost, the product can be used by a variety of market
segments. The types of markets for a particular compost product are highly dependent upon
the type of feedstock, quality of the product, and needs of the area. For example, in
densely-populated areas, agriculture may not be a feasible market. The following are potential
markets for compost products [2]:

• agriculture

• bare roots nurseries

• Christmas tree farms

• forest seedling nursery, reforestration

3-30

golf courses, cemeteries, amusement parks, athletic fields, etc. for grounds maintenance

highway construction and maintenance

hydromulching

land reclamation (landfills, quarries, strip mines, tailings areas)

landfill cover

industrial and commercial property landscaping

parks and recreation areas

public agencies

residential landscaping and gardening

sod farming

Agriculture

In connection with its use in agriculture, both the organic matter and the nutrient content of
compost are of importance [24]. The fertility of the soil is a valuable environmental asset. In
order to safeguard this fertility, the soil must be supplied with sufficient organic matter. Ac-
cording to Geilinger [25], compost is the best source of organic matter for this purpose.

A number of tests have been conducted on the effect of compost application on crop yields.
Tests have shown that, when the compost has been properly processed and applied, high yields
have resulted [3,5,20,26]. For example, application of MSW compost to vineyards in France
has resulted in increased yields of 13% to 14% [5].

As part of an MSW compost project in Tennessee, MSW compost was applied to fields
annually from 1968 to 1972. Field com was grown annually from 1969 through 1983 using
conventional soil tillage techniques. Com grain yields were measured each year. Data
collected over a 19-year period demonstrated that the beneficial effects of MSW compost
application include sustained higher crop yields, a more favourable soil pH, increased organic
matter and cation exchange capacity, and enhanced supplies of primary and secondary plant
nutrients [3].

Research tests have also demonstrated that use of compost in conjunction with chemical
fertilizers can be beneficial. In tests on com production in Minnesota, fields treated with both
compost and fertilizer achieved yields 17% higher than fields spread with commercial fertilizer
alone [26]. Compost can increase efficiency in chemical fertilizer utilization [2,27].

Difficulties in exploiting the agriculture market include: 1) high costs associated with transport
of compost products; and 2) difficulties in applying compost to the fields.

Nurseries

Compost can be utilized in a wide variety of nursery applications. Examples are bare roots
nurseries, Christmas tree farms, container production, forest seedling nurseries. Results of a
marketing survey conducted in the metropolitan area of Portland, Oregon, indicated that about
60% of nurseries surveyed used bark or barkdust products in their business, either as a soil
amendment or in potting mixes. Next in terms of volume of use were sawdust, manures, and
peat moss [2].

Tests in which compost served as a potting soil amendment have shown increases in growth
that ranged from 0% to 50%. The use of compost in potting soils is attended by a slow
release nitrogen, phosphorus, potassium, calcium, and other essential nutrients. It also increases
porosity and aeration for healthier root development [28].

3-31

Landscapes

Significant quantities of organic soil amendments are used by landscapes, gardeners, and sod
producers. Bark or barkdust is often used as a top dressing, topsoil primarily as fill for new
plantings, and compost as a soil amendment [2]. New construction projects (e.g., residential
housing developments and commercial buildings) create a high demand for the products.

Research by the U.S. Department of Agriculture and at Rutgers University has demonstrated
that on soils with poor physical properties, compost used correctly will lead to the production
of a better turfgrass than is true with the use of mineral fertilizers alone. Compost on
turfgrass, leads to the slow release of nitrogen, and also imparts the resilience needed to absorb
normal traffic wear and reduce compaction which can damage roots [29].

Public Agencies

Municipalities and other government agencies often require organic soil amendments for use as
a soil conditioner or top dressing. Examples of uses are: parks, recreation areas, landscaping,
turf repair, landfill cover, land reclamation, and highway construction and maintenance
[2,21,30,31].

Residential Gardening

Large quantities of compost can potentially be utilized by the residential sector. The amounts
are highly dependent upon the population density of an area and the type of housing, i.e.,
residents of single-family dwellings typically use greater quantities of soil amendment products
than residents of multi-family dwellings.

Compost is generally used by the residential sector for the following purposes:

• as a soil amendment by improving the organic and nutrient content of the soil and
increasing the soil's moisture holding capacity;

• as a mulch to aid water retention, inhibit weed growth, and add to the organic matter of
the soil; and

• as a top dressing by improving appearance, inhibiting weed growth, and adding to the
organic matter of the soil.

3.5.1.3 Competitive Products

In order for compost to have external markets, either markets must be expanded or compost
substituted for another product [32]. Examples of materials that can compete with MSW
compost for the soil amendment market include: bark and barkdust, manure, peatmoss,
sawdust and shavings, straw, woodchips, topsoil, worm castings, and fish meal [2,33,34]. The
kinds of products that would compete with compost are highly dependent on the geographic
location, in particular the type of industry and population density.

3.5.1.4 Existing Markets

Efforts to market the finished compost products are meeting with a great deal of success in
some locations and with some types of composts. The Middle East is an example of an area
in which the demand for compost is great. With one exception, all of the facilities have
existing markets capable of absorbing more compost than can be produced. In fact, many have
one to two-year waiting lists for the product. Compost, with its high water retention
capabilities, is ideal for desert countries where the agriculture is heavily dependent on irrigation
[19].

3-32

A listing of markets (actual, targeted, or planned) for a number of composting operations
world-wide is provided in Table 3-5. As can be seen from the table, a wide range of markets
for the composts is being exploited.

3.5.2 Marketability

3.5.2.1 Product Quality

For a product to be marketable, it must meet the requirements of the user. Compost is no
exception. The following criteria have been found to be of particular importance to potential
compost users: quality; availability (convenience, steady supply, etc.); and cost [2].

Characteristics of High Grade of Compost

Product quality is generally considered to be the most important of the factors that affect the
marketability of compost. Regardless of the type of compost operation, quality of the product
is a function of the physical, chemical, and biological characteristics of the product. Examples
of desirable characteristics are as follows:

Physical: dark colour

uniform panicle size

pleasant earthy odour

absence of contaminants

absence of clumps

no visually identifiable contaminants (e.g., glass shards and pieces of

metal and plastics)
moisture content <50% (for ease of transport)

Chemical: available nutrients (NPK)

minimal levels of heavy metals, PCBs, PCPs, and

pesticides/herbicides
low salinity concentration

Biological: sufficiently mature

high concentration of organic matter
absence of pathogenic organisms
absence of weed/crop seeds

The characteristics listed above are of importance because they render the product attractive to
users, and guarantee that it is safe to use [10]. As may be concluded from the information in
Table 3-6, the quality requirements for a compost sold on the market may need to be adjusted
depending upon the particular needs of the user [1]. An example of how a grading system can
be utilized for different qualities of compost, and how those grades of compost are suited for
particular applications, is given in Table 3-7.

Problems with compost quality vary with the type of feedstock Table 3-8 presents the
findings of a study conducted in Portland, Oregon, in which a comparison was made between
yard debris, sewage sludge, and MSW composts with respect to their physical, chemical, and
biological characteristics. As shown in the table, the sewage sludge compost evaluated in this
particular study had relatively high concentrations of heavy metals and low levels of PCBs. In
contrast, both the yard debris and MSW composts had lower levels of heavy metals, although
the MSW compost had a high concentration of PCBs.

3-33

TABLE 3.5
Listing of Markets for Compost Products

Feedstock/location

Reference Market

Market Status*

LEAF
U.S. (various locations, New Jersey)

U.S. (Cleveland, Ohio)

Egypt (Abbis, Alexandria)

Egypt (Giza)

France (Brametot)

Frnnoo (HornuFidy)

Fi ante (unst^rc ! f ied)

Iraq (Mosul)
Oman (Muscat)
Qatar (Doha)
United Arab EmirBtes (Abu Dhabi)

United Arab Emirates (Al Ain)
United Arab Emirates (Sharjah)
U.S. (Broward Cty., Florida)

U.S. (Sumter Cty., Florida)
U.S. (Mew York, Neu York)

MSW/SLUDGE

Austria (Liezen)

Italy (Lanerossi, Sehio)
Soviet Union (Minsk)
Soviet Union (Minsk)
Soviet union (Minsk)
West Germany (Lemgo)

1*8,

493

General Public

Topsoil Companies

Nurseries

Public Works & Park6

Dopopinumta

1461

General Public
Lsndg capers
Nurseries

[19]

a)

Large Demand (market not

Specified)

(19)

e)

Large Demand (market not

specified)

[1]

Farmers

Pi]

Am'ehelte Tie Ida

[26]

Vineyards

£5]

a)

Large Demand (market not

specified)

H9]

8)

No Demand

C19]

a)

Municipal ity

[19]

a)

Municipality (70%)
General Public (30%)

[193

a)

Farmers

[19]

a)

Large Demand (market not

specified)

[17]

Horticulture
Landscaping
Blended Products

150]

Nurseries

Soil Amendment Dealers

[26!

Landfill Cover

151]

Soil Conditioner

Agriculture

Landscaping

[6!

Difficult Market

[38]

Horticulture b)

[38]

Horticulture

[381

Horticulture

[8]

(market not specified)

SLUDGE

Italy (Pesaro)
Italy (Senigatlia)

Netherlands (Halweg)
Spain (Veldemingomez)
U.K. (Canterbury)
U.S. (Denver, Colorado)
U.S. (Durham. New Hampshire)

[8]

[83

[8)
[8]
[8]
1523
(52)

free for Municipal Use

Municipal Services

Vegetable Growers

Sold (no market specified)

Agriculture

None - Conducting Trials

Potting Soil

Street & Parks Departments

3-34

TABLE 3.5 (Cont'd)
Listing of Markets for Compost Products

Reference Market

Market Status*

SLUDGE (CONTINUED)
U.S. (Columbus, Ohio)

U.S. (Screnton, Pennsylvania)

U.S. (Hampton Roads, Virginia)

West Germany (Hi Ichenbech)

West Germany (Horn Bad, Meinberg)

SLUDGE/SAUDUST
France (Nante6)

SLUDGE/WOOD UASIE/SAUDUST
France (Blois)

[47]

LsndscBpers

Nurseries

Golf Courses

Topsoil Suppliers

Parks

Cemeteries

General Public

[52]

Publ ic Agencies

(some marketed by broker)

[52]

Street & Parke Deportments

[8]

Municipal Use

[8]

Municipal Use

[1]

Truck Farmers

Horticulturists

Nurseries

[1]

Retail Sates

Large-scale Farming

YARD DEBRIS

U.S. (Sen Mateo, California)

U.S. (Brookhaven, New York)
U.S. (Davl6, California)

[53]

[22]
[54]

Stockpi led for

Landfill Cover
Parke Department
Commercial Gardeners
Local Agencies
General Public
Municipal Projects
General Public
Local Landscapers
Housing Developments
Commercial Construction
Nurseries
Small Farmers

A = Actual Market P = Planned T = Targeted

0 According to text, most of the plants in the Middle East now process MSU only, instead of H4
Sludge; which ones are unknown.

b) Compost restricted to horticultural applications because of high heavy-metal concentrations.

3-35

TABLE 3-6

Examples of How Quality Requirements for Compost are
Affected by the Needs of the Users [1]

Use

Requirements

Mushroom growing;

Vineyards:

Arboriculture:

Truck gardening and
vegetable farming:

Large-scale farming:

fresh product (heat contribution is required)
humidity rate as low as possible, preferably below
35% of gross weight

minimal amount of inerts, if the mushroom compost
is to be used in agriculture afterwards
acceptable levels of heavy metals since they tend
to Infiltrate mushrooms very easily

low level of "impurities"

importance of maturity and particle size will

depend primarily on the intended use of the compost

(maintenance or replanting)

organic content and moisture content values

important for comparative costing

heavy metal content should be monitored

clean product, low level of Impurities
maturity is of lesser importance
organic content and moisture content values
important for comparative costing
particle size of little significance
heavy metal content should be monitored

free of sharp items since compost spreading

is often done manually

requires preferably the use of fine or very fine

grade compost

maturity very important

must be absolutely free of any seeds and of any

risk of phytotoxidty

salinity must be closely monitored

metal content must be monitored since metals are

readily assimilated by a number of plants and may

be concentrated in the edible portion of the plants

level of impurities important, must be free of

contaminants such as plastics (visual impact)

organic matter content must be high in order to

optimize the economic value of the compost

NPK fertilizing components may also be considered

when calculating the economic value of the product

coarse particle size not acceptable

no fresh compost; requirements for product maturity

depend on compost, spreading periods

heavy metal content must be monitored

3-36

TABLE 3-7
Applicability of the Different Grades of Compost [24]

Landfill Soil Soil Amendment Care of

Reclamation Amendment Larger Scale Gardens

Coarse compost ++ + +

Fine compost 4+ ++

Compost/sand + ++

"Quality compost" * +

* Quality compost is defined as having characteristics that are superior to the other materials

and would not present hazards to the public health. Specifics would be determined by
each locale.

++ Primary application
+ Secondary application

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3-38

Approaches to Improve Quality

Ultimately, product quality is a function of two factors: 1) composition of the feedstock; and
2) type and thoroughness of the processing operation [8,16].

The trend in composting today is towards controlling the quality of the finished product, to the
extent possible, by restricting the materials entering the compost process. For example, some
compost plants in the Middle East that originally treated both MSW and sewage sludge are dis-
continuing the treatment of sludge because of the high salinity of sludge [19]. Similarly,
because the higher concentration of heavy metals are in industrial rather than in residential
sludges, one method of reducing the heavy metal content of sludge compost would be to treat
only residential sludges.

Certain aspects of product quality can be affected only by controlling or adjusting the compost
process itself. For example, because pathogens are intimately associated with sewage sludge,
the feedstock cannot be altered to increase the quality of the compost. Instead, the number of
pathogenic organisms must be reduced to a safe level in the compost product by controlling the
compost process, i.e., by maintaining thermophyllic temperatures in the compost mass over a
sustained period. Similarly, although pesticides and herbicides in yaid debris would be difficult
to control through feedstock adjustment, their concentrations can be adequately reduced by way
of appropriate process control.

Compost from mixed MSW typically has relatively high levels of inert materials (e.g., glass
shards, scrap metal, and plastics). Unacceptable levels of heavy metals and PCBs have also
been a problem in some instances. Attempts to ameliorate these problems are being made both
by changing the composition of the feedstock and by altering the processing operation.
Removal of contaminants by controlling the feedstock is the recommended approach, because it
results in an improvement in compost quality. Moreover, market value of the product is
boosted, wear-and-tear on equipment is reduced, and faculty operating costs are thereby
decreased [22].

The practice of source separating MSW for composting is gaining popularity world-wide
[4,6,18,33-36]. In fact, Bezner (West Germany) predicts that in the future the sorting of MSW
materials will be taken for granted.

He names the advantages of source separation as the following [18]:

• highest possible degree of materials separation;

• continuous supply of high grade secondary materials for the reprocessing industry;

• simple separation of undesirable and toxic waste products, including batteries, paints,
lacquers, pharmaceuticals, etc.; and

• flexible adaptation to constantly changing consumer habits.

Bezner further recommends that, in addition to source separation, two processing lines be
utilized to further insure product quality. A high grade of compost for garden and plant use
would be produced from yard debris. A lower grade material derived from organic waste and
sewage sludge would be used for road banks, playing fields, and sinular projects [18].

Levasseur (France) agrees that source separation can be the best solution, but cautions,
however, that its efficiency is heavily linked to public participation, type of urbanization, etc.
Because, according to him, none of the existing treatment methods are fully efficient in treating
all types of MSW, integrated waste management must rely on separate collection as a way to
optimize the process [6].

3-39

Market analyses conducted by The German Compost Quality Assurance Organization indicate
that compost from mixed MSW and from sludge is being rejected more and more frequently by
potential users because of perceived high levels of toxic and inert substances. In contrast,
compost produced from separately collected, exclusively organic waste, is accepted without
reservation by 50% to 75% of all potential users [37].

The concern about heavy metals in compost from mixed municipal wastes is an important
factor in the trend towards source separation. Baccini (Switzerland) believes that inasmuch as
heavy metals must be almost entirely absent from mature compost, they must be present in
limited quantity in the raw material and must be controlled in order to produce an acceptable
compost. He advocates the separate collection of biological wastes (e.g., garden and kitchen
wastes, land and forest products wastes, and food products industry wastes) for feedstocks to
compost operations [33].

The heavy metal contents of various type of composts are presented in Table 3-9. The data in
the table are indicative of the effect of various feedstocks and levels of separation on compost
quality.

As is discussed in Section 6, specifications for compost quality have been developed by the
CEC, ANRED, and in various countries, some Canadian provinces and some U.S. States.
Specifications generally serve the following two purposes [1,8]:

• encourage producers to set processing objectives and improve the quality of their
compost; and

• provide consumers with a guarantee of consistent quality and safety.

3.5.3 Developing Markets

Many approaches to compost market development have been tried, with varying degrees of
success. The following aspects of market development are discussed in this section: key
elements of a marketing program and importance of public education. Examples of existing
practices are given.

3.5.3.1 Key Elements of a Marketing Program

An abundance of advice is available in the literature with regard to developing markets for
compost products. No single approach is applicable to all situations. Differences in products
as well as differences in soils, agronomic practices, social patterns, and climate create a new set
of variables for each project [45].

The following is a summary of general suggestions for compost market development
[15,21,27,31,45]:

• Market Research ~ The first step in developing a marketing program is to research
existing and potential markets, quantify all of the markets, and develop target markets.

This requires a knowledge of the product, product use, constraints on use, and value of the
product to the user.

• Product Quality ~ As discussed earlier, the product should have a consistent quality.
This is especially important for sales to commercial operations. The product should be
geared for the market being targeted (see Tables 3-6 and 3-7).

3-40

TABLE 3-9

Actual Values of Heavy Metals in Composts
(ppm, dry wt.)

Locat ion/Feedstock

Reference

Lead

Cadmium

Chromium

Copper

Nickel

Mercury

Zinc

FEDERAL REPUBLIC OF GERMANY

[38]

463

3.2

48

173

24

3.8

Mixed MSW

902

Source separated
(kitchen/yard)

[38]

12

1

33

59

166

Source separated
(kitchen/yard)

[38]

38

0.5

18

21

18

190

Source separated
(kitchen/yard)

[33]

135

1.66

35

70

16

356

Yard waste compost

[39]

35. 6

0.31

42.2

22.8

15.3

0.25

110

Source separated
(kitchen/yard)

[39]

135

1.8

3S.5

71

19.5

352.5

Mixed MSU

[8]

513

5.5

71

274

45

2.4

1570

Source separated MSU

18]

133

1

36

33

29

408

Tree and shrub pruntngs.

[8]

27

<1

16

22

21

<1

80

and agricultural wastes

MSU from urban areas and
the city center

MSW from urban, rural and
central areas with Intense
trading

MSW from city cent&r

MSW from urban areas

MSW from city center and
areas with medium scale
industrial activities

MSW from Athens area and
other areas with high
Industrial activities

MSW from urban areas and
central part of Athens

ITALY

Mixed MSW

[40]

447

3.9

109

322

71

3.9

1054

[8]

527

3.2

162

127

89

3.7

886

[41]

197

5.3

64

109

38

151

[41]

143

2.8

294

131

143

770

[41]

140

2.4

77

121

43

729

[41]

167

1.4

86

151

52

778

[41]

214

0.7

182

586

108

815

[41]

180

2.1

56

309

38

1308

[41]

241

7.6

80

208

41

742

[40]

3-41

TABLE 3-9 (Cont'd)

Actual Values of Heavy Metals in Composts
(ppm, dry wt.)

Locat ton/Feedstock

Reference

Lead

Cadmium

Chromium

Copper

Nickel

Mercury

Z1nc

JAPAN

MSW

[4]

0.9

0.5

Sewage sludge

[4]

2.3

0.8

Manure

[4]

2.6

0.2

Bark

[4]

0.2

0.3

NETHERLANDS

Mixed MSV

[42]

800

7

160

600

110

1700

Mixed MSV with mechanical
separation of non-organ1cs

[42]

420

1.6

40

100

25

520

Source separated MSW

[42]

160

1.0

30

50

10

230

Vegetable, fruit, and
yard wastes (median)

[43]

54

0.65

55

26

11.5

175

Vegetable and fruit
wastes/chipped wood

[35]

42

0.97

36

28

7.1

0.08

170

Vegetable and fruit
wastes/organ ics

[35]

38

0.55

32

23

10

0.08

135

SOVIET UNION

Sewage sludge/MSW

[44]

315

<5

50

130

23

10.4

12400

Sewage sludge/MSW

[44]

350

<5

250

270

70

9.9

11000

Sewage sludge/MSW

[44]

215

<5

37

140

13

20.6

11000

SPAIN

Mixed MSW

[11]

422

3

146

225

80

350

Mixed MSW

[11]

442

4

63

145

36

394

Mixed MSW

[11]

796

6

77

738

72

972

UNITED STATES

Yard debris

[2]

72.9

0.B

24.2

25

21

0.05

160

Yard debris

[2]

71.5

0.8

21.6

42

22.7

0.08

160

Sewage sludge (average of
10 samples)

[2]

384

26.2

288

485

126.0

1368

Mixed MSW

[2]

913

4.8

56

.190

32.8

3.7

1010

3-42

• Product Testing - The compost should be subjected to laboratory testing to ensure
product quality. Field tests can also be conducted to demonstrate product utility. Often
the tests are conducted by local university staff.

• Compost Samples -- Prospective clients should be provided with compost samples and
specification sheets.

• Product Labelling -- All products should be shipped along with a description of the
product. This description should include results of laboratory tests.

• Reliable Supply -- Commitments to buyers must be fulfilled.

• Diversity -- Production of a variety of products broadens the potential market base.

• Market Location - Due to the relatively low economic value of the material, its low
bulk density, and its high moisture content, transportation costs of compost sold in bulk
form can be prohibitive to market development. Therefore, local markets should be
sought. Sales beyond 80 kilometres generally are not economically feasible for bulk
compost unless specialized, high-graded mixes are made. Transportation constraints are
not as rigorous for the packaged retail market.

• Product Identity - A positive identity which becomes familiar to the public is an
important factor in successful mass marketing of a compost. A trade name is needed
that connects the product to the area, or with a popular area feature.

• Prospects ~ Sound rule of thumb of marketing is to have good prospects for at least
twice the production.

• Continuing Effort - Aggressive marketing is necessary to assure that all product is
utilized and that revenues are optimized.

• New Markets - Work on developing new markets. This may include working with
landscape architects on developing specifications for use, or with government agencies
regarding use in highway construction and maintenance.

Marketing services can be contracted out. For example, in the United States, many New Jersey
towns have hired private firms to manage their leaf compost programs. The participating
municipality supplies publicly-owned sites, equipment, and operators. The company provides
technical and management support, site supervision, and marketing services for the compost
[32].

Another approach to compost marketing that is becoming increasingly popular is to market the
product through a broker. The broker buys the compost at a low price, takes responsibility for
product testing, compliance with regulatory constraints, and promotion. The compost can be
marketed alone or as a component of a series of mixes [21].

3.5.3.2 Public Education

Public education is an important facet of a compost marketing program. Because the product
is derived from waste material (whether it be MSW, sewage sludge, yard debris, or animal
manure), the product has a stigma that acts as a barrier to market development. This barrier
cannot be avoided, but it can be overcome using consumer education and demonstration of
product value [2,27,45].

3-43

Results from a market study conducted in the metropolitan area of Portland, Oregon, provide
an example of the stigma that can be attached to compost produced from recycled wastes. In
the study, residents were questioned regarding their feelings about using any one of three
compost products, namely, yard debris, sewage sludge, and MSW. Of the residents surveyed,
over one-third expressed some concern about using any of the composts or with one of the
composts in particular. Although most of the residents indicated they were familiar with the
products, most of their concerns were directed at all three composts. Some of the more
frequently mentioned concerns were [2]:

Disease transmission

Contamination, chemicals, hazardous wastes

Harmful to children or pets

Harmful to plants

Dislike of human wastes in yard

Dislike of garbage in yard

Odour

Flies and mosquitos

Health concerns

Heavy metals in sewage sludge

Safety for edible produce

Uncertainty as to contents

Cleanliness

Appearance

3.5.3.3 Examples of Existing Marketing Programs

The following are examples of approaches utilized by individual programs to market compost.

3.5.3.3.1 The Greater Cleveland Ecological Association

Three approaches have been proven successful in marketing compost produced from yard
debris in the Cleveland, Ohio (U.S.) area [46]. They are:

1. Bag and bushel program - Small scale gardeners bring their own containers and pay
88 cents per generous bushel. Market is open five months (April through June, and
September through October).

2. Bulk load pickup ~ Facility personnel load the customer's truck and charge $ 20/rri.

3. Home delivery - This is the most popular approach and accounts for 60% to 70% of
the compost sold. A local topsoil dealer does the hauling. Home delivery is available
four days a week during the spring, summer and fall. The minimum residential sale is
1.5 m3; maximum is 8 m3. The charge is $ 77 for 1.5 m3 of regular grade compost,
and $ 274.40 for 8 m\ including delivery charge and taxes. For out-of-county delivery,
there's an added $ 23.50 charge. Semi-truckloads delivered to landscapes and
commercial growers are sold at a discount to encourage the use of composted materials
on lawns and in potting medium for nursery stock.

The Association has also utilized publicity to promote the program. The publicity includes: 30
to 40 publicity stints a year on TV shows, articles in newspapers, and newsletters emphasizing
the ecological benefits of the compost.

3-44

3.5.3.3.2 Oman (Middle East)

There is a strong demand for high quality organic fertilizers in the agricultural country of
Oman. A market study for the end product was conducted prior to construction of the plant.
The studv demonstrated that 12,000 tonnes/yr could be marketed, assuming a high quality
compost was produced [10]. The finished product was tested for pathogens and parasites.
Twelve people were employed for the marketing and distribution of the compost. Oman is a
country with a very low population density of about 5 people/km2. Consequently, farms are
spread out and distribution costs are high. The following breakdown of production costs
demonstrate the amount allocated to selling and distribution:

Processing costs 30%

Administrative costs 8%

Selling and distribution costs 24%

Depreciation 20%

Interest on loans, etc. 8%

3.6 References

3.6.1 Technologies

[1] Tonge, Peter, "Green Grows Garbage," The Christian Science Monitor (March 1, 1988).

[2] "Waste Plant to Turn Garbage Into Soil, The Gastonia Gazette (July 14, 1988).

[3] Marques, Aminda, "Firm Turns Trash into Plant's Delight," The Miami Herald (May 25,
1989).

[4] Reveron, Derek, "Agripost's Decade of Work Starts to Pay Off," The Miami Herald
(November 14, 1988).

[5] Goldstein, Nora, "A Guide to Solid Waste Composting Systems," BioCycle, 30(l):38-47
(January 1989).

[6] "Regional Roundup," BioCycle. 29(7):11-14, 19-25 (August 1988).

[7] Noffsinger, Jan, "Sumter County Showcases State's First Volume Reduction Facility,"
Solid Waste News Report. 1(2) (Fall Quarter 1988).

[8] Environmental Recovery Systems, Inc. Informational Proposal.

[9] "Solid Waste Disposal: Avoiding a Crisis," Environmental Recovery Systems, Inc.

[10] "Proven, Practical Waste Processing Systems," Buhler Miag, 1989.

[11] "Waste Processing Systems," Buhler Miag, 1989.

[12] "Economical Recycling of Refuse and Sewage Sludge," Buhler Miag.

[13] Personal communication with Luigi Castelli, Daneco, Inc. (July 1989).

[14] Correspondence from W.L. Garlin, WPF Corporation (June 22, 1989).

[15] "Solid Waste Disposal Recycling Process," WFP Corporation.

3-45

[16] "Process Description," American Bio Tech.

[17] "American Recovery Corporation: Conserving the Nation's Resources with Proven
Technology."

[18] "American Recovery Corporation: Sorain Cecchini Technology."

[19] Correspondence from John B. Nutter, American Recovery Corporation (July 6, 1989).

[20] Communication with Jack O'Brien, Ashbrook-Simon-Hartley (July 1989).

[21] "Information on the Company's Technology for Large-Scale Co-Composting of
Municipal Solid Waste and Sewage Sludge," Bedminster Bioconversion Corp.

[22] "The Cost Effective Alternative to Sludge Disposal Problems," Compost Systems Co.

[23] "The Paygro System Enclosed Dynamic Composting System," Compost Systems Co.

[24] "The Dynatherm Modular Composting System," Compost Systems Co.

[25] "Fairfield Composting Process," FaL-field Engineering Co.

[26] "Fairfield Digester System," Fairfield Engineering Co.

[27] "Fairfield Resource Recovery Process," Fairfield Engineering Co.

[28] "The Composting Specialists," International Process Systems.

[29] "ln-Vessel, Fully Controlled Composting Systems for Agricultural, Industrial, and
Municipal Organic Wastes," International Process Systems.

[30] "The Siloda Process," OTV.

[31] Mousty, P. and J. P. Levasseur, "The Silorco-Siloda Process," Resources and
Conservation. 14:309-320 (1987).

[32] "PURAC Bioreactor Composting: The ABV Systems," PURAC Co.

[33] "PURAC In Vessel Composting Systems," PURAC Co.

[34] "The Enclosed Dynamic Composting System from Royer," Royer.

[35] "The Taulman/Weiss Composting System: The Worldwide Leader for ln-Vessel
Composting Systems," Taulman/Weiss.

[36] "St. Palais, France: Sewage Sludge Accelerated Composting Plant," Harbert/Triga.

[37] "The World of Waste Treatment," Dano.

[38] Riedel Waste Disposal Systems, Inc., Company Brochure, July 1989.

3-46

3.6.2 Economics of Composting

[I] Derr, D.A., The Economics of Leaf Composting, Rutgers, State University of New

Jersey, p. 4, 1985.

[2] Goldstein, N. "Problem Solving At a First Generation Facility," Biocycle. 29(8):30-32
(September 1988).

[3] Craig, N. "Solid Waste Composting Underway in Minnesota," Biocycle. 29(7):30-33
(August 1988).

[4] Gorham, D. and R. Zer, "Portland Moves to Solid Waste Composting," Biocycle,
29(7):34-37 (August 1988).

[5] Elliott, J.C. and A.J. Polidori, "Scranton Expands Compost Facility," Biocycle.
29(i):44-48 (January 1988).

[6] Cerenzio, Peter, F., "Turnaround in Sussen County," BioCycle. 28(4):26-28 (April
1987).

[7] "Racetracks Bet on Composting," Fiocvcle. 29(3):38-39 (March 1988).

[8] Johnson, J., J.F. Donovan, and A.B. Princince, "Operating & Cost Data for In- Vessel
Composting," Biocycle. 30(4):40-43 (April 1989).

[9] Spielmann, B., "A Yard Waste Primer," Waste Age. 29(2):44-52 (February 1988).

[10] Goldstein, N., "Technology Evolution at Compost Sites, " Biocycle.
28(10):28-33 (November-December 1987).

[II] "Agripost News Construction of Compost Facility," Biocycle. 29(10):13-14

(November-December 1988).

[12] Logsdon, G., "Calculating Costs of Leaf Composting," Biocvcle. 29(9):43 (October
1988).

[13] Swift County Solid Waste Compost/Recvcling Project, prepared by Cal Recovery
Systems, Inc., for Swift County Auditor, Benson, Minnesota, March 1988,
updated November 1988.

[14] Taylor, A.C. and R.M. Kashmanian, Study and Assessment of Eight Yard Waste
Composting Programs Across the United States. Office of Policy, Planning, and
Evaluation, U.S. Environmental Protection Agency, EPA/530-SW-89-038, 1988.

[15] Benedict, A.H., et al, "Municipal Sludge Composting Technology Evaluation,
Journal WPCF. 58(2) (April 1986).

[16] El-Halwagi, M.M., et a], "Assessment of the Performance of MSW Composting
Facilities under Egyptian Conditions," Resource Conservation and Recycling
1:97-109, 1988.

[17] Taulman/Weiss, "The Taulman/Weiss Composting System: The Worldwide Leader for
In-Vessel Composting Systems."

[18] Compost Systems Company, "The Paygro System Enclosed Dynamic Composting
System."

3-47

(19] Rasper, V. and Derr, D.A., Sludge Composting and Utilization: an Economic Analysis
of the Camden Sludge Composting Facility, New Jersey Agricultural Experiment
Station, Rutgers College, New Brunswick, New Jersey.

[20] Alpert, J.E. and Johnson, P. "Cost Analysis of Static Pile Composting in the United
States," Proceedings of the International Conference on Composting of Solid
Wastes and Slurries. University of Leeds, Leeds, England, September 1983.

[21] Chertow, M.R. Garbage Solutions. National Resource Reccovey Association and U.S.
Conference of Mayors, Washington, D.C., 1989.

[22] Project Report: 1983-1986 Pilot Compost Program. East Bay Municipal Utility District,
Oakland, California, June 1987.

[23] Feasibility Evaluation of Municipal Solid Waste Composting for Santa Cruz County.
California, prepared by Cal Recovery Systems, Inc. for Santa Cruz County and
the California Waste Management Board, December 1983.

3.6.3 Marketing Compost Products

[1] de Lauzanne, R., "Methodologies a *d Technologies in Compost Production: The French
Experience," presented at the International Symposium on Compost Production
and Use, S. Michele AU'Adige (Trento), Italy, June 1989.

[2] Portland Area Compost Products Market Study, prepared by Cal Recovery Systems, Inc.
for the Metropolitan Service District, Portland, Oregon, October 1988.

[3] Mays, A., and P.M. Giordano, "Landspreading Municipal Waste Compost," BioCycle.
30(3):37-39 (March 1989).

[4] Kubota, H., adn K. Nakasaki, "State of the Art of Compost Systems: The Current
Situation adn Future Outlook in Japan," presented at the International
Symposium on Compost Production and Use, S. Michele AU'Adige (Trento),
Italy, June 1989.

[5] Shimell, Pamela, "Refuse Derived Compost Boosts Vineyard Yields," World Wastes.
26(ll):8-9 (November 1983).

[6] Levasseur, J.P., "Household Refuse Recycling in France," BioCycle. 29_(6):32-33 (July
1988).

[7] Porter, Colin, "French Farmers Favour Cordon Bleu Compost," Surveyor, pgs. 14-16
(September 1981).

[8] L'Hermite, P., "State-of-the-Art of Composts Systems: Current Situation in Europe and
Future Outlook," presented at the International Symposium on Compost
Production and Use, S. Michele AU'Adige (Trento), Italy, June 1989.

[9] Robotti, A., G. Ramonda, A. Nassisi, A. Rattotti, and A. BariUi, "Optimization of
Composting Process Utilizing Urban and Agricultural Wastes," pp. 666-675,
Compost: Production. Quality and Use. M. de Bertoldi, M.P. Ferranti, P.
L'Hermite, and F. Zucconi, eds., Elsevier AppUed Science, 1987.

[10] Dhingra, V.K., and J.P. Levasseur, "An Example of Private Venture in Household
Refuse Composting," Proceedings of the International Symposium on
Environmental Management: Environment '87. Istanbul, 1987.

3-48

[11] Sana, J., F. Giro, M. Soliva, and P. Florensa, "Approccio Metodologico Nella
Valutazione della Qualita del Compost della Catalogna, Spagna," presented at
the International Symposium on Compost Production and Use, S. Michele
All'Adige (Trento), Italy, June 1989.

[12] Naylor, L.M., G.A. Kuter, and D.J. Hagen, Shredded Magazines and Glossy Paper as a
Bulking Agent: Composting Demonstration Trial, prepared by International
Process Systems, Inc., May 1989.

[13] Spaggiari, G.C., G.L. Spigoni, R. Jodice, and M. Consiglio, "Transformation of Urban
Sludges Mixed with Grape Stalks into Organic Fertilizers," pp. 100-109,
Compost: Production, Quality and Use. M. de Bertoldi, M.P. Ferranti, P.
L'Hermite, and F. Zucconi, eds., Elsevier Applied Science, 1987.

[14] Gerrits, J.P.G., "Compost for Mushroom Production and its Subsequent Use for Soil
Improvement," pp. 431-439, Compost: Production, Quality and Use. M. de
Bertoldi, M.P. Ferranti, P. L'Hermite, and F. Zucconi, eds., Elsevier Applied
Science, 1987.

[15] Yard Waste Programs and Policies for Carver County, prepared by John and Michele
Genereux, January 1989.

[16] Composting Technologies. Costs. Programs, and Markets, prepared by Cal Recovery
Systems, Inc. for the Congress of the United States, Office of Technology
Assessment, Washington, D.C., January 1989.

[17] Goldstein, N., "Key Issures in Solid Waste Composting," BioCycIe. 29(9):29-34
(October 1988).

[18] BeznenMaschinen aus Ravensburg," Maschinenfabrik Bezner, Ravensburg, West
Germany.

[19] Hughes, E. Glynn, "Performance of Compost Plants in the Middle East," BioCycIe,
30(7):36-38 (July 1989).

[20] Levassseur, J. P., "Recycling of Household Refuse by Siloda and Silorco Processes,"
Centre Francais du Commerce Exterieur, 1985.

[21] Yard Waste Management Action Plan for San Jose. California: Final Draft Report,
prepared by John Madole Associates, March 1988.

[22] O'Brien, J.K., "Prospects for Year-Round Composting of Municipal Yard Waste,"
Resource Recovery, pgs. 26-27 (February 1989).

[23] Eggerth, L.L., L.F. Diaz, and S. Gurkewitz, "Market Analysis for Multi-Compost
Products," BioCvcle. 30(5):29-34 (May 1989).

[24] Tomer, Lars, "Marketing Possibilities for Compost."

[25] Geilinger, M., "Municipal Composting - A Practical Model," Phoenix International,
109:28-33 (February 1987).

[26] Pollack, C, "Mining Urban Wastes: The Potential for Recvcling," Worldwatch Paper
76, April 1987.

3-49

[27] Feasibility Evaluation of Municipal Solid Waste Composting for Santa Cruz County.
California, prepared by Cal Recovery Systems, Inc. for Santa Cruz County and
the California Waste Management Board, December 1983.

[28] Kuter, G., and L. Naylor,"Compost for Nursery Crops."

[29] Naylor, L. and G. Kuter, "Compost for Turfgrass and Landscaping."

[30] "Compost Markets: California DOT Says More Study Needed Before Use," Waste Age.

20(3): 195 (March 1989).
[31] Salimando, J., "Woodhue Compost ... or Wouldn't You?" Waste Age. 20(5):63-66 (May

1989).

[32] Chertow, M.R., Garbage Solutions: A Public Official's Guide to Recycling and
Alternative Solid Waste Management Technologies. 1989.

[33] Baccini, P., and P.H. Brunner, "Sortierung in der Abfallwirtschaft: Wie gross ist ihr
Beitrag zu einem ressourcenschonenden und umweltvertraglichen Stoffhaushalt9"
Gas. Wasser. Abwasser. 68(1 1):617-622 (1988).

[34] Mayer, M., H. Hofer, and U. Maire, "Trends in Yard Waste Composting," BioCvcle
29(6):60-62, (July 1988). '

[35] Roosmalen, G.R., and J.C. van de Langeerijt, "Green Waste Composting in the
Netherlands," BioCvcle. 30(7):32-35 (July 1989).

[36] Golueke, C.G., and L.F. Diaz, "Quality Control and Waste Management," BioCvcle
30(7):65-67 (July 1989).

[37] Funke, U., "Marketing Problems," presented at the International Symposium on
Compost Production and Use, S. Michele All'Adige (Trento), Italy, June 1989.

[38] Funke, U., "Economics from Household to Compost Through a Complete System in the
Federal Republic of Germany," presented at the International Symposium on
Compost Production and Use, S. Michele All'Adige (Trento), Italy, June 1989.

[39] Stegmann, R., and U. Krogmann, "Composting of the Organic Fraction of
Municipal Solid Wastes Separated Through Selected Collection," pre-
sented at the International Symposium on Compost Production and Use,
S. Michele All'Adige (Trento), Italy, June 1989.

[40] Krauss, P., R. Blessing, and U. Korherr, "Heavy Metals in Compost from Municipal
Refuse: Strategies to Reduce Their Content to Acceptable Levels," pp. 254-265,
Compost: Production, Quality and Use. M. de Bertoldi, M.P. Ferranti, P.'
L'Hermite, and F. Zucconi, eds., Elsevier Applied Science, 1987.

[41] Kapetanios, E., M. Lodzidou, and E. Matiou, "Heavy Metal Levels and Their Toxicity
in Composts from Athens Household Refuse," Environmental Technology
Letters. 9:799-802 (1988).

[42] Oosthock.J., and J.P.N. Smit, "Future of Composting in the Netherlands," BioCvcle
28(6):37-39 (July 1987). *—'

[43] Lustenhauwer, H.W.A., et al, "Source Separation and Collection of Compostables "
BioCvcle. 28(6):33-36 (July 1987).

3-50

[44] Peterson, C, and A. Perlmutter, "Composting in the Soviet Union," BioCycle.
3_0(7):74-75 (July 1989).

[45] Albrecht, R., "How to Succeed in Compost Marketing," BioCycle 28(8):26-27
(September 1987).

[46] Logsdon, G., "A Business-Like Approach to Leaf Composting," BioCycle. 3JX3):22-24,
(March 1989;.

[47] Walter, Scott, "Is There a Market for Compost?"

[48] "Options for Municipal Leaf Composting," BioCvcle. 29(9):38-43 (October 1988).

[49] Meade, K., "Waiting for the Leaves to Fall," Waste Alternatives/The Disposal Crisis.

[50] Personal communication with M. Olson, U.S. Waste Recovery (May 1989).

[51] "Refuse Hygienization Plant for Liezen: Solution Towards a Clean Future,"
Voest- Alpine AG, Austria.

[52] Goldstein, N., "Compost for Sale," 3ioCycle. 28(8):25 (September 1987).

[53] Bergeron, AT., "Recycling Plant Materials," BioCvcle. 29(2):29 (February 1988).

[54] Gertman, R., "Davis Waste Removal Compoany Compost Program."

4.0 EVALUATION OF REPRESENTATIVE NORTH AMERICAN FACILITIES

4.1 Operating and Proposed Composting Facilities in Canada

Several communities in Canada are investigating the feasibility of municipal composting
programs. A few municipalities have implemented leaf composting programs and back yard
composting programs and two Canadian municipalities have programs to handle household
organic wastes at a centralized facility. A brief summary of some of the existing and proposed
composting activities is outlined below.

4.1.1 Municipal Programs

Rilev. Alberta

The community of Riley started a composting project in June 1989. Residents are provided
with a small garbage can to collect household organics and a large can to collect outdoor
organic yard wastes. Approximately 95% of the households in Riley participate and are
currently diverting about 100 tonnes per year from the landfill.

Amos. Quebec

This facility has been operating since the Fall of 1988. The mixed municipal waste is hand
sorted for recyclable material. The organics are composted in windrows. The facility has a
capacity of 3600 tonnes per year.

Rawdon, Quebec

A composting and recycling plant will be operational in Rawdon in October 1989. The plant
will serve four communities and have a capacity of 30,000 tonnes per year. The plant will
cost approximately $ 3 million. The processing includes manual recovery of paper, plastic and
glass followed by magnetic separation for ferrous metal. The remaining residue will be
composted in two funnel reactors. Septic sludge may be added to the process.

Essex-Windsor. Ontario

Essex-Windsor plans on developing a composting program that will potentially accept
residential food and yard waste, industrial/commercial organic waste and sewage sludge. The
initial processing facility will have a capacity of at least 50 tonnes per day and provisions for
expansion to at least 100 tonnes per day. A modified windrow system will be used to process
the compost.

City of Windsor. Ontario

The City of Windsor is composting approximately 20,000 tonnes per year of municipal sewage
sludge. The sludge is mixed with wood chips and shredded rubber tires as bulking agents.

The sludge is composted using the forced aeration static pile method for 30 to 40 days. It is
then screened and cured in another forced air static pile.

Most of the compost is used by the City's Parks Department. Some is sold to greenhouses.

Metro Toronto. Ontario

Metro Toronto is selling 12,000 backyard composting units to interested residents at a quarter
of the actual cost of the unit. Metro believes that the household composting program will pay
for itself in five years by avoided collection and disposal costs.

4-2

Metro Toronto will also be starting a pilot project to collect organic yard wastes from the curb.
The pilot will include 10,000 households and 30,000 tonnes of organic wastes are expected to
be diverted. Participating households will be given clear, non-biodegradable plastic bags for
the collection of glass clippings, hedge clippings and other miscellaneous organic yard wastes.
Residents will be asked to bundle brush separately. Collected yard wastes may be composted
at existing leaf composting facilities if the Certificates of Approval can be amended.

Recommendations from a preliminary study on European composting systems will be presented
to Metro Toronto in September 1989. A 190 tonnes/day composting facility may be built to
handle commercial organic wastes. Waste sources may be supermarkets, restaurants and food
processors.

City of Peterborough. Ontario

The City of Peterborough is interested in implementing a composting program. The City has
not yet determined what program type or strategy will be used. A system study will be carried
out in 1988-1989.

Region of Halton. Ontario

Halton is encouraging its residents to compost their organics in the backyard. The Region
provides information on how to build rr where to buy composter bins. The Region is
interested in implementing a wet/dry collection process and may start a pilot program in the
fall of 1989. Program specifics have yet to be finalized.

Hamilton-Wentworth. Ontario

A 30,000 tonnes/year facility will be built adjacent to a solid waste transfer station. Organics
will be screened from the mixed waste stream using mechanical and hand sorting. The
organics will be composted with sewage sludge from a nearby waste water treatment plant in a
high rate vessel system. The Region is hoping to go to tender for the facility in the Fall of
1989.

City of Guelph. Ontario

A wet/dry recycling pilot program will commence in August 1989. The pilot study is expected
to last two years. The study area will be divided into three groups:

Group A

Group B
Group C

wet waste in green bin

recyclable dry waste in blue bin

non-compostable and non-recyclable waste in regular garbage bags

wet waste in green bin

recyclable and non-recyclable dry waste in regular garbage bags

wet waste in green bin

recyclable and non-recyclable dry waste in blue bin

The wet waste will be composted at a pilot plant. University of Guelph faculty members will
assist the City by running field trials and tests on the compost.

Region of Peel. Ontario

The Region of Peel will be commencing a composting pilot project once they receive a
Certificate of Approval from the MOE. A study area of 1,206 homes has been selected. The
area will be divided into three groups with different containers to bring the organics to the
curbside.

4-3

• Group 1 will be provided with a 17 gallon "Rubbermaid" curbside container,

• Group 2 will be provided with a 10 gallon "Rubbermaid" curbside container, and

• Group 3 will be provided with a poly-tie plastic bag.

Each household will be provided with a "Kitchen Catcher" container and green "Kitchen
Catcher" bags. Once the bags are full they will be placed in the large curbside container. All
yard waste will go in the large curbside container. If the curbside container is filled, additional
poly-tie bags will be provided.

The organic wastes from the pilot project will be composted by Grow Rich Fertilizers Ltd. (See
4.1.2 below).

4.1.2 Private Sector Composting Initiatives in Ontario

Several private sector companies in Ontario are planning to develop composting systems.
Some private sector initiatives are briefly outlined below.

WCI Waste Conversion Inc.

WCI Waste Conversion Inc. are planning to construct a composting facility at their Waste
Wood Recycling plant in Brampton, Ontario. The company is also the designer of the
Hamilton-Wentworth Regional compostine facility recently partially funded by the Ontario
Ministry of the Environment. The latter facility will be a 30,000 tonnes/year high-rate aerobic
composting facility incorporating the WCI channel system.

Grow-Rich Fertilizers Ltd.

Grow-Rich is presently operating a 70,000 tonnes/year composting facility in the Niagara
Region. Grow-Rich accepts organic papermill sludges and wastes from local industries and sells
the compost to garden centres, landscapes, land reclamation projects and greenhouses. Grow-
Rich is assisting the Region of Peel with a municipal organic waste composting pilot project.
Grow-Rich offers turn-key systems to industry for the composting of their wastes and markets
the product for its own account.

Philip Environmental

Philip Environmental in Hamilton, Ontario is experimenting with high rate-high volume
composting systems using an aerated agitated bed. They plan on providing municipalities and
industries with rum key, privately operated or owner operated facilities.

Loamcrafters Inc.

Loamcrafters Inc. is a new Toronto-based company that has recently been formed to
commercially compost sludges and yard wastes.

4.2 United States

4.2.1 Introduction

The formidable combination of a shortage of land available for landfilling, dramatic raises in
tipping fees, and the imposition of increasingly restrictive legislative measures has led to a
revival of composting as a viable alternative for waste management in the United States. Com-
posting is currently utilized in the U.S. to process MSW, sewage sludge, yard debris, and other
organic wastes.

4-4

Composting was given consideration as a solid waste treatment process in the U.S. as early as
the 1950s. However, a number of factors in the late 1960s combined to discourage the
prospects for composting MSW: 1) the high carbon-to-nitrogen ratio of mixed refuse in the
U.S.; 2) an absense of a market; and 3) the low cost of landfilling.

A rekindling of interest in composting arose in the early 1970s as a method to dispose of
sewage sludge. It was not until the end of the 1970s and the beginning of the 1980s that
composting again began to be seriously considered as a viable option in the U.S. for the
management and disposal of municipal solid waste. At the present time, however, composting
and co-composting of MSW and sludge are receiving considerable attention. This is attested
by the fact that as of this writing, five full-scale MSW composting facilities are in operation,
and at least thirty facilities are in the construction, planning, or negotiation stages.

The desperate shortage of landfill capacity has prompted a closer scrutiny of all residues
coming to the landfill" site and of their suitability to composting. It was soon realized that yard
and garden debris are very amenable to composting. As a result, hundreds of facilities to
compost these wastes have become operational in the U.S. [1].

4.2.2 Sewage Sludge

Composting as a sludge management and disposal option received little anention until the early
1970s. By that time, waste generation tad accelerated at a rate such that available landfill
space was 'shrinking at an alarming rate. Moreover, a mounting concern about environmental
quality and public health began to be manifested by tighter restrictions on all aspects of
landfilling. Regulations regarding landfill disposal of sewage sludge were made even more
stringent than for municipal solid waste.

The combination of land shortage and environmental and public health concerns prompted a
serious exploration of options other than landfill for the disposal of sludge. Although at first,
incineration seemed to be an attractive option, later developments brought to light serious
problems, not the least of which are the very high costs involved. In addition, the solid and
gaseous emissions from sludge incineration require careful and expensive control measures.
Consequently, composting began to appear increasingly attractive in terms of the environment,
public health, and economics.

The spread of composting as a sludge management practice began primarily in the northeastern
pan of the U.S. The number of operational sludge composting plants has risen dramatically
during the years 1983 through 1988, from 61 to 115 [2].

4.2.2.1 Systems, Numbers, and Status

The types of sewage sludge composting facilities in operation in 1988 are listed in Table 4.1.
According to the table, the static pile technology is the most widely represented, with 61
operational facilities.

The number of facilities using the mrned-windrow technology is less than one-half that of
facilities using the static pile system, i.e.. 29 as compared to 61. The in-vessel approach ranks
third in terms of number" of facilities with 19.The extent of sludge composting practice in the
U.S. in 1988 is indicated by the data listed in Table 4-2. According to the data, the number of
facilities in operation at that time exceeded the total number of those in the pre-operational
stages, i.e., 115 operational vs. 104 pre-operational. If all of the facilities in pre-operational
stages were to progress to the operational stage, the total number of active facilities would be
219. Even so, the amount of sludge being landfilled would substantially surpass the amount
subjected to composting.

4-5

TABLE 4-1

Types of Operational Sewage Sludge Composting
Facilities in the U.S. as of 1988 [1]

Type Number

Aerated static pile 61

Turned windrow 29

In-vessel 19

Aerated windrow 5

Vermi composting 1

Total 115

4-6

TABLE 4-2

Status of Sewage Sludge Composting Projects
in the U.S. as of 1988 [1]

Number of
Status Projects

Operational 115

Pilot 14

Under construction 14

Planning, design 40

Consideration _36

Total 219

4-7

The smaller number of in-vessel facilities presently in operation may be explained by cost
factors and some operational difficulties. However, the number of in-vessel facilities in the
consideration, planning, and design stage is greater than that of any of the other systems.
Among the reasons offered for the apparent preference for in-vessel systems are: 1) site
constraints; 2) expected satisfactory process and odour control; and 3) projected lower labour
costs. However, the validity of these reasons is as yet to be conclusively demonstrated since
operators of in-vessel systems have experienced problems with odors as well as mechanical
breakdowns.

As for experience with turned windrow systems, it too has not been free from odour and
operational difficulties. These difficulties have been attributed to climatic factors (e.g.,
excessive rainfall, snow, and freezing temperatures). Some facilities have placed most of their
operation in enclosed structures in order to alleviate the problems resulting from inclement
climate. Problems involving the release and control of unpleasant odors are common to both
in-vessel and windrow systems.

4.2.2.2 Odours

A major problem confronting the sludge composting industry today is generation and escape of
foul odours. It also is the most difficult to solve or at least, to control. Consequently, many
research and development programs aimed at finding effective ways of controlling odours have
been proposed and conducted. Because it was felt that the causes of foul odours generation are
well known, the approaches investigated in the programs were designed to contend with the
odours rather than to prevent their generation. An unfortunate result has been that insufficient
attention is directed to the prevention of the generation of malodors through appropriate process
control. Among the odour treatment approaches that have been investigated are wet scrubbing,
use of biological filters, and the addition of lime.

4.2.2.3 Future

Unlike the unsuccessful ventures in composting MSW in the late 1950s and early 1960s,
composting has developed into a sound and cost-effective method of treating municipal sewage
sludges. Nevertheless, for the success to continue into the 1990s, two, or possibly three,
obstacles must be overcome. The first of the obstacles is mostly associated with the degree of
development of the industry as a whole, in that capacities for some systems as yet are not well
defined. The second obstacle relates to certain shortcomings in the quality of the sewage
sludge compost product. For example, the pervading variability of physical characteristics, of
moisture content, and of concentrations of nutrient chemicals constitutes an impediment to
many agricultural applications and to marketing the product in general. However, a potential
obstacle much more serious than the preceding two is the presence of hazardous substances
(heavy metals and toxic organic compounds) in the product. Fortunately, this obstacle applies
mostly to the composts produced by wastewater treatment plants that combine the treatment of
industrial and residential sewage. Since industrial sewage contributes the greatest share of the
hazardous substances, a potential solution to this obstacle is to pretreat industrial wastewaters
that contain toxic compounds prior to discharge. By instituting source prevention, the
quantities of toxic substances entering the waste stream can be significantly reduced.

A fairly recent development is the search for substances that can satisfactorily replace wood
chips and sawdust as bulking agents. The search is prompted in pan by the rising cost and
frequent unavailability of the two wood wastes. Among the materials that have been used are
shredded tires, plastics, yard debris, and certain field crop residues.

4-8

4.2.2.4 Summary

Composting of sewage sludge in the U.S. did not become popular until the early 1970s. The popularity
was brought about by the increased production of sludge, combined with the increased costs of
alternative disposal methods. Implementation of sludge composting projects was accelerated by the
stringent regulations controlling landfill disposal of sewage sludge. The number of sludge composting
facilities nearly doubled between 1983 and 1988 (i.e., from 61 to 115).

The majority of the composting facilities use windrows, particularly the static type. It is expected
that the number of in-vessel systems will increase in the next few years. This is attributed to the
concern about odors and area requirements.

One of the most serious problems facing the sludge composting industry is odor containment and
control. In addition, in-vessel facilities have had a number of materials handling problems.

Most sewage sludge composting facilities use sawdust or wood chips as bulking agents. However, due
to the cost of the forest products, facility operators have been actively searching for materials that can
be substituted for them. Some of these materials include shredded tires, plastics, yard debris, and the
organic fraction of MSW.

Sewage sludge composting is not widely practiced in the countries that were surveyed. The main
exception is Japan where it has been reported that there are 31 plants in operation. Regulations
imposed on landfilling and land application are expected to increase the number of sewage sludge
composting plants.

4.2.3 Municipal Solid Waste

Circumstances that in the 1970s served as an impetus to sewage sludge composting and led to its
eventual widespread application are now combining to do the same for the organic fraction of MSW.
As had been the case with sewage sludge disposal, in the 1980s, landfill shortages, high disposal fees,
and legislative prohibitions regarding the disposal of unprocessed MSW on the land are increasing the
attractiveness of the composting option. The option is made even more attractive by the availability
of financial assistance programs in some states (e.g., Massachussells, Minnesota, and Iowa). Recently,
several states have passed legislation regarding alternatives for managing solid wastes. Typically, the
laws establish a hierarchy of alternatives in which recycling, composting, and reduction in waste
generation are at the top, and incineration and landfilling are at the bottom. Finally, the U.S.
Environmental Protection Agency recently proposed new regulations for landfills that certainly would
increase the monetary cost of land disposal, thereby enhancing the appeal of composting.
The current high level of interest in MSW composting is not without its dangers. In some cases, the
process is being chosen without having conducted an adequate analysis of alternatives or having
considered certain problems and costs that come with composting MSW.

The problems and costs mentioned in the preceding paragraph are due to the fact that composting
municipal solid wastes is a complex undertaking. The degree of the complexity depends upon the level
and type of separation that must be carried out at the facility. Because of the amounts of material
involved and sharp time limitations, separation at the facility is almost invariably done mechanically.
The problem is that, of the several steps in the processing of MSW to form a feedstock for compost-
ing, mechanical separation poses the highest challenge. Finally, it is again emphasized that the quality
of the finished product is largely dependent upon the type, efficiency, and thoroughness of the
separation process [3,4].

4-9

4.2.3.1 Facilities in Operation

As of 1988, there were five MSW compost facilities in operation in the U.S. (see Table 4-3).
As the data indicate, capacities represented by the facilities range from about 13 to
900 tonnes/day. Other than the plant in Wilmington, Delaware, the composting facilities are
relatively small and simple, and began operation within the past three years.

Judging from personal observations and information obtained in discussions with designers and
operators existing compost facilities in the U.S. generally are characterized by a relatively low
capital investment, limited throughput, and an over-simplifieti design (see Section 3.4 on
economics of composting). The composting phase is emphasized, whereas the attention
directed to the segregation of organic from inorganic matter is less than would be desirable.
Similarly, the use of finished product is not receiving the attention it warrants.

Wilmington. Delaware

The Wilmington plant is designed to process about 900 tonnes of municipal and commercial
solid waste per day. Processing includes size reduction, air classification, magnetic separation,
and screening to recover metals and glass and to produce a refuse-derived fuel (RDF). In
addition to the recovery and the RDF production, the process also generates about 227 tonnes
of highly organic residue. The residue is mixed with an equal amount of sewage sludge (total
solids about 20%) and is then deposited into one of four reactors. Each of the reactors has a
capacity of 159 tonnes. The material is held in the reactor for about five days, dunng which
time it is mixed and aerated.

Analysis of the compost produced by the plant, indicated that the product had concentrations of
PCBs in the range of 4 to 5 ppm. Such concentrations ruled out the original plan to market
the product as poultry litter. Current plans are to market the product for use in horticulture.

Sumter County. Florida

A windrow composting operation located in Sumter County has been on-line since mid-1988.
Operators of the facility state that 65 to 70 tons of residential and commercial wastes are
received each day. Treatment is begun by passing the wastes through a flail designed to break
open bags and packages, thereby allowing their contents to mingle with the waste stream. The
waste stream is then subjected to magnetic separation to remove ferrous metals. Aluminum
and some inerts are removed manually. The waste stream is then size-reduced to an
approximate 5 x 5 cm. particle size and transferred via trucks to the windrow area. It is then
stacked to form a 1.8 m high by 3 m wide windrow. A bacterial implant is added. Operators
indicate that the compost is ready to be marketed after six weeks.

As of May 1989, no finished compost had been marketed. According to the operators of the
facility [5], they are planning to sell the material to nurseries and soil amendment dealers.
However, marketing efforts are being delayed until state guidelines for compost are finalized by
the Florida Department of Environmental Regulation.

4-10

TABLE 4-3
MSW Composting Facilities in Operation in the U.S. as of 1988

Location

Capacity
(tonnes/day)

Years
Established

Type of System

Material Added

Markets

Fillmore Co.,
Minnesota

13 to 18

1987

Windrow

None

Portage,
Wisconsin

27

1986

In-vessel/drum

Sewage sludge

None

St. Cloud,

Minnesota

45

1988

In-vessel/drum

Sewage siudge

None

Sumter Co.,
Florida

59 to 64

1988

Windrow

--

None

Wilmington,
Delaware

900

1984

In-vessel/silo

Sewage sludge

None

This facility was designed to process about 900 tonnes/day of MSW to recover RDF, glass and
metals. An organic residue is mixed with sludge and composted in an in-vessel system.

4-11

Other Operational Facilities

Very little detailed information is available on the quantity or quality of the finished compost
produced at the other three operational facilities. Moreover, their output of compost product
has not been large enough to permit a long-term definition of the market for their respective
products. The insufficient and sporadic production are explained by the fact that the facilities
are in the testing and permitting stages.

4.2.3.2 Future Potential

The potential for implementing MSW composting facilities in North America appears to be
bright Composting is a particularly important alternative because it can easily be integrated
with other material-recycling schemes and even with incineration. In addition, the possibility
of using the refuse as a bulking agent for composting sewage sludge increases the potential
considerably.

Before composting's bright future can be attained, a few obstacles must be removed. Among
these obstacles is the present unavailability of MSW compost product in quantities sufficiently
large to permit market evaluation and uevelopment. Another and serious obstacle is the rela-
tively poor quality of the product to date. And lastly, reliability of the mechanical equipment
must be improved.

4.2.3.3 Summary

The combination of high disposal fees, landfill shortages, and regulatory measures prohibiting
the disposal of unprocessed MSW have increased the viability of composting as an option to
manage MSW.

As of mid- 1989, there are five full-scale MSW composting facilities in the U.S. Four of the
facilities are relatively small and began operation after 1 986. Only two of the plants (St. Cloud
and Wilmington) were built by established vendors. With the exception of the processing plant
in Wilminton, the other facilities process the entire waste stream. In general, limited information
is available on the quantity of compost that is produced in each facility. Furthermore, the results
of tests on the quality of the finished product are not readily available. It is apparent that these
facilities have not been able to market the compost.

Since the majority of vendors have not built any MSW composting systems in the U.S., the
following observations are based on the authors' experience. System vendors can be divided
into those that offer equipment as well as operation and maintenance of the facility, and those
that only offer equipment as well as operation and maintenance of the facility, and those hat
only offer equipment. Some of the vendors such as Buhler-Miag and Dano have built several
composting plants throughout the world However, little information is available on the
performance of the plants and the marke lability of the compost.

Composting in other countries has been practiced for several years. Composting of MSW has
been carried out in European countries at dilicrent rates. France, Germany, Italy, and Switzerland
have been composting MSW with mixed success. Regulations controlling the use of MSW
compost are such that the material cannot be beneficially used, particularly when the compost is
made from mixed MSW. Thus, the current trend is to institute source separation and only
compost the organic fraction. The largest fraction of the compost produced in Europe is used
in large-scale agriculture (mushroom, farming, and viticulture).

4-12

4.2.4 Co-Composting

Co-composting is discussed at some length in Section 2, "Generic Composting Description."
However, at this point, a few additional comments are mentioned, particularly with regard to
the use of MSW as a bulking agent:

• Undesirable effects due to the shortcomings of raw refuse can be satisfactorily reduced
or even be avoided through a combination of: careful pre-processing, avoidance of
high moisture content, and application of suitable mixing and aeration procedures.

• Regarding the relative economics of using wood chips as a bulking agent and those of
using processed MSW, the appreciable monetary credits that would accrue from the use
of MSW should be taken into account.

• Not to be overlooked is the possible sale of the co-compost product, and the utility of
the product in soil reclamation and agriculture.

On the basis of this cursory comparison, one might conclude that in the future, the substitution
of processed refuse for wood chips could be economically justified [6].

4.2.4.1 Co-Composting Facilities

As of early 1989, only three of the existing operational MSW composting facilities were
practising co-composting: Wilmington, Delaware, St. Cloud, Minnesota and Portage,
Wisconsin. Eleven MSW/sludge co-composting facilities were in the consideration and design
stages. In addition, four facilities for co-composting sludge and yard wastes were in the
consideration and design stages.

Although co-composting is being done at the Wilmington plant, only a fraction of the MSW is
involved. The greater portion of the MSW is processed into refuse-derived fuel. The highly
organic residue from the RDF processing is composted with sludge. However, all of the
organic fraction of the MSW is co-composted at the Portage, Wisconsin, plant.

Although the composting of yard and garden debris and similar residues is a practice of
long-standing, it was not until this decade that it attained its present prominence. This
prominence is attested by the impressive number of active yard waste and leaf composting
facilities throughout the U.S. Moreover, there are ample reasons for expecting that within a
few years, many additional facilities will be in operation.

The following four factors are especially responsible for the popularity: 1) The waste is easily
composted. 2) The required technology is minimal. 3) Thus far, regulatory requirements are
not demanding. 4) Recovery and utilization of yard waste are simple, yet highly cost-effective
means of diverting the waste from disposal facilities.

Quantities of yard waste vary from region to region. The size of the contribution of the waste
to a community's waste stream is not insignificant. Results obtained in waste characterization
studies indicate that yard waste may comprise from 5% to 30% (by weight) of the municipal
solid waste stream. The size of the contribution is a function of season and geographic area.
Typically, the output of grass and yard waste is greatest from late spring until mid-autumn. On
the other hand, most (about 70%) of the annual output of leaves is collected in the autumn.
This can be a burden on the collection and disposal system. It should be noted that although
grass and leaves are both constituents of yard waste, they often are handled separately.

4-13

The relative ease with which yard waste can be diverted from the landfill has prompted
hundreds of municipalities to establish yard waste utilization programs. The movement is
encouraged by legislative measures, some of which ban the disposal of yard waste in landfills.
For example, in 1988, the State of New Jersey banned the disposal of leaves in landfills.
Minnesota, Wisconsin, and Illinois have passed similar legislation.

Table 4-4 lists current and projected North American municipal yard and garden composting
facilities.

4.2.5.1 Collection Strategies

To take full advantage of the basically organic nature of yard waste, it should be collected in a
manner such that it remains free of objectionable contaminants. The establishment of drop-off
sites and the institution of curbside collection are two effective strategies for avoiding such
contamination.

Use of a drop-off site is the simplest and least expensive means of collecting yard debris. The
drop-off site approach involves the placement of large containers in which the general public
can deposit its yard waste in one or more strategic locations. The approach has an important
drawback in that it relies upon the public to segregate the material as well as to transport it to
the drop-off site. Thus far, experience with the approach has been characterized by a relatively
low level of participation.

Several methods are available for curbside collection of yard debris. With all methods, the first
and principal step required of the individual resident is that he or she segregate the yard waste
and move it to a designated collection point. With one collection option, the waste is simply
piled by the curb to await collection. The collection can be done either manually or
mechanically. Another option calls for the resident to store the yard waste in a container for
later collection. The container may be a can, box, or bag. The type of bag (i.e., plastic, paper,
or biodegradable plastic) used by the resident exerts an impact on the remainder of the
processing steps.

The collection of leaves from deciduous trees is a task of monumental proportions in some
parts of the country. Because of the large quantities involved, collection and processing
systems are established specifically for leaves. One such system consists in the use of vacuum
trucks, although the cost these systems can be high (i.e., more than $ 88/tonne).

4.2.5.2 Compost Systems for Leaves

A very simple system for composting leaves is simply to stack them and then allow sufficient
time for decomposition to take place. The retention time with such an approach may be as
long as 18 months or more. The occasional emission of objectionable odours is inevitable
during the first few months. This approach may be adequate where sufficient land is available.
In situations in which unpleasant odours would not be tolerated, a more sophisticated approach
may be required. This would involve processing the leaves using either the turned windrow or
static pile technology. In essence, use of the both systems involves stacking the leaves in piles
or windrows. With the turned windrow system, aeration is done by periodically turning the
material. With the static pile, aeration is done by means of blowers. Moisture content and
other parameters are suitably controlled. If either of the two systems is properly applied, the
required detention time is a matter of weeks. The process can be expedited by adding a source
of nitrogen. The two technologies are described in more detail in Section 2 and in the
following subsection.

4-14

TABLE 4-4
Examples of Communities in Canada Composting Yard and Garden Waste

Durham, Ontario

Essex- Windsor, Ontario

Guelph, Ontario

Metro-Toronto, Ontario

City of Toronto, Ontario

Ottawa, Ontario

Peel Region, Ontario

Peterborough, Ontario - Planning Stage

Waterloo, Ontario

Riley, Alberta

Halifax, N.S. - Planning Stage

Cap Rouge, Quebec

Urban Community of Montreal, Quebec - Planning Stage

Urban Community of Quebec City, Quebec - Planning Stage

Region of Quebec (City), Quebec

He d'Orleans, Quebec - Planning Stage

Verdun, Quebec

Kirkland, Quebec

Sherbrooke, Quebec - Planning Stage

Communities in U.S. Composting Yard and Garden Waste

Brookhaven, N.Y.
Davis, CA

Mecklenburg County, NC
Midland, Mich.
Milwaukee, Wise.
Modesto, CA
Montclair, NJ
Palo Alto, CA
San Jose, CA
Scarsdale, N.Y.
Tenafly, NS
Urbana, II
Wellesley, NJ
West Caldwell, NJ
Westfield, NJ

4-15

4.2.5.3 Compost Systems for Yard Wastes

Composting mixed yard waste is a complex undertaking. Consequently, it is unfortunate that
some communities choose to follow a very low-technology approach. With such an approach,
the material merely is stacked in piles as high as 3 to 6 m, and are allowed to remain
undisturbed for period as long as 18 months or even longer. Almost inevitably this minimal
approach leads to the development of nuisances, and during the dry season may result in a fire
hazard.

In the paragraphs that follow are described compost systems that are appropriate for yard
waste. Although the systems were described generically in Section 2, they are again described
in this section, but in terms more specific to yard waste.

Turned Windrow and Static Pile

The turned windrow and the static pile are the systems most commonly used for composting
yard debris. Aeration is accomplished by mechanical turning, by forced aeration, or by a
combination of the two. Experience with the use of static pile system for composting yard
waste has not been favourable. When used for composting yard waste, the static pile system
can lead to an excessive drying and cooling of the composting mass, especially when tree
trimmings and dried vegetation (leaves, stiaw) constitute a large fraction of the waste material.
Ultimately, the excessive drying and cooling are due to the very porous nature of the wastes.
The extensive porosity permits relatively unimpeded movement of air and diminishes the
moisture retention capacity of the windrowed mass.

Equipment

It is essential to the success of a yard waste compost undertaking that a shredder or grinder be
available that has the capacity to process the input intended for it. Despite the fact that this
requirement seems to be obvious, lack of a shredder (or possession of an inadequate shredder)
has been and is one of the more frequently encountered problems in yard debris compost
projects.

To have an adequate capacity, the shredder must be able to size reduce fairly large branches
and brush, as well as twigs, tree primings, and other woody material to a particle size small
enough to permit easy manipulation and to promote biological breakdown. In addition, the
shredder should be sufficiently rugged to contend with occasional foreign objects such as rocks,
bricks, and pieces of metal. If the shredder is inadequate, branches and other woody debris can
accumulate at the site. This accumulation eventually can reach unmanageable proportions,
become unsightly, and may even become a serious fire hazard.

With small operations, turning can be done satisfactorily with the use of a front-end loader or a
bulldozer equipped with a standard blade. A mechanical turner specifically designed for the
task would be necessary for large operations [7].

Moisture Content

The importance of maintaining the moisture content of the composting mass at a satisfactory
level is often overlooked, usually because the water source is either inconveniently accessible
or absent entirely. Even though extending a water line to the composting site may be costly,
effective composting is impossible without water. A possible, but doubtfully acceptable,
solution that might be tried if sufficient space is available, is to allow the piles to remain
undisturbed until the rainy season comes. At that time, the compost program could be begun.

4-16

Product

The compost product is an excellent soil amendment and partial source of fertilizer elements,
providing the yard waste had been maintained free of objectionable contaminants. After
subjection to suitable screening, the product could be used for all landscaping activities.

4.2.5.4 Summary

The popularity of yard debris composting has increased substantially during the last few years.
The main reasons for the popularity arc: 1) the high costs of landfilling; and 2) the simplicity
of composting. The number of composting facilities has grown from just a few to literally
hundreds. This growth can also be attributed to legislative measures which prohibit the
disposal of yard debris in landfills.

Processes generally involve size reduction and screening. The system most commonly used for
composting yard debris is the open windrow. Both turned and static pile systems are used.
Unfortunately, despite the fact that size reduction, aeration, and moisture control are essential to
proper composting, a number of projects ignore these requirements. This has led to long
composting times, the generation of nuisances, and even spontaneous combustion of the
material during the dry summer months.

4.2.6 General Summary and Conclusions

At present in North America, composting seems to have a good position as a method of waste
management. The number of projects for composting sewage sludge has grown substantially
since the 1970s. Despite the occurrence of some potentially serious problems in recent years
regarding heavy metal and toxic organic compound contaminants, the favourable trend probably
will continue for the next few years.

Composting yard waste has certainly become very popular, as is evidenced by the tremendous
increase in number of undertakings involving the composting of leaves and yard waste in
general. A major drawback is the prevalence of the tendency to oversimplify. This tendency
begins with design and continues through operation. Often, the tendency develops to a point at
which management becomes non-existent. The oversimplification all too often is responsible
for the generation of nuisances, fires, and production of a low quality compost. Nevertheless,
the composting of yard debris will continue to be used as a means of diverting wastes from the
landfill. This is particularly true in Ontario where a high level of government funding support
and public enthusiasm prevails.

The composting of MSW will also continue to grow in the U.S., but probably not at a rate
equal to that of yard debris. Major difficulties facing MSW composting include: 1) lack of
basic design data; 2) absence of standards for the finished product; 3) insufficient experience
on the part of most designers, vendors, and clients; and 4) overly optimistic expectations
regarding markets and uses for the compost product [4,7,8].

Currently composting seems to have considerable public support and a good position as a waste
management alternative. At present, there are hundreds of composting facilities throughout the
world. The largest number of plants seems to be concentrated in the U.S. Similarly, there are
several vendors offering various designs for treating organic residues through composting. It is
extremely difficult to conduct a critical evaluation of each of these facilities by merely relying
on information in the open literature. It is possible, however, to indicate some general
advantages and disadvantages based on both the literature and the authors' observations.

4-17

Municipal Solid Waste

As of mid-1989, there were five MSW composting plants in the U.S. Only two of the plants
were built by established vendors, i.e., Fairfield and Eweson. Unfortunately, the facility using
the Fairfield unit only composts a fraction of the waste stream (rejects from RDF production).
The Eweson plant, in St. Cloud, Minnesota, seems to be working adequately, although limited
information is available on the quality of finished product.

Two of the other facilities (in Fillmore County, Minnesota and Sumter County, Florida) were
designed specifically to meet the needs of the locale. Both designs incorporate manual separation.
The Fillmore plant uses handpicking before size reduction. The Sumter plant uses manual
separation after flailing. The facility in Portage does not rely on any type of separation prior to
composting. These plants are all characterized by a relatively low throughput. The plants seem
to still need to pay attention to the quality of the finished product. All facilities are making a
concerted effort to evaluate and acquire equipment to process the finished compost. Types of
equipment that have been evaluated include size reduction, screening, and air classification.

As of mid- 1989, none of the facilities were selling their compost. Their inability to sell the
compost was due to a combination of quality and absence of regulations applicable to compost
from MSW.

Sludge

Sludge composting has grown substantially during the past few years. Currently windrow
composting seems to be the most popular alterative. In-vessel composting is expected to increase
in popularity. This is attributed to land requirements and containment of odors.

Most of the plants using windrows are operating satisfactorily. Most of them use some type of
wood waste as a bulking agent. However, the price of the bulking agent is forcing some
facilities to seek other materials. The main problem facing some of these plants deals with odor
control. Some plants have had to completely enclose the composting areas.

There are several designs of in-vessel systems. They vary in shape and in orientation. Most
of the plants seem to be meeting the U.S. EPA's time-temperature requirement. The majority
use sawdust as a bulking agent. Several of the facilities initially had difficulties in marketing
the compost. Some market their own product whereas others use a broker.

The major problem areas experienced by in-vessel systems are materials handling and odor
control. The experience gained with the existing systems will be invaluable in the design,
construction, and operation of future in-vessel systems.

Yard and Garden Debris

Thus far, most yard debris composting programs have not been designed and implemented by
vendors. The majority of the processes are relatively simple. They typically involve size
reduction by means of "tub" grinders. Yard debris composting projects have been largely
encouraged by bans on the disposal of the wa^ics on landfills.

4.3 References

[1] "Composting Saves Landfill Space," World Wastes. 28(12):29-31 (1985).

[2] Goldstein, N., "Steady Growth for Sludge Composting," BioCvcle, 29(10):27-36
(November-December 1988).

4-18

[3] Savage, G.M., and L.F. Diaz, "Key Issues Concerning Waste Processing Design,"
Proceedings of the 1986 ASME National Waste Processing Conference. Denver,
Colorado, June 1986.

[4] Diaz, L.F., CM. Savage, and C.G. Golueke, "Production of Refuse-Derived Fuel from
Municipal Solid Waste," presented at the 79th Air Pollution Control Association
Annual Meeting, Minneapolis, Minnesota, June 1986.

[5] Personal communication with Mike Olson, U.S. Waste Recovery, May 1989.

[6] Savage, G.M. and C.G. Golueke, "Major Cost Elements in Co-Composting, BioCycle,
27(l):33-35 (January 1986).

[7] Savage, G.M. et al, Engineering Design Manual for Solid Waste Reduction Equipment.
Report by Cal Recovery Systems, Inc. under U.S. EPA Contract No.
68-03-2972, 1982.

[8] Diaz, L.F., G.M. Savage, and C.G. Golueke, Resource Recovery from Municipal Solid
Waste. Vol. I. "Primary Processing". CRC Press, Inc., Boca Raton, Florida,
1982.

5.0 EVALUATION OF REPRESENTATIVE INTERNATIONAL FACILITIES

5.1 Introduction

Many of the same problems in waste management are being faced by nations worldwide:
unavailability or unsuitability of land for landfills, increasing quantities of waste and poor
acceptance of waste disposal facilities by the people. Numerous options to landfilling of wastes
are being considered and implemented. Composting of organic wastes is among these options.

Although it is true that composting is an almost worldwide agricultural practice of long standing,
it only began to be considered as an approach to waste management in the second half of the
twentieth century. Since organic wastes typically constitute a large portion of the waste stream,
treatment of these wastes can substantially reduce reliance on landfilling. In industrialized
countries, composting has gained acceptance principaUy because it constitutes a means of waste
disposal. In developing countries, the value of compost as a means of reclaiming the organic
matter in waste is also an important factor. Restoring organic content of soil is essential to soil
fertility, and thus to the production of dwindling food supplies in these countries.

The status of composting in North America was discussed in Section 4. The status internationally
is approached in this section by discussing the current situation in some representative areas:
Federal Public of Germany, France, Italy, Japan, South America, Soviet Union, Switzerland and
the United Kingdom.

All costs in this section are in Canadian dollars.

5.2 Federal Republic of Germany

The Federal Republic of Germany faces many of the same waste management problems that are
being faced by other countries: increasing quantities of waste requiring disposal or treatment;
scarcity of areas suitable for new landfills; and poor acceptance of waste disposal facilities. An
integrated approach to waste management has been selected in the Federal Republic of Germany
as the most appropriate approach to waste management.

Approximately 30 million tonnes of waste were generated in Germany in 1980. At that time,
the three disposal methods used were landfilling, incineration and composting [1]. About 1
million tonnes of waste were composted in 17 composting facilities. Processing facilities for
the treatment of wood waste, bark and sludge were put into operation.

The quantity of sludge generated in 1980 was on the order of 40 million m3 at 5% total solids.
At that time, 40% of the sludge was used in agriculture, 40% disposed in landfills and 10%
burned [1]. About 40 plants were composting sewage sludge [2].

The estimated amount of compost produced in 1983 is presented in Table 5-1. The data show
that more than 700,000 tonnes of compost were produced. At that time, difficulties were
experienced in marketing the composts, in particular those made from MSW and bark. These
difficulties were attributed to excessive supply and poor quality [3].

Due to the high concentrations of heavy metals, as well as glass and plastics, the composting
of MSW is expected to decline [2]. The trend in Germany now is towards the separate collection
of organic and inorganic items [2,4].

5-2

TABLE 5-1
Estimated Amount of Compost Produced in Germany in 1983 [3]

Quantity
Feedstock (tonnes)

MSW and Sewage Sludge 220,000

Sewage Sludge 55,000

Leaves 100,000

Bark 200,000

Rumen Contents 40,000

Other Wastes 100,000

TOTAL 715,000

Separate collection of organic and inorganic items is not new to Germany. As early as 1903,
an ordinance was passed in Hamburg which stipulated mat each household have three waste
storage receptacles: one for food wastes; a second for rubbish (paper, glass, pottery, etc.); and
a third for ash, sweepings and dirt [5]. Research is currently being conducted in Germany on
the effect of separate collection on the quality of the compost product. A demonstration study
in the Mainz-Drais communities developed modelling systems to show the relation between
various separate storage methods at the residence and associated methods of collection on the
compost process feedstock The modelling included the effect of composting method on important
environmental and health parameters as well as on quality of product. Approximately 2,500
inhabitants were involved. With respect to product quality, results showed that heavy metal
concentrations were substantially reduced through separate collection [5].

Systems for source separated collection of recyclable materials are continuing to be implemented
in Germany. Currently, approximately 5% of residential waste is collected on a segregated basis
and reprocessed, but it is expected that these quantities will increase to 30% to 45% [6].

Separate collection of the vegetables, fruit and yard waste (VFY) has been tried in about 80
communities at the pilot level. In the process, the VFY wastes are collected and taken to a
composting facility. Results of pilot tests have demonstrated through separated collection of
FVY, the concentrations of heavy metals in the compost can be reduced substantially.
Demonstration projects concerned with the composting of vegetable-fruit-yard waste combinations
are in progress in a number of cities including Heidelberg, Witzenhausen and Hamburg-Harburg
[2].

Programs have also been implemented to collect decomposable materials in a container separate
from other waste materials. This type of system (called 'Biodrum') is considered the best method
for outlying areas. As shown in Table 5-2, the quantities of vegetable debris and biowaste
produced in outlying areas is much greater than those produced in high density areas. Currently,
approximately 350,000 German citizens are participating in this type of program. Plans are to
eventually involve about 3 million of the population [6].

5-3

TABLE 5-2

Potential Amounts of Vegetable Debris

and Biowaste Collected in Germany

(kg/inhabitant/yr)[6]

Population Segment

Population Density

Vegetable
Debris

Biowaste

City

High Density

Middle Density

Rural

2,000/km2
l,000/km2

500/km2
150/km2

20
25
30
35

50

70

90

160

5.3 France

Composting of organic residues, in particular MSW, has been practised in France for a number
of years. It has been estimated that 95 processing facilities treat about 1.3 million tonnes of
MSW a year. These facilities produce about 650,000 tonnes of compost [7-9].

There are about 8,000 municipal wastewater treatment facilities in France. These plants generate
on the order of 600,000 tonnes of sewage sludge per year. Based on information collected in
1988, the sludge is treated or disposed in the following manner:

Landfilling 40% to 45%

Direct land application 40% to 45%

Incineration 5% to 10%

Composting and thermal drying 5%

Based on these data, it is apparent that landfilling and land application are the most popular
waste management alternatives. The popularity is primarily due to economic reasons.

Currently there are five sewage sludge composting plants in France. Three plants use an in-
vessel system, one windrow turning, and the other one static pile. It is expected that the number
of sludge composting facilities will increase because of the constraints imposed upon landfilling
and land application.

The agency responsible for dealing with wastes in France is the Agence Nationale pour la
Recuperation et l'Elimination des Dechets (National Agency for Waste Recovery and Disposal),
popularly known as ANRED. ANRED has been actively promoting the development of land
application [7].

Furthermore, the Agency, long ago, recognized the importance of MSW composting in France
and set up a special team to evaluate the status of the process. The team conducted a series of
investigations to assess the impact of mechanical processing, in particular size reduction, on the
quality of the compost, conditions for optimum separation and other aspects of waste processing

5-4

[8]. Typical mechanical processing systems include: size reduction; density and ballistic
separation; air classification; and electro-magnetic separation. Manual separation sometimes is
included in the processing schemes.

Composting methods used in France are classified as rapid fermentation and open air natural
fermentation [9,10,11]. Rapid fermentation generally involves mechanical separation of organic
matter and then the use of either vertical or horizontal reactors. Environmental conditions in
the reactors are controlled. Aeration is accomplished through mixing, tumbling or forced
injection. Some of the systems used include: OTVD, Sogea, Siloda and Triga [9,12].

Open air natural fermentation is conducted by stacking the material in windrows. Aeration is
provided by periodically turning the piles. Windrow turners may or may not include size
reduction [9].

Maturation follows the active composting state. The windrows are aerated at regular intervals
(usually bi-monthly). The maturation period depends upon the intended use of the compost and
may last up to eight weeks.

The French government has promoted composting through publicity and the provision of
subsidiaries and low interest loans to municipalities [11,13]. An in-vessel composting facility
capable of treating about 120 tonnes of residential waste per day cost about $ 1.2 million in the
early 1980s. The operating costs were on the order of $ 10 per input tonne. Income from the
sale of the compost was reported as $26,000 per year or about $2.60 per tonne of compost [13].

Approximately 650,000 tonnes of compost were produced in France in 1984. About 555,000
tonnes or 85% of the material was sold [9]. The approximate distribution of the end users is
presented in Table 5-3. The data in the table show that mushroom growing, large-scale farming
and viticulture account for nearly 90% of the total output. The average selling price is about $
3.76 per tonne at the facility [9].

TABLE 5-3
Uses of Compost From MSW in France [9]

Use Weight (%)

Mushroom Growing 36.6

Large-Scale Farming 28.7

Viticulture 24.3

Tree Farming, Horticulture Nurseries 4.3

Arboriculture 4.0

Miscellaneous (Retail) 2.1

5-5

5.4 Italy

The estimated quantities of wastes generated in Italy are presented in Table 5-4. The date in
the table show that about 173 million tonnes of wastes are generated each year. About 18
million tonnes or nearly 10% of the wastes are generated in urban cities each year [14].

The strategies followed for managing urban wastes include energy and material recovery.
Composting is one of the approaches adopted for stabilizing the organic matter in the wastes.

A summary of the status of composting facilities is given in Table 5-5. The information in the
table show that there are 21 facilities currently in operation capable of treating about 3,300
tonnes of refuse per day. It is expected that 97 more facilities will be on line in the near future.
The total daily capacity would be on the order of 20,100 tonnes/day. Eleven facilities incorporate
sludge. The types of facilities include: circular reactors, rotating cylinders, primary cells, vertical
reactors, rectangular reactors and windrows. All systems incorporate a rapid (accelerated)
composting phase and a maturation phase. The most common maturation process is the windrow.
Process duration ranges from two to 152 days. The average duration is 50 days.
In the areas where compost is used, demand is concentrated in the spring and fall seasons. This
is primarily related to agricultural practices. The selling price for the compost varies from about
$ 4.70/tonne to $ 40/tonne, with the most common being $18/tonne. Some facilities propose to
sell the material in bags for about $ 59/tonne and densified and bagged for approximately $
118/tonne.

5.5 Japan

The use of organic residues for composting and land reclamation attracted a considerable amount
of attention in Japan in the mid-1950s. The interest declined after 1967 and reached a low in
1976. The energy crisis for the 1970s resulted in the development and construction of new
facilities [5].

The use of mechanical systems for composting MSW in Japan began in 1955. The number of
plants reached its peak of 29 in 1967. However, due to the increase in plastics and heavy metals
in the waste as well as the availability of chemical fertilizers, the number of plants decreased
sharply to about 7 in 1976. The energy crisis of the 1970s led to the development of mechanical
refuse processing systems. Some of these systems involve simultaneous size reduction and
classification [16]. In 1983, about 69% of the MSW was incinerated and less than 1% was
composted. This corresponds directly to the first line of Table 5.6. The facilities composting
MSW are located in small communities and subsequently are small in size. Composting was
primarily practised in these communities through the collection of source separated organic
residues [17].

It has been estimated that more than 1.8 million dry tonnes of organic residues currently are
generated in Japan. The data in Table 5-6 show that presently there are over 2,132 composting
plants in Japan. Most of the plants have been designed to process animal manures. In addition,
there is a considerable amount of organic waste generated by industry. Some of this waste is
composted. Unfortunately, the actual amounts are now known [15,18].!

5-6

TABLE 5-4
Estimated Quantity of Wastes Generated in Italy [14]

Quantity
Type (tonnes/yr)

Urban 18,000,000

Industrial 50,000,000

Agricultural 100,000,000

Sewage Sludge 5,000,000'

TOTAL 173,000,000

Municipal sludge at 20% total solids.

TABLE 5-5
Status of MSW Composting Facilities in Italy [14]

Quantities Treated
Status Number (tonnes/day)

In Operation

21

Under Construction

16

Planned

81

3,300
3,600
13,200

TOTAL 118 20,100

5-7

TABLE 5-6
Estimated Number of Composting Facilities in Japan [15]

Residue. Number

MSW 22

Sewage Sludge 31

Night Soil* 9

Manure > 2,000

Ba^ 70

Industrial Unknown

TOTAL > 2,132

Untreated human excrement

The number of sewage sludge compos ±ig facilities increased from less than five in 1977 to 31
in 1989. The Association for the Utilization of Sewage Sludge was established in 1977. The
Association is actively promoting the use of sewage sludge [9j. It has been estimated that about
54% of tne sludge is incinerated snd only 9% is composted [15].

The most common types of composting systems are the in-vessel systems. These systems
generally include either vertical or horizontal reactors. The reactors are equipped with units to
provide forced aeration and mechanical agitation [20].

The most common problem associated with piani operation is the control of moisture content of
the substrate. The most common methods to adjust the moisture content are by means of either
recycling some of the finished product or adding a dry organic residue. Odour and odour control
also are two important operating problems. Most of the facilities are equipped with odour control
devices [20].

Tne average sale price for the finished product varies from $ 41 to $ 91 per wet tonne in bulk
form. Bagged compost is sold from $ 113 to $ 175 per wet tonne.

Capital costs for composting facilities range from $ 14,000 to more than $ 1.4 million. The
average operating costs fluctuate from S 76 to $ 376 per wet tonne of compost. The major
fraction of the operating costs are attributed to labour costs [15].

The construction of most composting plants was carried out with government subsidies. The
ratio of subsidy to capital cost ranges from 25% to 88% [15].

5-8

5.6 South America

In comparison with other areas, composting has not received much attention in South American
countries. Most countries in the area still rely on land disposal as the primary means of waste
management. One exception is Brazil.

The City of Sao Paolo, Brazil, for example, has two composting facilities that treat municipal
solid wastes utilizing the Dano process. One plant has a rninimal capacity of 210 tonnes/day,
and the other a capacity of 420 tonnes/day. The City is in the process of increasing the capacity
of one of the plants from about 150,000 tonnes/year to approximately 264,000 tonnes/year [21].

A 660 tonnes/day facility was built in 1986 in Brasilia, Brazil, to process mixed municipal solid
waste. The recyclable materials are sorted from the compostables and rejects. The organic
stream is added to the top of vertical concrete towers where it is processed for approximately six
days. The material is then cured in windrows for an additional 30 to 60 days. The compost may
then be screened or shredded, depending upon intended markets [22].

Recent efforts in improving the quality of the compost has developed a market in the producers
of "organic fertilizers" in Brazil. In Sao Paolo, it is also expected that the compost will be used
for sugar cane farming. The pricing policy for the compost is expected to be as follows: cured
compost will sell for $ 5.30/tonne and the new upgraded product will sell for $ 11.80/tonne [21].

In Brazil, the compost is presently being sold for one-third the cost of commercial mineral
fertilizers. The high demand for organic soil amendments is the result of poor soil conditions
in the area [22].

5.7 Soviet Union

Despite the increasing awareness of problems associated with landfilling in its more densely
populated regions, landfilling remains the usual method of municipal waste disposal in the Soviet
Union. Although not to the same degree, the problems are of the same nature and origin as those
in almost all industrialized countries. One such problem is that despite the vast land area of the
Soviet Union (22.3 million km2), there is a shortage of available area for siting landfills within
a reasonable distance from the communities in which waste is generated. For example, waste
from Moscow is currently transported 80 to 97 km for landfilling [23]. Undesirable impacts
exerted on soil and water resources by leachate from landfills are beginning to be recognized and
acknowledged.

The landfill situation, combined with both a hesitance to resort to incineration as an alternative
as well as new developments in compost technology, are enhancing the prospects for composting
in the USSR. Other factors are adding to the attractiveness of composting. One such factor is
an almost insatiable demand for soil conditioners and fertilizers [24]. According to Pickard, use
of fresh compost as a heating element in greenhouses and cold frames operated on state and
communal farms accounts for a significant part of this demand. (Use for this purpose involves
placing topsoil over 18 inches of fresh compost. The compost provides sufficient heat to extend
the growing season by several weeks.) Yet another helpful factor is the relatively high fraction
(33%) of food preparation wastes in the municipal waste stream. The composition of domestic
refuse from the city of Minsk is indicated by ihe data in Table 5-7.

5-9

TABLE 5-7
Composition of MSW in the City of Minsk, Soviet Union [24]

Component Average (%)

Paper 22.3

Food Wastes 38.0

Wood 1.2

Metal 3.8

Bone 1.7

Leather, Gum 2.0

Textile 2.9

Glass 6.0

Stones 3.0
Plastics 6.0

"Wastes" 12.0

Approximately eight mechanical composting facilities are in operation in the Soviet Union.

Sewage sludge and MSW are being co-composted at the Leningrad and Minsk plants. These
plants are designed to process 200,000 and 88,000 tonnes of MSW/yr respectively. The
mechanical composting operations in Leningrad and Minsk are typical of those in the Soviet
Union [23].

The plant at Minsk produces 45,000 tonnes of finished compost/year. It has four rotating drums,
each of which is 4 m in diameter and 35 m in length. The interior of each drum is equipped
with baffles. Freshly collected refuse is brought to the plant and dumped into a receiving bin.
The fresh refuse is then loaded without preprocessing into the drums by way of two independent
lines. Size reduction occurs as a result of the tumbling in the drum The material remains in
the drums over a two day period, after which it is transferred to the "crushing screen shell", in
which it is screened and separated into compostable and non-conipostable fractions. The screened
material is then windrowed and allowed to cure until there is a need for the finished product
[23,24].

5.8 Switzerland

Composting of organic residues has been practised in Switzerland for several years. It has been
estimated that more than 200,000 tonnes of waste were composted in 1975. However, the
increases in quantities of waste generated and in the concentration of potentially toxic chemicals
in the waste led to concern about excessively high concentrations of harmful substances in the
compost [25].

The need for means of waste disposal led to the expansion of incinerator capacity. Despite the
use of sophisticated air pollution control equipment, substantial concentrations of pollutants

5-10

escaped to the atmosphere. In addition, reliable methods of ash disposal were lacking. It was
concluded that environmental conservation rather than simply cost had to be the most important
criterion for waste disposal. Consequently, composting was again considered a viable alternative,
provided that low concentrations of toxic compounds in the finished product could be achieved
[25],

In order to evaluate the sources of heavy metals in the waste stream, a series of tests were
carried out in West Germany and in Switzerland. The results of the tests indicated that separation
of compostable items could be based on established criteria. Furthermore, the results showed that
compost produced from properly source separated organic matter would meet the desired
specifications (i.e., good appearance and low level of contaminants) [26-29].

Currently, there are a number of relatively small composting facilities throughout Switzerland.
The facilities have a capacity of 200 to 25,000 tonnes per year. The tipping fee has been
reported to range from about $ 35 to $ 59 per tonne.

Most new facilities take into consideration the concerns regarding emissions, as well as strict
standards regarding quality of the finished product [25].

5.9 United Kingdom

Approximately 20 million tonnes of municipal solid waste is generated in the United Kingdom
each year. Of this, about 18 million tonnes (approximately 90%) are landfilled annually, and
the rest is treated thermally. The major reason for the high percentage of waste going to landfill
is the relatively low cost of landfilling compared to that of alternative disposal schemes [30].

The first full-scale refuse composting facility in England was established in 1947 [31]. A survey
conducted in 1973 determined that 21 local authorities claimed some experience in composting.
The survey also found that there were 1 1 operating facilities. However, all of the facilities were
closed by the end of 1987. The primary reason for the closures was the lack of markets for
products.

Although much research work has been carried out on various aspects of composting, no full-
scale composting facilities are operating in the United Kingdom at this time [31-34]. Some in-
vessel systems currently are being used as a means to accomplish volume reduction prior to
landfilling [6].

5.10 References

[1] Lutz, W., "International Perspectives on Composting", BioCycle, 25(2):22-25 (March
1984).

[2] Stegmann, R. and U. Krogmann, "Composting of the Organic Fraction of Municipal Solid
Wastes Separated Through Selected Collection", presented at the International
Symposium on Compost Production and Use, S. Michele All'Adige (Trento), Italy,
June 1989.

[3] Mach, R., "Processing 700,000 Tons Per Year in Germany", BioCycle, 24(l):37-38
(January /February 1983).

5-11

[4] Salimando, J., "Glimpses of German Waste Solutions", Waste Aee 2(Y6):112-116 (June

1989).

[5] Funke, U. and G. Muller, Getrennte Werstofferfassung und Biokomnostierune.
EF-VERLAG fur Energie und Unwelrtechnik GmbH, 202 pp., 1988.

[6] Scheffold, Karlheinz, "Source Separation and Collection in Germam ", DicCvcle, 30C7V28-
29 (July 1989).

[7] Merillot, J.M., "Recycling Organic Municipal Wastes in France", BioCvcle. 30(7):30-31
(July 1989).

[8] Begnaud, B. and N. Noyon, "Processing Household Refuse by Separation and
Composting", Conclusions of the ANRED Program, 1984-1986.

[9] De Lauzanne, R., "Methodologies and Technologies in Compost Production: The French
Experience" presented at the International Symposium on Compost Production and
Use, S. Michele All'Adige 'Trento), Italy, June 1989.

[10] Mousty, P.A. and M. Reneaume, "Household Refuse Composting in France", BioCvcle.
25(2):26-29 (March 1984).

[11] "French Farmers Favour Cordon Bleau Compost", Surveyor (September 24, 1981).

[12] Lavasseur, J.P., "Household Refuse Recycling in France", BioCvcle. 29(6):32-33 (July
1988).

[13] Shimell, P., "Refuse Derived Compost Boosts Vineyard Yields", World Wastes. 26(11)8-
9 (November 1983). "~

[14] Zonzi, G. and G. Urbian, "Reality and Guidelines of the Italian Situation", presented at
the International Symposium on Compost Production and Use, S. Michele
All'Adige (Trento), Italy, June 1989.

[15] Kubota, H. and K. Nakasaki, "State of the Art of Compost Systems: The Current Situation
and Future Outlook in Japan", presented at the International Symposium on
Compost Production and Use, S. Michele All'Adige (Trento), Italy, June 1989.

[16] "Ebara Municipal Solid Waste Composting System", Ebara Environmental Corporation,
Greensburg, Pennsylvania, March 1989.

[17] Chanyasak, V. and H. Kubota, "Source Separation of Garbage for Composting" BioCvcle
24(2):56-58 (March-April 1983). ' —

[18] Kubota, H., S. Matsuda and M. Sasaki, "Composting Has Promising Future in Japan"
BioCvcle. 25(3):28-31 (April 1984).

[19] Golueke, C.G., "Wastewater and Sludge Management in Japan", BioCvcle 24(2V44-47
(March- April 1983). —

5-12

[20] Terasawa, M., M. Hirai and H. Kubota, "Soil Deodorization Systems", BioCycle, 27(6):28-
32 (July 1986).

[21] Guaraldo, C.R., "MSW Composting Facilities in Sao Paolo, Brazil", BioCycle. 30(6):82-84
(June 1989).

[22] Srucki, H. and F. Mitchell, "Processing Wastes in Brasilia", BioCycle, 30(7):60-61 (July
1989).

[23] Peterson, C. and A. Perlmutter, "Composting in the Soviet Union", BioCycle, 30(7):74-75
(July 1989).

[24] Pickard, R.O., personal communication to the Coordinator, Transportation and Works
Policy Committee, Regional Municipality, Ottawa-Carleton, Canada (September
21, 1988).

[25] Mayer, M., H. Hofer and U. Marie, "Trends in Yard Waste Composting", BioCycle.
29(6):60-62 (July 1988).

[26] Obrist, Walter, "Material Balance of the Composting Process", BioCycle. 28(2):32-33
(February 1987).

[27] Personal communication with representative from Switzerland, P. Selldorf, Consorzio per
l'Eliminazione dei Rifiuti del Luganese (June 1989).

[28] Baccini, P. and P.H. Brunner, "Sortierung in der Abfallwirtschaft: Wie gross ist ihr
Beitrag zu einem ressourcenschonenden und uniweltvertraglichen Stoffhaushalt?"
Gas, Wasser, Abwasser. 68(1 1):61 7-622 (1968).

[29] Obrist, W. and P. Baccini, "Auswahlkriterian fur Kompostierbare Abfalle", Wasser,
Energie. Luft - Eau, Energie, Air. 78(Heft ll/12):290-294 (1986).

[30] Bardos, R.P., "The Potential of Biological Processes in Municipal Solid Waste
Management Systems", presented at the Second Combustion Workshop,
Birmingham, England, December 1988.

[31] New, R. and R. Papworth, Glass Contaminant Removal from Refuse Derived Compost -
Interim Report, LR 692 (MR) M, Warren Spring Laboratory', Stevenage, England.

[32] Bardos, R.P. and J.M. Lopez-Real, "The Composting Process: Susceptible Feedstocks,
Temperature, Microbiology, Sanitation, and Decomposition", presented at the
EC Workshop in Waste Management, Monastery of Neresheim, Germany,
September 1988.

[33] Bardos, R.P., "Composting Studies Using Separated Fractions of Urban Waste from the
Byker Reclamation Plant, New Castle, U.K.", for presentation at the International
Symposium on Compost Recycling of Wastes, Athens, Greece, October 1989.

[34] Stentiford, E.I., T.J. Pereira-Neta, P.L. Taylor, D.D. Mara, J.M. Lopez-Real and E. Witter,
"Sanitisation Potential of Composting for Sewage Sludge and Refuse in a Static
Pile System", pp. 269-275, in Advances in Water Engineering, T.H.Y. Tebbutt,
Ed., Elsevier Appl. Science Publ., 1985.

[35] Personal communication with Brian Jones, July 1989.

6.0 DOCUMENTATION OF POLICIES, REGULATIONS,
STANDARDS AND/OR GUIDELINES

Although composting has been utilized as a means of waste management since the early 1940s,
most policies and regulations geared specifically at the compost facility, process, and maiket
either have recently been developed or are still in the developmental stages.

In Canada, only the provinces of Quebec and Ontario have developed policies specifically for
composting operations. Other provinces either apply existing regulations for land application of
sewage sludge, examine projects on a case-by-case basis, or have no applicable regulations (see
Table 6-1).

In the United States, the Environmental Protection Agency has been active in developing
regulations pertaining to the treatment and distribution of sewage sludge products (including
compost). Regulations related to the composting of municipal solid waste and of yard debris
generally have been the responsibility of state and municipal governments.

Internationally, the Commission of the European Communities has taken the lead in developing
policies and guidelines for compost operations in Europe. Individual countries, some of whom
are members of the CEC, that also have developed compost guidelines include Austria, The
Netherlands, Belgium, Switzerland, the Fer^ral Republic of Germany, Spain, and France.

A discussion of some of the policies and regulations that have been, or are being, developed
for composting operations is provided in the remainder of Section 6. The discussion is divided
into the following areas: compost quality and standards; facility siting and approvals; health and
safety requirements; and hazardous waste handling, storage, and disposal.

6.1 Compost Quality and Standards/End Use Regulation

Compost quality is a function of the physical, chemical, and biological characteristics of the
product. Some of the physical characteristics desired of a product are a dark colour, uniform
panicle size, a pleasant earthy odour, and absence of contaminants. The compost should be
free of clumps and should not' contain identifiable contaminants such as glass shards and pieces
of metal and plastics.

Regulations regarding the use of compost from solid waste and sewage sludge have primarily
centred around the potential public health problem of introducing toxic compounds into the
food chain. Heavy metals, PCBs, and other toxic materials are present in wastewater streams
and in some solid wastes. Consequently, they can be present in the compost to be applied to
the land or used as a growing medium in containers. Since some amounts of the toxic
compounds are assimilated by plants, they can potentially be transmitted to animals and
humans consuming the crops. Most compost standards, therefore, limit the concentrations of
toxic materials in the compost product. Other standards that can be applied to compost
products include particle size requirements, limits on the percent of foreign material present in
the finished product, and degree of maturity.

6-2

TABLE 6-1
Canadian Policies, Regulations, Standards and/or Guidelines

Newfoundland - None.

Waste Material Disposal Act (1973) covers land application of
manure only.

Nova Scotia - None.

Projects or proposals will be examined on a case-by-case basis.

Prince Edward Island - None.

New Brunswick - None.

Projects or proposals will be examined on a case-by-case basis.

Quebec - The following are requirements for a solid waste composting

plant:

0 at least 150 m from a floodplain and lands designated by

a municipal government as residential, commercial or
mixed residential/ commercial;

at least 150 m from any municipal park, golf course,
alpine ski trail, recreation area, public beach, ecological
reserves, parks, oceans, rivers, streams, ponds, swamps
or sandbanks;

at least 300 m from any dwelling, educational institution,
religious edifice, food processing establishment,
campground, restaurant, hotel, holiday camp and health
and social service establishments;

0 at least 300 m from any lake;

have a sign identifying the facility and the operating
permit posted;

only solid waste, non-contaminated biomedical waste
which is solid at 20°C other than human anatomic waste,
non-toxic residues solid at 20°C from pulp and paper
plants and sawmills, non-toxic mud capable of being
shovelled and a maximum of 100 m3 of earth and sand
impregnated with less than a mass of 5% hydrocarbons
per period of four months and non-toxic mud that is not
capable of being shovelled;

not bum any wastes;

6-3

TABLE 6-1 (Cont'd)
Canadian Policies, Regulations, Standards and/or Guidelines

composting residues and solid waste not accepted at the
composting facility must be landiUled; and

ensure that wastewater meets storm sewer regulations.

Internal Interim Guidelines on Composting (1982) are used for
approval purposes.

Exemption from Environmental Assessment Act if facility
produces less than 200 tonnes/day of residual waste after
composting.

Ontario

Manitoba

None.

Saskatchewan

None.

Alberta

None.

Proposed projects would be evaluated using existing regulations
for land application of sewage sludge and water quality
guidelines.

British Columbia

None.

Northwest Territories -

None.

Yukon

No information.

Environment Canada -

None.

6A

Sewage sludge composts and, to a smaller degree, MSW composts can contain human coliform
bacteria and other potentially harmful pathogens and fungi. Utilization of proper composting
methods, especially maintenance of thermophyllic temperature levels, has been demonstrated to
be effective in destroying pathogens. Studies have shown that in windrow composting it is
necessary to maintain a minimum temperature of 65°C for at least one week to produce a
hygienically safe product [1]. Generally, in-vessel systems require less time.

Compost produced from yard debris may also contain toxic compounds such as insecticides and
pesticides. This material may also be the source of weed seeds and plant pathogens [2].

In summary, both final product standards and operational regulations have been found to be
necessary to control the quality and safety of the compost product. Ultimately, compost quality
is a function of the composition of the feedstock and of the type and thoroughness of the
separation process.

6.1.1 North America

In Canada, contacts with provincial governments indicated generally that no policies,
regulations, standards, or guidelines were in effect regarding compost quality. The exceptions
were Quebec who have guidelines and Ontario who utilize "internal" guidelines for approval
purposes.

In the United States, the Environmental Protection Agency has been involved in developing
regulations regarding sewage sludge treatment and disposal. Recently, proposed guidelines
were developed regulating contaminant limits for compost and other sewage sludge products
that are intended for distribution and marketing. The contaminant limits are based on annual
sludge application rates (see Table 6-2) and include many pesticides and herbicides that
presently are not regulated by individual States. The U.S. EPA also proposed a set of limits
for sludge products intended for non-agricultural land (Table 6-3). The proposed limits do not
apply to compost from MSW or yard debris. These limits may be revised. They are the most
current as of writing.

A number of States in the U.S. have developed compost quality standards which regulate
compost products intended for distribution. Compost standards from nine States are presented
in Table 6-4 as examples of guidelines in the U.S. As shown in the table, all nine of the
States regulate the concentrations of heavy metals in the compost, and most regulate PCB
concentrations as well. Florida, in its draft regulations, has developed more stringent guidelines
for compost products by setting standards for compost maturity, maximum particle size, and
foreign material content.

As shown in the table, compost from sewage sludge is regulated more often than MSW or yard
debris composts, primarily because large-scale facilities have been operational for a longer
period of time, and also because of the relatively high levels of heavy metals and pathogens in
raw sewage. The number of States that are developing regulations for MSW compost is
increasing as more facilities are becoming operational. In many cases, the regulations for
MSW compost have been adapted from those for sludge.

Yard debris compost is generally regulated less stringently than composts from sewage sludge
or MSW, because the compost is considered to pose less of a potential environmental hazard.
Of the States listed in Table 6-4, Massachusetts is the only one that includes yard debris
compost in its contaminant testing requirement. Florida has a classification for compost
generated from yard waste or manure, but compost generators are not required to subject their
product to laboratory tests. It is assumed that the concentrations of heavy metals in yard debris
compost will be within the limits listed in Table 6-4.

6-5

TABLE 6-2

U.S. EPA Distribution and Marketing Pollutant
Limits for Sewage Sludge Products [3]

---ual Whole Siu

::!.

/ha):

3

5

15

20

25

30

35

40

Max

iinum Skace

Concentrati

on fo/ks

,.*,«.

=is.s)

**rin/c«Wr,n

16

5.5

3.3

1.5

1.1

0.S2

0.65

0.55

0.47

3.41 :.

•>-. ; -i

Arsenic

703

230

MO

70

47

35

28

23

20

13

15 14

5en:o(a)py-e-e

3C

25

15

7.7

5.1

3.6

3.1

25

2.2

1.3

1.5

Zaraitn

9C0

310

180

90

61

46

37

21

25

23

:: is

:--.-ar«re

22.500

7.500

J. 500

2.2C0

1.5C0

1.100

900

750

640

550 i

:o 450

:.u.romilE

25. SM

5. SCO

5.300

2.7C0

1.770

1.323

1.360

sac

760

660 5

93 530

Ic:ce-

2.200

770

460

230

150

110

92

77

65

£7

31 45

::• ::-: ::: sat

ai;a

46

15

9.2

4 6

3.1

2 3

1.8

1.5

1.3

1.2

0 92

■testach'.cr

7=

26

19

7.9

5.2

3.9

3.2

2.6

2.2

2 :

3 1 :

-iexscnicrc=e-:e'

;e

16

15

9.1

4 5

3

2.3

1.3

1.15

1.3

1.14 !.

51 0.91

-exacr icrcr. -.;;:•

•-•

11.500

u.eoo

B.200

4.100

2.700

2. 100

1.500

1.40C

1.200

1.000 9

13 320

.ea=

6.000

2.100

1.300

600

400

313

253

2::

180

150 :

.'-da-e

293.300

97.800

58.700

29.3S0

19.570

14.630

U.7«

3.780

3.330

7.340 =.:

00 5.570

"-rcL-ry

1.990

660

400

199

133

99

80

66

57

50

a a;

HlCKel

3. SCO

1.300

780

390

260

200

160

130

110

98

37 75

:olycMcr mated

ersyls

49

19

20

15

10

7

6

4

1

:■ 3

Selemjn

8.105

2.702.1

1.600

810

540

410

320

270

250

200 1

e: 150

-c«=neie

117

39

23

12

7.8

S3

4.7

3.5

3.3

2.9 i

.5 2.3

line

6.500

2.900

1.700

860

570

430

340

290

25:

220

= 3 170

s] C3T - 2.2-Si!
BE • l.l-Bi!

: :- '
i(ch]

crccneiy

l)-l.l.l-tr

11-2.2-dtc-.
!)-2.2-d1ch

icnloroet?
lorcethyle
loroe'.hane

™

6-6

TABLE 6-3

Proposed Pollutant Limits for Sewage Sludge Compost
Applied to Non-Agricultural Land [3]

Maximum Concentration
Pollutant (mg/kg, dry wt. basis)

Aldrin/dieldrin 0.33

Arsenic 36

Benzo(a)pyrene 6.9

Cadmium 380

Chlordane 24

Chromium 3100

Copper 3300

DDT/DDE/DDD (total)3) 0.11

Dimethyl nitrosamine 1.4

Heptachlor 1.5

Hexachlorobenzene 2.8

Hexachlorobutadiene 6.8

Lead 1600

Lindane 92

Mercury 30

Molybdenum 230

Nickel 990

Polychlorinated biphenyls 0.11

Selenium 64

Toxaphene 0.97

Trichloroethylene 180

Zinc 8600

a) DDT - Bis 2,2-(chlorophenyl )-l, 1,1-trichloroethane
DDE - Bis l,l-(chlorophenyl)-2,2-dichloroethene
DDD - Bis l,l-(chlorophenyl)-2,2-dichloroethane

6-7

TABLE 6-4
Compost Quality Standards for Various States in the U.S. (ppm)

6-8

A few U.S. States have developed a classification hierarchy in which compost products meeting
the most stringent requirements are allowed the widest distribution, i.e., non-restricted use.
Conversely, composts with higher levels of contaminants are restricted in use to non-food chain
crops, or to use as landfill cover or in land reclamation projects. Table 6-4 presents the
acceptable concentrations for the various applications for Florida, New York, Massachusetts,
and Minnesota.

6.1.2 International

The Commission of the European Communities (CEC) has been actively involved in the
development of specifications for different types of compost. In addition to the CEC, a
number of countries have also developed guidelines for compost quality. A discussion of
compost quality standards developed by the CEC, France, Austria, Switzerland, Spain and
Japan are presented below.

6.1.2.1 Commission of the European Communities

The CEC's objective is to develop compost quality specifications that would be accepted
throughout the member nations and would "guarantee users a specific product quality and
properties which would remain standard over time and which would be tailored to the different
ways in which compost is used." [12] The CEC takes the position that in order to be
marketed, compost must be accompanied by specifications relative to its origin, composition
and degree of stabilization [1]. Compost specifications proposed by the CEC define the
following physical and chemical parameters: particle size and organic matter, moisture content,
inerts, mineral contents, initial and final C/N values, salinity, and pH.

Currently, CEC specifications are at variance with national legislation or current practice in
some of its member nations including Belgium, France, Federal Republic of Germany, and The
Netherlands. The United Kingdom does not currently have guidelines for limits on heavy
metals and other contaminants in MSW compost, but has not accepted the limits proposed by
the CEC. As of June 1989, Ireland, Italy, and Denmark were expected to approve the
proposed specifications [12].

Particle Size. Organic Matter, Moisture, and Inerts - Four grades of compost product are
proposed by the Commission of the European Communities. Table 6-5 presents the acceptable
limits for particle size, biodegradable organic matter content, moisture content, and inerts (glass
and plastic) for the four grades of MSW compost. Moisture content is an indication of
progress in the composting process. A compost with a relatively low moisture content is also
beneficial in that it avoids the unnecessary transportation of water, and it helps in sieving,
storing or spreading operations. Agricultural use of compost requires a product substantially
free of inert matter. In addition to meeting the maximum levels for glass and plastics
presented in Table 6-5, ferrous metals should be practically absent, and non-ferrous metals only
present a low level [1].

Nutrient Content - Minimum levels for nitrogen, potassium, phosphate, calcium, and
magnesium also are included in the specifications developed by the CEC. The CEC
specifications are compared with actual average values from France in Table 6-6. The CEC
also recommends that the initial and final C/N ratio for each compost product be specified. As
an example, when the starting material has a C/N ratio in the range of 35 to 40 or slightly
above, the final C/N ratio should be below 22 in order to achieve the degree of stabilization
required. When wastes contain nitrogen-rich products, the final C/N values are expected to be
proportionally lower, yet not below 11 to 12.

6-9

TABLE 6-5

CEC Requirements for MSW Compost Characteristics
According to Grade of Product [1,12]

Very
Fine

Fine

Medium

Coarse

Sieve size (mm)

8

16

24

40

Maximum inerts (% dry wt)

Glass -- Present
Future

1
0.1

2

4
2

6
3

Plastic -- Present
Future

0.4
0.2

0.8
0.4

1.6
0.8

3.5
1.6

Maximum moisture (%) 30 35 40 50

Minimum biodegradable
organic matter (% dry wt)

Present 20 25 30 35

Futur* 30 35 40 45

6-10

Heavy Metals -- The heavy metal content of compost has received the greatest amount of
attention by the CEC and its member nations [12]. Table 6-7 presents a sampling of
concentration limits that have been developed by various nations in Europe, as well as actual
values from compost analyses. As shown in the table, the concentrations of heavy metals in
compost from source separated MSW are much lower than those from the other MSW
composts presented. Also presented, for comparison purposes, are heavy metal concentrations
for compost prepared from plant residues and agricultural wastes; these show the lowest values.

Salinity and pH - The following guidelines have been developed by the CEC for salinity and
pH [12]:

Salinity 2 g salt/litre

pH Range of 5.5 to 8.0 (compatible with plant growth)

6.1.2.2 France

Composting has been used for MSW treatment in France for years, and currently approximately
650,000 tonnes/year of MSW compost are produced. In 1987, the French Agency for Wastes
Recovery and Disposal (ANRED) recognized the need to regulate MSW composting.
ANRED's two-fold approach involved proposing a compost treatment scheme and developing
specifications for two classes of MSW compost. "Quality certificates" are awarded to composts
meeting the requirements for either Class A or B (see Table 6-8). Composts must also meet
the French Standard NF U 44051 limiting maximum concentrations of heavy metal in soils
[13].

6.1.2.3 Austria

Guidelines for compost quality were developed by the Standards Committee in Vienna, Austria,
as early as 1984 [14]. The standards (ONORM S 2022) address the following areas: organic
substance content, nutrient content, physical properties, plant tolerance, impurities, and heavy
metals. Table 6-9 lists some of the parameters developed under ONORM S 2022, and their
respective nominal ranges.

6.1.2.4 Switzerland

The environmental protection law in Switzerland regulates the quality of compost products by
defining limits, method of control, and sanitation rules. Waste-derived compost is excluded
from the market if it is of questionable quality. The criteria used for judging the quality of
compost include physical properties, degree of maturity, contaminant level, particle size, and
pollutant content [15]. A last of the pollutant limits is presented in Table 6-10.

6.1.2.5 Spain

The quality of commercial compost has been regulated in Spain as early as 1970. As shown in
Table 6-11, early laws included parameters for moisture content, organic content, nutrients, and
particle size. Regulations passed in 1988 are more stringent in nutrient content and also in-
clude maximum concentrations for potential toxic elements [16]. The data in Table 6-11
provide a comparison of national legal requirements from 1970 to 1988.

6-11

TABLE 6-6

Comparison of CEC Specifications for Minimum Levels of Nutrients
in Compost with Actual Values from France (%, dry wt. basis)

Nitrogen

Phosphate

Potassium

Calcium

Carbonates

Magnesium

CEC
Specificat
[1]

ions

Actual Values

France

[12]

0.6

1.1

0.5

0.6

0.3

0.6

2.0

7.1

3.0

0.3

1.0

TABLE 6-7

Maximum Permitted Concentrations of Heavy Metals in MS W Composts
for Various Countries [12] (mg/kg, dry wt.)

Belgium
Food Non-Food

The Netherlands
1987-1992 1993-2003

Federal Republ i«_
Germany

Zinc

1000

1500

1300

250

375

Lead

600

1000

500

150

150

Copper

100

500

400

50

150

Chromium

150

200

300

100

150

Nickel

50

100

60

50

25

Mercury

5

5

3

1.5

3.2

Cadmium

5

5

3

1.5

2.5

6-12

TABLE 6-8
Specifications for Two Classes of MSW Compost in France [13]

Maximum Limits (dry wt)
Parameter Unit Class A Class B

Particle size

mm

40

40

Light plastics (size >5 mm)

%

1.6

2.5

Heavy particles (size >5 mm)

%

6

12

Total inert materials

%

20

35

Lead

ppm

800

800

Mercury

ppm

8

8

Cadmium

ppm

8

8

Nickel

ppm

200

200

6-13

TABLE 6-9

Partial Listing of Compost Quality Parameters
Developed in 1984 for Austria [14]

Unit Nominal Range

Nutrients

Total Nitrogen

% DS

Total Phosphate

% DS

Total Potassium

% DS

Calcium

% DS

Carbonates

% DS

Magnesium

% DS

Physical Properties

Moisture Content

% FS

PH

Impurities

Oversized Grain (11.2 mm)

% DS

Glass (2 mm)

% DS

Plastics (4 mm)

% DS

Heavy Metals

Chromium

ppm DS

Nickel

ppm DS

Copper

ppm DS

Zinc

ppm DS

Cadmium

ppm DS

Mercury

ppm DS

Lead

ppm DS

0.5

to

1.5

0.4

to

0.8

0.3

to

1.0

2.0

to

12.0

3.0

to

20.0

0.5

to

3.0

25

to

35

7.0

to

8.5

0

to

3

0

to

3

0

to

3

50

to

300

30

to

200

to

1000

300

to

1500

1

to

6

1

to

4

200

to

900

DS = dry substance
CS = fresh substance

6-14

TABLE 6-10
Swiss Limits for Pollutant Content in Waste Compost [15]

Limits
Element (soluble, ppm)

Lead 1.0

Cadmium 0.03

Fluoride 25

Copper 0.7

Nickel 0.2

Zinc 0.5

TABLE 6-11

A Comparison of Legal Requirements for Compost
Quality in Spain - 1970 to 1988 [6]

Parameter 1970 1988

Maximum moisture content (%)

Minimum organic content (%)

Minimum nitrogen content {%)

Particle size (% passing 25 mm)

Maximum heavy metal content (ppm)

Cadmium

Copper

Nickel

Lead

Zinc

Mercury

Chromium

40

40

25

25

0.5

1

90

90

40

--

1750

--

400

--

1200

--

4000

--

25

--

750

6-15

6.1.2.6 Japan

The application of organic fertilizers on the land in Japan is controlled by the Ministry of
Agriculture (MOA). The MOA enacted the Law of Fertilizer Control. According to the law,
the maximum concentrations (in mg/kg, dry wt.) of heavy metals in the compost are as follows
[17]:

Mercury 2.0

Cadmium 5.0

Arsenic 50.0

6.2 Compost Facility Siting and Approvals

Similarly to compost quality standards, regulations regarding the siting of compost facilities are,
in many jurisdictions, still in the developmental stages. This is particularly true for MS W and
yard debris composting. In lieu of regulations geared specifically to composting operations,
many such facilities fall under the restrictions applied to solid waste facilities in general.

As defined in Table 6-1, the province of Quebec regulates certain aspects of compost siting.
Regulations include restrictions regarding the surrounding area; facility identification; types of
wastes; waste disposal; and leachate control. Interim internal guidelines are in effect in
Ontario, although facilities producing less than 200 tonnes/day of waste are exempted from the
Environmental Assessment Act. Other provinces either do not regulate compost siting or
examine each project on a case-by-case basis.

In the U.S., the responsibility for facility siting is that of the State or municipal government.
Even though most States have not as yet established specific regulations governing the siting
and approval of sludge and MSW composting facilities, all States have general construction and
environmental protection laws that apply to compost facilities. These laws enable the States to
regulate proposed facilities and prevent them from causing an environmental hazard or
nuisance.

The States listed in Table 6-12 have developed specific regulations governing the operations
and process control of sludge and MSW composting. The table summarizes the requirements of
each State. Except as noted on the table, the steps involved in the permitting process for a
compost facility are similar to those in the following generic description: Initially, a regional
map and a site plan are required. These regional maps should show the site in relation to
zoning and regional use, highways, population centres, airports, bodies of water, and other
pertinent features. The site plan should show the facility layout, drainage and water well
features, roads, and property lines. The operational plan must begin with a detailed description
of the wastes to be processed and an anticipated waste quantity and traffic flow summary. The
facility design must be described, including the type and size of equipment and the expected
processing rates. Provisions must be made to meet the process to significantly reduce
pathogens (PSRP) and the process to further reduce pathogens (PFRP) which involve time and
temperature standards of composting. Other requirements include drainage and leachate control
systems to protect surface and groundwater, air pollution control devices, and a marketing and
distribution plan for the finished compost. Additionally, the site must have a sign or
registration clearly stating the name of the owner and operator of the facility.

6-16

TABLE 6-12

Facility Siting and Approvals for Sludge and Municipal
Solid Waste Composting in the U.S.

New

York Florida

[4] [7]

New Pennysl-
Jersey vania Oel aware
[18] [19] [10]

Site location acceptability
and zoning approval

Engineering map of site

Description of wastes

Operational plan

Schedule of operations
Traffic load
Equipment description
Storage description
Processing and tr.atl flow
Monitoring plan
Aeration capacity

".ass balance

Description of PSP.P PFRPa)

Groundwater protection
runoff and leachate control

Product marketing or
distribution plan

Air emission control plan

Specific ownership

Personnel descriptions

Yes

Yes

Yes

Yes

Yes

Detailed Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

NS

Yes

Yes

Yes

Yes

NS

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

NS

Yes

Yes

NS

Yes

YeS

Yes

Yes

Yes

Yes

NS

Yes

NS

NS

Yes

Yes

Yes

Yes

NS

Yes

NS

Yes

NS

Yes

Yes

Yes

Yes

Yes

Yes

Yes

General

Yes Yes
Yes Yes
Yes Yes

Yes
Yes
Yes

Yes
Yes
Yes

Yes
NS
NS

NS = not specified

a) PSRP = Process to significantly reduce pathogens
PPP.P = Process to further reduce pathogens

6-17

Yard waste composting facilities are generally viewed as posing a minor environmental risk.
Nevertheless, some U.S. States do have formal permitting procedures for these facilities (see
Table 6-13). The regulations are similar to those for MSW and sludge composting, but usuail>
with less detail and specific operational requirements. The regulations are broad enough to
allow operators to select a level of technology and composting procedure appropriate to their
needs. The primary concern with yard waste composting is surface and groundwater pollution
from leachate. Drainage and leachate control standards are therefore the central focus of yard
waste composting legislation.

A few states (e.g., Delaware, Pennsylvania, and Michigan) have specifically exempted all yard
waste composting facilities from the permitting process, but nonetheless have environmental
pollution standards that the facilities must meet [10,20,24]. Most central and western states do
not have a specific permitting procedure in place for yard debris compost facilities.

Many States have developed exemptions from the permit process for small generators of yard
waste compost or operators of standard fanning composting practices. Florida, for example,
has exempted backyard composting, normal farming operations, and facilities which process
yard waste for other uses such as mulch [7]. New York has exempted facilities that compost
less than 2,295 m3 of yard waste and those at which only food processing waste and/or animal
manure are processed [4]. Wisconsin requires no permit for backyard and neighbourhood
composting sites less than 38 m3 in size [21] Due to New Jersey's ban on leaf landfilling, the
State has granted during 1989 an emergency exemption for the full leaf composting permit
requirement. Communities have been allowed to get a temporary approval to operate while
their formal permits were under review by the Department of Environmental Protection [22]

6.3 Health and Safety Requirement

Health and safety requirements for composting operations often fall under the regulations in
effect for solid waste disposal facilities or wastewater treatment plants (for sewage sludge
composting). The primary focus of the requirements is that the facility be operated in a safe
manner and nuisance control measures be taken when appropriate.

Safety regulations in Canada and the U.S. include fire safety procedures, such as the provision
of hoses and extinguishers around the piles and equipment. Nuisance control measures
generally include vermin and vector control, odour control, dust mitigation, and liner control
procedures. Non-processibles and other material not suitable for composting are usually not
allowed to be stored for any length of time on the facility grounds. Health and safety
requirements at yard waste composting sites are less stringent and specific than those for sludge
and MSW composting, since these facilities involve less machinery and handle less putrescible
waste.

Examples of public health and safety regulations concerning MSW and sludge composting
operations for several U.S. States are presented in Table 6-12. Although it is generally
recognized worldwide that "operative conditions in composting installations are warranted
which may safeguard the health of the operators" [12], little specific information is available in
the literature regarding procedures for doing so.

The potential hazards to workers from airborne pathogens in composting faculties is addressed
by P. Boutin and J. Moline [25]. They stress the importance of incorporating dust control
measures in the design of the facility. Specifically, the following recommendations are made:
prohibit hand sorting of refuse; enclose the main dust emitting devices; equip refuse and
compost handling places with superpressured cabins supplied with fresh filtered air; aid dust
dilution by increasing air circulation through the use of sheds instead of enclosed premises; and
isolate process premises from hygiene rooms [25].

6-18

TABLE 6-13
Facility Siting and Approvals for Yard Debris Composting in the U.S.

Permit to construct/ Yard waste co
ooerate a comoostir.g pasting pemi
facility for the pro- (ever 50 yd)
cue: :on of organic
products

faci lity permit

6-19

6.4 Hazardous Waste Handling, Storage, and Disposal

It is the consensus worldwide that wastes contaminated with hazardous materials should not be
used for the preparation of organic soil amendments [1]. Source separation of feedstocks to the
compost operation is the recommended method of reducing the introduction of materials that
would potentially contaminate the compost [1,12,14,26,27]. Alternatively, pre-processing of the
solid wastes is recommended to restrict composting to the organic fraction by removing inerts
prior to composting and thus limit the transfer of heavy metals to the compost product. [1,12].

In the provinces of Ontario and Quebec, the types of wastes that can be processed at a compost
facility are restricted (see Table 6-1). Restrictions address biomedical waste, and other types of
hazardous and toxic wastes.

In the U.S., Florida has legislated that hazardous waste, used oil, and wastes containing
asbestos should not be processed into compost except for small quantities normally found in
household waste. It is the responsibility of plant operators to reject any loads found to contain
the hazardous waste materials [7].

In Austria, standards have been developed (ONORM S 2100) which specify the special and
hazardous wastes that can be composted safely [14].

Regulations have been developed by the State of New York to limit the amounts of hazardous
wastes entering MSW compost by requiring that a household hazardous waste collection system
be in place in any residential area serviced by a MSW composting facility. The household
hazardous waste collection system must be approved by the New York Department of
Environmental Conservation and operated according to Section 360- 1.7(b)(6) of the Pan 360
Solid Waste Management Facility Regulations. The regulations specify that an approved site
be utilized for clean up days of household and farming hazardous waste. The site must be
fenced, staffed by qualified personnel, and operated in accordance with approved segregation
and packaging plans [4].

6.5 Summary

Several regulations have been developed to control the use of composts. Some European
countries have had regulations for a number of years. In addition, the CEC has taken the lead
in trying to establish regulations common to all member countries. In most cases, European
regulations are more stringent than those in the U.S.

In the U.S., the EPA has been heavily involved in the development of guidelines controlling
the treatment and distribution of sewage sludge products. The guidelines currently are under
evaluation and are expected to be modified.

Regulations applying to composts produced from MSW and yard debris have been developed
by some states. In most cases, the regulations have been developed without the benefit of
having the composts tested and evaluated. Unlike sewage sludge compost, limited tests have
been conducted on MSW and yard debris composts. Thus, in several cases, the regulations
were based on those for sewage sludge.

After regulations had been developed in one or two states, other states followed suit by
adapting those regulations to their particular situation. Consequently, the latest regulations are
modifications of those developed in states like New York and Minnesota. Most regulations
limit the use of the composts based on the concentration of heavy metals and some toxic
organic compounds. Very few states, if any, have carried out agricultural or horticultural tests
on the finished products.

6-20

Compost made from yard debris has very few restrictions and regulations.

Guidelines for permitting, siting and operating composting facilities are essentially the same as
those for any other solid waste management facility. The guidelines currently are being tested
and are in a process of evolution. States that do not have these guidelines in place are relying
on guidelines developed for other states.

Most states are encouraging the development of yard debris compost projects. Consequently,
requirements for permitting and siting are not as stringent as those for other solid waste
management facilities.

As more composting facilities are built, more states will institute guidelines that are specifically
developed for their particular conditions (i.e., climate, population). Furthermore, established
regulations and guidelines will be modified to reflect the nature of the compost feedstock as
well as available processes.

In Canada, Ontario and other provinces have not yet adopted regulations or guidelines on
compost quality. Ontario and some other provinces do, however, have guidelines on siting of
new composting facilities.

6.6 References

[1] Zucconi, Franco, and Marco de Bertoldi, "Specifications for Solid Waste Compost,"
BioCycle. 28(5):56-61 (May/June 1987).

[2] Portland Area Compost Products Market Study, prepared for the Metropolitan Service
District, Portland, Oregon, by Cal Recovery Systems, Inc., October 1988.

[3] "EPA Sludge Disposal Regulation Proposed," BioCvcle, 20(3):44-47, (March 1989).

[4] Six NYCRR. Pan 360 Solid Waste Management Facilities, New York State,
Department of Environmental Conservation, Subpart 360-5, December 31, 1988.

[5] Regulation for the Land Application of Sludge and Septage, Massachusetts Department
of Environmental Quality Engineering, 310 CMR 32.00, November 10, 1983.

[6] Regulation of Water Supply. Sewage Disposal and Solid Waste, Subtitle 04, Maryland
Department of the Environment.

[7] Criteria for the Production and Use of Compost Made from Solid Waste, Florida
Department of Engineering Regulations, Workshop No. 2, Draft Regulations,
May 1, 1989.

[8] Guidelines for the Agricultural Utilization of Sewage Sludge. The Rules and
Regulations of the Department of Environmental Resources, Commonwealth of
Pennsylvania, Pg. 2, May 1988.

[9] Pan 391, Design Criteria for Sludge Application on Land. Chapter E, Subtitle C, Title
35, Illinois Environmental Protection Agency, January 1, 1984.

[10] Guidance and Regulations Governing the Land Treatment of Wastes. State of Delaware
Depanment of Natural Resources and Environmental Control, Subsection 1003,
p. 198, August 1988.

6-21

[11] Domestic Sewage Sludge Regulations, Colorado Department of Health, 5CCR, 1003-7,
1 986.

[12] L'Hermite, P., "State-of-the-Art of Composts Systems: Current Situation in Europe ana
Future Outlook," Presented at the International Symposium on Compost
Production and Use, S. Michele All'Adige (Trento), Italy, June 1989.

[13] Merillot, J.M., "Recycling Organic Municipal Wastes in France," BioCvcle. 30(7V30-3l
(July 1989).

[14] Lutz, Willibald, "Austria's Quality Requirements for Solid Waste Compost" BioCvcle
25(5):42-44 (July/August 1984). V *"*

[15] Mayer, M., H. Hofer, and U. Maire, "Trends in Yard Waste Composting," Biocvcle
Vol. 29 (July 1988). B y

[16] Sana, J., F. Giro, M. Soliva, and P. Florensa, "Approccio Metodologico Nella
Valutazione Delia Qualita del Compost Delia Catalogna (Spagna)," Presented at
the International Symposium on Compost Production and Use, S Michele
All'Adige (Trento), Italy, June 1989.

[17] Kubota, H. and K. Nakasaki, "State of the An of Compost Systems: The Current
Situation and Future Outlook in Japan," Presented at the International
Symposium on Compost Production and Use, S. Michele All'Adige (Trento)
Italy, June 1989.

[18] Chapter 26, New Jersey Division of Waste Management, Section 7:26-2B.6, Supplement
October 19, 1987.

[19] Guidelines for Leaf Composting Facilities. Pennsylvania Department of Environmental
Resources, Bureau of Waste Management, June 7, 1988.

[20] Guidelines for Preparation of an Application for a Permit to Construct and Operate a
Leaf Composting Facility, State of Connecticut Department of Environmental
Protection, September 1988.

[21] Wisconsin DNR Codes and Guidance Concerning Composting Sites, State of
Wisconsin, October 1987.

[22] Compost — Permit Requirements. New Jersey Department of Environmental

Protection/Division of Solid Waste Management, September 1, 1987.

[23] Environmental Quality Board Municipal Waste Management Regulations. Pennsylvania
Bulletin, Vol. 18, No. 15, Chapter 281, Composting Facilities, p. 1793, April
1988.

[24] Personal Communication, Ware Koser, Michigan Department of Natural Resources
Department of Waste Management, June 1989.

[25] Boutin, P., and J. Moline, "Health and Safety Aspects of Compost Preparation and
u,se' Compost: Production. Quality and Use. M. de Bertoldi, M.P. Ferranti, P
L'Hermite, and F. Zucconi, eds., Elsevier Applied Science, 1987.

[26]

Golueke, Clarence G. and Luis F. Diaz, "Quality Control and Waste Management'
BioCycle, 2Q(7):65-67 (July 1989). 6 '

6-22

[271 Reijenga Femke, "Separate Collection of Compostables," BioCyclg, 30(7):62-64 (July
1989).

7.0 OTHER EMERGING TECHNOLOGIES

7.1 Irradiation of Sewage Sludge for Composting

7.1.1 Introduction

Municipal sludge contains many nutrients beneficial to plant growth - nitrogen, phosphorous and
trace minerals are examples. Advantage can be taken of these fertilizer or soil conditioning
properties, provided that some potentially harmful sludge components are reduced or eliminated.
Regulations generally encourage sludge use, however, cost effective and reliable pathogen and
parasite elimination or reduction can be a stumbling block to achieving more successful utilization
programs.

Research and long-term operating units have demonstrated that irradiation is an effective means
for reducing or eliminating pathogens and parasites in sewage sludge and other wastes to levels
where reuse in public areas meets criteria for protection of the public health [1]. The irradiation
process does not increase the extractability and plant uptake of a broad range of nutrients and
heavy metals from sludge-amended soils [2]. However, it does eliminate the hazards associated
with pathogen and parasite contamination when applying sludge to land.

The key to understanding why radiation processing is being used is to remember that gamma
radiation is an effective and readily available method of destroying microorganisms. It is for
this reason that irradiation is considered as a viable pasteurization alternative for sludges and
other non-toxic wastes.

7.1.2 Sludge Irradiation Experience and Regulation

Since 1975, scientists at New Mexico State University in New Mexico, USA, have been using
irradiated sewage sludge in an extensive research program encompassing biology, crop and soil
sciences, animal sciences and agricultural economics [2]. The sludges used in all research
projects were first irradiated at Sandia National Laboratory's 8-ton-per-day pilot plant irradiator.
Jointly sponsored by the U.S. Environmental Protection Agency and the Department of Energy,
the research work at Sandia has shown that irradiation of dewatered sludge effectively eliminates
pathogens without affecting the beneficial soil conditioning qualities of sludge (see results in
Section 7.1.3).

Composting tests carried out in Japan have found that C02 production almost ceases within two
or three days in irradiation-pasteurized sludge compost piles, as opposed to more than 10 days
in unpasteurized sludge compost piles [3]. This significantly longer composting time in
unpasteurized sludge is due to the slowing down of composting bacteria action when high
temperatures are maintained to eliminate pathogens.

The process has also met with World Health Organization (WHO) approval [4]. A WHO
working party on sewage sludge disinfection processes recommends providing for a minimum
irradiation dose of 500 krad (.5 Mrad) for unconstrained use of sludge.

7-2

A full-scale sewage sludge, irradiation-pasteurization plant has been operating in Geiselbullach,
West Germany, since 1973. The plant is designed to process sludge generated by a region
whose population is 240,000 people. Plant operators have reported that this pasteurization process
is economically attractive when compared to other available processes and that irradiation is safe,
effective and reliable [3]. Regulations regarding the treatment and use of municipal sewage
sludge have received increasing attention around the world. The U.S. Environmental Protection
Agency, for instance, has designated gamma-irradiation treatment as a method of pathogen
reduction in its regulations [6]. EPA land application criteria stipulate that irradiation, when
preceded by a process such as anaerobic digestion, effectively protects public health from sludge-
borne pathogens.

In other countries, the Swiss Parliament has decreed that sewage sludge must contain no more
than 100 enterobacteria per gram and no viable infectious worm eggs at the time of delivery if
sludge is used as a fertilizer on grazing areas and areas used for horticulture [7]. In the Federal
Republic of Germany, sewage sludge must be treated with a state-approved process to render it
non-infectious before it can be applied [8].

7.1.3 Effects of Irradiation on Pathogens

Numerous pathogen inactivation studies have confirmed that gamma radiation will kill bacterial
and fungal pathogens, viruses and parasites found in sludge, but the sensitivities to irradiation
of different pathogens vary.

Pathogenic fungi can grow in sludge, particularly during composting. The sensitivity of one of
these, Aspergillus Fumigatis, to gamma irradiation was studied at Sandia National Laboratories
[9]. A D10 value (the dose required to reduce contamination levels by 90%) of 0.05 to 0.06
Mrad was obtained for fungal spores, indicating that irradiation is an effective method of
destroying them in sludge. The ova and cysts of protozoan and helminthic parasites sometimes
found in wastewater are resistant to inactivation by physical and chemical processes. These
parasites are not common to all sludges, but may be found where local morbidity is sufficient
to provide a source to the wastewater treatment stream. The resistant ova and cysts are heavier
than bacteria and viruses, so a great majority will settle into sludge during primary clarification.

Dosages of 0.2 Mrad consistently caused reductions of three or more orders of magnitude in
viable parasitic eggs, whether in liquid or composted sludge.

Results obtained from the West German sludge irradiator indicate that a dose of 0.3 Mrad is
sufficient to inactivate two to three orders of magnitude of enterococci (fecal streptococci) and
five to six orders of magnitude of enterobacteria (fecal and total coliform) [5].

Up to 1 x 105 enteric viruses/g are reportedly excreted by infected individuals and over 1 x
10/L have been recovered from raw wastewater. Studies have shown that anaerobic digestion
removes about 90% of detectable viruses from sludge [9]. But because viruses are small and
have simple chemical structures, they prove to be most resistant to irradiation.

Biologists at New Mexico State University have shown, however, that when irradiation-
pasteurization is coupled with a treatment such as anaciobic digestion, then viruses are reduced
below detectable limits [1].

A review of the research/studies that have been published to date yields the following information
on chemicals in irradiated sludge.

7-3

to a repon presented to the International Atomic Energy Agency at Vienna, on "High Level
Radiation in Waste Treatment", researchers Dr. Lessel and Dr. Suess stated "The irradiation
tteatment does not change significantly the chemical compounds of the sludge. This observation
holds true also for organic nitrogen compounds ... However, sometimes the dewatered irradiated
sludge seemed to be richer in phosphate than the non-irradiated sludge ... This may be explained
by an indirect effect of the treatment, rather than a direct one."[10]

Sv!. IX? Werl °erman itudy 0f ilTa(iiated sluage, it was concluded that, "As the irradiation
taxes place at temperaturs between 25»C and 30°, no breakaown of organic nitrogen compounds
is induced and no obnoxious smells are registered". [5] vw»u*

Research on a sludge irradiator, largely carried out by a number of departments at the New
Mexico State Umversity, included chemical studies, with results as follows:

The irradiation process does not increase the extractability and plant uptake of a broad
range of nutrients and heavy metals from sludge-amended soils.[ll]

Soil chemistry aata from experiments with herbicide residues, PCBs and pthalate esters
have shown degradation of the organic residues, but in no case was the persistence of
these compounds extended in sludge-amended soil.[ll]

In addition, the University carried out a five-year study of range beef cows and breeding ewes
ted feed supplements containing 7 to 50% gamma irradiated sewage sludge. Tne ewes were
fed the sludge supplement continuously over the 5 year period, while the cows received the
supplement for 4 months of each year for 5 years. Results reported incLde:[i2]

long-term consumption of gamma irradiated sewage solids caused no changes in activities
ot enzymes for biotransformation of xenobiotics suggestive of toxicosis; and

there were no lesions of toxicosis evident at slaughter, nor any buildup of neavy metals
and refractory organic residues in organs and tissues.

In addition to the research that has already been carried out, please note that the University of
PcU, m , >TaU0na1, ^ 0nlari0 Veterinary Council and the Whiteshell Nuclear Research

bstabhshment in Manitoba are involved in a two-year study of irradiated and un-irradiated

d? thXa eWag£ T0XiC °rganiCS "■ incIuded 'm ^ stud>'- which sho"l<i yield more in-

7.1.4 Summary

A typical sludge management system consists of processes for thickening stabilization
oewatenng, disinfection and disposal. Composting call assist with sludge/Se SStiS
dewa tenng, disinfection and preconditioning of the sludge for composting8 taLSwSS
S^^Ve,hand 'k 3ble ^^ °f *fafcata- W"" P^ ^watered sludge if pasteuS by
more Spry1 ^ COmpOStine Process can te comPlet£d more ouickly, more easily and

nrocf^n^i011 ^ vdy bC TSt 5?dely USed a£ *» add-°n t0 facmtie* *««« a stabilization
process, such as anaerobic or aerobic digestion, already exist and a disinfection process must te
added to promote the sale of the sludge. Sludge cold pasteurization maj eSeZ storage and
long-distance transportation characteristics of sewage sludge. ' S

7-4

7.2 References

[1] "Irradiation as a Means to Minimize Public Health Risks from Sludge-Borne Pathogens",
J.G. Yaeger, R.T. O'Brien (1983) in J. Water Pollution Control Federation, 55,
977-983.

[2] "Sewage Sludge: A Beneficial Byproduct", G.A. O'Connor, NMSU, Us Cruces, New
Mexico (1980).

[3] "Economic Feasibility of Irradiation-Composting Plant for Sewage Sludge", S. Hashimoto,
K. Nishimura, S. Machi; Takaski Radiation Chemistry Research Establishment,
Japan Atomic Energy Research Institute, Takasaki, Gumma 370-12, Japan (1987).

[4] "Survey of Sewage Sludge Disinfection Processes", Commission of the European
Communities, Environment and Waste Recycling Programme (1987).

[5] "Gamma-Irradiation for Disinfection and Conditioning of Sewage Sludge - The
Geiselbullach Demonstration Project", T. Lessel, A. Seuss, E. Englmann;
Abwasserverband Ampergruppe, Haupstr. 37, D8031, Eichenau (1979).

[6] United States Environmental Protection Agency (1979), Tide 40, Code of Federal
Regulations, Part 257.

[7] Swiss Parliament, Sewage Sludge Decree, 18 April 1981.

[8] Federal Republic of Germany, Sewage Sludge Decree, 25 June 1982.

[9] "Pathogens in Sludge: Occurrence, Inactivation and Potential for Regrowth", R.L. Ward,
G.A. McFeters, J.G. Yaeger, Sandia National Labs, New Mexico (July 1984).

[10] "Technical and Economical Aspects of Irradiation", A. Suess, T. Lessel and A. Haisch;
Bayerische Landesanstalt fur Bodenkultur unjd Pflanzenbau, Munchen (1982).

[11] "Irradiation of Municipal Sludge for Agricultural Use", S.B. Ahlstrom, CH2M Hill Inc.,
Albuquerque NM. Published in Radiation Physics & Chemistry Journal, Vol. 25
(1985).

[12] "Final Technical Completion Report", Contract #DE-AC04-83AL21776, New Mexico
State University.

8.0 ALTERNATIVES TO COMPOSTING

8.1 Introduction

Several alternatives exist that can handle organic wastes other than composting. These
alternatives are briefly discussed below.

8.1.1 Animal Feed

Historically, livestock have been fed kitchen scraps and food byproducts. These practices
continue today but on a much smaller scale. Approximately one percent of the United States
hog production is raised on such waste feeding operations (BioCycle, 1985).

The nutritional requirements of hogs are similar to humans and therefore hogs are ideal for
utilizing these wastes. Carcass quality is not significantly different between animals fed food
wastes and animals fed grain.

Before the food waste is fed to the hogs, care must be taken to guard against inducing human
and animal health problems. Most waste food classes must be steamed a minimum of 30 minutes
at 212°F.

Farmers collect food wastes from local restaurants, cafeterias and food processors. Food waste
recycling projects are only viable when the farms are located clo^e to a concentration of food
waste producers.

It is not feasible to include residential food waste in a hog waste feeding system due to
purification problems resulting from the long residence time in the home before the waste is
put out for pick-up.

8.1.2 Biogas Production

8.1.2.1 Introduction

Biogas is generated when microbes break down organic material under anaerobic conditions.
The biogas consists mainly of methane and carbon dioxide with approximately 65% of the gas
consisting of methane. Its gross heat value is approximately 7 kwh/m3. The fermentation period
to produce biogas is 15 to 20 days. The biogas can be used as fuel in furnaces or boilers. The
remaining digestate can be spread on fields.

The major advantages of anaerobic digestion are:

• low sludge production; and

reactor remains stable even when shut down for several months.

The limitations of anaerobic digestion are:

• the process is slow to start-up;

• slow recovery from accidents; and

• requires careful surveillance.

Anaerobic digesters are usually used to treat wastes from cattle and hog raising stations, high
BOD food processing wastes and sewage sludges.

8.1.2.2 Biogasification of Municipal Solid Wastes

Studies at the Sanitary Engineering Research Laboratory (SERL) of the University of California
(Berkeley) investigated the reduction and stabilization of the organic fraction in municipal solid
waste via anaerobic fermentation [1-4]. The SERL digestion studies led to the conclusion that
the organic component of MSW can be readily digested with the exception of wood and to some
extent printed paper. At an organic loading rate of about 1.12 g volatile solids/L-d (VS/L-d), a
detention time of 30 days and a temperature of 35°C, approximately 0.4-0.6 L of gas per gram
of volatile solids introduced (L/gVS) can be expected.

Investigations to evaluate the feasibility of digesting mixtures of sewage sludge with the entire
organic fraction of MSW were carried out in the early 1970s [5-6]. Gas production fluctuated
from 0.12-0.45 L/gVS added depending on loading rate, temperature and detention time.

Other experiments were conducted by Klass and Ghosh [7-8] centred on the digestibility of
sludge when mixed with the organic fraction of refuse. Gas productions equivalent to 280 to
570 L of methane per person per day were reported.

The Dynatech R&D Corp. [9] team came to the conclusion that biogasification was both
technically and economically feasible.

A demonstration project in Pompano Beach, Florida evaluated the commercial feasibility of
digesting the organic fraction of refuse. Waste Management Inc., under contract with the
Department of Energy, evaluated the technology and economics involved in converting up to 90
tonnes of refuse per day into methane gas.

Gossett and McCarty [10] investigated suitable ways of enhancing the anaerobic biodegradability
of refuse. They found that exposing refuse to a temperature of 133°C and a pH of 1 over a 3
hour period could almost double the biodegradability of digested refuse. The additional
expenditure in energy required to attain the high temperatures may exceed the amount of resulting
energy from the enhancement in gas production.

A study at the University of California (Berkeley) used the organic fraction segregated in a
resource recovery system developed by the University. The study allowed for the integration
of various unit processes such that valuable materials (e.g. ferrous metals and papers) could be
recovered for refuse. Each process was selected such that the residue from one became the
input to a second process [11].

8.1.3 Landfarming

Landfarming is a broad term adopted fairly recently by the waste management profession referring
to a method of destruction or disposal of an undesirable waste. In the method, the soil is the
principal agent of destruction. The soil is such an agent in that it not only is the medium, but
it also is a reservoir of macro- and micro-organisms that break down the residue. Although the
designation "farming" may be somewhat misleading, it is useful in that it is a means of
distinguishing between the practice of using manure, crop residue and sewage sludge as a soil
amendment or source of fertilizer elements and the relatively recent innovation in which the role
assigned to the soil is to serve as an agent of destruction and stabilization. Furthermore, use of
landfarming in the context of composting also is somewhat far-fetched. One relation between
composting and landfarming is that boih involve waste destruction and stabilization. Another
equally tenuous relation is that composting and landfarming do to a limited extent share several
parameters and requirements.

8-3

In the past decade, a considerable amount of research and number of applications related to
landfarming have been and are directed to its potential in the disposal of petroleum sludges. A
more recent development is a gradual expansion of research effort directed to the landfarming
of other hazardous wastes.

8.1.3.1 Municipal Solid Waste

Most of the formal research on landfarming municipal solid wastes took place in the late 1960s
at the University of California (Berkeley) [12, 13]. The underlying concept of landfarming
investigated by the University was based on the rationale that land should be an essential part
of the treatment. However, the manner of the treatment should be such that the land need not
be permanently dedicated to wastes disposal, as is the case with landfill. According to this
rationale, the land serves as a means of processing rather than of disposal. The processing is
accomplished by adapting the bioxidation phase of the growth-decay cycle prevailing in soil to
the oxidation and stabilization of the organic matter in the wastes. With such an adaptation,
the land is loaded to the limit of its ability to accept wastes without disrupting the growth-decay
cycle. (Exceeding this limit leads to production of objectionable odours and other nuisances.)
A variation would be sequential cropping and waste treatment.

One application of the concept involves two key steps: 1) rninimally process the wastes; and
2) immediately incorporate the processed wastes into the soil. The name given the system by
its developers, "low-cost biostabilization" is used in this report. The term is apropos because
this particular system includes variations that range from those in which only a minimum of
segregation and grinding precede incorporation of the refuse into the soil to those in which some
composting precedes incorporation. In practice, a given plot of land receives a loading of ground
raw and unsegregated refuse or of roughly composted refuse once or twice each year throughout
the time in which the site is dedicated to waste disposal. The frequency of the loading is a
function of the rate of decomposition or stabilization of the wastes in the soil.

When the time comes to divert the land to another use, loading is stopped and the land is
allowed to recover. Nondegradable material remaining exposed on the soil is removed and
buried elsewhere. Inasmuch as only the top 1 to 2 ft of the land would be involved, settling
would be negligible and the land could be put to a different use immediately.

In the University study, each plot received solid waste once each year. However, to represent
a real-life situation in which refuse is produced and must be processed year-round, waste was
applied to one group of plots in the summer, to a second group in the autumn, a third group in
the winter, and a fourth group in the spring. The organic material was spread on the land, after
which the land and its surface layer of refuse was tilled with a heavy-duty tiller. At loadings
above 300 tons/acre-yr, it was necessary to remove the top 6 in. of soil before applying the
refuse, return this soil to the top of the applied wastes, and, finally, to till and mix soil and
refuse. Therefore, with such high loadings, specialized equipment would be required.

Results obtained in the research indicated that: 1) difficulties would be encountered in applying
refuse during wet seasons and also in incorporating large amounts of refuse into the soil; and 2)
the aesthetics of the operation would be unacceptable as would be associated vector and rodent
problems. In short, a full-scale operation would take on many of the objectionable characteristics
of an open dump.

8.1.3.2 Petroleum and Other Hazardous Wastes

Landfarming of petroleum and other hazardous wastes differs from that of municipal solid waste
in that it usually calls for: 1) frequent working of the soil to ensure satisfactory aeration; 2) the
addition of macronutrients that might be in short supply in the wastes; 3) a long-term dedication

8-4

of land area; and 4) a more specialized microbial population. A fifth difference arises from the
involvement of hazardous materials. Because of this involvement, operation and maintenance
controls are more rigorous and must be carefully observed. All gaseous, liquid, and solid
emissions must not be released into the environment without having been rendered innocuous.
The present trend among local, state, and federal regulatory agencies is to require the operation
to be sheltered such that control is had at all times on all emissions, beginning with delivery of
the waste and ending with the completion of treatment. In the event that treatment does not
render the product completely innocuous, the potentially hazardous treatment product must be
stored or disposed at some appropriately regulated site.

Landfarming procedures vary with the type of waste to be treated. Oily wastes (e.g., sludges
from petroleum storage tanks) are spread upon the field and then are disked into the soil to a
depth determined by the need to maintain aerobiosis, i.e., not deeper than 15 to 18 cm (6-7 in.).
Frequency of disking is determined by the fact that breakdown of oily wastes occurs only under
aerobic conditions. (The situation may differ somewhat with certain hazardous wastes (chlorinated
hydrocarbons). Such wastes may require an anaerobic phase in addition to the aerobic phase.
The sequence of the two phases differs according to the waste requiring treatment.)

Retention times usually are in terms of 12 to 24 months.

Microbial Population - Broadly speaking, for almost every type of organic hazardous waste
manufactured thus far, a particular species of microbe capable of breaking down that waste can
be isolated from the soil [12-15]. Thus, most of the so-called breakthroughs regarding hazardous
waste and the microbes to break them down actually have already been made, but without fanfare.
The practical significance of the existence of such microbes in nature is that in landfarming,
particular strains of microbes needed are indigenous, albeit as minute populations. On the other
hand, the real problems are to identify the factors that slow the process and develop technolog-
ically and economically feasible means and ways of coping with them In other words, the
engineering aspects constitute the biggest problem

Difficulties of a biological nature are the poor ability of the desired species to compete under
natural conditions with other species present in the soil. Compensating for this inability usually
takes the form of setting up enrichment conditions, i.e., conditions favourable to the desired
species, but less so or even inhibitory to potential competitors. This problem of competition and
abihty to thrive under practical and economical conditions is the major obstacle to practical use
of "engineered" microorganisms.

Because the indigenous active strains of microbes usually are present as minute populations,
incorporation of the waste into the soil usually must be followed by a lag period. The lag
period is the time in which particular strains adapt to the waste and proliferate. The lag period
can be materially shortened by repeatedly using the same land area, inasmuch as the microbial
populations developed in the preceding treatment cycle will be present.

8.2 References

[1] Golueke, C.G. and McGauhey, P.H., Comprehensive Studies of Solid Wastes Management,
2nd Annual SERL Report No. 69-1, Sanitary Engineering Research Laboratory,
University of California, Berkeley, 1969.

8-5

[2] Chan, D.B. and E.A. Pearson, Comprehensive Studies of Solid Wastes Management:
Hydrolysis Rate of Cellulose in Anaerobic Fermentation, SERL Report No. 70-
3, Sanitary Engineering Research Laboratory, University of California, Berkelev.
1970.

[3] McFarland, J.M. et al., Comprehensive Studies of Solid Wastes Management, Final
Report, SERL Report No. 72-3, Sanitary Engineering Research Laboratory,
University of California, Berkeley, 1972.

[4] Klein, S.A., "Anaerobic Digestion of Solid Wastes," Compost Science. VoL 13, No. 1,
January-February 1971, pp. 6-11.

[5] Pfeffer, J.T., "Reclamation of Energy from Organic Refuse", Solid Waste Program, EPA
Grant No. EPA-P-800776, Department of Civil Engineering, University of Illinois,
Urbana, 111., April 1973.

[6] Pfeffer, J.T., "Anaerobic Processing of Organic Refuse", Proceedings, Bioconversion
Energy Research Conference, Institute for Man and His Environment, University
of Massachusetts, Amherst, Mass., 1973.

[7] Klass, D.L. and Ghosh, S., "Fuel Gas from Organic Wastes", Chemtechnologv. Vol. 3,
November 1973, pp. 689-698.

[8] Ghosh, S. and Klass, D.L., "Conversion of Urban Refuse to Substitute Natural Gas by
the Biogas Process", presented at Fourth Mineral Waste Utilization Symposium
Chicago, 111., 1974.

[9] "Fuel Gas Production from Solid Waste, 1974 Semi- Annual Progress Report", NSF
Contract C-827, Dynatech Report No. 1151, 1974.

[10] Gossett, J.M. and McCarty, P.L. "Heat Treatment of Refuse for Increasing Anaerobic
Biodegradability", NSF Grant GI-43504, Dept. of Civil Engineering, Stanford
University, 1974.

[11] Diaz, L.F. et al., "Biogasification of Municipal Solid Wastes", Journal of Energy
Resources Technology. Vol. 103, June 1981, pp. 180-185.

[12] Ed. G.B. Brown. G.B. Evans, Jr, B.D. Frentrup, "Hazardous Waste Land Treatment",
Butterworth Publishers. Boston-London, 692 pp., 1983.

[13] E.J. Opathen, H.K. Howard, and J.J. Bond, "Biological Treatment of Leachate from a
Superfund Site," Environmental Progress. 8(1):12-18 (February 1989).

[14] J.B. McDermott, et al, "Two Strategies for PCB Soil Remediation: Biodegradation and
Surfactant Extraction," Environmental Progress. 8(1):46-51 (February 1989).

[15] M.R. Overcash, "Decomposition of Toxic and Nontoxic Organic Compounds in Soils
Ann Arbor Publishers. 455 pp., 1981.

9.0 CONCLUSION

This study has demonstrated that composting is being recognized as a viable waste management
alternative in many European countries and the North America. As a result, many different
technologies have been developed to separate compostable material from the municipal waste
stream and to accelerate the process.

Composting technologies can be broadly divided into four groups: turned windrow, static pile,
in-vessel and hybrid. Feedstocks range from using organic material from the municipal solid
waste stream to sewage sludge, either separately or mixed together. Industrial organic wastes
and sludges are also being used as composting feedstocks where conditions are economically
favourable or mandated by circumstance.

Little information is available in the literature concerning the construction and operation of
composting facilities in Canada. It is difficult to make an economic comparison in Canada of
operating facilities and composting technologies used in other countries due to: climate
differences, variable wages, equipment availability/sharing, accounting practices and variable land
costs.

The reported operation and maintenance costs for sludge composting facilities ranges from $ 40
to $ 54 per dry tonne. Reported operation and maintenance costs for yard waste composting
facilities range from approximately $ 5.20 to $ 65 per tonne of yard waste. Tipping fees reported
for MSW composting facilities (both operational and proposed) range from about $ 26 to $ 118
per tonne of MSW. The value of any program to compost wastes is greatly increased when an
end use for the product is secured; the quantities of wastes requiring landfill are reduced, a
beneficial use for the product is found and a revenue is generated from the sale of the compost.

Two communities in Canada are currently composting the organic component of municipal solid
waste: Riley, Alberta and Amos, Quebec. Several other municipalities will be initiating pilot
programs in the near future.

In the United States, the number of projects for composting sewage sludge has grown
substantially since the 1970s. In 1988, there were 115 operational sewage sludge compost
facilities. As of 1988, there were five MSW composting facilities in operation in the United
States. The States of New Jersey, Minnesota, Wisconsin and Illinois have banned the disposal
of leaves in landfills. Private and municipal composting of yard wastes has become very
prevalent in many States.

Many countries around the world are using composting to reduce the reliance on landfills. In
industrialized countries, composting has gained acceptance principally because it constitutes a
means of waste disposal. In developing countries, compost is also valuable in land reclamation
and improving soil fertility.

Most policies and standards pertaining to compost facilities, processing and markets have either
been recently developed or are in the developmental stages. In Canada, only the provinces of
Quebec and Ontario have developed policies specifically for composting operations.

In the United States the Environmental Protection Agency has been active in developing
regulations pertaining to sewage sludge products (including compost). State and municipal
governments are generally responsible for regulating MSW and yard waste composting.

9-2

The Commission of the European Communities has taken the lead in developing policies and
guidelines for compost operations in Europe. Individual European countries have also developed
compost guidelines, including: France, Austria, The Netherlands, Belgium, Switzerland, the
Federal Republic of Germany and Spain. The United Kingdom does not currently have guidelines
for limits on heavy metals and other contaminants in MSW compost, but has not accepted the
limits proposed by the CEC.

APPENDIX A
LITERATURE SEARCH

The foDowing databases were searched for information relating to composting. Key words were
carefully selected to narrow the total number of papers to specific subjects pertaining to the study.

Toud Number
Database of Entries Number of Selected Papers

100
150
300
100
50
50
20

4,575 770

NTIS

154

Enviroline

492

Pollution Abstracts

1,066

Agricola

1,273

Biosis

1,395

Embase

175

Medline

20

APPENDIX B
PARTIAL LIST OF VENDORS AND FACILITIES*

American Recovery
Corporation

Italy

buhler Miag

Belgium

Germany

Great Britain

Italy

Spain

Switzerland

Turkey

Daneco

Lebanon

Italy

Dano

United Arab Emirates

Austria

Brazil
Egypt

France
Great Britain

Germany
Italy

Cassino
Perugia

Mons
Tournai

Dusslingen
Ormesheim

Isle of Wight

Bressanone

Barcelona
Valencia

Schauffhausen

Izmir

Beirut

Ceresara

Pieve di Coriano

Tclmezzo

Termoli

Dubai

Fujairah

Ajman

Burgenland
West Tirol

Sao Paulo

Alexandria
Ghiza

Parenti

Anglesea
Manchester

Bad Kreuznach

Viareggio
Pollenza

APPENDIX B
PARTIAL LIST OF VENDORS AND FACILITIES*

Fairfield Service Co.

International Process
Systems (IPS)

Recomp
Taulman

Switzerland
United States

Schaffhausen

Wilmington, Delaware

United States

Lebanon, Connecticut
Fairfield, Connecticut
Portland, Maine
Baldwinsville, New York

United States

St. Cloud, Minnesota

Japan

Iwamisawa City
Towada
Abashiri
Tanko

Sweden

Fargesta
Landskrona

West Germany

Bad Liebenzell

Bickenbach

Oberer Karichbach

Waldmicheibach

Schlitz

Erbach

The above list is not intended to be comprehensive. Individual vendors should be
contacted for complete lists of facilities.