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Bureau of Mines Information Circular/1976
Copy 1 1976
Recycling Trends in the United States:
UNITED STATES DEPARTMENT OF THE INTERIOR
Information Circular 8711
Recycling Trends in the United States:
By Max J. Spendlove
College Park Metallurgy Research Center, College Park, Md.
UNITED STATES DEPARTMENT OF THE INTERIOR
Thomas S. Kleppe, Secretary
BUREAU OF MINES
Thomas V. Falkie, Director
This publication has been cataloged as follows:
trends in the
United States: a
Bureau of Mines 
25 p« illus
., tables. (U.S.
Bureau of Mines.
1. Recycling (Waste, etc.)
I. U.S. Bureau of
no. 8711 622.06173
U.S. Dept. of
the Int. Library
Mineral supply and recycling system 3
Mineral deficits 5
Origin of mineral wastes 7
Relative values in wastes 8
Urban ore 10
Refuse processing 12
Common refuse disposal options 12
Resource recovery from raw refuse 14
Product recycling 16
Recycling problems 18
Areas for research and development 20
The future of recycling 21
1. Mineral supply and recycling systems in the U.S. economy 4
2. Production, recycling, and waste disposal in the metal supply system 7
3 . Products extracted from municipal incinerator residues 15
4 . Products extracted from municipal raw refuse 15
5. Typical items made from products recovered from municipal refuse.... 16
6 . Conventional and product recycling systems 17
1. Estimated tonnage of copper, lead, and zinc in use in the United
2. Average composition and estimated value of raw refuse and municipal
incinerator residues 11
3. Estimated amount and value of recovered products from raw refuse and
incinerator residue 12
RECYCLING TRENDS IN THE UNITED STATES: A REVIEW
Max J. Spendlove 1
This Bureau of Mines publication reviews current recycling trends in the
United States. Although near -term prospects are poor for recycling most
present wastes, urban refuse is an important exception. Such wastes comprise
a mine above ground, and much less processing energy is normally required to
recycle the constituents of urban ore than to obtain them in equal amounts
from natural raw materials.
This review of U.S. recycling arises from the Bureau of Mines research in
this area, which has been in progress since the Bureau's foundation in 1910.
Although the problems are complex, achievements to date are significant and
there appears to be no practical alternative to the present high costs of
refuse disposal and the waste of mineral and energy -related resources involved
in disposing wastes without recycling.
Raw materials of mineral origin comprise the most vital ingredients for
building or maintaining the economy of any industrialized nation. The wealth
and economic viability of the entire industrialized world are determined
primarily by the availability of mineral resources. Their importance is
emphasized by the fact that, in addition to our supplies of direct mineral
origin, many of our nonmineral products, such as meat and vegetables, are
indirectly of mineral origin. For example, fertilizers and other chemicals
are used extensively in many parts of the world to grow the vegetation
essential for raising domestic animals and poultry. Furthermore, owing to
technological advances during the past few decades, agriculture has become
highly energy intensive in connection with fertilizer production and the
manufacture and use of heavy equipment in growing, marketing, and processing
farm products .
Some nations possess relatively abundant resources and others have
virtually none, but no industrialized nation can develop and maintain
economic growth and viability without a continuous and adequate supply of
•"•Metallurgist (now retired) .
many raw materials of mineral origin. In recent years, most nations have
become more intensely concerned with their long-range supply of mineral
reserves, believing that the natural resources of the entire world are finite
and therefore will eventually be totally consumed as the needs of society
continue to mount.
In a somewhat different approach, Brooks and Andrews (J5) discuss a view
that natural resources are not actually being depleted as commonly believed.
Instead, they appear to be vanishing only because the industrial world cannot
yet afford the high cost of exploiting the more abundant but lower grade
resources. Typical of such a resource is the average uppercrust of the earth.
One cubic kilometer is said to contain 2 X 10 a tons of iron, 800,000 tons of
zinc, and 200,000 tons of copper (J5) . As an ore, the average grade of this
crust is very low indeed, and the cost of extracting and refining the market-
able constituents is unquestionably prohibitive. In most cases, the cost of
processing natural minerals increases generally exponentially as the average
grade diminishes. This simply means that, regardless of their apparent great
abundance, the metals and minerals in the average crust of the earth are not
yet within economic reach, nor will they likely be reachable in the foresee-
able future without profound technological advances in extraction processes
and/or in energy conversion. The same applies to the low -value or negative -
value industrial waste materials.
At this point, it is important to note the difference between resources
and reserves. Resources refer to our natural fuel and nonfuel mineral
deposits and other natural entities such as forests, rivers, and geothermal
wells. Reserves comprise only that part of a resource that can be extracted
and marketed economically under prevailing prices and marketing conditions.
Reserves are thus conditional quantities the magnitude of which depends on
nearly all factors affecting the national economy. Given appropriate economic
conditions they may include materials currently discarded as waste; for
example, in municipal refuse.
The U.S. aluminum situation can be cited as an example of this resource-
reserve relationship. Although the United States has unbelievably large
deposits of anorthosite, clay, and shale which contain aluminum in tremendous
quantities (resources) , it has no significant domestic reserves of aluminum
minerals because there are no processes that will extract aluminum from our
domestic resources in economic competition with the Bayer and Hall processes
now employed for treating imported bauxite. In fact, our greatest domestic
aluminum reserves are the secondary materials which we have been recycling
for many years from the reservoir of recoverable materials still in use by the
consumers, the goods -in -use reservoir.
In the future many other materials besides aluminum may be recovered from
municipal refuse. Today this refuse is at best a resource; when recovery can
be done economically, it will become a large manmade reserve of many raw
2 Underlined numbers in parentheses refer to the reference list at the end of
MINERAL SUPPLY AND RECYCLING SYSTEM
Support for recycling in the United States is indicated by the growing
deficits in the national economy originating primarily in the mineral supply
system. The demand for goods and services of mineral origin has increased
markedly in unison with the national economic growth. Concurrently, the
Nation's ability to supply these growing demands from domestic resources
has faltered seriously. On a value base of current U.S. dollars, the 1971
gross national product (GNP) of $1,055 billion was accompanied by a national
mineral deficit of $4 billion. At the end of 1974, the GNP had reached
$1,397 billion, and the mineral deficit was $24 billion. The relatively low
probability of meeting future deficits by discovering large new domestic
resources or by significantly improving minerals supply and/or energy con-
version technologies in the near future emphasizes the importance of recycling.
The following discussions dwell almost exclusively with situations and
systems in the U.S. mineral supply economy. Although no data on other coun-
tries are readily available, there is little doubt that similar if not
identical parallels can be drawn for any other of the more advanced nations.
Referring to figure l, 3 minerals, crude oil, gas, coal, and water valued
at $55 billion were taken from the U.S. reserves in 1974 by extraction
industries such as mining, crude oil, and gas producers. The U.S. import of
mineral raw materials in 1974, valued at $20 billion, came mainly from
foreign mineral operations of U.S. and/or foreign firms. Reclaimed materials
of mineral origin from the recycling industries were valued at $4 billion.
Accordingly, the U.S. mineral processing industries such as smelters, refiners,
and fuel producers consumed these total raw materials valued at $79 billion to
produce energy and processed materials valued at $210 billion. The manufac-
turing and services industries in turn consumed these to generate a gross
national product in 1974 of $1,397 billion. Exports from this sector of the
economy amounted to $18 billion, but imports from foreign firms amounted to
$22 billion. Thus, the net value of goods and services consumed in 1974
by the U.S. population was $1,401 billion. A total of more than 4 billion
tons of new materials of mineral origin was supplied, amounting to 40,000
pounds for each U.S. citizen. More than 18,000 pounds of this was for energy
materials (19) .
We have now arrived at what may be considered the headwaters of the small
but important recycling channel of the mineral supply system. First, note
that some consumer products such as gasoline, electric power, and fertilizers
are totally consumed and therefore lost from the recycling channels forever,
but that very large quantities of other consumer goods continue to be
accumulated by all sectors of society. This accumulation was previously
referred to as the goods -in-use reservoir. Although attempts have been made
to develop reliable data on the magnitude, composition, and location of this
growing reservoir, no conclusive data are yet available on all materials
entering into it. However, the total quantities involved are undoubtedly
tremendous. As the goods in use become obsolete, worn out, and discarded,
3 Figure 1 is a modification of graphic information presented in reference 19.
oil, coal, gas, etc
Mining, oil-gas production
Milling, smelting, power
SECTOR OF ECONOMY
GOODS IN USE
Collecting and processing
RAW MATERIALS OF
MINERAL ORIGIN ^^^
Ore, petroleum, coal, sand
( I M PORTS $20 BILLION)
$79 BILLION TOTAL
(EXPORTS, $18 BILLION)
Goods and services
(IMPORTS, $22 BILLION
$1,401 BILLION NET
FIGURE 1. - Mineral supply and recycling systems in the U.S. economy, estimated values
substantial quantities are channeled into the secondary materials industries
that produced the previously cited $4 billion worth of raw materials sub-
sequently channeled to the mineral processing industries in 1974.
An analysis of figure 1 reveals several points that strengthen the
arguments for drastically improving the recycling sections of this complex
system. For example, it will be noted that in 1974 imports of mineral raw
materials and processed materials of mineral origin exceeded exports by
$24 billion. This is a very sizable mineral deficit in the balance of trade
and contributes to an unfavorable imbalance in the U.S. economy. Such a
large mineral deficit indicates that the United States is not self-sufficient
in many of its mineral materials needs by a very significant margin. Also
note that only $4 billion worth of materials was recycled from a total raw
materials consumption of $79 billion.
The nature of the mineral deficit is indicated by the fact that, to
supply its total 1974 mineral demands (19) , the United States imported nearly
90 percent of its raw materials for producing aluminum; more than 75 percent
of its needs for titanium, tin, mercury, bismuth, nickel, and potassium;
more than 50 percent of its silver, tungsten, zinc, and gold; and more than
25 percent of its iron, cadmium, vanadium, and lead. Even with its tremen-
dously large copper resources, the United States imported about 6 percent of
its 1974 copper demand.
While there has been a sizable increase in U.S. mineral demands and a
parallel increase in product, the demand for materials of mineral origin has
grown rapidly worldwide. Concurrently, ever larger quantities of waste are
being generated and waste disposal costs have reached an alltime high. Super-
imposed upon the unfavorable trade deficit situation are the growing environ-
mental problems in the minerals and minerals -related fields. Establishment of
more rigid regulations calling for cleaner air, water, and land no doubt will
add new production costs in nearly every segment of the goods and services
industries so that future mineral deficits may be greater than expected. In
addition, grades of our most important resources such as copper and iron are
steadily declining. The underlying question behind all of this is, "What can
be done about the present and future U.S. mineral deficits?"
There are numerous suggestions for a partial solution of deficit problems,
one of the most obvious being to find more natural resources for those mate-
rials in greatest short supply. Many proposals have been made for doing this,
but at the present or foreseeable rate of development in mineral exploration
technology, it does not appear that any significant breakthrough is likely in
the near future. One solution that has been suggested is to control the use
of mineral commodities in short supply by some type of governmental rationing
based on the potential for maximum national benefit. However, with a large
shortage of so many different materials, the rationing system would have to be
widespread, expensive, and difficult to manage, and might lead to unprece-
dented black marketing.
Another partial solution to the deficit problem would be to improve the
efficiency of extraction processes or to develop new ones applicable to the
more abundant lower grade resources. It should be remembered, however, that
a very great effort to do this has continued for many years in government and
private laboratories and plants around the world. Many extraction technolo-
gists point with pride to the fact that it is possible to produce copper
economically from ores that contain only 0.5 percent copper. It is possible,
in fact, to economically extract some metals from process solutions containing
only 1,000 parts or less of metal per million parts of solution. Every effort
should be made to continue extractive research and development at an accel-
erated rate, but progress in this area of technology is difficult, tradi-
tionally slow, and often underfunded. Accordingly, we cannot depend heavily
on this approach to meet many of our immediate mineral demands.
Common experience shows that processing costs per unit of additional
product will normally increase almost exponentially as the extraction
efficiency achieved approaches 100 percent. For example, if the assumed cost
of producing a pound of aluminum is 28 cents in the conventional processing
of a 50 -percent aluminum ore, we would expect to extract 90 percent of the
aluminum contained in 1 ton of ore, or 900 pounds, at a total cost of $252.
The process residues would still contain 100 pounds of aluminum, some of which
might be recovered in a more sophisticated and more efficient process. How-
ever, the residues would comprise a 5 -percent ore and the additional sophis-
tication needed to extract an additional 90 percent (90 pounds) of aluminum
from such low-grade materials may well exceed the cost of recovering the
first 900 pounds. Even at the same total cost per ton of ore, each of the
additional 90 pounds would cost $2.80.
If abundant cheap energy should become available in the near future,
it would not alter our extraction capabilities significantly, but it would
bring them well within the range of economic application on many low-grade
resources. There is no firm evidence, however, that the mineral situation
will change significantly in the foreseeable future unless a major and
unexpected breakthrough is made in either extraction or energy -conversion
technology or both. A breakthrough in energy conversion would probably offer
the greatest ultimate benefit because present extraction capabilities of
85 to 98 percent or better are common. Although the chances for greatly
improved energy-conversion processes within the next several decades are
a highly controversial subject, recent reliable reports are not profoundly
optimistic (1_, _16) . Many of those engaged in the development of new atomic
energy processes predict that the breeder reactor will provide the best
practical solution to the growing national energy demands, but others claim
that the problems of radioactive waste disposal and safeguards against
potential radiation accidents will keep development in this field to a
minimum (9^) .
It has happened that critical mineral shortages have occurred con-
currently with widespread pollution and fears of inundation by our own wastes.
These shortages and the general deterioration of the environment have focused
our concerted attention more directly on one of the best opportunities for
reducing large and uncomfortable national mineral deficits --simply by improv-
ing and extending the age-old practice of recycling to its fullest possible
The potentials of wastes as a renewable resource are not easy to analyze
because recycling within the complex systems of mineral supply and demand is
influenced by a host of interdependent and seemingly uncontrollable variables.
The most important of these factors include inflation, environmental regula-
tions, poor recycling incentives, tax structures, import -export policies,
embargoes and property acquisitions by other nations, the quantity, grade,
and distribution of domestic reserves, the state of pertinent technology, and
the great divergence of recycling concepts and opinions among national, State,
and urban officials, the engineering and scientific communities, and the
general public. Based on personal discussions with informed people from the
major mineral -consuming areas of the globe, it appears that many of these
variables are essentially identical in all industrialized nations. In general,
however, a critical examination of mineral resource supply and demand cycles
reveals waste disposal practices that could be modified to improve recycling.
ORIGIN OF MINERAL WASTES
The potentials for recycling can best be determined by considering the
makeup of the system which generates the bulk of wastes.
Figure 2 illustrates how wastes are generated in metal production, but
the process of making almost
any one of the millions of
items used in modern society
leaves a trail of wastes
along the routes of produc-
tion all the way back to the
very origin of all constit-
uents. This trail of wastes
occurs in much the same man-
ner for all consumer prod-
ucts --from straw hats to
Refined meta I
Supplies and parts
dusts, drosses, «
dusts, smokes, ^^~
Spent fuels, gases
and particulates ^^
GOODS IN USE
, * ,
Reclaimed goods ___ RECYCLING —
and wastes I .
FIGURE 2. - Production, recycling, and waste disposal in
the metal supply system.
The relative amounts of
wastes generated are nearly
always greatest at those
operations in the supply
channel nearest the natural
resource, such as mining,
dredging, and quarrying. In
the production of most
metals and nonmetallic
mineral products, mountains
of overburden are moved
literally from one point to
another (29) . In Utah and
other Western States,
gullies and canyons have
been filled to the brim with
copper mine overburden and
subgrade rock rubble that
was moved only to gain
access to the underlying or
adjacent ore bodies. In Minnesota, enormous piles of iron -mine rubble rise
high above the flat countryside near cavernous iron-mine pits. Similar, but
perhaps smaller, quantities of mine wastes are produced at phosphate mines,
coal mines, marble quarries, gravel pits, and similar operations (6, 29) .
Having moved the overburden at the mine site, mining companies extract
the ore that is delivered to beneficiation mills, where a very large fraction
of the unwanted matrix minerals is removed and sent to tailing ponds or banks.
The fraction that is ultimately discarded as tailings varies according to type
and grade of incoming ore and the efficiency of beneficiation operations. Con-
centrates produced in the beneficiation mills are sent to smelters that pro-
duce rather large fractions of slag wastes along with waste stack gases and
solid particulate matter. The smelter produces crude metal, which is sent to
metal refining plants where more slag and stack wastes are generated. Refined
metals are sent to fabricators where still more wastes are generated. Some
scrap is sent back to the smelters or used elsewhere in the fabrication
plants. Worthless materials are usually piled in dumps or covered in landfill
operations. In the vast majority of production operations, waste disposal
restrictions are rapidly becoming more rigid, and the disposal of such wastes
is one of the most pressing problems in nearly every industry in the United
RELATIVE VALUES IN WASTES
Updating earlier data (14, 23 , 30) , the total of all solid wastes
generated in the United States in 1974 is estimated at 4.7 billion tons, of
which the greatest amount (2.5 billion tons) was of agricultural origin. The
mineral industry wastes totaled 1.8 billion tons. Municipal, urban, indus-
trial, and institutional solid wastes accounted for at least another 300 mil-
lion tons; this figure includes garbage, trash, demolition debris, utility fly
ash, and other such solid wastes, but excludes sewage sludge. Although
agricultural wastes are far greater than the others, they are not considered
here except incidentally.
Of all the mineral wastes, it was determined (6) that only 8 of the
80 mineral industries were generating 80 percent of the total mineral wastes
prior to 1970. The copper industry generated the greatest amount, iron and
steel industries ranked second, and bituminous coal and phosphate rock
producers were third and fourth, respectively. Most of the mineral wastes
generated by the mining and milling industries (fig. 2) are very large in
quantity and very low in value. This happens simply because our most capable
industries consistently extract nearly all values of importance from their
raw materials; consequently the wastes are worthless or of negative value.
The slags, drosses, and fumes generated in the smelting and refining indus-
tries are considerably less in total quantity than wastes from mining and
milling, and they usually contain higher levels of potentially valuable con-
stituents. Nevertheless, the levels are often much too low for economic
It is now important to note the consecutive concentration of values that
occurs within the entire supply -recycling -disposal system. In every industry
nearly all of the valuable constituents are extracted from incoming raw
materials and transferred to an outgoing product. Thus, nearly all of the
constituents of greatest value are eventually transferred to product
materials that eventually end up in consumer goods or services. Even though
vast amounts of nonrecoverable wastes are generated in the metal supply system
(fig. 2), most such wastes have virtually no economic importance in the
present technological climate. These wastes comprise a liability, and the
environmental aspects of disposal are becoming paramount. In the United
States, disposal of such mineral wastes has, in the past, affected the
environmental quality of the land, lakes, and streams. Although measures
are being taken to correct polluted conditions in lakes and streams, it is
likely that most of the affected lands cannot be returned to their original
condition in the near future because the cost would be so much greater than
the net environmental benefit. The present approach to the problem appears
to be based on improving future disposal practices and regulations. In this
regard, it has been suggested that the best disposal of very low- or negative-
value wastes generated in the future would be to send them back to the site
of their natural origin, such as vacated mine sites. But even this apparently
simple solution would cause overwhelming new problems in nearly every segment
of the supply and recycling channels, problems far beyond the scope of this
Some of the wastes generated in the system (fig. 2) are currently being
recycled by the secondary metals industry. There is also inplant and intra-
industry recycling in which wastes of one industry are used to make the prod-
ucts of another. The importance of recycling metals in the United States has
been described previously in considerable detail (14, 23-24). Therefore, it
is sufficient to state here that the U.S. recycling industries are now supply-
ing 25 percent of all the aluminum and zinc consumed, 40 percent of the copper,
45 percent of the iron, and 50 percent or more of the lead.
The rate at which copper, lead, and zinc are accumulating in the goods -
in-use reservoir is shown in table 1. The three metals in table 1, together
with many other metals and nonmetallic materials such as plastics and paper,
comprise a very valuable reserve. It is most difficult, however, to determine
the real potential of this reserve because of the very wide range of material
types entering the reservoir and the exceedingly long time lapse between entry
and exit dates. For goods such as copper pipe, electrical conductors, and
brass ornaments, the in-use time often exceeds 50 years. For other goods,
such as automobile radiators and batteries and machinery parts, the average
time lapse may only be 2 to 10 years. In either case, the secondary materials
industries presently recycling materials of this type are quite as efficient
as the primary producers of the same or equivalent commodities. It is likely,
therefore, that the quantities of materials entering or leaving the goods -in-
use reservoir will not be changed significantly by any anticipated improvements
in extraction technology, so this reserve will continue to grow.
TABLE 1 . - Estimated tonnage of copper, lead, and zinc
in use in the United States, 1940-74 1
(Thousand short tons)
Copper 3 Lead 3 1 Zinc
information gathered from Bureau of Mines, Office of
Mineral Resource Evaluation.
1907 base of reference.
3 1939 base of reference.
The mass of materials discarded by the urban society of the United States
is commonly known as urban refuse. The Bureau of Mines refers to these wastes
as urban ore. In contrast with many natural resources, urban ore is growing
in abundance, rich in grade and variety of value, and comparatively simple to
process (14, 26 ) . It is also very costly to dispose of by conventional
methods, but the overall economics of recovering large quantities of minerals,
metals, and organic materials of significant value are favorable (17 , 25-26) .
Ultimately, many successful demonstrations of recovery and recycling systems
will not only increase domestic mineral and energy material supplies signif-
icantly, but will also offer a variety of answers to the growing dilemma of
evaluating waste disposal options.
Urban ore is conspicuously heterogeneous, comprising an astounding
variety of postconsumer items. Although speeches and publications on refuse
disposal and utilization number in the thousands, municipal officials have
been hampered in their long-range planning for new waste disposal or process-
ing facilities by lack of firm decisionmaking information. Only recently has
meaningful information begun to emerge. This probably stems from the fact
that each municipal entity is unique and every proposed system must be
evaluated under a wide variety of conditions corresponding to a wide range
of local situations .
About 210 million people in the United States are presently generating
about 145 million tons of residential -commercial -institutional urban ore
annually. The average combined refuse collection and disposal cost in the
United States now exceeds $20 per ton. The cost in some of the major cities
approaches $40 per ton (31) . All but about 30 million of the 145 million tons
collected goes directly to landfills. The remaining 30 million tons is incin-
erated, a process which reduces the volume by about 90 percent and reduces the
weight by about 80 percent. The remaining residues after incineration are
Other refuse, amounting to untold millions of tons, does not enter munic-
ipal collection systems. This type of refuse, such as utility fly ash, demo-
lition wastes, and industrial wastes, is disposed of in private dumps or
abandoned where it originates. Some of this refuse is taken to the dumps by
private collectors, but much of it becomes widely scattered litter. The aver-
age composition of U.S. municipal refuse (145 million tens) and municipal
incinerator residues (7.5 million tons) is given in table 2, and values of the
products from both sources are shown in table 3. The estimated values shown
are based on products and processing costs obtained during the Bureau of Mines
pilot plant operations and process development and cost evaluation studies in
two different pilot plants (12 -13 , 17 , 25 -26) . Others (_2) have investigated
the economics of prototype processes for extracting values from municipal
refuse based on a conceptual arrangement of mostly conventional equipment to
yield products of assumed grade and values. A comparison is made (2) of eco-
nomic benefits in resource recovery systems that recover only noncombustible
materials (metals and glass) with those that recover both noncombustibles and
energy. It was concluded that favorable economics must be based on more than
one source of revenue, and the addition of energy recovery systems would bene-
fit most communities. It was also concluded that other uncertain factors,
such as location of markets, quantities of wastes, and composition of wastes,
could alter the overall economics unpredictably. It is thus evident that
municipal waste disposal problems are different in each municipality and each
one should consider its own situation as unique.
TABLE 2 . - Average composition and estimated value of raw
refuse and municipal incinerator residues
Ash and slag
Dirt, ceramics, etc
1 Lowe, R. A. Energy Conservation Through Improved Solid
Waste Management. U.S. Environmental Protection
Bureau of Mines, College Park Metallurgy Research Center.
Resource Recovery Group. Work sheets, 1974.
TABLE 3 . - Estimated amount and value of recovered products from raw refuse
and incinerator residue
Amount generated annually million tons..
Gross values 1 per ton. .
Total gross values millions . .
1 Product value at the plant; does not include transportation or marketing
Only a small number of innovative refuse collection methods have been
studied in recent years, and only a few of these are now in use on a practical
scale. The two most interesting are the pneumatic transport system and the one-
man collection truck equipped for automatic pickup and dumping of special
roadside refuse containers into the collector truck. As yet, however, there
is no practical substitute for general use to replace the common packer truck
with its pickup crew.
Little or no effort was made in the United States to develop large -
capacity systems to recover values from municipal refuse prior to enactment
of the Solid Waste Disposal Act of 1965 (28) . Immediately thereafter, com-
posting was among the first large-scale processes considered (_7, 2_2) . Now
it is among the least attractive utilization methods, particularly in the
United States. Of 18 composting operations started in the United States since
1966, only 2 are still operating, and as yet there are no records to show
that composting is economical. Except in a very few unique situations, the
interest in composting must certainly continue to decline in the United States
because the percentage of putrescibles in the average municipal refuse is
steadily decreasing, and there is no evidence that a significant demand for
compost of municipal origin as a soil amendment can develop in competition
with available commercial fertilizers.
Common Refuse Disposal Options
There are only six general types of refuse disposal practiced in the
United States. Included are (1) ocean dumping, (2) open-land dumping,
(3) open -dump burning, (4) landfilling, (5) incineration, and (6) resource
recovery disposal systems. The first three are now banned in the vast
majority of municipalities, and a total ban will probably be enforced in the
near future .
Landfilling is the most extensively practiced refuse disposal method,
and incineration is next with 200 or more incinerators now in operation.
Although there were few attempts to recover valuable constituents from
refuse before 1965, by 1974 both the scope and diversity of recycling methods
under consideration increased markedly. It now appears that the number of
basically different concepts has reached a maximum, but the level of develop-
ment on several types of systems continues to increase. This trend is likely
to continue during the next decade.
There are only three basic incineration systems, as follows --
1. Incineration and disposal of residues.
2. Incineration with energy recovery only.
3. Incineration with energy and resource recovery.
In the first method, refuse is delivered to a holding pit at the
incinerator plant and charged at a uniform rate to the incinerator combustion
chamber. Resulting combustion gases and some particulates are discharged into
the stack, and the ashes and noncombustible materials are discharged into
water quenching pits. Some stacks are equipped with electrostatic precipita-
tors to remove most of the particulates from the stack gases. The precipi-
tated solids and the quenching pit residues are hauled to disposal dumps or
landfills. In some cases, ferrous metals are magnetically recovered from the
residues prior to dump disposal.
The same basic operations are performed in the second method (energy
recovery) , except that in this case the hot combustion gases generated in
the incineration section are conducted through a boiler system where steam
energy is recovered. In some energy -recovery systems, bulky ferrous metals
are magnetically recovered from the raw refuse before it is incinerated.
Since Europe encountered the problems of high -cost energy and refuse dis-
posal much earlier than the United States, refuse energy plants are more
common in Western Europe. For example, about 16 West German plants currently
generate power from refuse-fueled systems (8) , and the Netherlands produces
6 percent of its total electrical energy from refuse. The United States is
only now entering this area of energy supply.
The third method (energy and resource recovery) is much more com-
plicated if it is performed for total recovery of contained values. In
this method, energy is recovered essentially the same as in the second
method, but the residues are sent through first -stage separation units to
produce crude fractions of glass, metals, organic materials, and residuals.
Upgrading of the crude products is performed in second- and third -stage
operations to produce high-grade metal fractions (ferrous, aluminum, and
copper-zinc), and a high-grade glass fraction (mixed flint, amber, and green).
A small part of the incoming residues (sand, ceramics, dirt, and unburned
organics) is hauled to the dumps or used for other purposes.
Resource Recovery From Raw Refuse
The five basic methods for recovering values from raw refuse are--
1. Incineration with direct energy conversion.
2. Recovery of combustibles for direct use as fuel.
3. Recovery of combustibles and conversion to fuel products (solid fuel,
oil, and methane).
4. Recovery of combustibles and separation into fuel and nonfuel
products (paper for fiber or fuel, putrescibles for fuel or direct conversion
to animal food, plastics, and other combustibles for fuel).
5. Maximum recovery of all values (paper, plastics, and organics for
fuel or recycling; and ferrous metals, copper -zinc metals, aluminum-base
metals, flint glass, and amber and green glass for recycling).
The first method (incineration) has been described under the incineration
grouping. It is included here only because it has raw refuse input.
In the second raw refuse method (combustibles for direct use as fuel) ,
the common procedure is to first shred the refuse to liberate all constituents
and reduce them to some convenient, uniform size. This is usually followed by
air classification to separate lightweight constituents (paper, light
fabrics, and plastics) from the heavy constituents such as metals, glass,
stones, heavy plastics, and rubber. The light fraction may then be reduced
in size, or it may be used as is for supplemental fuel.
The third method (conversion of combustibles to fuel products) follows
essentially the same procedures as the second except in the use of light -
fraction materials. In this case, the light fraction can be dried and
pulverized to produce an improved solid fuel material. Alternatively, it
can be processed in a reactor to produce a low-sulfur oil fuel, or it can
be treated by a hydrogasification process to produce substitute natural gas.
The fourth general raw refuse process (recovery of combustibles and
separation into fuel and nonfuel products) is simply a slight modification
of the third process. It provides optional methods for utilizing the
recovered combustible materials to better satisfy a wider range of marketing
situations. Some of the paper, for example, may be recovered either as a
paper fiber product or as a solid fuel product. It might also be converted
to oil or fuel gas, as in the third method. The putrescibles, if present in
sufficient amounts, may be converted to animal food (11) .
The fifth (maximum recovery) process is essentially the same as the
fourth except that it includes additional systems for recovering the non-
combustible values. In this system, several consecutive stages follow the
initial air classification. The light fractions are processes as in the
third and fourth methods, but the heavy fraction of the initial classification
FIGURE 3t - Products extracted from municipal inciner-
is subjected to further pro-
cesses such as secondary
shredding and air classify-
ing, secondary magnetic sep-
aration, jigging, screening,
and froth flotation. Obvi-
ously, the combination of
such unit operations and the
degree of upgrading products
are optional, depending upon
the quality of product needed
for optimum marketability.
The literature is
replete with information on
various research and devel-
opment activities in the
development of refuse pro-
cessing systems (3_, 1_5, 20 ,
31) , and the number of pub-
lications is growing rapidly
When the Solid Waste
Disposal Act (28) became law
in 1965, the Bureau of Mines
was already deeply involved
in recycling research, which
it had been conducting since
1910, when it was founded.
Since passage of the act,
the Bureau has conducted a
number of investigations,
most of which have produced
positive and often surpris-
ing results (15) . The
resource recovery program
(18, 27 ) has included a very
diverse list of projects
ranging from the conversion
of animal manure to oil and
fuel gases, to the extrac-
tion of gold from electronic
scrap. The program has
included pilot plant investi-
u w5»' w^ * „ gations of municipal refuse
Products extracted from municipal raw recovery and utilization sys-
refuse, terns since 1970. Interested
organizations and individuals from around the world have visited these plants
and received the most detailed data available on system options, equipment per-
formance, processing efficiency, product quality analysis and control, eco-
nomic evaluations, and product use options. The systems demonstrated in the
FIGURE 5. - Typical items made from products recovered from municipal refuse.
Bureau of Mines pilot plants have been adopted in whole or in part in many
of the commercial -scale systems under construction or in the planning stage.
Typical products from incinerator residue processing plants are shown
in figure 3. Similar products from raw refuse processing are illustrated
in figure 4. Several typical end uses for products extracted from municipal
refuse are illustrated in figure 5.
The most widely recognized recycling channel originates in the waste
collection and disposal industries where postconsumer goods and wastes are
processed for salvage or disposal (fig. 6). The most common practice is to
sort incoming materials and prepare selected or sorted materials for the
secondary materials industries. The secondary materials industry output
comprises raw materials that are used by the primary materials industries
with substantial supplies from natural reserves. Here the recycled materials
lose their identity, except statistically. For example, there is no way to
i raw ■
M.»__ Recycled^ _ Jf
FIGURE 6, - Conventional and product recycling systems.
distinguish the part of a new aluminum lawnmower housing derived from second-
ary aluminum from the part derived from virgin aluminum. This type of
recycling provides hundreds of thousands of tons annually of secondary
products for the buyers of bulk minerals, metals, and other raw materials.
The methods employed are relatively efficient and well established in the
The other basic recycling channel , which has not received the attention
it deserves, involves the recovery and reconditioning of postconsumer items
such as electric motors, car generators , carburetors, and bumpers. A compari-
son of the economics in the two channels suggests an immediate need for
greater attention to the potentials of product recycling through the recondi-
tioning channels. Recycling automobile scrap in the United States provides
a typical case in point. The average new automobile, which sells for about
$4,000, is only worth about $30 at the junkyard after 8 to 10 years. Most
junk autos are now processed in huge shredding machines which grind them up
into fist-size nuggets of metal and nonmetallic debris. The metal is cleaned,
sorted, and marketed. After shredding, if all of the constituent metals are
separated into individual lots, the combined value of the iron, copper, alu-
minum, zinc, lead, and other materials increases to about $200 per junked
Consider now that we start with an identical junk automobile and first
remove the starter motor, the alternator, the carburetor, and the two bumpers.
We can recondition these five items to be as good as new or better. Their
total reconditioned value will then be about $261. In this case, the five
reconditioned parts are worth $61 more than the value of the shredded compo-
nents of the entire automobile. Obviously, the amount of energy required to
recondition articles of this type is several orders of magnitude less than the
total energy required to produce the same articles from natural resource
materials . It is reported that even the normal methods of recycling already
save enormous amounts of energy (4, 21_) . Recycled copper saves 32,700
kilowatt -hours per ton over that required for the production of primary copper,
Recycling a ton of aluminum saves 62,000 kilowatt -hours , a ton of recycled
steel saves 7,500 kilowatt -hours , and even a ton of recycled paper saves
3,500 kilowatt -hours . Still greater energy savings could be achieved by
reconditioning units and parts for recycling without the conventional need
for remelting, refining, fabrication, and manufacturing.
Reconditioned items are presently sold by repair shops where the demand
is somewhat limited; hence, only a small fraction of repairable postconsumer
goods (mostly automotive parts) is being recycled through that channel. It is
thus clearly evident that tremendous quantities of materials and energy could
be saved in any industrialized nation if it could simply develop the full
potential of product recycling. This effort could be helped considerably if
manufacturers would design more products for reconditioning and establish a
practice of accepting a maximum number of reconditioned items for factory use
rather than limiting their use to maintenance and repair shops only.
The technology for processing urban refuse has developed rapidly during
the past decade. Several different systems are currently being demonstrated,
and others will be demonstrated in the near future. However, the number of
problems involving the selection and successful application of any system is
too great to discuss in depth here, so only the most important general
problems are considered.
The greatest problem is that of marketing the recovered products,
particularly those recovered from municipal refuse. In most cases the
questions of product quality and geographical location are paramount.
Although the commercial value of such products can be estimated, it is
very difficult to negotiate firm long-term sale contracts based on a few
thousand pounds of pilot plant products. Before they can agree to long-term
purchase agreements, prospective buyers first want a large supply of product
materials provided over a reasonably long period of operation in order to
evaluate the consistency of product quality and the stability of the supply.
This unfortunate situation is complicated by the fact that no such large-scale
supplies can be produced until large-scale demonstration plants are producing
at full capacity. A dilemma then arises when it is found that only limited
funds are likely to be available for large-scale demonstration plants until
after a satisfactory market survey of products is completed. The difficulty
in these cases stems from the fact that the market surveys are not conclusive
because without large quantities of real products available for evaluation,
the surveys must be based on hypothetical plant productivity and products
and hypothetical market prices, all of which lead to many other questions
that cannot be answered completely.
Another major problem appears to be in the eventual need to consume
large quantities of glass, metals, paper, and plastic that are to be produced
at great distances from locations where they are normally needed as raw
materials. Many municipalities are so remote from potential markets that
transportation costs preclude the sale in the common marketplaces of products
recovered from refuse. This means that unconventional uses must be found for
the recovered products. Paper that cannot be sent to distant markets must be
used locally as fuel, for making roofing felt, for thermal insulating material,
for wallboard, for conversion to oil, or perhaps for other uses not yet con-
ceived. Glass that cannot be shipped to a distant bottle plant must be used
locally for making brick, tile, glass wool, poultry grit, aggregate, and
Before any of these possibilities can become a reality, some individual
or firm must first decide to become involved in the local recycling effort by
establishing new plants to consume the refuse plant products in new ways.
Here again, it is essential that large amounts of refuse products are avail-
able so that the new uses can be developed with real rather than hypothetical
products. If materials are made available in sufficient quantity, new uses
will probably develop almost automatically.
The third most distressing problem lies in the unusually large number
of authorities that inevitably become involved with Federal, State, county,
and city participation in municipal refuse problems. In many local cases,
for example, it is difficult for city councils to arrive at a firm decision
on what needs to be done with waste disposal problems or how to do it. If
there should be any agreement, new problems are usually encountered with
county, State, or Federal authorities and regulations. In view of these
problems, it is gratifying that any significant progress has been made in
the many persistent efforts to conserve resources and increase recycling.
It is remarkable that more private and industrial capital is moving into the
development and operation of recycling systems. Now that it has begun, this
trend should continue as more demonstration plants are completed and the
economics of the various systems are found to be favorable.
AREAS FOR RESEARCH AND DEVELOPMENT
If our atomic scientists should successfully develop systems for con-
trolled fusion reactions, the U.S. minerals deficits would melt away and
probably be gone forever. With virtually unlimited cheap power, we could
afford to process abundant resources that are presently far beyond economic
processing parameters. With fusion energy, not only would there be a limit-
less supply of fuel (deuterium and tritium) in sea water, but both the reactor
heat and the fast neutron product of fusion could be used. The former would
generate power, and the latter, a "fusion torch," is reported to perform a
long list of remarkable feats such as "...vaporize garbage, turning it into
its basic elements for recycling" (10) . It is also believed that the torch
could be employed to produce methane, synthetic natural gas, and methanol from
abundant resources and thus eliminate our need for imported fossil fuel. For
the present, however, we must view this as a possible dream and remain alert
to present realities.
Most, if not all, of the basic systems for reclaiming values from urban
wastes have been conceived, and the exchange of technology has been extensive.
Most of the basic concepts have been demonstrated, at least on the pilot plant
scale. This suggests that future research in this field should be concentrated
on the problems of increasing the efficiency of unit operations and devices
such as shredding, air classification, and sorting of mixed colored glass and
Research on heavy media separation should continue toward better methods
and devices for separating mixed plastics, mixed metals, and glass. Much more
work should be done on electrostatic and other methods for separating mixed
papers, plastics, particulate metals, and minerals.
The tremendous opportunities for recycling repaired consumer goods have
received little or no attention. The field of product design for recycling
is indeed essentially a virgin area.
Another area in which little or no research has been conducted is the
separation of the high -value components from home appliances and similar
bulky postconsumer goods.
The potential of designing landfills for eventual methane recovery should
be conducted with concurrent extensive studies on the recovery of gases and
other values from existing landfills. Rapid conversion of organic materials
to fuel products should be pushed with greater vigor. It might well be that
this approach will be the most efficient and direct method for capturing
energy from the sun.
New extensive studies should also be made on other disposal systems such
as subsurface disposal of slurried, zero-value wastes by high-pressure
hydraulic techniques .
Finally, one of the most promising and important areas for future research
is in the utilization of products reclaimed from urban wastes. This should
center on possible new uses for large amounts of glass, paper, metals, and
putrescibles in urban refuse. It is logical to assume that a wide range of
new uses will be found as soon as a continuous and significant supply of
recycled raw materials is assured.
THE FUTURE OF RECYCLING
The most accurate predictions of the future are most often derived from
a thorough analysis of related matters of the past and present. Putting this
approach to use, we readily observe that recycling certainly is not new. It
appears, in fact, to be one of the most obvious laws of nature, much like the
seasons, the tides, and the life and death processes. It is not surprising,
therefore, that the greatest motivating force behind present recycling efforts
is the worldwide concern for the deteriorating natural environment. Histori-
cally, there has been no concern about resources until they were found to be
in short supply, nor has there been any alarm about the environment until it
became disturbingly bad.
Recycling mineral resources first began during the stone age when flint
arrowheads were retrieved from slain animals. The recycling of more materials
continued as civilization progressed. Now there exists the greatest oppor-
tunity ever available to recycle needed resources and concurrently improve the
Mining natural ores of iron, copper, aluminum, and all of the other metal
commodities is commonplace, as are the extraction of materials for making
glass and plastics and the growing and harvesting of papermaking raw materials,
In striking contrast, urban ore need not be mined, and the contained values
are already in a refined state, ready for immediate recycling after they have
been separated. The technology for making such separations has been developed
for prompt extensive application, and some applications are in fact accom-
plished or underway. Furthermore, considerable decisionmaking information is
beginning to emerge, and the results are generally favorable. Considering the
high cost of conventional waste disposal in terms of dollars and the potential
value of an improvement of the environment, there is no sound reason to
delay the exploitation of waste resources wherever the opportunity exists.
There is no question that disposal costs must enter the economic aspects
of recycling the constituents of urban ore. However, it will also be noted
that the potential improvement of the environment has seldom been given the
full value it deserves in the economic considerations. What is the dollar
value of a clean lake or a river? How much does the value drop when the land,
air, and water environments become polluted? It appears that society has
considered these questions and concluded that the environment is valuable.
The cost of any recycling needed to maintain the quality of the environment
must be balanced against the value of that environment.
The annual gross value of the constituents of municipal wastes alone is
estimated at nearly $2 billion. If these wastes are processed for recycling,
there could also be an annual savings of $3 billion or more in disposal costs,
and a large undetermined amount of energy could be saved. Accordingly, the
practice of recycling will continue to increase steadily as the demand for
improved environmental quality persists and the demand for more resource
materials continues to rise. These trends will occur at a much higher rate,
at least during the next decade. By then, industries, municipalities, and
governments will have overcome the major obstacles and will have established
integrated systems and coordinated operations in all of the industrialized
countries. Fortunately, it is expected that the developing nations will have
ready access to all advanced recycling technology as it develops and they, too,
will adopt recycling more extensively as they achieve higher standards of
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*U.S. GOVERNMENT PRiNTING 0FF,CE: 1976-603-755/Z0O
INT.-BU.OF MINES, PGH., PA. 2 1169
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