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Bureau of Mines Information Circular/1976 


Copy 1 1976 

Recycling Trends in the United States: 
A Review 


Information Circular 8711 

Recycling Trends in the United States: 
A Review 

By Max J. Spendlove 

College Park Metallurgy Research Center, College Park, Md. 


Thomas S. Kleppe, Secretary 


Thomas V. Falkie, Director 

This publication has been cataloged as follows: 




?ndlove, Max 



trends in the 

United States: a 



ington] U.S. 

Bureau of Mines [1976] 

25 p« illus 

., tables. (U.S. 

Bureau of Mines. 

Information circu* 

lar 8711) 

Includes bibliography. 

1. Recycling (Waste, etc.) 

I. U.S. Bureau of 

Mines. II. 




no. 8711 622.06173 

U.S. Dept. of 

the Int. Library 



Abstract 1 

Introduction 1 

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 

Collection 12 

Composting 12 

Common refuse disposal options 12 

Incineration 13 

Resource recovery from raw refuse 14 

Product recycling 16 

Recycling problems 18 

Areas for research and development 20 

The future of recycling 21 

References 23 


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 

States 10 

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 



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 
materials . 

2 Underlined numbers in parentheses refer to the reference list at the end of 
this paper. 


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. 

Minerals, crude 
oil, coal, gas, etc 

Fuels, metals, 



Mining, oil-gas production 


Milling, smelting, power 





transportation, services, 










Collecting and processing 

Ore, petroleum, coal, sand 




PRODUCT, 1974 
$1,397 BILLION 
Goods and services 



Junk, scrap, 


FIGURE 1. - Mineral supply and recycling systems in the U.S. economy, estimated values 
for 1974. 

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 
proportions . 

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. 


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 
automobiles . 

Secondary raw 





Tailings, dusts, 


Slags, goses, 

Secondary raw 

Residues, scraps, 
drosses, rejects 

Rejects, scraps, 
metallic dusts 

Crude metal 


Slogs, goses, 

Refined meta I 



Supplies and parts 



Consumer products 




Products distribution 

Grindings, residues, 
dusts, drosses, « 

Sludges, drosses, 
dusts, smokes, ^^~ 
tumes, discords 

Spent fuels, gases 
and particulates ^^ 
containers and 
advertising materials 



Spent products 
Packaging, spoilage 

LPostconsumer goods 
, * , 
Reclaimed goods ___ RECYCLING — 
and wastes I . 

Slags, drosses, 
dusts, solutions 


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 
States . 


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 




Copper -zinc 

Ferrous metals 

Ash and slag 


Food waste 

Yard waste 


Leather, rubber.... 



Dirt, ceramics, etc 

Raw refuse, 

Incinerator residue, 

percent 1 

percent 2 



























1 Lowe, R. A. Energy Conservation Through Improved Solid 
Waste Management. U.S. Environmental Protection 
Agency, 1974. 
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 

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 
costs . 



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- 
ator residues. 

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 


Natural raw 






i raw ■ 



i« H 




Repaired parts 

and units 


M.»__ Recycled^ _ Jf 

parts | 

Supplies I 













,Goods and 



Scrap and 
salvaged items 









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 
U.S. economy. 

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 
other products. 

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. 



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 
nonferrous metals. 

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 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 
deteriorating environment. 

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 



1. Abelson, P. H. The Deteriorating Energy Position. Science, v. 185, 

No. 4148, July 26, 1974, 309 pp. 

2. Abert, J. G., H. Alter, and F. Bernheisel. The Economics of Resource 

Recovery From Municipal Solid Waste. Science, v. 183, No. 4129, 
Mar. 15, 1973, pp. 1052-1058. 

3. Bi-weekly Business Newsletter (Silver Spring, Md.). Solid Waste Report. 

V. 5, No. 3, Feb. 4, 1974, p. 29. 

4. Bravard, J. C, H. V. Flora, and C. Portals. Energy Expenditures 

Associated With the Production and Recycling of Metals. Oak Ridge 
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6. Council on Environmental Quality. Environmental Quality (1st Annual 

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8. Environmental Science and Technology. Refuse -to -Energy Plant Uses First 

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9. Farney, D. Ominous Problems; What To Do With Radioactive Wastes. 

Smithsonian Mag., v. 5, No. 1, April 1974, pp. 20-27. 

10. Fialka, J. Harnessing Fusion. Washington Star News, Aug. 15, 1974, 

sec. A, p. 1, sec. D, p. 20. 

11. Grumman Ecosystems Corp. Selectomatic Commest. The Real Recycling 

Story. History, Operation, Economics. 1973, 10 pp. 

12. Henn, J. J. Updated Cost Evaluation of a Metal and Mineral Recovery 

Process for Treating Municipal Incinerator Residues. BuMines 
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4 Title enclosed in parentheses is a translation from the language in which the 
item was originally published. 


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Proc. 4th Mineral Waste Utilization Symposium, cosponsored by Bureau 
of Mines and IIT Research Institute, Chicago, 111., May 7-8, 1974, 
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18. Mineral Waste Symposium (Proceedings). Cosponsored by Bureau of Mines 

and IIT Research Institute. 1st Symp . , Chicago, 111., Mar. 27-28, 
1968; 2d Symp., Chicago, 111., Mar. 18-19, 1970; 3d Symp., Chicago, 
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1965, Stat. 306, 10 pp. 


29 ' "196^2™ ° f ^ Interi ° r - SUrfaCe Mining and 0ur Environment. 

30. U.S. Office of Science and Technology, Executive Office of the President 

Washington, D.C., May 1969, 111 pp . president 

31. U.S. Office of Solid Waste Management, Environmental Protection Agencv 

Resource Recovery and Source Protection. No. SW-122, 1974^12 pp 

*U.S. GOVERNMENT PRiNTING 0FF,CE: 1976-603-755/Z0O 

INT.-BU.OF MINES, PGH., PA. 2 1169 



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