This publication (SW-2r) was written
for the Solid Waste Management Office by
P.H.McGAUHEY
U.S. ENVIRONMENTAL PROTECTION AGENCY
Solid Waste Management Office
1971
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This publication is also in the Public Health Service
numbered series as Public Health Service Publication
No. 2023; its entry in two government publication
series is the result of a publishing interface reflecting
the transfer of the Federal solid waste management
program from the U.S. Public Health Service to the
U.S. Environmental Protection Agency.
Environmental Protection Publication
LIBRARY OF CONGRESS CATALOG CARD NO. 70-608444
For sale by the Superintendent of Documents
U.S. Government Printing Office
Washington, D.C. 20402
Price 25 cents
ENVIRONMENTAL PROTECTION AGENC7
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FOREWORD
THERE IS AN ACCUMULATING body of evidence that composting of
municipal refuse provides a tool for solving only a small portion of
this Nation's solid waste disposal problems. At present, however,
composting is the only solid waste disposal process that salvages the
organic fraction and is accordingly deserving of research
consideration. In fact, since the Solid Waste Disposal Act of 1965
specifically directed that research be carried out on the recycling and
reclamation of waste materials, it would appear that the composting
process cannot be ignored by the managers of solid waste systems as
x long as it remains the only known means of reclaiming organic solid
wastes.
,, When the Federal solid waste program became operative in 1966,
I • composting with sewage sludge was the subject of one of the first
'} research projects undertaken. The cooperation of the Tennessee
Valley Authority, the municipality of Johnson City, Tennessee, and
the Bureau of Solid Waste Management made possible a
demonstration of composting on municipal scale—the joint U.S.
Public Health Service-Tennessee Valley Authority Composting
Project at Johnson City.
Based on a full year's experience of plant operation, with
concomitant research on the health aspects of compost use and
processing as well as investigation of the engineering and economic
factors, the Bureau felt that it would be able to make an initial
evaluation of the composting process as a means of managing
municipal solid wastes and sewage sludge by late 1969. As
background preparation for completing such a position document,
Professor McGauhey, of the University of California and a Public
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Health Service consultant with longwhile interest and many years of
investigation on the subject, was asked to contribute his present
judgment on the value of composting municipal refuse in solid waste
management systems.
In his review of the current status of composting and related
research in the United States, Professor McGauhey notes that
interest in this subject has developed in response to three factors:
the increasing population and pollution resulting from disposal of
waste products; a growing affluence that has multiplied the per
capita quantities of wastes generated; an enlarging critical mass of
entrepreneurs, conservationists, and persons interested in specialty
agriculture, including organically-grown foods.
Research conducted in the early 1950's, and verified from time to
time since then, has defined the operating parameters for
composting municipal and other organic refuse as well as the
disposal of the final compost. More recently, the role of composting
as only one of a number of processes in the optimum regional
management of solid wastes has been found important.
Even though composting is by no means a profit-making solution
to municipal refuse disposal, as claimed by some of its more
enthusiastic adherents, reliable information on process costs is
needed. Such information has been obtained through the Bureau of
Solid Waste Management research efforts. With respect to the value
of compost as a resource, Professor McGauhey concludes that the
conversion of a "low-value waste material that nobody wants" into a
"low-value resource that nobody wants" should be deferred; this
might be done by placing solid wastes in sanitary landfills until such
time that their value warrants their mining and recovery.
-RICHARD D. VAUGHAN
Assistant Surgeon General
Acting Commissioner
Solid Waste Management Office
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PREFACE
THE PURPOSE OF THIS PAPER is to review the status of composting as
a process for the management of municipal solid wastes and to
ascertain what research and development may be appropriate to
composting in 1969—when considered against the urgency of other
components of the national solid waste problem and the budgetary
limitations of the Bureau of Solid Waste Management. The
evaluation is based on the author's own judgment and opinions.
These are derived from his experience in solid waste research, which
began in 1951 with a study of the fundamentals of the composting
process and which continues in 1969 with a research program
involving all aspects of solid waste management. This present
experience is supplemented by service on various committees,
including the National Academy of Sciences-National Research
Council-National Academy of Engineering, Committee on Solid
Waste Management.
URBAN MAN
Mired in the benthic interface
Where sky meets land and sea
He stands, possessed of affluence,
Amid his own debris.
He smells the fetid waters.
He sees brown atmosphere.
He amplifies the decibels
That smite his fragile ear.
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Blind hate degrades his reason.
Welfare breeds on urban blight.
Noonday darkness strangles sunlight.
Neon day pollutes his night.
-P. H. McGAUHEY
VI
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MARCH 1969
OF THE VARIOUS PROCESSES that have been associated with the dis-
posal of municipal refuse, only deposit on land or under the sea
has had the potential to accept all fractions of the solid wastes
generated by a modern urban society. All other processes in
themselves have been only capable of dealing with some particular
fraction in some selective way. In more specific terms, it might be
said that we may, with current technology, put essentially all
urban-generated wastes in a landfill, or on the ocean floor, if we wish
to develop the necessary techniques. In contrast, composting and
incineration are directly concerned with the conversion of the
organic component of the overall wastes, although as processes they
are in reality but components of some overall management system.
Of the two conversion processes, only composting salvages the
organic matter. It is therefore worthy of research consideration,
both because of a general feeling of people that organic resources
should be conserved and because of the specific requirement of such
rationale in the Solid Waste Disposal Act of 1965 that research be
directed to recycling or conversion of waste materials. To this end, a
major effort in research, development, and demonstration of
composting has been undertaken. Composting, however, is but one
of the many aspects of solid waste management requiring similar
attention. It is appropriate therefore to inquire at this time whether
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the results of this program have established the composting process
as a viable waste treatment method, demonstrated its unsuitability,
or left important aspects unexplored. To approach an answer, it is
necessary to consider the historical and technological aspects of
composting, as well as the state of the art which has now been
achieved or demonstrated, in the light of cultural and social
attitudes.
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DEVELOPMENT OF THE COMPOSTING PROCESS
Historical Notes
Attempts to systematize the compost heap by which individual
farmers and gardeners have for centuries reclaimed organic matter
for return to the soil began in the 1920's, when Sir Albert Howard
developed his Indore Process in India and Beccari patented his
process in Italy. The Indore Process, however, was labor intensive
and required a long period of anaerobic degradation in soil pits.
Beccari likewise employed an anaerobic process, although in
concrete cells.
The Indore and Beccari processes were readily adaptable to
mechanized methods, but for several reasons were not attractive to
U.S. cities. The time factor involved was unsuited to American
cultural patterns; the objective was foreign to the American heritage
of wastefulness and unrelated to any recognized compelling need of
Americans; and the process involved land areas not suited to our
urban centers nor to the volume and variety of our wastes.
Furthermore, anaerobic composting accomplished nothing that a
good sanitary landfill might not do in time with less cost and
trouble, particularly when no demand for the final product was
evident, as was the case in India.
Modern composting had its beginning in the 1930's when
attempts were made to speed up the process by aerobic
decomposition, and to mechanizing it as well. The Vuilafvoer
Maatschappij (VAM) began operations in Holland, the Dano process
appeared in Denmark, and Eweson patented a process in the United
States. In 1949 the Frazer Process was developed in the United
States.
420-471 O - 71 - 2
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By about 1950, composting began to be considered as a possible
partial answer to municipal solid waste problems for a variety of
reasons. First, the wartime growth of small towns into fair-sized
cities overwhelmed their primitive systems of open dumps, overran
and obliterated the hog farm, and introduced the air pollution factor
into environmental considerations. Next, a growing affluence
multiplied the volume of urban-generated wastes and so
compounded the problem of disposal. Finally, opportunistic
entrepreneurs, dedicated conservationists, and food faddists came
together in a critical mass. The first group sought to sell to
hard-pressed public works officials untried and unevaluated
composting processes, generally conceived by caprice or in
well-meaning naivete. The second group comprised citizens of all
classes who had, and continue to have, the uneasy feeling that the
Nation cannot forever go on wasting its resources. The last group,
though small in number, were the organic gardeners who, by rational
deduction or as "true believers," had come to stress the importance
of organic fertilizers as compared to inorganic chemicals in the
nutritive value of foods.
In the foregoing situation, despite claims and process patents, no
one in fact knew the scientific rudiments or the engineering
parameters of aerobic composting. One of the most highly advertised
and most insistent tenets of the entrepreneur was that a special
inoculum, which good fortune and scientific dedication had revealed
to him alone, was the key to quick and successful composting of
municipal refuse. In some cases, both a special inoculum and unique
cells and equipment were required to carry out the secret
proprietary process. In one instance, carbon dioxide generated at the
bottom of the composting mass was presumed to acquire unusual
characteristics and so rose through the composting mass, shedding
the blessings and magic on which the process depended. Chemical
additives, pH control, forced aeration, and numerous other features
all had supporters when composting was proposed.
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Need for Research
Under pressure from advocates of various systems, and
confronted with newspaper articles both heralding composting as the
answer to municipal refuse problems and berating the public official
for his shortcomings, officials turned to the engineering profession
for the answer. In a few cases, they turned also to various
arrangements to set up composting plants. It was at once evident
that the engineer, whether he be skeptical or gullible, could not
provide the required technical and economic answer. The limited
knowledge of biology, which at that time characterized the public
works engineer, led many to accept the concept that special
inoculums and a great deal of recycling and reseeding were
necessary. The latter concept was supported by experience in
sewage sludge digestion, which had been found to benefit from
continuous mixing. An equally unsatisfactory answer could be
obtained from microbiologists, because at that time the profession
of biology had not yet turned its attention to ways in which
engineered systems might put biological knowledge to work for
overall environmental goals.
Research was needed, therefore, in order to determine the entire
basis of the composting process. This included: (1) determination of
the scientific fundamentals of aerobic degradation of heterogeneous
organic matter; (2) determination of the environmental conditions
to be maintained to maximize the rate of aerobic composting and of
methods for controlling the conditions; (3) evaluation of the effects
of inoculums, recycling, and reseeding on the composting process;
(4) determination of the materials handling necessary for a success-
ful composting process (preprocessing, etc.); (5) determination of
the fate of pathogens, fly larvae, and other disease vectors in
composting; (6) evaluation of the fertilizing and soil-conditioning
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values of compost; (7) determination of the cost of producing
compost; (8) evaluation of the utility of the finished compost.
Early Research Findings
Research programs begun in 1950 by the State of California, the
University of California, the U.S. Public Health Service, and others
had established by 1955 a number of findings that are particularly
important now to the evaluation of the research program to which
this review is addressed.1"4 Among the most important
accomplishments of this program were: (1) The fundamentals of
aerobic composting and the necessary operating parameters were
established for municipal refuse. (2) Windrow composting in the
open was shown to be a simple procedure. (3) Inoculums were
shown to be unnecessary and those offered for sale to be worthless.
(4) Recycling for reseeding purposes was shown to be of little, if
any, value to the process and the reasons established in terms of
sequence of microorganisms. (5) Simple turning was shown to be an
effective way of maintaining needed aeration. (6) Aerobic
composting was shown to be a semi-aerobic process requiring far less
aeration than the term implied. (7) Forced aeration was shown to be
technologically difficult to accomplish and the least likely way to
aerate a composting mass. (8) A composting mass permitted to
become anaerobic was found to resume aerobic decomposition if
aerated again by turning. (9) The process was found to continue to
completion without further aeration after a relatively short period of
composting under aerobic conditions. (10) The process was found to
be applicable to animal manures, cannery wastes, and other organic
refuse. (11) Fly control and destruction of disease vectors was found
to occur in the process. (12) Finished compost was found to be a
lowgrade fertilizer, more valuable for its soil-conditioning and
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moisture-retaining properties than for its content of nitrogen and
phosphorus. (13) The feasibility of reducing the area of land
required for landfill by composting and compacting the organic
fraction of municipal refuse was demonstrated and evaluated. (14)
The cost of composting was variously postulated, but it was evident
that the process was not destined to be a source of income to cities
which would pay much of the cost of refuse disposal. (15) Serious
doubts were cast upon the marketability of any large amount of
compost.
More Recent Findings
The research and development activity of the early 1950's
established the environmental conditions that any composting
procedure would need to maintain in order to exploit the process
successfully. These conditions established the objectives of the
design of any technological process. Early attempts to commercialize
the process that paralleled the early research gave some notice as to
what technological difficulties needed to be resolved. For example,
economical segregation of refuse was found to be difficult; excessive
wear and failure of shredding equipment was experienced; and
pelletizing of compost was found to be exceedingly hard on
equipment. Compounding technological problems was the continued
insistence of some proprietary equipment owners that elaborate
procedures (pre-dating the early research) were essential to the
composting process, rather than simply features of their own
particular devices.
Constraints upon the compost plant designer were among the first
findings of research following the original fundamental studies.1
Among the most significant of the findings were the following: (1)
The open windrow method of composting requires land area not
readily available in urban areas, together with a degree of
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"housekeeping" that traditional practice has not led the public to
expect. (2) The city cannot, itself, with its own funds, undertake to
develop a technologically and economically untried process, nor can
it enter into a marketing business under its charter. (3) Public
officials and the public itself prefer a housed, factory-type
composter that receives refuse at one end and discharges compost
ready for market at the other. (4) The problems of siting of a
compost plant within a community are just as difficult as those of an
incinerator or transfer station. (5) The idea that compost must be
produced for sale at a profit is exceedingly persistent. (6) The idea
that composting will solve all municipal solid waste problems while
conserving a national resource and yielding a neat profit to the city
continues to be rediscovered and projected at regular intervals not
exceeding one lunar month.
More recent findings of private enterprise and of demonstration
grants by the Bureau of Solid Waste Management have established
several additional facts.5"7 These follow: (7) Composting in a
full-scale mechanized plant is technologically feasible, and involves
mechanical problems which can be surmounted as operational
experience accumulates. (8) The fundamental requirements of
composting can be met by straightforward design which eliminates a
considerable amount of the initial and operating costs of the older
proprietary systems. (9) The economics of composting can not be
fully established without first solving the problem of what to do
with the compost. (10) In some cases, at least (e.g., Fresno), the
most economical system of regional solid waste management
involves composting of organic wastes prior to landfill.
Some Current Concepts
Before turning to a specific evaluation of the current status of
composting and the role of the Bureau of Solid Waste Management
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in the future of the process, additional background may be found in
examining some current concepts of composting.
The first, and most persistent, is the concept of composting as a
reclamation of the organic fraction of solid wastes for immediate
return to the land via sale to agriculturists and related smaller users
of fertilizers.
The second concept, originally demonstrated by the Public
Health Service at Phoenix, Arizona, and recently verified in studies
at Fresno, California, under PHS sponsorship, is that composting
may materially reduce the volume of solids substantially and so
conserve available landfill sites, reduce the insult to the land
environment, and shorten the period between completion of a
landfill and subsequent beneficial use of the filled area.
A third concept currently advocated by the author and others, is
that in effectively reclaiming the resource values of solid wastes in a
production-composting-use cycle, a time period may be necessary at
either the production-composting or the composting-use phase of
the cycle.
Implications of each of these three concepts have been examined
in the following discussion.
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EVALUATION OF THE COMPOSTING PROCESS
Value of Compost as a Soil Conditioner
THE VALUE OF COMPOST as a soil conditioner may be considered
from three viewpoints: (1) As a fertilizer in comparison with
chemicals. (2) As a source of income to defray some of the cost of
* solid waste management. (3) As a resource to be conserved.
Compost in the Soil. There is ample evidence upon which to
evaluate compost as a soil conditioner in relation to commercial
chemicals. It generally contains less than 1 percent of nitrogen, 0.05
to 0.2 percent phosphate, plus 0.2 to 0.3 percent potassium. Thus,
unless fortified with chemicals, compost may not be sold in the
United States as a fertilizer. Agriculturists point out that the amount
of nitrogen and phosphorus present in compost can be bought more
cheaply in commercial fertilizer. Furthermore, chemicals are much
more readily and cheaply applied to the land, therefore, the value of
compost on the soil depends largely on its characteristics as a humus
and, perhaps, on its content of trace elements.
The ability of humus to improve the physical characteristics of
soil, to hold moisture, and to comprise a biological system from
which nitrogen is released over a period of time, is well established
and is one of its major virtues. Numerous experiments have shown
that lawn areas treated with compost show superior growth when
compared with adjacent areas treated only with fertilizers. In
commercial agriculture, this value is not apparent. The use of liquid
f ammonia as a fertilizer offsets the nitrogen-holding virtue of
compost. In humid regions, soils often have a good organic content
and receive adequate rainfall; and in irrigated areas water is applied
as needed. Experiments over a 100-year period in Illinois and in
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England show that root structure alone is sufficient to provide the
organic content needed in soil, even though the plants are harvested
and removed from the land. Even in the semi-arid Southwest, where
temperatures are conducive to year-round activity of soil micro-
organisms and where soils might be expected to need added humus,
there has been found as yet no compelling need for adding humus to
maintain productivity.
Thus, the value of compost in soils in the short run is effectually
depreciated unless trace elements can be shown to be the critical
consideration. Evaluations of this sort are more appropriate to the
Agricultural Experiment Stations than to the Public Health Service.
However, the case for compost on the basis of trace elements rests
largely with the organic gardening enthusiasts, who are few in
number and might be written off as "faddists," even though time
might prove them to be prophets. Furthermore, the trace-element
argument for composting is weakened by the rationale that the crop
residues available for production of compost are grown with
commercial fertilizer, garbage is increasingly ground to the sewer,
the resulting sludge disposed of by incineration, and that municipal
refuse is increasingly characterized by carbonaceous organic matter
and synthetics. The conclusion from this line of reasoning is that
compost is derived from materials with no source of trace elements
but the soil; in the absence of evidence that the soil bank is about to
go broke, the easy thing to do is to forget the trace element
question.
The foregoing considerations mean that compost in the soil must
be evaluated from a long-term resource viewpoint.
Compost in Resource Conservation. As solid waste management
takes on regional aspects, more than household refuse is involved in
organic refuse. Tree and grass trimmings, animal manures, crop
residues, and demolition debris are added to the total degradable
mass. Thus, both composition and amount of compost which might
be produced is changed. If resource conservation and recycling of
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resource materials continue to develop as an aspect of solid waste
management, however, much of the paper and other wood products
may be removed from the waste stream ahead of the composting
process. The concept of composting then becomes that of salvage of
remaining organic resources value for the land in maintaining
productivity. The idea that such resource conservation will be
necessary in America in the forseeable future is widely accepted by
the public on a rational basis. Thus there is public support for
composting as a conservation measure and justification for research
and development of the process by public agencies if such research
and development activity is needed. As previously noted, the Solid
Waste Disposal Act requires research of this nature, leaving the
decision as to need for research on any particular process to the
proper administrative agency. There seems little reason to doubt that
composting is one way to conserve and recycle resource values
existing in solid wastes.
The question, then, is how and when these salvaged resources are
to be put to use.
Compost as a Paying Process. Because composting was first
proposed as a process for solving the solid waste management
problem, it was natural that the first concept should be that the soil
conditioner and resource conservation merits acclaimed by its
adherents should be made to pay the increase in cost over the
primitive disposal methods that had created the waste management
problem in the first place. Thus, the first of the three concepts of
composting (See section on Some Current Concepts) come into
being, i.e., that compost should be produced and sold to the user on
a continuous basis similar to that of the fertilizer industry. This
concept was supported by experience abroad, particularly in
Holland, Germany, and Switzerland, where compost has for many
years been disposed of in agriculture.
This over-optimistic concept proved so attractive that 15 years of
frustration and failure in every commercial attempt at composting
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during that period has not erased it completely. In evaluating the
research and development program of the Bureau of Solid Waste
Management (See section on Evaluation of Research and
Development Needs), it is necessary, first, to explore the reasons for
failure of commercial composting in the United States.
To begin with, the analogy between European and United States
conditions was invalid. Compost in Europe was, indeed, being sold,
but to the specialty farmer who operated small holdings with a great
deal of hand labor. That this type of farming comprised much of
European agriculture and very little of U.S. agriculture was
overlooked. The truth was that there was a similar, although vastly
smaller, market in the United States in the nursery business, in home
gardening, and in other special cases. This market, however, was
already partially saturated by steer manure and by small-scale
composting production by the users themselves. In California, for
example, it was estimated that the marketable steer manure is
equivalent to two bags per year for every member of the States's
population, hence the competition in the soil conditioner market is
not encouraging.
From early attempts to commercialize composting in the 1950's
and from estimates of the volume of compost that might come from
U.S. cities, it was soon evident that if compost was to be marketed
in this nation it would have to be sold to large-scale agriculture,
except for a few local situations where the specialty market was
particularly favorable.
The proposition that compost can be sold to large-scale
agriculture has proved invalid also for a number of reasons: (1) In
the irrigated West, the application of fertilizer by airplane, or by
dissolution in irrigation water, is an established and economical
practice. (2) The use of liquid ammonia has proved both economical
and technologically simple. (3) Agriculturists are sufficiently
satisfied with present practice and commercial fertilizers that
disposal of even animal manures in the country is an agricultural
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waste problem analagous to the municipal waste problem of the
urban center. (4) The mechanics of applying compost to the land are
a nuisance. Heavy equipment moving over wet soil is detrimental to
agriculture. Compost deposited on snow may wash away to lakes and
streams causing problems of pollution. This run-off problem has not
yet been resolved with respect to animal manures and agricultural
residues. (5) Usually, large-scale agriculture is distant from
significant sources of compost, hence transport further complicates
the economics of composting.
Experience of the last 15 years makes it amply evident that the
U.S. farmer is not currently interested in compost. Recent evidence
from abroad is that the European farmer is likewise becoming
disinterested wherever commercial fertilizer is available, except for
certain small-scale intensive specialty enterprises.
Conclusion. In view of the foregoing situation, the author has
reached the following conclusions relative to the value of compost as
a soil conditioner: (1) Compost has important value as a soil
conditioner beyond its modest contribution of major fertilizer
elements. (2) Composting is a process capable of salvaging and
recycling inorganic and organic resources in solid wastes. (3) The soil
conditioning and resource values of compost are far too small to
make compost attractive to U.S. agriculture at this time. (4) Except
for local situations where sale of compost for special private or
public purposes is favorable, commercial composting for immediate
use as a soil conditioner is not economically feasible.
These conclusions lead to the greater, and perhaps forlorn,
conclusion that the value of compost for immediate use as a soil
conditioner is essentially zero. How this conclusion may be modified
in the future is considered in the following section of the report.
Composting for Landfill Disposal
From the preceding sections, it may be concluded that although
composting for immediate sale to agriculture is not presently
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hopeful, the process has potential as one component of an overall
solid waste management system. Specifically, benefits from
composting for landfilling may lend economic justification to the
process. Here there may be two different objectives. Under the first,
the biochemical stability, smaller volume, and compressibility of
compost results in savings of land area, or in accelerated use of the
filled area, which offset processing costs. The filled area, however, is
of the nature of reclaimed land rather than a stockpile of reclaimed
organic resources that might be mined in the future.
The second objective is also related to land-use economics, but
requires a different land-use plan, in which the compost would be
considered as in storage until such time as its value as a soil
conditioner might justify removing it from storage and to apply it to
agricultural land. Here limited and valuable land space might justify
composting, but use of the filled area should not be allowed to
involve activities that through investment or presumption become
vested interests capable of defeating the long-range objectives of
resource stockpiling.
Both of these two objectives involve economic determinations
pertinent to a local situation rather than to the national situation.
One element of the system, however—the nature and cost of a
composting plant of specified capacity—is subject to resolution by
the research and development efforts of industry and the Federal
government. With the cost of processing available, or subject to
known parameters, the economics of producing compost for any
local project is then subject to well-established engineering methods.
In the case of resource stockpiling as an objective to be achieved
by the economic savings from reduced landfill area, the problem
requires a careful analysis of alternatives, not all of which are easily
evaluated in dollars. The question that the author is inclined to ask
(See section on Some Current Concepts) is: Why compost at the
"production" bridge rather than at the "use" bridge of the resource
stockpiling system? The answer depends upon many local factors,
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but it seems increasingly evident that in many cases long-distance
transport to fill sites is inevitable. Shipping charges and nuisance
problems might be reduced by composting refuse in the
waste-generation area. On the other hand, when land is valuable
enough to require export of waste, the normal difficulties of siting
refuse processing installations makes composting prior to transport
an unlikely solution. Once the material has reached the fill site, there
is no justification for the expense of composting, since space is not
critical, and eventual demand for the stockpiled resource is vague as
to both time and scale.
The advantages of stockpiling the unsegregated refuse in a landfill
are self-evident. Anaerobic composting of the organic matter will
begin the process, and it can quickly be finished aerobically at the
time of demand. In addition, the accumulated pile of refuse
becomes, with time, of such magnitude that separation of the
resource values, when needed, can be accomplished economically
with industrial-scale equipment.
Cost and Optimum Size of Plants
Questions as to the cost and optimum size of composting plants
have largely been predicated on the assumption that compost is to
be marketed, and hence that the system should be scaled to yield the
most favorable economic picture. If, as the author herein contends,
sale of compost is not a realistic objective except in individual
situations, generally not involving large-scale agriculture, the whole
question becomes academic. The scale of the composting plant is
governed either by the volume of wastes available for processing, or
by the market which will absorb the product. The cost of
composting then depends on a scale determined by considerations
other than economic optimization. It also depends upon the method
of composting to be used.
Composting has been accomplished by three basic approaches:
(1) windrows, in the open or under shed cover; (2) completely
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mechanized industrial plants; (3) mixing with soil surface and
finished compost.
The first of these methods requires considerable land area, plus a
limited amount of preprocessing and materials handling equipment
and housekeeping procedures.
The second requires a complex mechanical system, often with
dust, odor, noise, and vector control.
The third proceeds with essentially only minimal agricultural-type
equipment on appreciable land area.
In the cultural climate of the United States and in light of current
environmental goals, it seems prudent to assume that the
mechanized system will prevail. Certainly, it is the only one of the
three that might require research and development expenditures.
The question for further consideration (See section on Evaluation of
Research and Development Needs) then becomes: whether such
development has already been accomplished to a degree justified by
the prospects for utilizing the composting process in solid waste
management.
If the question of cost and optimum size of plant is posed in the
context of processing refuse for landfill efficiency, the answer must
again be sought by evaluating a known process against the local
waste volume and land value considerations.
It is inconceivable to the author that composting will be applied
to the processing of organic wastes as a matter of national policy of
resource conservation by stockpiling, when both logic and
economics suggest that the same policy might be implemented by
stockpiling the raw refuse and deferring processing until the
indefinite future. Thus, optimization of plant size as a factor worthy
of research and development seems purely academic, and the
problem again resolves to one of having technology sufficiently
developed to meet the needs of today.
Moreover, the manufacturers of existing compost systems already
know the optimum scale for their respective plants, and at least one
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has published a brochure indicating 200 tons per day as the
"breakpoint."8
Public versus Private Operation of Plants
As noted in the first section of this review, the original concept of
early entrepreneurs was that the public should build and operate
composting plants. Aside from the obvious motives of the seller,
there was the real question of ownership and the title to the raw
material to be processed. Because only municipal refuse was
involved, the public was the obvious owner of the raw material.
Inherent conservatism of any public works system and the charter
limitations on mercantile business by cities suggested that the
logical operator of the compost plant should be private industry.
Industry, however, had the same technological handicap as the city,
plus the problem of control of its raw material. To acquire rights to
refuse on a long-term basis was financially too risky for industry. To
subsidize industry on a long-term basis was politically risky to the
city should the venture result in a profit to the processor.8 To top it
all, the concept that compost must be sold, and stockpiled for
seasonal sale as well, could not be documented as valid.
It required only a limited experience with attempts at commercial
composting before the question split into two questions. (1) Why
compost at all? (2) Should the public or private industry take on the
task of converting a low-value material that no one wants, into a
low-value resource material that no one wants?
The first question has been answered in preceding sections in
relation to composting for landfill and to overall management
systems. The second is highly dependent upon other questions which
are currently being pondered. To the author, it seems that if the
public utility concept suggested by the NAS-NRC-NAE task
committee8 should become the pattern of regional solid waste
management, such a public or semi-public agency should operate the
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composting plant. On the other hand, if composting is to be an
adjunct to landfilling, it might best be turned over to private
industry as an adjunct to salvage of other resource materials in urban
wastes. This does not imply that public agencies cannot perform the
task, but rather that to compound further the systems that a city
must operate simultaneously does not, to the author, seem advisable.
If the time comes when resource values are to be extracted from
old and extensive landfills, particularly those serving regional needs,
private industry is the logical agency to do the job.
Evaluation of
Research and Development Needs
In evaluating past research on composting and the composting
process itself, the basic question raised by the considerations cited is
whether composting is now sufficiently developed to meet the
present needs for, and foreseeable potential of, the process. In
answer, it is the author's judgment that: (1) Various current research
projects dealing with composting and supported by the Bureau of
Solid Waste Management are patently redundant. Specifically,
several researchers have set out to determine the basic fundamentals
of composting established by similar projects some 15 years ago. In
addition, attempts to accelerate composting by blowing air through
a compacted mass are being financed despite the history of
exploration of the principles, the futility, and even the absurdity of
the notion dating back to the 1930's in Europe and to the 1940's in
the United States. (2) The principles of composting that engineered
systems must be designed to exploit are well established as a result
of past efforts of the Communicable Disease Center of the Public
Health Service, and, subsequently, the Bureau of Solid Waste
Management.1>2>7>9>10 There is, therefore, little need for research
on the principles of composting, as distinct from other possible
systems of biodegradation. (3) Development of mechanized
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composting is a justifiable investment in order to make available to
engineers the information necessary to adapt it to local situations in
•which use of the process is worthy of consideration; however, such
work should be confined to the exploration of certain units of the
system, rather than to setting up a demonstration of an already
well-known system. (4) Due to private enterprise and to support by
the Bureau of Solid Waste Management, the composting process is
now developed to a point where debugging in actual operating
experience can complete the task. (5) The limited feasibility of
composting as a process for solid waste management at the present is
such that: existing technology is adequate to the potential; scale of
plants is governed by the limited feasible objectives; hence there is
no particular purpose in seeking to determine the optimum size of
plants. (6) It seems unlikely that the state of the art of composting
will be the factor that limits its use in solid waste management. The
Bureau of Solid Waste Management has made a major contribution
to the development of the art of composting, and further major
investment in research and development should now be laid aside in
favor of more urgent components of the overall solid waste system.
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REFERENCES
1. Reclamation of municipal refuse by composting. Technical
Bulletin No. 9, Series 37. Sanitary Engineering Research
Project. Berkeley, University of California, June 1953. 89 p.
2. MAIER, P. P., E. R. WILLIAMS, and G. F. MALLISON.
Composting studies. I. Composting municipal refuse by
the aeration bin process. In Proceedings; 12th Industrial
Waste Conference, Purdue University, Lafayette, Ind., May
13-15, 1957. Engineering Extension Department, Extension
Series No. 94 Engineering Bulletin, 40(3):590-595, Sept.
1958.
3. GOLUEKE, C. G., B. J. CARD, and P. H. McGAUHEY. A
critical evaluation of inoculums in composting. Applied
Microbiology, 2(l):45-53, Jan. 1954.
4. GOTTAAS, H. B. Composting; sanitary disposal and reclama-
tion of organic wastes. World Health Organization Mono-
graph Series 31. Geneva, World Health Organization,
1956. 205 p.
5. McGAUHEY, P. H. Refuse composting plant at Norman,
Oklahoma. Compost Science, 1(3): 5-8, Autumn 1960.
6. AEROJET-GENERAL CORPORATION. A systems study of
solid waste management in the Fresno area; final report on a
solid waste management demonstration. Public Health
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Service Publication No. 1959. Washington, U.S. Government
Printing Office, 1969. [411 p.]
7. GAINESVILLE MUNICIPAL WASTE CONVERSION
AUTHORITY, INC. Gainesville compost plant; an interim
report. Cincinnati, U.S. Department of Health, Education,
and Welfare, 1969. [345 p.]
8. NATIONAL ACADEMY OF ENGINEERING-NATIONAL
ACADEMY OF SCIENCES. Policies for solid waste
management. Public Health Service Publication No. 2018.
Washington, U.S. Government Printing Office, 1970. 64p.
9. WILEY, J. S. Pathogen survival in composting municipal
wastes. Journal of the Water Pollution Control Federation,
34(1) :80-90, Jan. 1962.
10. WILEY, J. S. Refuse and refuse-sludge composting. Journal of
the Boston Society of Civil Engineers, 49(1): 13-25, Jan.
1962.
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OPO : 1971 O - 420-471
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