EPA-600/2-76-148
August 1976 Environmental Protection Technology Series
FUEL AND ENERGY PRODUCTION BY
BYCONVERSION OF WASTE MATERIALS
State-Of-The-Art
LIBRARY
U. S. ENVIRONMENTAL PROTECTION AGENCY
E01SON, N. A, 08817
• Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-148
August 1976
FUEL AND ENERGY PRODUCTION BY
BYCONVERSION OF WASTE MATERIALS
State-of-the-Art
by
Sylvia A. Ware
Ebon Research Systems
10108 Quinby Street
Silver Springs, Maryland 20901
Project Officer
Leo Weitzman
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
.RY
J. S. ENVIRG.;;y!ciifAL PROTECTION AGENCY
DiSON, N. J, 08817
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publication,
Approval does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommendation
for use.
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollution
to the health and welfare of the American people. Noxious air, foul
water, and spoiled land are tragic testimony to the deterioration of
our natural environment. The complexity of that environment and the
interplay between its components require a concentrated and integrated
attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact,
and searching for solutions. The Municipal Environmental Research
Laboratory develops new and improved technology and systems for the
prevention, treatment, and management of wastewater and solid and
hazardous waste pollutant discharges from municipal and community
sources, for the preservation and treatment of public drinking water
supplies, and to minimize the adverse economic, social, health, and
aesthetic effects of pollution. This publication is one of the
products of that research; a most vital communications link between
the researcher and the user community.
This state-of-the-art summary discusses biological conversion of
solid waste, both municipal and agricultural, to fuels. Bioconversion
holds promise of reducing the amount of solid waste which enters the
environment and helping conserve valuable fuel resources. Such a
summary provides the basis for designing research strategies and
developing specific research programs in the field.
Francis T. Mayo, Director
Municipal Environmental
Research Laboratory
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ABSTRACT
This report is a state-of-the-art summary of biological processes
for converting waste cellulosic materials (agricultural, municipal and
lumbering wastes) to fuels. It indicates the locations and quantities
of suitable wastes and discusses the status of the current processing
schemes. The processes discussed are:
• acid hydrolysis followed by fermentation
• enzyme hydrolysis followed by fermentation
• anaerobic digestion of manure and municipal solid waste
• biophotolysis
Cost data for these processes are given and, where possible, compared.
The range of cost was $1.39 to approximately $5.00 per million BTU of net
energy output.
It was concluded that energy production by these methods on a national
scale can, at best, produce the equivalent of only about 3 million barrels
of oil per day by 1980. These may, however, be an economical and environmentally
acceptable means of waste management which should be explored further.
-------
TABLE OF CONTENTS
Page
INTRODUCTION ............................................. 1
SECTION A - SOURCES, QUANTITIES AND DISTRIBUTION OF
THE MAJOR WASTE STREAMS
Agricultural Wastes ......................................... 4
Crop Wastes ........................................... 4
Animal Wastes ......................................... 11
Forestry Wastes ........................................... 15
Municipal Solid Wastes ....................................... 16
Industrial Wastes ........................................... 23
SECTION B - BYCONVERSION PROCESSES TO TREAT CELLULOSIC WASTES
(EXCLUDING PROTEIN PRODUCTION)
Waste Management With Reclamation of Energy ......................... 24
Acid Hydrolysis and Fermentation ................................ 25
Enzyme Hydrolysis ......................................... 26
Anaerobic Digestion ......................................... 30
Introduction .......................................... 30
Digestion of Manures ..................................... 30
Digestion of Municipal Solid Waste ............................. 34
Biophotolysis ............................................. 39
Environmental Impact ........................................ 39
Economic Analysis .......................................... 40
APPENDICES:
APPENDIX A. Cost Estimates for Alternate Systems to Reclaim Energy
from Cellulosic Wastes .............................. 46
APPENDIX B. Methanol Production by Pyrolysis and a Brief Evaluation
of Methanol and Ethanol as Automotive Fuels ................ 57
APPENDIX C. List of References ................................ 60
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LIST OF GRAPHICAL ILLUSTRATIONS
A. LIST OF TABLES
Page
Table:
1 — Estimates of Organic Wastes Available in the United States 2
2 — Field Residues for a Number of Selected Crops 4
3 — Estimated Collectability of Excreta from Livestock 11
4 — Gas Production from Animal Wastes 11
5 — Lists of Major Animal Production States, 1974 14
6 — Volume of Logging Residues Created in 1970 on All Forest Lands 15
7 — Energy Potentially Recoverable from Municipal Solid Wastes 16
8 — Detailed Status of Recovery System Implementation, January 1975 17
9 — Potential Candidate Areas (SMSA's) for Energy Recover in 1974
(projected to 1980) 18
10 — Number of Animals Required to Economically Support Methane
Generation Treatment of Animal Wastes 31
11 — Relative Feasibility of Utilizing Various Energy Recovery Processes
to Convert Dairy Cow Manure to Usable Energy 31
12 — Advantages and Disadvantages of Anaerobic Digestion of Cellulosic Wastes 37
13 — Advantages and Disadvantages of Hydrolysis and Fermentation of
Cellulosic Wastes 38
14 — Comparative Costs of Alternate Systems to Reclaim Energy from Wastes,
1975 Dollars 42
15 — Costs of Production of Methane from Manures, Jacobs
Engineering Figures, 1975 44
16 — Marginal or Break-Even Economics of Seattle Solid Waste Methanol
or Ammonia Project (1978) 58
B. LIST OF FIGURES
Figure:
1 — Projected Amount of Energy Readily Available from Major
Waste Streams in 1980 3
2 — Sugar Cane Production in the United States, 1973 5
3 - Rice Production in the United States, 1973 6
4 - Oats Production in the United States, 1972 7
5 - Barley Production in the United States, 1972 8
Vl
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B. LIST OF FIGURES-Continued
Page
Figure:
6 - Wheat Production in the United States, 1972 9
7 - Corn Production in the United States, 1972 10
8 — Distribution of Cattle with Readily Available Manure in
the United States, 1973 12
9 — Distribution of Poultry with Readily Available Manure in
the United States, 1972 13
10 — Structural Formula of Cellulose 27
11 - Cellulosic Microfibril 27
12 — Enzymatic Hydrolysis of Cellulose 27
13 — Anaerobic Stabilization of Complex Organics 27
14 — Products from Hydrolysis of Cellulose 28
15 — Alternate Anaerobic Fermentation Designs 33
VI l
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PREFACE
"The World's consumption of fuel has become so enormous as to show that our present
supplies cannot possibly last for many generations more. Coal and oil are strictly limited in quantity
and can never be replaced when once removed from the earth. As an alternative, alcohol is
beautifully clean and efficient, and can be produced from vegetable matter of almost any kind. The
waste products of our farms are all available, and even the garbage of our cities."
- Alexander Graham Bell, 1922.
vm
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EXECUTIVE SUMMARY
Current methods of disposal of organic solid wastes, principally land-fill or incineration, are
becoming economically and environmentally unacceptable. By 1980, an estimated 1,061 million
dry tons of organic solid wastes will be generated each year by municipalities, industry and
agriculture. Recent trends in the management of these waste streams have emphasized energy
resource recovery by a number of processes including bioconversion.
Bioconversion is the biological stabilization of organic wastes through the action of a living
organism. Anaerobic digestion of cellulosic residues produces methane and carbon dioxide through
the activities of at least three sets of bacteria. Alternatively, organic wastes can be biodegraded to
glucose by the fungus, Trichoderma viride, and fermented to ethanol using yeast cultures.
Bioconversion processes can be used to make single cell protein (SCP) from wastes, however this
report concentrates on energy production by the two methods mentioned only.
Anaerobic digestion of manures has already been demonstrated as feasible for 350 head of
dairy cattle on a farm in Michigan and is entering the commercial exploitation stage. Three firms
have signed contracts to build plants processing tens of thousands of tons of cattle dung per year to
produce methane for the energy requirements of the feedlots supplying the waste and/or to feed
directly into local gas pipelines. The process looks economically favorable, producing methane at a
gross cost of from $1.39 to $3.19 per 106 BTU's of net energy output. The Southeastern and
Southwestern regions of the United States would be ideal areas to apply this technology for a
number of reasons, including availability of wastes, potential market for methane and climatic
conditions minimizing the need for external energy to maintain the digestion process.
Anaerobic digestion of municipal solid wastes (MSW) has not yet been demonstrated on a
large scale, but negotiations are underway between Waste Management, Inc. of Illinois and the
Energy Research and Development Administration (ERDA) to build a pilot plant digester in
Florida. The gross cost of digestion of MSW is less attractive than combustion processes currently
being utilized as the gross cost of producing pipeline quality methane, excluding any credits, is in
the range of $3 to $5 per 106 BTU's of net energy output. An increase in the price of natural gas
and expected shortfalls in its supply along the Eastcoast where the concentration of MSW is
greatest, would make the Atlantic seaboard the target area for utilization of this technology.
Cellulosic wastes can be more efficiently hydrolyzed to glucose by the fungus, Trichoderma
viride, than by sulfuric acid. Recent increases in the cost of producing ethanol from ethylene, due
to the current energy crisis, have made the production of ethanol by fermentation very competitive.
Improvements in the technology of fermentation, particularly the computer-monitoring of the
-------
reaction, have made the design of large-scale fermentation plants feasible. The production of
ethanol from organic wastes via glucose would substitute for fossil fuels currently used to derive a
wide range of industrial chemicals.
It is not proposed that energy production from cellulosic wastes will solve the energy crisis, as
the amount of energy produced would be equivalent to only 3 million barrels of oil per day
assuming complete utilization of all of the solid wastes projected to be potentially available in 1980.
However, the bioconversion of cellulosic wastes to produce energy is an economically and
environmentally acceptable means of solid waste management that should be further explored and
exploited.
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Introduction
The purpose of this study is to provide the U.S. Environmental Protection Agency's Solid and
Hazardous Waste Research Program with an overview of the status of bioconversion in this country
so that an informed decision can be made relative to the feasibility of the U.S. Environmental
Protection Agency undertaking a major bioconversion research program. The need for such a study
arises from consideration of two seemingly unrelated problems: the magnitude of the current
energy crisis and the increasing problems of solid waste disposal.
In the United States, the total energy input for 1970 was estimated at 68.8 x 1015 BTU's.
Energy needs are expected to double in the next 15 years.1 Current resources of fossilized fuels,
with the exception of natural gas, are abundant but are not unlimited. This knowledge, together
with the political energy crisis, has stimulated the search for alternative sources of fuel.
One possible source of energy is the reuse of the organic wastes that are at present causing an
environmental problem. These wastes include municipal refuse — both garbage and sewage —
agricultural crops and food wastes, animal manure from feedlots, forestry waste products, and
organic industrial wastes. It is estimated that by 1980, 200 million dry tons per year of organic
wastes will be readily available for energy conversion of a possible 1,061 million dry tons of waste
generated,2 (see table 1). The oil potential from these available wastes in 1980 is approximately
255.5 million barrels per year, which is equivalent to 70% of the crude oil imported directly from
the Middle East in September 1973, or 2.2% of all energy consumed in the United States in 1970.
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FIGURE 1. PROJECTED AMOUNT OF ENERGY READILY AVAILABLE FROM
MAJOR WASTE STREAMS IN 1980*
100%
70%
36%
13%
11%
O MANURE
MUNICIPAL SOLID WASTE
CROP RESIDUES
ALL SOLID WASTE
CRUDE OIL IMPORTED FROM THE MIDDLE EAST, SEPT. 1973
Based on oil imports of 1 million B/DOE
Quantities oil calculated using 1.25 barrels/ton of dry organic waste
As a percentage of crude oil imported from the Middle East, Sept. 1973
Source of raw data; Table 1.
-------
SECTION A. SOURCES, QUANTITIES, AND DISTRIBUTION OF THE
MAJOR WASTE STREAMS
Agricultural Wastes
Crop Wastes
The generation of field wastes by major agricultural crops is high (an estimated 390 million
tons in 1970)3 but is generally spread over such vast areas as to make collection and utilization of
these wastes an uneconomic proposition. Currently, the wastes are either burned in situ to kill
topsoil micro-organisms, or left to prevent erosion, and to return humus and nutrients to the soil.
Enforcement of pollution control regulations is limiting the former means of disposal.
Some residues are found in centralized locations, notably bagasse from sugar mills, corn cobs
and stalks, milling wastes from wheat, rice, and other grains. The following maps (figures 2-7) are an
attempt to locate these available crop wastes by state. While there is no conclusive proof that crop
waste quantity is directly related to crop yield, the assumption is made that the greatest
concentration of a particular waste is found in the states with the largest crop harvest.
The prunings from orchards and vineyards constitute problem wastes which may be
incinerated or landfilled; incineration contributes toward air pollution, and landfilling may
propagate plant diseases and insect pests.
An extensive state-by-state inventory of all agricultural wastes will be concluded shortly at
Stanford Research Institute. One report has already been issued;4 the complete findings will be the
most complete and accurate record of the nature, magnitude, and distribution of agricultural wastes
across the entire United States.
TABLE 2. FIELD RESIDUES FOR A NUMBER OF SELECTED CROPS
Billion/'Pounds (Bib)
Crop of Residues (wet)
Barley 36.7
Corn 376.0
Oats 58.5
Rice 13.4
Wheat 108.0
Sugar Cane 17.2
Total 609.8
Source: Problems and Opportunities in Management of Combustible Solid Waste,
IRT, D.C., October 1972, p. 27.
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Animal Wastes
Animal wastes were once valued as a fertilizer, but with the ready availability of the more
convenient commercial fertilizers, and the concentration of large quantities of animals in feedlots,
manures have become a disposal problem. Manures may be safely applied to land at a rate of 10
tons of waste per acre per year,5 but land disposal of the thousands of tons of waste generated by
cattle, swine, and poultry feedlots is obviously an impossibility. Animal wastes eroded from feedlots
have been identified as the cause of fish kills and stream eutrophication. The Water Pollution
Control Act Amendments of 1972 which applied to feedlots with a pollution equivalent of 1,000
head of cattle or more were judged to be illegal in court, March 1975, due to the size limitation
requirement. Pollution control legislation will apply to all operations soon. The current costs of
waste collection, storage, and disposal are high enough to make the possibility of offsetting costs
through energy and/or protein production look very attractive.
By 1980, an estimated 266 million tons of manure will be generated per year. Not all of this is
readily available for energy conversion. Estimates of the collectability of manures from different
types of livestock have been made by the United States Department of Agriculture (USDA),
Agricultural Research Service.6 These estimates are based on the practicality of collecting and
processing the wastes either on the farm, or a centrally located processing station (see table 3).
Figures 8 and 9 are an attempt to indicate the locations of the greatest quantities of available cattle
and poultry wastes, based on these collectability figures.
TABLE 3. ESTIMATED COLLECTABILITY OF
EXCRETA FROM LIVESTOCK
TABLE 4. GAS PRODUCTION FROM
ANIMAL WASTES
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Cow Placements
Other > 227 kilograms
< 227 kilograms
Dairy Cows
Replacement Heifers
Breeding
Market Hogs
Stock Sheep
Sheep & Lambs on feed
Laying Hens & Pullets
Pullets & Other Chickens
Broilers
Turkey (growing)
Turkey (breeder)
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1, 000 Ib. milk
cow
1,000lb. steer
100 Ib. pig
5 Ib. hen
Gas*
Productions
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30.00
3.00
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Energy**
Value
(BTU's/day)
20,000
15,000
1,500
150
Source: Yeck, Robert G., Recovery of Nutrients From Animal
Wastes — an Overview of Existing Options & Potentials
for Use in Feed, Univ. of Illinois, April 21-24, 1975,
p. 10.
Source: Producing Methane Gas From Animal Wastes,
USDA Agricultural Research Service, August
1974, p. 3.
*an approximation based on multiplying waste pro-
duction rates by a gas production of about 6cu.ft./lb.
of dry matter.
**for a gas of 50% methane, 500 BTU's/scf. of gas.
The percentage collectability is based on the
practicality of collecting and processing wastes on the
farm or a centrally located processing station. The 90%
collectability figure for beef cattle weighing over 227
kilograms, refers to manure from cattle in feedlots,
being fattened before slaughter.
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Forestry Wastes
Logging residues produced in 1970 amounted to almost 1.6 billion cubic feet; 58% of the
total were softwoods and 42% were hardwoods. While the residues are widely scattered over
thousands of logging locations throughout the country, the greatest concentrations are found in
Washington, Oregon, and Northern California. Of the total softwood residues of the entire United
States, 36% are found in the forests of Western Washington and Oregon where slash-fuel weights
range from 37 to 27 tons per acre.7
The volume of softwood residues generated in the South is much lower than in the West due
to the presence of an expanding pulpwood industry utilizing most of the bole, and because the
standing timber volume per acre is less than that in the West. Logging slash does not accumulate
because the climatic and biotic factors in the area favor speedy decomposition. Hardwood residues
are more numerous (over 400 million cubic feet) but are widely scattered.8
The accumulation of logging slash may be ecologically beneficial in a number of ways, but
timber experts agree that physical removal of the slash would be acceptable if it could be
accomplished with the minimum disturbance of soil or riparian habitats. Removal of logging slash
discourages the growth of insect and rodent populations and is usually helpful in preparing the
ground for seeding and planting. The appearance of timber harvest residues is considered by many
people to be esthetically unpleasant and evidence of bad timber management. In the past,
environmental groups have made it necessary to alter harvesting practices despite economic loss.
The collection and utilization of these residues to produce energy would presumably be very
acceptable to these powerful groups, but only if accomplished with the minimum of environmental
disturbance.
TABLE 6. VOLUME OF LOGGING RESIDUES CREATED IN 1970
ON ALL FOREST LANDS
AREA
North
South
Rocky Mountains
California
Pacific Northwest
(Douglas Fir
sub-region)
(Ponderosa Pine
sub-region)
(Alaska)
Total
Volume Created in 1970
Softwoods
(mil/ion scf)
62
263
103
92
404
(330)
(34)
(39)
924
Hardwoods
(mil/ion scf}
222
421
-
13
16
(16)
—
-
672
% of Totals by Specific Subgroup
Softwoods
1
28
11
10
44
(35)
(4)
(4)
100
Hardwoods
33
63
-
2
2
(2)
—
-
100
Source: Report of the Close Timber Utilization Committee, USDA, Forest Service, June 28, 1972, p. 31.
15
-------
Municipal Solid Wastes
EPA estimates that about 125 million tons of municipal wastes were generated from
residential and commercial sources in the United States in 1971, (3.32 Ibs per person per day).9 By
1980, the U.S. National Average is expected to be around 3.91 Ibs per person per day; and the
Urban Area Average to be about 4.33 Ibs per person per day.10 The energy equivalent potentially
recoverable from the Standard Metropolitan Statistical Area (SMSA), waste stream is projected to
be about 1,085 trillion BTU's per year, the equivalent of over 512,000 barrels per day of oil
equivalent (B/DOE) or 187 million barrels per year of oil equivalent (B/YOE), (see table 7). Note
that this quantity is substantially higher than the estimate given in table 1, but represents a more
recent evaluation of the amounts.
TABLE 7. ENERGY POTENTIALLY RECOVERABLE FROM MUNICIPAL
SOLID WASTE, 1980
Theoretical
Available
Projected
Implementation
Potential
Candidates
BTU's
(trillion)
1,440
1,085
85
558
Barrels/day
oil equivalent
(thousand)
680
512
40
263
B/YOE
(million)
248
187
15
96
Source: Lowe, Robert, Energy Conservation Through Improved Solid Waste Management, USEPA Report
SW125, 1974, p. 12.
16
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TABLE 9. POTENTIAL CANDIDATE AREAS (SMSA's) FOR ENERGY RECOVERY IN 1974
(With Potential Energy Recoverable Projected to 1980)
Standard Metropolitan Statistical Areas Population 1970 (thousands)
1. New York, New York 11,572
2. Chicago, Illinois 6,979
3. Philadelphia, Pennsylvania 4,818
4. Detroit, Michigan 4,200
5. Washington, D.C. - Md. - Va. 2,861
6. Boston, Massachusetts 2,754
7. Pittsburgh, Pennsylvania 2,401
8. St. Louis, Missouri 2,363
9. Baltimore, Maryland 2,071
10. Cleveland, Ohio 2,064
11. Newark, New Jersey 1,857
12. Minneapolis — St. Paul, Minnesota 1,814
13. Milwaukee, Wisconsin 1,404
14. Atlanta, Georgia 1,390
15. Cincinnati, Ohio 1,385
16. Patterson, New Jersey 1,359
17. San Diego, California 1,358
18. Buffalo, New York 1,349
19. Miami, Florida 1,268
20. Denver, Colorado 1,228
21. Portland, Oregon 1,009
22. Columbus, Ohio 916
23. Providence, Rhode Island 911
24. Rochester, New York 883
25. San Antonio, Texas 864
26. Louisville, Kentucky 827
27. Memphis, Tennessee 770
28. Albany, New York 722
29. Toledo, Ohio 693
30. Akron, Ohio 679
31. Hartford, Connecticut 664
32. Gary, Indiana 633
33. Jersey City, New Jersey 609
18
-------
TABLE 9 -- Continued
Standard Metropolitan Statistical Areas
34. Nashville, Tennessee
35. Jacksonville, Florida
36. Wilmington, Delaware
37. Knoxville, Tennessee
38. Bridgeport, Connecticut
39. New Haven, Connecticut
40. Peoria, Illinois
41. Little Rock, Arkansas
42. Chattanooga, Tennessee
43. Madison, Wisconsin
44. Rockford, Illinois
45. Lawrence, Massachusetts
46. Charleston, West Virginia
47. Eugene, Oregon
48. Brockton, Massachusetts
Total Population, 1970
Total Population, 1980
Waste Generation, 1980 - Annual
Daily
Number of Equivalent 1,000 TPD Plants
Energy Recoverable
Population 1970 (thousands)
541
529
499
400
389
356
342
323
305
290
272
232
230
213
190
71,786
78,462
62.0 Million Tons
170 Thousand Tons
170
558 Trillion BTU's
Per Year
263,000 Barrels Per Day
of Oil Equivalent
96 Million Barrels
Per Year of Oil
Equivalent
Source: Lowe, Robert, Energy Conservation Through Improved Solid Waste Management, USEPA SW-125, 1974, p. 18.
Note: Recoverable energy is a function of waste generation, which is a function of population.
19
-------
In 1980, it is projected that almost 30 cities and counties around the country will be
operating the equivalent of about thirty-six 1,000 tons per day (TPD) plants, recovering an
estimated 85 trillion BTU's per year, (40,000 B/DOE, or 15 million B/YOE).11 These communities
have already taken steps toward implementing such an energy recovery system. Such steps include
actual construction, solicitation of proposals, legislation to implement, or an active planning effort.
Of these identified cities, 21 are considering or implementing the technology of using solid waste as
fuel, 3 are interested in pyrolysis, and 4 in water wall incineration.
A number of additional communities have been selected from the SMSA's as having local
conditions in 1974 which favor implementation of an energy recovery system by 1980.12 These
conditions are:
1. economics — high disposal and alternative fuel costs
2. market — available technology to implement the scheme
3. public interest — a high enough level of public interest will encourage energy recovery even
though the economic conditions are unfavorable.
The public interest factor was identified as being strong(S), adequate(A), nominal(N), or
opposing(O) resource recovery. Of over SMSA's screened, no active opposition was recorded and
over 55% of the cities considered expressed strong or adequate interest. In the following areas,
public interest in energy recovery was significantly more important than other factors in the
decision to designate a SMSA as a potential candidate:
1. Denver, Colorado
2. Bridgeport, Connecticut
3. Peoria, Illinois
4. Chattanooga, Tennessee
5. Lawrence/Haverhill, Massachusetts
6. Portland, Oregon
7. New Haven, Connecticut
8. Madison, Wisconsin
9. Rockford, Illinois
10. Eugene, Oregon
Survey by International City Management
International City Management Association, Washington, D.C., conducted a survey of 2,000
cities in the United States with populations exceeding 10,000 to determine which of the cities had
plans to develop a capital intensive resource recovery system in the next five years.13 They found
that of the 1,025 cities replying to the question, 166 or 16% had such plans and 859 or 84% did
20
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not. Including those cities which did not reply, this gives a figure of over 300 cities entertaining
plans for capital intensive resource recovery systems in the next five years.
There is a growing interest in the use of municipal solid wastes to generate energy, but it is
likely that as the focus of interest is at present on non-bioconversion technologies, that these
processes will be further implemented as more cities develop energy recovery systems. Bio-
conversion of MSW to produce methane would be particularly attractive along the East coast, which
relies most heavily on imported fuels, and expects short falls in supply of natural gas this winter
reaching as high as 15%. The Southeastern portion of the United States is probably more favorable
than the Northeastern section as the higher temperatures, particularly in winter, would decrease the
energy requirements of the digester. The digesters planned by Waste Management Inc. at Pompano
Beach, Florida are to be added to the front-end resource recovery system already built. Other small
cities with resource recovery systems might consider similar additions. The Southwest of the United
States also seems an attractive area for digestion: the temperatures are high and, as anaerobic
digestion does not require large quantities of water, the aridity is no deterrent.
It is clear from the results of the International City Management Survey that smaller
communities do not have the same commitment to a capital intensive resource recovery system as
the larger cities with the more acute waste disposal problem. It is possible that small towns in rural
areas would react favorably to agricultural waste digestion units with a small capital outlay as sugar,
corn logging and poultry wastes are plentiful in the Southeast.
21
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Industrial Wastes
Wood Related. — Wood related wastes are generated at sawmills, and in the pulp and paper
industries. Much of the sawmill wastes are used as a fuel, for the manufacture of pulp and paper, or
for production of particle board and plywood. Primary wood manufactures in Oregon and
Washington report up to 80-94% reuse of wood and bark residues. Even so, the total wood
manufacturing and construction amounted to 29.42 B Ib.14 Projections into 1990 show certain
areas in Washington, Oregon, North Carolina, Virginia, Massachusetts, and New York to have
especially large concentrations of these wastes.
Pulp, paper and allied industries are employing a number of different chemical recovery cycles
expected to bring about a 50%15 reduction in wastes generated by 1990.
Other Industries. — Paper plant trash is generated in all manufacturing processes. Cellulosic
wastes are produced by a number of industries, primarily the food, textile and clothing, paper and
printing, and leather industries.
Much of the food wastes can be used as an animal feed. The, food processing and canning
industries are producing approximately 100,000,000 Ibs. of waste per day with a potential yield of
10 cu.ft. of methane.16 Both beet sugar and tomato cannery wastes have yielded about 8 cu.ft. of
total gas/lb. of BOD.17 The Western and Southern regions of the United States produce a large
percentage of these food wastes.
Residues from textile and clothing manufacture are concentrated in the Middle and South
Atlantic States, particularly in North and South Carolina and Georgia.
23
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SECTION B. BYCONVERSION PROCESSES TO TREAT CELLULOSIC WASTES
(EXCLUDING PROTEIN PRODUCTION)
Waste Management with Reclamation of Energy
In the past the emphasis of waste management has been on disposal rather than reclamation,
however, newer methods of management have emphasized the reclamation of waste materials both
for inorganic and organic content. Energy may be obtained from organic refuse by a number of
processes including:
1. Direct combustion to produce steam for heating or electricity
2. Cofiring with coal to produce electricity as at the St. Louis plant
3. Pyrolysis or destructive distillation to produce fuel oil, gas, and a carbon char or other
products
4. Catalytic reduction to produce fuel oil
5. Bioconversion
Bioconversion is the biological stabilization of organic wastes through the action of a living
organism—a fungus, yeast, alga, bacterium, or a fly. Given time, nature will accomplish the
biodegradation of wastes. Landfills anaerobically digest the cellulose content of the fill to produce
methane. The NuFuel Company has commenced methane recovery from the Los Angeles County
Palos Verdes landfill and is negotiating for other landfill testing rights in California, Arizona,
Illinois, New Jersey, New York and Pennsylvania. The Los Angeles Power and Water Department
together with the city's Bureau of Sanitation are presently driving a 200 kw. electric generator by
combustion of methane drawn from the city's Sheldon-Arleta landfill. The recovery of gas has its
greatest potential from canyon fills in very dry climates, and cannot be considered to have great
potential as an energy recovery system—particularly in the Northeast where the need is greatest, but
the climate is damp and the landfills shallow. Methane recovery from a fill peaks after a few years
and gradually declines.
The University of Florida is conducting preliminary experiments on the recovery of methane
from anaerobic lagoons. The University of Minnesota is considering the possibility of covering an
outside lagoon to determine if gases from the lagoon can be tapped as an energy source.18
Anaerobic lagooning of hog wastes has been explored by Muehling at the University of Illinois in
1969. In 1970, Claybaugh suggested the use of a plastic bubble over a lagoon to collect methane for
use on the farm.
Methane from landfills or lagoons is in a sense an after-thought to the process. Of much
greater interest are technologies developed specifically to maximize energy production, notably
anaerobic digestion to produce methane and hydrolysis and fermentation to alcohol. In addition to
manufacture of methane and ethanol from cellulosic wastes, it is possible to produce protein for
human and animal consumption by a number of different fermentation processes. Perhaps at some
future date, the processes to produce food or energy will be in competition with each other for the
reactant wastes.
24
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Acid Hydrolysis of Cellulose and Fermentation to Ethanol
The bench-scale production of sugar by acid hydrolysis of municipal solid wastes has been
investigated by the Thayer School of Engineering. The process can be accomplished in a continuous
flow reactor to produce about 52-54% yield of sugar.22 The reaction is carried out isothermally at
230°C using 1% weight of sulfuric acid and a reaction time of 20 seconds.23 The yield was found to
be a function of time of reaction, temperature, concentration of the acid and solid-to-liquid ratio in
the slurry. As the hydrolysis conditions also favor the decomposition of the sugar, the maximum
yield expected is 53% conversion of cellulose to sugar.
A hot slurry of wastes is mixed with sulphuric acid prior to entering the reactor, a 5 foot long
steel tube. The temperature and pressure in the reactor are carefully monitored, and the products of
hydrolysis are cooled in a quencher and collected at 25-30°C in a product accumulator. If the slurry
is kept at 230°C for less than 15 minutes prior to entering the reactor, there is little thermal
degradation of cellulose.24 Difficulties experienced on the small scale could be eliminated on a
larger scale; there is a definite need to study the kinetics of the reaction in a large-scale flow reactor.
For large plants, Converse et. al. assume the pretreatment of the wastes by possibly the
FIBRECLAIM or HYDRASPOSAL process of the Black Clawson Company.25 The HYDRA-
SPOSAL process though more costly, was found to allow greater sugar yields per ton of initial raw
refuse. The cost of the sugar produced was found to be dependent on the paper content of the
MSW. Costs varied from under 24 to 4tf per Ib., (from 40% paper to 60%).26
Fermentation of the products of hydrolysis with the organism, Saccharomyces cerevisiae, in a
800 ml. fermenter gave yields of from 85-93% of ethanol after approximately 20 hours (rate
achieved from molasses is about 80%).27 The rate of fermentation increased with higher
concentrations of sugar (from 4g/100mls. to 12g/100mls) but not the yields.
Cost analysis of the process shows that ethanol can be produced at a lower cost than the
current market price.28 The ethanol produced could be used as the starting point in the synthesis of
a number of organic chemicals presently derived from fossil fuels, thus resulting in an energy
savings. It should be noted that the Exxon Corporation's synthetic ethanol plant in New Jersey29
recently closed because the equipment was old, and the ethanol could no longer be marketed at a
competitive price. The Tennessee Eastman Company has ceased marketing synthetic ethanol, and
absorb the alcohol they manufacture internally, as there is an increased demand as an intermediary
for their own products.
Until recently, there has been little use of continuous fermentation on a large scale, due to
difficulties in maintaining a sterile system, lack of knowledge of microbial behavior and chances for
harmful mutation within the enzyme system. Knowledge advances in both the biochemistry and
engineering of the system have made the design of large scale continuous fermentation plants
feasible.30 Computer coupled fermentation systems will provide immediate and continuous systems
analysis permitting the regulation of environmental conditions within the fermenter, including
oxygen transfer rate, homogeniety of nutrients, sterility and stability of the system.31
25
-------
The firm of Microbic Operations32 reports a zero failure rate in their system of fermenters;
they apparently achieve an optimum inoculum for a 10,000 liter reactor by step up fermenters of
30 mls,100 mis. and 1,000 mis.
Georgia-Pacific Corporation chemical plant at Bellingham, Washington, has reported that it is
converting spent pulp to high grade alcohol.
Enzymatic Hydrolysis of Cellulose
The world authorities in the field of enzymatic hydrolysis are the researchers of the Army's
Natick Laboratories. However, other investigators are extending their inquiries, notably Dr. Wilke at
Berkeley and the USDA Forest Products Research Laboratory in Madison, Wisconsin.
Researchers at Natick have developed a mutant strain of the fungus, Trichoderma viride,33
which can manufacture enzymes to break down both the crystalline (Ci) and the amorphous form
of cellulose (Cx). (see figures 10-13). The cellulases, of enzymes produced by the fungus to convert
cellulose to glucose, will bring up to 90% 34 conversion of the cellulose fraction of waste materials
in about 24 hours (6 hours for a feedlot substrate), depending on the nature of the substrate. The
product—glucose—has many possible uses (see figure 14). Natick researchers estimate that the cost
would be about 2^/lb.35 with credits for disposal costs and recycling of metals. Researchers at the
University of California quote estimates of around 26^/kg,36 with ethanol fermented from the
glucose at 8^ per liter—about one-half of the current market price.
Enzymatic hydrolysis involves initial preparation of the enzymes by growth of Trichoderma
viride on a starving diet of cellulosic wastes (0.75%) at 25-28°C and a pH carefully controlled to
prevent hyperacidity.37 The fungus produces enzymes to break down the cellulose molecule to
sugar, which it then consumes. Once the broth has grown and the enzymes are in solution, the broth
is filtered. The filtrate containing the cellulase complex is fed into the hydrolysis reactor where at
50°C and atmospheric pressure, the enzymes break down a cellulose rich slurry (pH 4.8) into sugar.
After up to 24 hours, the syrup is harvested and some of the slurry is recycled. The economic
bottleneck of the process is in the initial pretreatment of the wastes to break up the crystalline
structure of the cellulose.
Researchers at Natick are investigating a variety of methods to prepare the cellulose for the
enzymes. These methods include: chemical and/or physical means (ball-milling), ionizing
radiation, ultrasonics and development of other enzymes. The feasibility study currently underway
at the USDA Forest Products Laboratory includes an examination of this pre-hydrolysis step, in
order to produce non-crystalline cellulose with better surface presentation for subsequent
hydrolysis.38 Dr. Erikson, in Finland, is concentrating on the removal of the lignin fraction which
apparently shields the crystalline cellulose from attack by the Q enzyme.
The pre-pilot stage at present operating at Natick at a capacity of 1,000 Ibs/month and
interfaced with a computer for rapid data analysis and process estimation, will increase capacity
26
-------
FIGURE 10. STRUCTURAL FORMULA OF CELLULOSE
CHoOH
O,
FIGURE 11. CELLULOSIC MICROFIBRIL
(After Cowling and Brown)
amorphous region
crystalline region
FIGURE 12. ENZYMATIC HYDROLYSIS OF CELLULOSE 20
C, Cx ®
Native Cellulose——^Linear Cellulose Chains ->Cellobiose-
> Glucose
FIGURE 13. ANAEROBIC STABILIZATION OF COMPLEX ORGANICS
21
Complex Organics-
-^Organic Acids-
-^Methane and Carbon Dioxide
CELLOBIOSE- A WATER -SOLUBLE DISACCHARIDE
27
-------
FIGURE 14. PRODUCTS FROM HYDROLYSIS OF CELLULOSE
CELLULOSE
28
-------
steadily to 4,000 Ibs/month. Data collected will permit a scale-up to a larger unit. Current
calculations indicate that as the scale goes higher, the kinetics of the reaction improve.
Enzymatic hydrolysis has a number of advantages over acid conversion of cellulose:
1. Expensive corrosion resistant equipment is unnecessary
2. Process conditions such as temperature do not have to be so closely monitored
3. The conversion can approach 90% compared to the 50% level recorded for acid hydrolysis
4. The process is not energy intensive
Another factor that makes this a potentially very attractive process is the complete utilization
of the materials involved. In addition to using the sugar, the solid wastes from the fermenter,
principally lignin, could be used as a fuel, and the fungus itself as an animal food if they could be
harvested separately. It will be possible to buy the enzyme and conduct the hydrolysis at small local
sites.39 The research team in California reports that if the paper wastes generated per year were
converted to ethanol, this country could produce 49 billion liters of alcohol per year, with energy
equivalent to 10% of the annual gasoline production.40 Even if the ethanol is not used as an
automotive fuel, it is a valuable chemical feedstock. As the process is technically feasible, it is not
unlikely that the large scale production of glucose from cellulose will be a reality by 1980.
29
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Anaerobic Digestion
Introduction
The first recorded attempt to build a digester to produce methane from organic wastes was in
India in 1900.41 Since then, anaerobic digestion of human wastes has been extensively utilized, and
the methane gas produced has been used for practical purposes in India, Taiwan, Africa and Europe.
By 1963, over 70% of waste water treatment plants in the United States used anaerobic digestion to
stabilize the organic fraction of liquid wastes. The process has been well used, but has a reputation
for unreliability. The sensitivity of operation can be upset by design inadequacies in the plant,
unskillful operation or heavy metal contamination in the feed. For some years, there was a decline
in interest in the process, and incineration was thought to be'the solution to sludge disposal.
The current burst of interest in biogasification research began in India in the 1940's, and led
to the formation of the Gobar Gas Research Station and emphasis on village level production of
methane by such men as Ram Bux Singh.42 In the United States, economic and cultural factors
emphasized the disposal of wastes rather than their use. The sludge and gas from digestion have
been regarded as waste disposal problems. However, in some cases the gas has been used to power
generators and pumps in the treatment plants. The Los Angeles Hyperion Sewage Treatment Plant
generates enough methane from primary sludge treatment to power its 24-2,000 hp. diesel engines.
The following section summarizes current research interest in anaerobic digestion of
municipal solid waste and animal manures in the United States. The process is essentially the same
for either feedstock and involves biodegradation of the cellulose fraction of the wastes by at least
three sets of bacteria, cellulolytic, acetogenic, and methanogenic bacteria. Initially the cellulose is
converted to short chain volatile acids. The methane forming bacteria then convert the products of
acidogenesis to a mixture of methane and carbon dioxide, (see figure 13). The compositions of both
waste streams have been shown amenable to anaerobic digestion.
Anaerobic Digestion of Manures
It is well established that manures can be effectively digested anaerobically to produce
methane gas. Important environmental and operational parameters are now being delineated to
maximize the production/cost efficiency of the process as applied to cattle, swine and poultry
wastes. Calculations made by Dr. W. Jewell at Cornell University indicate that anaerobic digestion is
the most feasible method for converting cow manure to energy on a New York Dairy farm.43
The number of animals required to economically support methane generation from animal
wastes has also been determined by Dr. Jewell and co-workers.44
30
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TABLE 10. NUMBER OF ANIMALS REQUIRED TO ECONOMICALLY SUPPORT METHANE
GENERATION TREATMENT OF ANIMAL WASTES**
ANIMAL
Beef
Dairy
Poultry
Swine
Number of Animals
Energy Only
570
380
57,000
2,800
Energy and Nitrogen
155
80
5,200
585
Source: Jewell, W. J.; Morris, G. R.; Price, D. Ft.; Gunkel, W. W.; Williams, D. W. and R. C.
Loehr, Methane Generation from Agricultural Wastes: Review of Concept and
Future Applications, presented by the ASAE, West Virginia University, August
18-21,1974, p. 5.
TABLE 11. RELATIVE FEASIBILITY OF UTILIZING VARIOUS ENERGY RECOVERY
PROCESSES TO CONVERT DAIRY COW MANURE TO USABLE ENERGY
Processes Capable of Capturing Energy
1. Biological Aerobic Fermentation
(ambient temperature)
2. Biological Anaerobic Fermentation
(at a raised temperature)
3. Thermophilic Aerobic Digestion
Dry Method
Slurry Method
4. Destructive Distillation
Hydrocarbonization
Pyrolysis
*lndex of Feasibility
Energy Recovery
5.5
14.7
7.6
6.8
3.6
3.5
5. Incineration
0.7
Source: Jewell, W. J., Energy from Agricultural Waste — Methane Generation, Cornell University,
Agricultural Experiment Station, New York; p. 5.
Note: A high index indicates that the method is easier to implement and that a larger amount of energy
will be available than with lower indices. Factors considered in arriving at the index were availability of
technology, availability of full scale equipment, skilled operation, required operation time commitment,
complexity of process and operation by agriculturally trained personnel.
31
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They find that if the residues left after digestion are to be economically exploited as a fertilizer or
feed for ruminants, in addition to the marketing of the methane produce, the number of animals to
break-even becomes surprisingly small (see table 10). Other researchers support the conclusion that
the economic potential of anaerobic digestion of manures lies in the selling of the residues. The
limiting environmental and operational parameters differ, depending upon the source of the manure
and diets of the animals providing the wastes. Much research is underway to identify the problem
areas, and to resolve the technical difficulties. One point of interest is the effect of fermentation
design on efficiency and cost.
Alternative Fermentation Designs
Completely Mixed (Mesophilic) Digestion. — The process currently applied to municipal
sewage sludges. The waste is immediately and uniformly digested from periods of 15-30 days and
temperatures of 30-40°C. The effluent is withdrawn at a rate equal to the inflow rate to maintain a
constant volume. Mesophilic digestion has produced yields of from 1.3 scf methane/lb. of dry
matter to 3 scf methane/lb.45 Optimization of conditions produces yields double this value for
cattle manure. Hog wastes have produced from 7.7 to 16.8 scf of total gas per Ib. of volatile solids
destroyed, with 60% methane.46
Completely Mixed (Thermophilic)Digestion. —Operates above 50°C with additional energy
expenditure. Investigators at the Northern Regional Research Center, USDA, under the direction of
Dr. Rhodes, have developed this process to produce yields of about 4 scf methane/lb. of dry matter
(cattle).47 Several important challenges imposed on their fermenters have significantly added to
understanding of the process:
1. They have operated a stable digester with loading rates as high as 16 g. volatile
solids/liter/day (commonly quoted, c.f. 1.6-3.2 g/liter/day)48
2. Recirculation of the effluent gas has quickly improved the health of failing fermenters.
3. Pretreatment of the feed material with sodium hydroxide (up to 8% solution) with
neutralization prior to digestion increases the solubilization of the lignin fraction of the
wastes. There are indications that solubilization is a major rate limiting factor.
Partially Mixed (Liquid Displacement). — The capital and operational costs are lower than the
completely mixed process but the biodegradation and gas production are also less.
The Batch Load Digester. — Employs two completed mixed reactors, one of which ferments
while the other is fed, resulting in an increase in efficiency. Like the completely mixed process, it is
necessary to premix and dilute the manure with an increase in capital and operational costs.
However, there is also an improvement in biodegradation and gas production.
The Plug Flow Longitudinal Reactor. — As planned for use by the Montford Feedlots
involves no intermixing of the contents of the digester. Costs are lower but so is gas production and
end-stablization rate.
32
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FIGURE 15. ALTERNATIVE ANAEROBIC FERMENTATION DESIGNS
COMPLETELY M IXED ( MESOPHILI C )
COMPLETELY MIXED
PARTIALLY M IXED
PLUG - FLOW
BATCH
Source of original information = MORRIS, Gary R. etal, ALTERNATIVE ANIMAL WASTES ANAEROBIC
FERMENTATION DESIGNS AND THEIR COSTS, Cornell University, 1974
33
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Several commercial animal/gas production units are under construction:
(a) Calorific Recovery Anaerobic Process Inc. of Oklahoma City has signed a contract with
Natural Gas Pipeline Company of America, Chicago, to provide gas generated from cow
dung at a plant to be built in the Oklahoma Panhandle.
(b) ERA Inc., Lubbock, Texas signed a contract in June 1975, to provide Natural Gas
Pipeline Co. with 650 million cu.ft. of methane per year from 80,000 tons of cow dung at
a base price of $1.30 per thousand cu.ft.49 ERA has plans for building approximately 40
large manure-to-gas plants in feedlots around the country, if the Texas plant proves
feasible. The Texas plant will cost an estimated $2.6 million. The cost of the mathane is
higher than current domestic natural gas prices, but below other forms of synthetic and
natural gas currently being developed. Deregulation of domestic natural gas prices will
make a significant difference for all forms of anaerobic digestion. The digesters will
employ completely mixed mesophilic digestion to produce about 60% methane. The
company also sees application of their process to municipal solid wastes, wood slash, etc.
Patents are pending.
(c) Skelley B. Don & Associates of Denver will build a $4 million plant to gasify manure
for the Montford Feedlots. The plant is slated to have a capacity of 120 million
cu.ft./month of methane, 70 million of which will go to Montford to meet its gas
needs.50 The remainder of the gas will be sold to Colorado Interstate Gas, and fed
directly into their pipeline less than a mile from the site. The carbon dioxide produced in
the process will be used for the manufacture of dry ice. Montford will take back the
digested sludge at 50% moisture for use as a fertilizer. The plant which will be completed
by 1976 is based on the Plug Flow design of digester.
(d) Jerry Malstrom of Ludington, Michigan has built the largest digester of manures now in
operation. The digester, at present operating below capacity (350 head of cattle),
produces between 20,000-22,000 cu.ft. of gas daily from around 220-250 head of cattle.
The digester, which is fully automated, is loaded once a week and provides electricity for
use on the farm. Mr. Malstrom sees the break-even point as 100 head of dairy cattle. His
firm is now designing a 2 1/2 million turkey digester.51
(e) The University of Wisconsin is associated with a commercial digester which ferments the
wastes of 100-150 horses. The biogas is burned directly for space heat, but electrical
generating capacity will be added at a later date.52 The University also has plans for two
fowl-manure digestion units.
(f) Tennessee State is just completing construction53 of two steel 2,000 gallon digesters to
ferment the wastes from 60 head of cattle at a packing plant. The gas which will initially
be burned off, will eventually power an electric generator. Laboratory findings have
emphasized studies of the nutritional value of the sludge and the possibility of ground
contamination after land disposal of the sludge.
Anaerobic Digestion of Municipal Solid Wastes
After several years of laboratory-scale investigations, Dr. Wise, Dr. Kispert and co-workers at
Dynatech have completed an economic analysis of a pilot plant facility to process one ton per day
of municipal solid wastes. The plant has not yet been constructed. The conceptual design involves
34
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four major sub-systems: a feed preparation and storage sub-system, mixing tank and mesophilic
digester, scrubbing and dewatering sub-systems.54
After being dumped, the refuse passes through a hammermill shredder to reduce particle size
and facilitate removal of the inorganic fraction and into a magnetic separator to remove ferrous
metals. A revolving screen picks out the other metals and glass, and an air classifier completes
separation of the light organic fraction to be fed to a mixing tank. A 12% slurry is fed into the
circular concrete digester with lime for pH control, and sewage sludge with nitrogen and phosphate
chemicals for nutrients. Floating covers on the tank maintain a constant internal pressure. The gas
produced is sweetened by MEA contact and the remaining liquid dewatered by vacuum filtration.
The cake produced can be incinerated to provide heat for the digester, a portion of the filtrate is
recycled to the front end of the digester and the excess is sent to a sewage treatment plant.55
Thirty-nine percent of the energy consumed in the process is used in the scrubbing and drying
stages and 21 % of the cost. For a 1,000 TPD facility, this process could yield 3.7 x I06 cu.ft./day of
pipeline quality methane, the energy obtained amounting to about 2 2/3 the energy consumed.
Such a plant, corresponding to a population of approximately 1/2 million, could provide 9% of the
gas consumed locally; or if exploited in all SMSA's, this size and above, 1 1/2% of the entire gas
consumed in this country last year.56
The largest digester presently in operation is the 400 liter tank designed by Dr. John Pfeffer at
Urbana, Illinois. This digester is Batch operated at between 55-60°C with retention for ten days to
produce about 6 1/2 cu.ft. of gas/lb. of volatile solids added.57 Lime, sewage sludge and nitrogen
and phosphorus chemicals are added. A major problem of the process is in handling the slurry from
the digester. Addition of ferrous sulphate and polymers to the residues, followed by loading on a
centrifuge, produces a relatively clean liquid. Dr. Pfeffer has conducted calorimeter tests with the
dry cake to investigate the feasibility of incinerating the solid residues. The heat content of the cake
approaches 10,000 BTU's/'b. volatile solids, which for a 1,000 TPD plant amounts to 90-100
million BTU's/hr. as steam. To improve the economics of the system, the cake residue must be dry
enough for incineration. The centrifuges probably will have to be sized on the basis of solids loading
rather than liquid loading. The high concentration of solids in the slurry will overload the solids
handling capacity of the machine if it is sized on the basis of liquid flow rate.
One major attempt to improve the biodegradability of cellulose (currently 50-55%
conversion)58 is underway at Stanford University, where Dr. McCarty is concentrating on the efficacy
of prior heat treatment of the wastes from 25-250°C and pH values from 1-13.59 Conditions of
extreme acidity and alkalinity improved the solubilization and biodegradability of the previously
digested refuse provided by Dr. Pfeffer. Current research has evaluated temperatures up to 133°C;
the biodegradability of the predigested refuse nearly doubled after treatment at 133°Cfor3 hours
at pH 1. This is a 12%60 increase in overall biodegradability of undigested refuse. High pH
treatment might be preferred as the alkali added would be useful for pH control during digestion.
The Institute of Gas Technology, Chicago, is also working with anaerobic digestion. Their
35
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investigators believe that the gas yield and production rate increase exponentially as particle size
decreases from 1 in. to less than 1 mm.61 They prefer the mesophilic variation, siting an
improvement in gas yield and quality at the lower temperatures. They have also proposed a method
where digestion takes place in two stages in order to promote the individual growth requirements of
the different sets of bacteria.62 Research involving two-phase digestion is also underway at the
University of Pennsylvania.
It is obvious that some work is still to be completed before the commercial possibilities of this
process can be fully exploited. It is necessary to perform a proof-of-concept experiment to establish
the performance of a large digester. Operational and environmental parameters establishing a much
greater conversion factor must be sought, including large-scale comparison of the mesophilic and
thermophilic temperatures. A less expensive scrubbing process and residue handling system would
make for a more healthy economic picture.
Waste Management Inc., Oakbrook, Illinois, with subcontractors, Jacobs Engineering, have
signed a preliminary contract with ERDA to initiate the full design and construction plans for two
digesters, to be added to the front end assembly of their existing resource recovery facility located
in Pompano Beach, Florida. The digesters will process 50-100 TPD of municipal solid waste, and be
operational within two years.
Two firms who believe they have solved some of the stated problems are Penn-State
Engineering and Rec-Tech of Pennsylvania. They have approached pipeline companies in the area
with a proposal to build a prototype digester to process a minimum of 250 TPD of municipal solid
waste. The firms, hopefully, intend to produce 95% pure methane through modification of the
mesophilic process, employing high loading rates of a 12% slurry, and a closed loop system to
recirculate the initial effluents several times. The uniqueness of the process, which will permit
marketing of the methane at $2-2 1/2 per thousand cubic feet, is in the repeated circulation of the
effluents, and in removal of carbon dioxide.63 Patents are pending on this process.
36
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Biophotolysis
The symbiotic relationship between light-converting protein complexes and hydrogen
liberating enzymes will produce hydrogen from water by enzymatic reduction.64 If long lasting
films of these coupled proteins could be made, they could provide catalytic surfaces for the solar
production of hydrogen from water at temperatures up to 50°C. Calculations made by L. W. Jones
in 1971 indicate that a land area equivalent to 5 x 104 km.2 could provide hydrogen of energy
equivalent to the gasoline used in the United States.65
Purple photosynthetic bacteria which are found in sewage and industrial wastes produce
hydrogen during growth.
organic substrate ^- new cells + H2 + CO2
The presence of oxygen is incompatible with formation of hydrogen, but the gas could be mopped
up by blue-green algae with a high rate of oxygen respiration.66 Current research is concentrating
on developments of stable biological systems which would bring about the photosynthetic
decomposition of water.
Charles Scott67 of the Molecular Anatomy Program at Oakridge has suggested that an
attempt be made to use the biological system to process hydrogen from wastes employing a cyclic
system requiring a certain energy trade-off.
Biophotolysis is moving through the theoretical stages into the preliminary laboratory
investigations of the various biological systems to electrolytically decompose water.
Environmental Impact
As mentioned previously, there is a limit to the quantity of manure that can be safely
landspread; runoffs from feedlots have been implicated with water contamination and stream
eutrophication. Incineration of manures and agricultural field wastes is becoming ever more limited
as air pollution controls are enforced. After anaerobic digestion, the residues are odorless and
biologically stable. If the residues do find a market as a fertilizer or feedstock, there is no land
disposal problem; if the residues prove unmarketable, they can be land disposed of with less
difficulty than untreated wastes.
Anaerobic digestion of municipal solid wastes also produces residues that are biologically
stable; the liquid effluent can be treated with polymers to produce a practically clear liquid with a
particulate content of 16-17 mg. of suspended solids per liter.68 The solid residues might possibly
find a use as an incinerator cake, but if not, can be safely landfilled. Settling of landfills, a common
problem with untreated refuse, is minimized with biodegraded wastes.
Fermentation of sugars from acid hydrolysis of refuse produces an effluent with BOD of
6,000 ppm.,69 requiring treatment before disposal. Residues of enzyme hydrolysis will require no
39
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further treatment.
In addition to the decrease in water and air pollution brought about by initial biodegradation
of wastes, the production of energy in the form of methane or ethanol results in small but
significant conservation of fossil fuels. The possible replacement of synthetic ethanol with alcohol
from fermentation of glucose also conserves fossil fuels presently used in the chemical industry.
In summary, byconversion of solid wastes is a sound environmental practice with regard to
pollution abatement and energy conservation.
Economic Analysis
The difficulty of comparing the various cost estimates of the anaerobic digestion process lies
in the different operational and environmental parameters prevailing in each variation of the
process. For example, it is possible to include or exclude the cost of an elaborate front-end system
to recover resources from city refuse; the cost analyses may or may not include the cost of
scrubbing the gas to produce pipeline quality methane. The credits and penalties for municipal solid
waste are not identical to those for manures. Some systems employ a recycling of the gases
produced, resulting in a fuel economy within the system and lower operating costs.
The comparative costs of various processes are given in Table 14. In order to facilitate
comparison of the different cost estimates, the cost of the base unit system is considered to be the
gross costs involved from the point of entry of fuel into the digester, to the production of total gas
at the back-end. The figures in Table 14 do not include revenues from methane, as the price per unit
output should be the same for each system, nor do the tables include credit for fertilizer or
feedstock value of the residues of manure digestion.
The total costs/million BTU's for each set of figures has been calculated as follows:
Total Costs/million BTU's = Operating Cost/million BTU's +
Capital Costs/million BTU's
The estimates are for the plant's net energy production, and do not include internal energy leaks,
energy usage for pumps, etc. These factors which are different for each system are questions of
engineering judgment. The capital costs are given on the basis of a claimed lifetime of 10 years
(unless otherwise indicated) assuming operation at full capacity. Note that the lifetimes may be
extended to 15 years (as in the Jacobs' case) with some drop in annualized capital costs. The
systems can be extended beyond their acclaimed lifetime.
The Dynatech figures are substantially higher than the others and include costs of the
front-end resource recovery system and upgrading to pipeline quality. The credits will be high,
however, due to the revenues from reclaimed materials and the dump fee. Dynatech has
demonstrated that the ownership of the digester will make a substantial difference to the costs of
40
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the system.70 The example given is for a facility owned and financed with private capital. If the
facility were privately owned but financed through Pollution Control Revenue Bonds, or
alternatively, municipally owned and financed, the costs would be lower. For the above reasons, the
figures for Dynatech are probably a little high.
The costs of the Institute of Gas Technology System71 are for a small plant processing 571
dry tons of solid wastes and sludge per day. They include a front-end recovery system and a ME A
scrubber and are for a 25-year lifetime.
The figures quoted for Dr. Pfeffer refer to a base run of a computer study involving MSW
digestion at 60°C for a six day detention time.72 The costs include a front-end recovery system, a
gas purification step, and treatment of the residues. The capital cost is only the installed cost,
excluding site costs, engineering costs, legal fees, etc.
The three sets of Jacobs figures73 give some idea of the expense of scrubbing the system to
remove the carbon dioxide and produce high pressure, high quality methane. Both the USDA
figures and the Jacobs figures refer to digestion of manures, but the former is a thermophilic process
and the latter is mesophilic. Both the Jacobs and USDA researchers feel that the residue has great
potential as a feed or fertilizer. If the residues are not readily marketable, the cost of disposal will
increase the costs of both processes; if the residues do find a ready market—which seems quite
likely—both of these processes will be economically attractive. The Jacobs' figures are probably the
best estimates available, as they are the most recent.
41
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TABLE 15. COSTS OF PRODUCTION OF METHANE FROM MANURES -
JACOBS ENGINEERING FIGURES, 1975
PROCESS
Total Costs Per 106 Total Costs Per 1,000 cu.ft.
BTU 's Output (Gross) Methane (Gross)
Total Costs Per TPD
(Dry) (Gross)
Low Pressure, low
purity methane
Low Pressure, high
purity methane
High Pressure, high
purity methane
$1.39
$2.82
$3.19
$1.26
$2.54
$2.87
$11.27
$22.70
$25.70
Source: Weisberg E. and R. Krisnan, Engineering Design and Economic Feasibility of a Feed/of Waste Bioconversion System, paper
presented at Conference on Energy Recovery from Solid Wastes, College Park, Maryland, March 1975, pp.17-19.
Brief Comparison of the Bioconversion Process with Other Energy Recovery Systems
Comparison of the costs of the systems makes it clear that anaerobic digestion is in a
cost-range that is not uncompetitive with alternate technologies. Combustion to produce steam and
cofiring with other fuels is cheaper per 106 BTU'sof net energy excluding credits and penalties to any
of the systems. Anaerobic digestion produces both energy in the form of methane and residues with
a potential market as a fertilizer or feed, thus eliminating a charge for disposal of the residues of
digestion. The major economic output for anaerobic digestion of manures is in the upgrading of the
gas produced to pipeline quality methane (see Jacobs' figures). As every effort is being made to
optimize this process, it is not inconceivable that the costs will be reduced as a percentage of the
total outlay of capital. The digestion of manures can be successfully accomplished at mesophilic
temperatures (30-40°C), thus decreasing the need for external energy to maintain the reaction.
The use of solar energy to digest manures deserves attention. The technology has been
successfully applied to a farm of 350 cattle and several firms feel that the economic rewards of the
process justify large-scale ventures.
Anaerobic digestion of MSW is a little less attractive than that of manures. The front-end
recovery system is expensive to install; however, it does provide additional credits for the system.
(see Dynatech figures). The residues still require disposal, adding costs to the system. Digestion of
MSW is very dependent upon the going market price for methane in order to be economically
attractive. Given the political uncertainties of future energy policy, it is difficult to predict the
•j
future price of methane, except to indicate that it will definitely rise from the 53 cents/10 cubic
44
-------
feet (mcf) of interstate commerce and the $1-$2/mcf of the intrastate market.
As previously mentioned, cities presently interested in energy recovery from MSW are opting
for combustion or pyrolysis processes. As the technology of these alternate processes is more
developed and boilers to receive the wastes are already operating in many major metropolitan areas,
considering present economics, bioconversion of MSW would not be the first choice for these large
population centers. The possibility remains that digesters could be added to existing inorganic
resource recovery systems as proposed by Waste Management, Inc. for their Pompano Beach
facility. Local factors would determine whether this was both an economic and a practical
proposition. The disadvantage of steam production by combustion of wastes is that the energy is
not produced in a storable form, but must be put to immediate use. Methane produced by
bioconversion could be fed into local gas pipelines and used as required. Areas along the East coast
of the United States, which have the highest concentration of MSW and which are most heavily
dependent upon imports of natural gas, might find it feasible to investigate the anaerobic digestion
of MSW. It is very possible that digestion will prove both profitable and convenient for small towns
given their local conditions. The most recently conducted economic analyses may be considerably
modified in light of future advances in technology and market trends.
The hydrolysis and fermentation of MSW or agricultural wastes remains as a possible alternate
attractive means of energy production should ethanol be shown as a desirable additive to
automotive fuel. The complete economic impact of producing ethanol to substitute for chemicals
derived from fossil fuels has yet to be examined.
An indepth analysis of the possible markets for ethanol would clarify the desirability of large
scale hydrolysis and fermentation of wastes. The only figures given for this process refer to the total
costs of ethanol production through acid hydrolysis, and these figures appear to be comparatively
high ($6.46/106BTU's). Only the production of methanol by pyrolysis of MSW is indicated as being
more expensive.
The economics of the bioconversion processes discussed herein would not disqualify any of
these processes from future consideration as a means of solid waste disposal.
45
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Cost Estimates for Production of Methane by Anaerobic Digestion of Manures. USDA
Total Capital Investment = $558,600
Capital Investment / yr. = $55,860 (for a 10 year lifetime, 6% interest)
Gross Energy of Fuel = 3.411 x 10s BTU/day
Capital Costs/106 BTU = $55,860 x 106 F ~"
3.411 x 108 x 365
= $ 0.53
Operating Cost = $168,365 per annum
Operating Cost/106 BTU = $168,365 x106
3.411 x 108 x365
= $ 1.61
x 1.19
Total Costs = $2.14/106BTU
Source: Production of Power Fuel by Anaerobic Digestion of Feedlot Waste Space Systems Department of Hamilton Standard
Division, United Aircraft Corporation, for Fermentation Laboratory, Northern Regional Marketing and Nutrition Re-
search Division, Peoria, Illinois, 1974. Appendix II, pp. 9, 12.
47
-------
Cost Estimates for Production of Methane from MSW, Dynatech (Thermophilic)
These estimates exclude both penalties and credits:
Contribution of Capital Costs to Gas Cost = $2.17/mcf
= $2.17 x IP6 /106BTU
930x1,000
= $2.33/106BTU x (Index (1975)1
L 0974)J
Contribution of Operating Costs to Gas Cost = $1.92/mcf
= $1.92x 10s /106BTU
930 x 1,000
= $2.06/106BTU x [Index (1975)
[I
(1974)J
Capital Costs/106BTU = $2.33 x 1.19 = $2.77
Operating Costs/106 BTU = $2.06 x 1.19 = $2.45
Total Costs/106BTU = $5.22
Capacity = 1.222 x 109 scf/yr = 1.222x 109 x 930 = 3.25 x 109BTU/day
350
Source: Kispert, R. G., Anderson, L.C.D.H. Walker et. al.. Fuel Gas Production From Solid Waste, Dynatech R/D Company,
Report No. 1207, July 31, 1974, p. 78, 85.
48
-------
Cost of Anaerobic Digestion of Waste from Figures Presented by Dr. J. Pfeffer, 1974
For the Base run
Total Costs/hr. = $405.67
Methane production (mcf/hr) = 138, Methane production -L- — '- = 138x950x103
~|
J
Total Cost/106 BTU =$405.67x10* f. , (1975) _ n ., Q,
r x I i naex — — i. i oo
138x103x950 |_ (1974)
Total Costs/106 BTU = $3.67
Capital Costs/hr = $185.50
Capital Costs/106 BTU = $185.50 x 106 F (1975) _ -, 186~|
138 x 103 x950X|_n X (1974) ' J
Capital Costs/IP6 BTU = $1.68
Operating Costs/106 BTU = $1.99
Capacity (BTU's/day) = 138x950x24x 1,000 = 3.15 x 109
Note: Capital costs are installed costs. Site costs, engineering, legal, insurance, interest during
construction, etc. are not included in the capital cost.
Source: Pfeffer, John T., Reclamation of Energy from Organic Refuse Anaerobic Digestion Processes, paper presented at Third
National Conference on Waste Management Technology and Resource Recovery, San Francisco, California, November
14-15, 1974, p. 22.
49
-------
Cost Estimates for Production of Methane from MSW, Institute of Gas Tech.
For a small plant (471 TPD),
Capital Costs = $5.82 x 106 (for a 25 year lifetime, 5.1% interest)
Capital Costs/annum = $2.33 x 10s (for a 25 year lifetime)
Net Power Out - 5.20 x 109 BTU/day = 5.20 x 109 x 350 BTU/yr
r* • , ^ M^nTi, $2.33 x 10s x 106 L . (1975) 232.5
Capital Costs/106 BTU = x index = = 1
5.20x109x350 L
= $ 0.18
Operating Costs = $2,283/day
$2.28 x103 x 106
___~|
.367
J
Operating Costs/106 BTU = ^
5.20 x 10
$ 0.599
Total Costs/106 BTU = Capital Costs/106 BTU + Operating Costs/106 BTU
= $ 0.78
Source: Ghosh, S., and D. L. Klass, Biogasification of Solid Wastes, RFP submitted to NSF, P 31-3285, January 1970, p. 104.
50
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Costs for Production of Ethanol from MSW by Acid Hydrolysis and Subsequent
Fermentation
1 ton of refuse will yield 24.8 gallons of EtOH or 182 Ibs. of EtOH
BTU content of ethanol is 13,698 BTU/lb
BTU content of ethanol from 1 ton refuse = 182 x 13,698
= 2,493 x106
Net cost of extracting ethanol from refuse (1972 dollars; 6% interest assumed for 15-20 years as
is taken to be 52^/gallon data is unclear)
Total Cost of ethanol production ton = $ 0.52 x 24.8
= $12.90
Total Cost of ethanol/106 BTU = $12.90x 106
2.493 x 106
= $5.17x^6x1197511
L
For a 400 TPD plant, = $ 6.46
For a 400 TPD plant, = 9.97 x 108
Capacity (BTU/day)
Source: Problems and Opportunities in Management of Combustible Solid Wastes, International Research and Technology Corp-
oration, Washington, D.C., October 1972, pp. 136-152.
51
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Cost Estimates for Combustion of MSW to Produce Steam
1 ton of refuse produces 3,000 Kwh or 1 x 107 BTU
Fora 1,OOOTPD plant,
Total Costs/ton = $10.25
Total Costs/106 BTU - $10.25x 106
107
Total Costs/106 BTU = $ 5.5 x 106
10"7
= $ 0.55
Capital Costs/106 = $0.48
Capacity (BTU/day) = 1010
Source: Problems and Opportunities in Management of Combustible Solid Wastes, International Research and Technology Corporation,
Washington, D.C., October 1972, pp. 136-152.
52
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Cost Estimates for Combustion of MSW to Produce Electricity from Steam
1 ton of waste produces 3,000 Kwh = 1 x 107 BTU
Assuming 40% efficiency, 1 ton of waste produces 1,200 Kwh of electricity
1,200 Kwh = 10?x 1,200 BTU
3,000
Heat produced / ton of refuse = 4x106 BTU
For 1,000 TPD,
Total Costs = $12.75 / ton (lifetime of loan not known; assumed to be either 15-20 yrs.
at 6% interest)
Total Costs/106 BTU = $12.75
Total Costs/10 4
- $3.18
Operating Costs = $6.13/ton
Operating Costs/IP6 BTU = $6.13/4 = $1.53
Capital Costs/106 BTU = $1.65
Capacity / day = 4 x 109BTU
Source: Problems and Opportunities in Management of Combustible Solid Wastes, International Research and Technology Corpor-
ation, Washington, D.C., October 1972, pp. 136-152.
53
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Cost Estimates for Cofiring MSW as at the St. Louis Plant
Total Cost (5 days/wk) •= $5.16/ton (lifetime of loan and interest are not clear from data
given)
Assuming 40% efficiency of conversion from steam to electricity
1 ton of refuse will produce 1,200 Kwh of power or 4 x 106 BTU
= $ 1.85
Capacity is 980 TPD.
Capacity (BTU/day) = 4 x 106 x 980 = 3.92 x 109
Operation and Maintenance (260 day year) = $896,900/year
Operating Costs/1 06 BTU = $ 896,900 x 106
3.92 x 109 x260
= $ 1.08 x Index (1.12)
= $ 1.21
Capital Costs/1 06 BTU = $ 0.64
Source: Problems and Opportunities in Management of Combustible Solid Wastes, International Research and Technology Corpor-
ation, Washington, D.C., October 1972, pp. 136-152.
54
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Cost Estimates for Pyrolysis of MSW to Produce Fuel Oil and Char
1 ton of waste produces 450 Ib of oil at 12,000 BTU/lb
100 Ib of char at 11,000 BTU/lb
1 ton of waste - (450 x 12,000) + (100x 11,000) BTU
= 6.5 x 106BTU
Fora 1,OOOTPD plant,
Total Costs = $7.88/ton (1975 dollars; lifetime of loan unknown — assumed to be either
15-20yrsat6% interest)
Total Cost of 106 BTU = $7.88
6.5
Total Cost/106 BTU = $1.21
Capital Cost/ 106BTU = $0.42
Capacity (BTU/day) = 6.5 x 109
Source: Problems and Opportunities in Management of Combustible Wastes, International Research and Technology Corporation,
EPA contract 68-03-0060, October 1972, pp. 12, 125.
55
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Cost Estimates for Methanol Production from Pyrolysis of MSW
Capacity of plant = 300 tons/day
Production of methanol = 100,000 tons/year
Heat Content of Methanol = 8640 BTU/lb
Number of BTU/year = 8,640 x 100,000 x 2,000
= 1.728x 1012
Capital Costs = 56 x 106
_..,,,., $56x106 (for a 15 year lifetime)
Capital Costs/annum = v r '
15
r •* H~ */1A6DTI. $ 56 X 106 X IP6
Capital Costs/106 BTU =
15x 1.728x 1012
= $ 2.16
Operating Costs (1st year) = $13.7 x 106 (15 year debt, 8% interest)
Operating Costs/106 BTU = $13.7 x 106
1.728 x 1012
= $ 7.93
Total Costs = $ 10.09/106 BTU
Assume a 350 day year,
1.728x 1012 _ 4.94 x 109
Daily BTU output =
350
Source: Sheehan, Robert G., and Richard F. Corlett, Methanol or Ammonia Production From Solid Wastes by the City of Seattle,
169th. National Meeting, American Chemical Society, Vol. 20, No. 2, April 6-11, 1975, p. 52.
56
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APPENDIX B
METHANOL PRODUCTION BY PYROLYSIS AND A BRIEF EVALUATION OF
METHANOL AND ETHANOL AS AUTOMOTIVE FUELS
Methanol Production by Pyrolysis
The bulk of the methanol that is currently produced industrially is manufactured from
natural gas. The City of Seattle has plans to produce methanol by pyrolysis of city garbage, possibly
using the Union Carbide Corporation's Purox system.74 They intend to conserve natural gas as well
as to exploit the possibilities of using methanol as an automotive fuel.
In the Purox System, municipal solid waste is charged down a vertical-shaft furnace where as
it migrates downward, it is heated by rising gases generated from oxidation of the residues at the
bottom of the shaft. The gas leaving the top of the reactor which is mainly carbon monoxide,
hydrogen and water vapor, is processed through a closed gas cleaning system to remove water and
impurities. After absorption removal of sulfur to prevent pollution and future catalytic poisoning,
the carbon monoxide/hydrogen ratio is shifted to 1:2, the stoichiometric ratio for methanol
synthesis. Carbon dioxide produced in this shift is substantial and must be removed. Under specific
conditions of heat and pressure in the presence of a catalyst, the two gases combine to methanol.
CO + 2H2 *- CH3OH
It is also possible to produce ammonia by variations in the shift mechanism.
Mathematical Sciences Northwest, Inc. for the City of Seattle indicate that starting from
550,000 tons/year of MSW, it is possible to produce approximately 31 million gallons of
methanol/year or 120,000 tons of ammonia. Costs based on late 1974 prices indicate that for the
city to break-even from the project, the net annual cost must be no greater than the current costs of
landfill ($3.3 million).75 The financial feasibility of the project depends on the prices for the two
products. An economic summary of the process is found in table 16.
Methanol as an Automotive Fuel
Mathematical Sciences Northwest, Inc. conducted a study of the possibility of using methanol
as an automotive fuel either alone or in blends with gasoline.76 The blend contained up to 7%
methanol and was found to increase the efficiency of the operation of the automobile on a
mile/BTU basis, to decrease the emission of carbon monoxide and increases the octane number of
low-grade gasolines.77
The biggest problem encountered was in phase separation of the blend when traces of water
were present and at low temperatures. Addition of higher alcohols might solve this problem.
Corrosion of some automobile systems was significant.
The use of pure methanol as a fuel would require a modification in the engine to permit a
higher compression ratio and leaner equivalence ratio. These adaptions would permit the methanol
to operate with an increase in efficiency of approximately 20%78 in spite of its low heating value
(8,640 BTU/lb. compared to 19,080 BTU/lb. for gasoline).
57
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TABLE 16. MARGINAL OR "BREAK-EVEN" ECONOMICS OF SEATTLE SOLID
WASTE METHANOLOR AMMONIA PROJECT (1978)
(1)
Plant Nominal Product Size
Annual Product Yield
Capital Cost1
Debt Service2
Operation and Maintenance
First- Year Costs
Product Sales
Disposal Gain3
Marginal (Break-Even) Product
Price, First Year
Methanol Plant
(2)
300 T/Day
1 00,000 T/Year
(3 1,000, 000 Gal/ Yr)
$ 56,000,000
6,600,000
7,100,000
$ 13,700,000
$ 10,400,000
3,300,000
$ 13,700,000
33.6^/Gal.
Ammonia Plant
(3)
350 T/Day
120,000 T/Year
$ 65,000,000
7,500,000
8,100,000
$ 15,600,000
$ 12,300,000
3,300,000
$ 15,600,000
$103/Ton
Source: Sheehan, Robert G., and Richard F. Corbett, Methanol or Ammonia Production from Solid Wastes by the
City of Seattle, 169th National Meeting, American Chemical Society, Division of Fuel Chemistry, Vol.20,
No. 2, April 6-11, 1975.
'Gasifiers, gas cleanup, shift process, synthesis plant, site, tankage and associated facilities.
215-year life, 8% interest.
3 Disposal cost for equivalent transport and landfill.
58
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Ethanol as an Automotive Fuel
While there have been many laboratory tests on the performance of stationary automobile
engines operating on ethanol-gasoline blends, there has been no statistically designed fleet test of
the mixture reported. Dr. Scheller and Dr. Mohr of the University of Nebraska designed a two
million mile road test using 10% ethanol and 90% unleaded gas79 which is now in progress. This
comprehensive test will run for a period of 10-15 months and will involve 10 half-ton pick-up trucks
and 26 passenger cars. One third of the fleet will run on the 'Gasahol' blend, one third on unleaded
gasoline, and the remainder will change fuels midway through the test program.
In addition to normal vehicle maintenance, there will be periodic checks on the effect of the
fuels on cylinder wear, engine valves, spark plugs, and the exhaust system. Emission tests will be
performed on the 10 test cars. Preliminary analysis based on about 250,000 miles indicates that
significant facts in the fuel consumption are the driver of the vehicle, average daily temperature,
average relative humidity and maintenance schedule.80 The final results of this road-test should
clarify the possibilities of use of ethanol as a fuel additive.
59
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APPENDIX C
LIST OF REFERENCES
1. Anderson, Larry L, Energy Potential from Organic Wastes: A Review of the Quantities and Sources. U.S.
Bureau of Mines, Information Circular 8549,1972, p.1.
2. Ibid., p.8.
3. Ibid.
4. Inman, Robert E., An Evaluation of the Use of Agricultural Residues as an Energy Feedstock, Report
NSF/RANN/SE/GI-438597/PR/72/4, February 1,1975.
5. Yeck, Robert G., Agricultural Biomass Byproducts and Their Effects on the Environment, International
Biomass Energy Conference, Winnipeg, Manitoba, Canada, May 15,1973.
6. Yeck, Robert G., Smith, L.W., and C.C. Calvert, Recovery of Nutrients from Animal Wastes — An Overview of
Existing Options and Potentials for Use in Feed, International Symposium on Livestock Wastes, University of
Illinois, April 21-24,1975, p.10.
7. Report of the Close Timber Utilization Committee, U.S.D.A., Forest Service, June 28,1972, p.29.
8. Ibid., p.30.
9. Lowe, Robert, Energy Conservation Through Improved Solid Waste Management, USEPA Report sw-125,1974,
p.5.
10. Ibid., p.ll.8.
11. Ibid., p. 12.
12. Ibid., p. 14.
13. International City Management, 1975 Municipal Year Book, Washington, D.C.
14. Problems and Opportunities in Management of Combustible Solid Wastes, International Research and
Technology Corporation, Washington, D.C., October 1972, p.39.
15. Ibid., p.37.
16. An Inquiry into Biological Energy Conversion, A Report on a Workshop held October 12-14, 1972 at
Gatlinburg, Tennessee, RANN Grant G1 3.5970, p.27.
17. Ibid.
18. Boyd, I.C., Anaerobic Treatment of Animal Wastes: A Survey (J974). Montana State University, Research
Report 65, December 1974, p.5.
19. Cosset, James M., and Perry L. McCarty, Heat Treatment of Refuse for Increasing Anaerobic Biodegradability;
NSF/RANN/SE/GI-43504/PR/74/4, January 31,1975, p.12.
60
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20. Ibid., p.13.
21. Pfeffer, John T., Reclamation of Energy from Organic Refuse Anaerobic Digestion Processes, a paper presented
at the Third National Congress on Waste Management Technology and Resource Recovery, San Francisco,
California, November 14-15,1974, p.3.
22. Converse, A.O.; H.E. Grethlein, et al., Acid Hydrolysis of Cellulose in Refuse to Sugar and its Fermentation to
Alcohol, USEPA, Grant No. EP-00279, June 1973, p. viii.
23. Ibid., p.13.
24. Ibid., p.15.
25. Ibid., p.24.
26. Ibid., p.40.
27. Ibid., p.66.
28. Ibid.
29. Scheller, W.A., and Brian J. Mohr, Production of Ethanol and Vegetable Protein by Grain Fermentation, paper
presented at the 169th meeting of the American Chemical Society, Division of Fuel Chemistry, Vol. 20, No. 2,
April 6-11,1975, p.54.
30. Humphrey, Arthur E., "Current Developments in Fermentation," Chemical Engineering, December 9, 1974,
p.112.
31. Ibid., p.111,112.
32. Isenberg, Don L, article in Chemical Engineering, May 12, 1975.
33. Spano, L.A.; Madeiros, J., and M. Mandels, Enzymatic Hydrolysis of Cellulosic Wastes to Glucose, U.S. Army,
Natick Laboratories, January 7,1975. p.5.
34. Ibid., p.7.
35. Dr. L. Spano, U.S. Army Natick Laboratories, personal communication, July 11, 1975.
36. "Distilling a Better Fuel Solution/' Industrial Research, 16(6): 33-34, June 1974.
37. Spano, L., Enzymatic Conversion of Cellulosic Wastes to Glucose, tape recording of a presentation delivered to
the symposium, Energy Recovery from Solid Wastes, sponsored by the Washington Academy for Sciences, et.
al., University of Maryland, March 13,1975.
38. Dr. Rowell, U.S.D.A. Forest Products Laboratory; Madison, Wisconsin, personal communication, July 1975.
39. Dr. L. Spano, U.S. Army, Natick Laboratories, personal communication, July 11, 1975.
40. "Distilling a Better Fuel Solution," Industrial Research, 16(6): 33-34, June 1974.
61
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41. New Alchemy Institute, Methane Digesters for Fuel Gas and Fertilizer, Newsletter No. 3,1973, p.7.
42. Singh, Ram Bux, "The Bio-Gas Plant: Generating Methane from Organic Wastes," Compost Science, Vol. 13 (1)
20-25, January/February, 1972.
43. Jewell, W.J.; Morris, G.R.; Price D.R.; Gunkel, W.W.; Williams, D.W.; and R.C. Loehr, Methane Generation from
Agricultural Wastes: Review of Concept and Future Applications, presented by the ASAE, West Virginia
University, August 18-21,1974, p.5.
44. Ibid., p. 19.
45. Ibid.
46. Sparling, A.B., Energy Recovery from Livestock Waste, Department of Civil Engineering, Manitoba, Canada,
1973.P.4.
47. Production of Power Fuel by Anaerobic Digestion of Feed lot Wastes, Hamilton Standard Division, UAC, for
USDA, Northern Regional Marketing and Nutrition Research Division, Peoria, Illinois, 1974.
48. Ibid., phase II, pp. 4,7.
49. "Peoples Gas Unit Sets Accord to Buy Fuel Made from Manure," Wall Street Journal, J une 16, 1975.
50. "Methane from Manure," Chemical Week, 115 (1): 13, July 3,1974.
51. Jerry Malstrom, personal communication, July 11,1975.
52. Abeles, Tom P., Energy and Economic Analysis of Anaerobic Digesters for Farm Waste Management, University
of Wisconsin, Green Bay, p.2.
53. Dr. Busby, Department of Engineering, Tennessee State University, personal communication, July 24, 1975.
54. Kispert, Robert, An Evaluation of Methane Production from Solid Waste, taperecording of a presentation
delivered at the symposium, Energy Recovery from Solid Wastes, sponsored by the Washington Academy of
Sciences, et. al., College Park, Maryland, March 13, 1975.
55. Ibid.
56. Ibid.
57. Pfeffer, John T., Energy from Refuse by Bioconversion — Fermentation and Residue Disposal Process,
taperecording of a presentation delivered at the symposium, Energy Recovery from Solid Wastes, sponsored by
the Washington Academy of Sciences, et. al., College Park, Maryland, March 13,1975.
58. Cosset, James M. and Perry L. McCarty, Heat Treatment of Refuse for Increasing Anaerobic Biodegradability,
NSF/RANN/SE/GI-43504/PR/74/4, January 31,1975, p.21.
59. Ibid., Summary.
60. Ibid., p.110.
62
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61. Ghosh, S.; Conrad, J.R., and D.L. Klass, Materials and Energy Reclamation from Municipal Wastes, Institute of
Gas Technology, Chicago, Illinois; October 1974, pp.13-16.
62. Ghosh, S., "Two-Phase Anaerobic Digestion of Organic Wastes, Institute of Gas Technology, RFP to USEPA,
May 1974.
63. Jay Ort, Rec-Tech Corporation, personal communication, July 11,1975.
64. An Inquiry into Biological Energy Conversion, a Report on a Workshop held October 12-14, 1972, at
Gatlinburg, Tennessee, RANN/GI/35970, p.15.
65. Ibid., p.16.
66. Ibid., p.21.
67. Ibid., p.25.
68. Pfeffer, John T., Energy from Refuse by Bioconversion — Fermentation and Residue Disposal Process,
taperecording of presentation delivered at the symposium, Energy Recovery from Solid Wastes, sponsored by
the Washington Academy of Sciences, et. al., College Park, Maryland, March 13, 1975.
69. Converse, A.O., H.E. Grethlein, et. al., Acid Hydrolysis of Cellulose in Refuse to Sugar and Its Fermentation to
Alcohol, Thayer School of Engineers for USEPA, P.B.-221. 239, June 1973, p.66.
70. Kispert, R.G.; Anderson, L.C., D.H. Walker et. al., Fuel Gas Production from Solid Waste, Dynatech R/D
Company, Report No. 1207, July 31, 1974, pp. 113-119.
71. Ghosh, S. and D.C. Klass, Biogasification of Solid Wastes, RFP submitted to NSF, P 31-3285, January 1970,
p.104.
72. Pfeffer, John T., Reclamation of Energy from Organic Refuse Anaerobic Digestion Processes, paper presented at
Third National Conference on Waste Management Technology and Resource Recovery, San Francisco,
California, Nov. 14-15,1974, p.22.
73. Weisberg, E. and R. Krishnan, Engineering Design and Economic Feasibility of a Feedlot Waste Bioconversion
System, paper presented at Conference on Energy Recovery from Solid Wastes, College Park, Maryland, March,
1975, pp. 17-19.
74. Sheehan, Robert G.; and Richard F. Corlette, Methanol or Ammonia Production from Solid Wastes by the City
of Seattle, 169th National Meeting, American Chemical Society, Division of Fuel Chemistry, Volume 20, No. 2,
April 6-11,1975, p.47.
75. Ibid., p.48.
76. Cassady, Philip E., The Use of Methanol of a Motor Vehicle Fuel, 169th National Meeting, American Chemical
Society, Division of Fuel Chemistry, Vol. 20, No. 2, April 6-11,1975, p.59.
77. Ibid., pp.59-63.
78. Ibid., p.63.
63
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79. Scheller, W.A., and Brian J. Mohr, Performance of an Ethanol-Gasoline Blend in Automobiles and Light Trucks,
169th National Meeting, American Chemical Society, Division of Fuel Chemistry, Vol. 20, No. 2, April 6-11,
1975, p.71.
80. Ibid., p.23.
64
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1, REPORT NO.
EPA-600/2-76-148
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
FUEL AND ENERGY PRODUCTION BY BYCONVERSION OF
WASTE MATERIALS - State-of-the-Art
5. REPORT DATE
August 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Sylvia A. Ware
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Ebon Research Systems
10108 Quinby Street
Silver Springs, Maryland
10. PROGRAM ELEMENT NO.
6HE624
20901
11. CONTRACT/CJWHW NO.
68-03-0295
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
14. SPONSORING AGENCY CODE
EPA-ORD
15.SUPPLEMENTARY NOTES Project Officer: Leo Weitzman, (513)684-4484
Report prepared for Solid and Hazardous Waste Research Division, Office of Air, Land,
and Water Use, Municipal Environmental Research Laboratory, Cincinnati, Ohio 45268
16. ABSTRACT
This report is a state-of-the-art summary of biological processes for converting
waste cellulosic materials (agricultural, municipal and lumbering wastes) to fuels.
It indicates the locations and quantities of suitable wastes and discusses the
status of the current processing schemes. The processes discussed are:
o acid hydrolysis followed by fermentation
o enzyme hydrolysis followed by fermentation
o anaerobic digestion of manure and municipal solid waste
o biophotolysis
Cost data for these processes are given and, where possible, compared. The
range of cost was $1.39 to approximately $5.00 per million BTU of net energy output.
It was concluded that energy production by these methods on a national scale can,
at best, produce the equivalent of only about 3 million barrels of oil per day by
1980. These may, however, be economical and environmentally acceptable means of
waste management which should be explored further.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Methane
Hydrolysis
Fermentation
Ethanols
Digestion (decomposition)
Biomass
Anaerobic processes
Cellulose
Bioconversion
Ethanol production
Municipal solid waste
Anaerobic digestion
Acid hydrolysis
Enzyme hydrolysis
Methane production
10A
8. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
75
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
65
*USGPO: 1976 — 657-695/5499 Region 5-1
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