United States
Environmental Protection
Agency
Robert S Kerr Environmental Research EPA-600/2-79-142
Laboratory August 1979
Ada OK 74820
Research and Development
Recovery of
By-Products from
Animal Wastes
A Literature Review
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Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are'
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental 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.
ihis document is available to the public through the National lechnical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-142
August 1979
RECOVERY OF BY-PRODUCTS FROM ANIMAL WASTES--
A LITERATURE REVIEW
by
R. Douglas Kreis
Source Management Branch
Robert S, Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
-------
DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was established to coordinate
administration of the major Federal programs designed to protect the
quality of our environment.
An important part of the agency's effort involves the search for
information about environmental problems, management techniques and new
technologies through which optimum use of the nation's land and water
resources can be assured and the threat pollution poses to the welfare
of the American people can be minimized.
EPA's Office of Research and Development conducts this search
through a nationwide network of research facilities,,
As one of these facilities, the Robert S. Kerr Environmental
Research Laboratory is responsible for the management of programs to:
(a) investigate the nature, transport, fate and management of pollutants
in groundwater; (b) develop and demonstrate methods for treating waste-
waters with soil and other natural systems; (c) develop and demonstrate
pollution control technologies for irrigation return flows, (d) develop
and demonstrate pollution control technologies for animal production
wastes; (e) develop and demonstrate technologies to prevent, control
or abate pollution from the petroleum refining and petrochemical in-
dustries, and (f) develop and demonstrate technologies to manage pol-
lution resulting from combinations of industrial wastewaters or indus-
trial/municipal wastewaters.
This report contributes to the knowledge essential if the EPA
is to meet the requirements of environmental laws that it establish
and enforce pollution control standards which are reasonable, cost
effective and provide adequate protection for the American people.
. G-. JjcJlAJM)
William C. Galegar, Director
Robert S. Kerr Environmental
Research Laboratory
111
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ABSTRACT
The primary purpose of this report was to identify and summarize by-
product-from-animal-wastes-recovery processes from the current literature.
By-product recovery processes are distinguishable from wastes reuse and
recycle processes by the formation of a chemically or physically changed
product or by-product from the wastes as produced.
Most of the schemes investigated were grouped into either biological or
thermochemical processes. Methane production, a biological process utilizing
anaerobic fermentation of the wastes, is receiving the greatest amount of
popular and scientific attention,, The economics of methane storage is the
strongest deterent to the development of this process for widespread applica-
tion. However, the process does have promise if located near a constant
consumer of the gas or where it can be injected directly into a gas pipeline
or distribution system.
Thermochemical processes investigated include conversion to oil and oil-
like tars; anhydrous ammonia synthesis gas and ethylene; hydrogasification;
manufacture of carbon black, carbon black substitutes, and fillers and foaming
agents in foam glass construction materials; and other fuels and construction
products. Of these, the most promising processes appear to be the conversion
to ammonia synthesis gas and ethylene and the manufacture of glass foam
foaming agents.
None of the processes investigated have been demonstrated and optimized
for full scale commercial use. The costs of constructing and operating a
demonstration plant for even the most promising processes are prohibitive for
further involvement from the research segments of the universities and animal
production industry. This report covers a period from January 1, 1977 to
December 31, 1977 and was completed as of December 31, 1977.
IV
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CONTENTS
Foreword
Abstract
Figures
Tables
British to metric unit conversion
1. Introduction
2. Conclusions
3. Recommendations
4. Biological Processes
5. Thermochemical Processes
6. Other Byproduct Recovery Systems
7. Summary
References
111
iv
vi
vii
viii
1
3
4
5
15
42
43
45
V
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FIGURES
Number Page
1 Overall material flow-through anaerobic digesters 6
2 Components of bio-gas system 7
3 Continuous retort schematic 18
4 Partial oxidation of manure - flow diagram 28
5 Reactor details 29
6 Flow diagram for the partial combustion of manure utilizing
a clyclonic burner 35
7 Syn-gas-II flow schematic 36
8 Portable waste conversion pyrolysis unit 41
VI
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TABLES
Number
1 A Summary of the Average Results Obtained from a Completely
Mixed Two Stage Digester with a Capacity of 30 Gallons
Per Stage, Operating at 97° F and a Daily Feed Rate of
Six Gallons 9
2 Expected Gas Yields on a Per Animal Basis 9
3 Approximate High Heat Value of Certain Fuels 10
4 Performance Parameters for Anaerobic Digestion of Livestock
Wastes 11
5 Average Mineral Composition of Cattle Feces, Earthworms,
and Earthworm Castings (DM Basis) 14
6 Characteristics of Raw Products from the Pyrolysis of Manure 17
7 Economic Criteria for Evaluation of Process Costs 19
8 Composition of Oil from Manure 21
9 Estimated Capital Investment for Oil Process 21
10 Total Product Cost Estimate for Oil Process 22
11 Summary of Reactor Results for the Direct Hydrogasification
of Cattle Manure 23
12 Estimated Capital Investment for Hydrogasification Process . 24
13 Total Product Cost Estimate for Hydrogasification Process . . 25
14 Capital Investment Summary for Manure-to-Pipeline Gas Plant . 26
15 Operating Costs, Revenue Requirements, and Gas Prices for
Manure-to-Pipeline Gas Plant 26
16 Synthesis Gas Ratios of the Product Gases 27
17 Installed Cost of Major Equipment 30
18 Economic Criteria 31
19 Cost of Synthesis Gas Production 31
20 Estimated Capital Investment for Synthesis Gas Process ... 32
21 Total Product Cost Estimated for Synthesis Gas Process ... 33
22 Preliminary Ethylene Production from Manure Economics .... 37
vn
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BRITISH TO METRIC UNIT CONVERSION
PRESSURE UNITS
2 2
1 pound per square foot (Ib/ft2) = 4.885 Kilograms per square meter (Kg/m )
1 pound per square inch (Ib/in ) = 70.308 grams per square centimeter (gr/cm )
ENERGY UNITS
1 British Thermal Unit (BTU) = 777.9 foot-pounds = 107.5 Kilogram-meters
LENGTH
1 inch (in.) = 2.54 centimeters (cm)
VOLUME
3 3
1 cubic foot (ft ) = 0.028 cubic meters (m )
CAPACITY
1 gallon (gal.) = 3.785 liters (1)
1 barrel (bbl) = 42 gallons = 158.97 liters (1)
WEIGHT
1 pound (Ib) = 0.454 Kilogram (Kg)
1 ton (tn) = 0.907 metric ton (t)
TEMPERATURE
Celsius (c) = 5/9 (F-32) where F in temperature is degrees Fahrenheit
Vlll
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SECTION 1
INTRODUCTION
The number of beef cattle marketed in the United States has increased
from approximately 13 million head in 1960 to approximately 40 million head
in 1975. This increase is due to increases in population coupled with a
change in preference toward beef as a food item. The demand for more and
better quality beef has resulted in a radical change in animal production
methods. Prior to marketing, an increasing majority of animals for slaughter
are being fed under confined conditions. This trend even though most evident
with beef cattle has also been observed in the hog, dairy, poultry; turkey,
and sheep production industry. Recent unfavorable trends in grain and
slaughter market conditions have confronted the confinement animal feeders
in the past two to three years. Many small confinement feeding facilities
have given way to larger more economically stable feedlots. With the advent
of the concentration of animals into feedlots the industry was faced with
many new adversities. The greatest of these adversities has been the problem
of disposing of the horrendous amount of manure generated by these animals.
Traditionally, these manure wastes have been disposed of by spreading
and incorporating them into croplands where they served as a nutrient source
to the crop and as a soil conditioner. However, the accumulation of manure
on large feedlots is such that there is not sufficient land suitable for
disposal within an economical hauling distance (Wadleigh, 1968). Thus,
storage which virtually forms mountains of manure near large feedlots is
becoming a common problem.
This problem is compounded each time that a rainfall of an amplitude
sufficient to cause a runoff event comes in contact with feedlot or stored
manure surface. This runoff has been shown to transport large amounts of
highly organic, nutrient, and salt-rich pollutants. When feeding facilities
are located, as many of the earlier feedlots were, near a stream or other
body of surface water or such that runoff drains into surface waters, this
pollutant load causes dissolved oxygen sags and accelerated eutrophication
and/or salinity problems which in turn are responsible for fish kills,
degradation of aquatic communities, algal blooms, and a general deterioration
of water for many beneficial uses.
Agriculturally and environmentally oriented researchers from a variety
of government agencies, educational institutions, and industrial corporations
have directed their efforts toward developing processes for the utilization
of the wastes through recycle and/or byproduct recovery. Many of these
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processes are very imaginative and range from recycling these wastes as they
are produced as a feed ingredient back through animals to chemically and
physically transforming the wastes into building materials, synthetic gases,
plastics, and fabrics.
This report will identify and evaluate the current state-of-the-art of
those manure wastes utilization systems which can be classified as byproduct
recovery processes. The classic definition of byproduct recovery refers to
the production of a secondary product in addition to a principal product.
Considering meat, eggs, or animal fiber as a principal product, then manure
wastes is a byproduct.
Utilization of manure as a primary resource to either biologically or
thermochemically recover secondary byproducts which can be used as an asset
internally or marketed externally to offset the costs of pollution controls
is the primary consideration of this report. Byproduct recovery, for the
purposes of this report, fall into two categories as follows: (1) biological
processes including methanization, and "worm dirt" (worm castings or worm
compost) production and (2) thermochemical processes which produce various
gases, chars, oils, building materials, fertilizers, soluble hydrocarbons,
and heat energy sources.
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SECTION 2
CONCLUSIONS
By-product-recovery-from-animal-wastes-processes were found to be ex-
tremely varied. These range from biological fermentation for the recovery
of methane gas and a stabilized soil conditioner to thermochemical processes
to produce gases, such as ethylene and synthesis gas; liquids, such as oil,
tars, and fertilizers; and solids, such as lamp black substitutes, construc-
tion materials, and pet foods.
Many of these processes appear to be very promising both from an eco-
nomic and a wastes utilization standpoint based on the results of paper,
bench, and small pilot scale studies. However, none of the processes have
been developed or optimized to the extent that they can be reduced to com-
mercial practice. There has been considerable interest within the research
community and animal production industry to initiate and support these bench
and small pilot scale stages of these processes. These efforts are usually
discontinued due to the great expense involved with further demonstration
and optimization of the larger commercial scale designs.
Many of the processes require that large numbers of animal units be
located within a prescribed area to provide the quantity of wastes required
to support the economic breakpoint for the process. The number of such areas
is limited by the propinquity of animal production facilities„ The engineer-
ing design of many processes investigated could be altered or modified to
include other highly organic wastes, thus, reducing the number of animals
required by increasing the variety of acceptable feedstocks. This would in
turn make the process more economically feasible for a greater number of
areas and would relieve the problem of animal wastes disposal over a larger
expanse of the nation„
Of the processes investigated, biological fermentation is receiving the
greatest research effort on a national scale. The process is limited, how-
ever, by the economics of compressing methane gas» Methane generation may
have application if constructed near the site where the methane can be used
as produced or piped directly into a natural gas or methane gas distribution
line.
Based on available economic evaluations the Texas Tech Synthesis-
Ethylene gas process appears to be the process with the greatest economic
viability. A large number of animals are required within a relatively
small area to economically provide the feedstock for this process. However,
designing the facility to accept other organic wastes could improve the
outlook for the process by making it available in areas with fewer animals
while at the same time recovering synthesis gas and ethylene from a variety
of organic solid wastes.
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SECTION 3
RECOMMENDATIONS
1. Continued support should be given to the initiation and development
of new concepts in the area of by-product recovery from animal wastes.
2. Demonstration and optimization of the more promising processes such
as recovery of ammonia synthesis gas, ethylene, oil, lamp black, and construc-
tion materials should be accelerated. These processes not only have potential
animal waste reduction qualities but also have energy source and conservation
implications.
3. Engineering designs for by-product recovery processes should include
consideration for highly organic wastes other than animal production wastes.
The inclusion of wastes such as municipal refuse, field crop residues, stover,
cotton seed hulls, domestic sludges, etc., could provide a continuous source
of feedstock which could effectively make many of the processes available in
areas where concentration of animals are not ample to maintain an economical
feedstock supply.
4. Government agencies with research and demonstration responsibilities
in program areas dealing with animal waste management, energy, ecological
effects and the environment, and other related fields should review and
strongly encourage research and demonstration of by-product recovery process-
es by Government, private, and corporate entities.
5. Consideration should be given to the establishment of positive
governmental incentives which would encourage the installation, demonstration,
and optimization of large commercial scale by-product recovery processes by
corporate interests.
6. The characterization and evaluation of gaseous, liquids and solid
waste streams generated by the processes under development have not been
reported in the literature. These wastes will ultimately be discharged to
our environment either directly or through some disposal scheme. The char-
acteristics of many of these wastes may render them more harmful to the
ecological balances in receiving environments than the original wastes under
consideration. All process development and evaluation studies should in-
clude consideration for the evaluation of the environmental acceptability of
such waste streams.
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SECTION 4
BIOLOGICAL PROCESSES
METHANE GENERATION
Methane, which constitutes over 95% of the natural gas which supplies
about one-third of the total current energy consumption of the United States,
is a gaseous product of natural microbial anaerobic fermentation of organic
matter (Anon., 1974a). This process may be observed in nature as the bubbling
of "swamp gas" from swamps or lakes and streams receiving highly organic
pollutants. Bio-gas is produced naturally and uncontrolled under anaerobic
conditions typical of septic tanks, anaerobic lagoons, organic wastes storage
tanks, and sewage treatment plants. In many cases, bio-gas has been collected
and burned to supply the heat requirements of anaerobic digestion or used to
fuel internal combustion engines that can generate up to two-thirds of the
power requirements for modern sewage treatment plants (Sweeten, 1974). Sewage
treatment facilities in Chicago and Los Angeles are typical examples for such
use of bio-gas generated by their anaerobic digestion process (Anon., 1974a).
Bio-gas is produced naturally as a gas in swine buildings with slotted floors
over pits (Day, Hansen, and Anderson, 1965).
Historical Background
The formation of methane gas from natural anaerobic digestion was dis-
covered in 1776, but it was not characterized until 1806 (Goeppner and Hassel-
mann, 1974). In 1886, the fact that methane was formed by the biochemical
actions of microbial cultures (anaerobic digestion) was confirmed (Geoppner
and Hasselmann, 1974). A plant was installed in Bombay, India, in 1905, to
produce both methane and the good fertilizer residue (Singh, 1973). During
World War II, Germany built many plants for both methane and fertilizer due
to the shortage of conventional fuels. The compressed gas was used to drive
tractors and machinery (Anon., 1974a and Singh, 1973).
In the 1960's, Allred (1966) observed that methane utilization had ceased
in Northern Europe. However, dwindling supplies of fossil fuels and increas-
ing demands for the type of energy which they can produce has created a revived
interest in methane production by anaerobic digestion of animal manure (Sweeten,
1974). Today thousands of bio-gas plants are in use in Algeria, South Africa,
Korea, France, Hungary, and many other countries (Singh, 1973). A Redkey,
Indiana, farmer has constructed a methane generator. The gas produced is used
for fuel to operate a cook stove, refrigerator, gas light, small space heater,
and a water heater plus a converted gasoline engine generated electric welder
(Anon., 1974b).
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Process Dynamics and Design Consideration
In his treatise on methane production from animal wastes, Smith (1973)
presents a review of the literature pertinent to the chemical and biological
fundamentals of methane production. In this presentation he combines the
data reported by several researchers on such topics as: the presence and
effect of toxic substances on process operation; gas production as a function
of temperature and time; gas production and system performance; schematic
diagrams of methane generators; performance parameters for the anaerobic
digestion of livestock wastes by species; guidelines for maximum loading
rates; and an example calculation of the amount of electrical energy that
could be produced by a digestion-operated methane generator which in turn
utilizes the wastes from a given number of animals. Several other investi-
gators have described the basic principles of the process (Goeppner and
Hasselmann, 1974; Schneider, 1972; Fry, 1973; Loehr, 1974; Meenaghan et al.,
1970; and Savery and Cruzan, 1972). Figure 1 is a materials flow-through
diagram for anaerobic digesters (Anon., 1974a). Figure 2 is a schematic
diagram of a typical bio-gas generator (Fairbank, 1974). Schematic diagrams
were also depicted by Loehr (1974), Wolf (1974), and Goeppner and Hasselmann
(1974). Singh (1973) offers an engineering design for a bio-gas generator,
and Fry (1973) discusses the basic principles of methane digestion for fuel
gas and fertilizer and gives instructions for two working models.
Gas Characteristics and Yields
Bio-gas is characteristically a mixture of methane, CCL, and miscellaneous
other gases. Bohn (1971) reports that microbial fermentation yields a gaseous
mixture of up to 72% methane, 25% or more carbon dioxide, ammonia, and hydrogen,
plus small amounts of other gases such as mercaptans and amines.
Bio-gas production is dependent upon the activity of microorganisms which
reduce organic material in an anaerobic environment. Specific organisms have
varying temperature requirements. The most efficient of these microorganisms
are divided into two groups based on their optimal temperature requirements
(Savery and Cruzan, 1972) . The first are called mesophilic bacteria which
work at medium temperatures with optimum growth at 29° C. The second are
called thermophilic bacteria which work at elevated temperatures with optimum
growth at 51° C.
In-
Complex
organic
matter +
water
Out
i
DIGESTER
•Out
Supernatant (Water +
Dissolved and suspended
organics + bacteria )
Out
Figure 1.
(Solids with reduced
Sludge organic fraction +
water + bacteria)
Overall material flow-through anaerobic digesters (Anon, 1974a)
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ON-SITE ENERGY USE
Engine
pump
generator
Dryer
Heater
sludge
space
Sludge
Holding
In-Transit
Figure 2. Components of bio-gas system (Fairbanks, 1974)
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Savery and Cruzan (1972) report on the differences in gas characteristics
produced by these two groups of bacteria from a single source of chicken ma-
nure digested for eight days. Gas produced by digestion in the 29° C range
averaged 50% methane and 50% C02 at a rate of 46 I/kg of wet manure reacted.
By comparison the gas produced at the elevated temperature of 51° C averaged
69% methane and 31% CCL at a rate of 89 I/kg of wet manure reacted. Meso-
philic rates were much higher if allowed to digest for 20 days.
Inasmuch as time is important and better yields of gas with a larger
percentage of methane are produced thermophilically, most units are designed
to either use part of the gas produced as an internal heat source or to
utilize some outside heat source to elevate the reactor temperature into
the thermophilic range. Parker et al. (1974) have investigated the use of
solar heat to supplement the heat requirement of the digester. They have
determined that the system worked well enough to warrant additional investi-
gation and optimization.
In a study designed to determine the effectiveness of a two-stage anaer-
obic treatment system, Meenaghan et al. (1970) characterized the gases and
residues obtained from digestion of steer manure for a period of 10 days at
36° C (Table 1). Gas production for both stages averaged 3.56 ft /day/ft
capacity with the ratio of methane to other gases averaging 62.5%. Parker
et al. (1974) reported a total maximum gas production of 11.5 ft /lb of
volatile solids destroyed; gas composition was 60% methane and 40% CCL. The
composition of bio-gas produced by most researchers ranges from about 50% to
about 75% with the median production level being about 60% (Smith, 1973;
Meenaghan et al., 1970; Fairbank, 1974; Parker et al., 1974; and Taiganides,
1974).
Bio-gas with a methane content of 60% has a fuel value of 600 BTU/ft
(Fairbank, 1974 and Pfeffer, 1973). Sweeten (1974) summarizes that yields
of methane gas from animal wastes range from 4 to 6.2 ft /lb of dry solids
with a fuel value of 963 BTU/standard cubic foot (SCF). Table 2 is a com-
parison of expected gas yields on a per animal basis by species (Taiganides,
1974). According to Singh (1973) bio-gas in ^ndia tests about 650 BTU/ft as
compared tp natural gas at 1,100-1,200 BTU/ft and coal gas in England at
450 BTU/ft . For comparison purposes, Fairbank (1974) has compiled a listing
of approximate high heat value of certain fuels (Table 3). Smith (1973) has
compiled a rather complete listing of performance parameters for anaerobic
digestion of livestock wastes from the literature between 1963 through 1971
(Table 4).
One consultant to the feedlot industry suggests a "systems approach"
which incorporates bio-gas generation with refeeding (Andre, 1973 and Anon.,
1974c). This process dictates that fresh excreta cleaned from the feedlot
on a daily basis be separated into liquid and solid fractions. The liquid
then is fed directly into a bio-gas generator. The methane will be used to
generate the electrical needs of the feedmill and the drying needs of the
dryer in which the solid fraction is dried and sterilized. The dried solids
will then be incorporated with the feed for cows and calves and to a lesser
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Table 1. A SUMMARY OF THE AVERAGE RESULTS OBTAINED FROM A COMPLETELY
MIXED TWO STAGE DIGESTER WITH A CAPACITY OF 30 GALLONS PER STAGE, OPERATING
AT 97° F AND A DAILY FEED RATE OF SIX GALLONS (Meenaghan et al., 1970)
T 7
Gas Production, ft /day/ft capacity. Stage 1, STPa
Stage 2, STP
CH ,b %, Stage 1, STP
Stage 2, STP
C:N,C Feed
After 10 days digestion
pH, Feed
Stage 1
Stage 2
Volatile Acids, mg/1, Stage 1
Stage 2
Alkalinity, mg/1, Feed
Stage 1
Stage 2
Average BOD5, mg/1, Feed
After 10 days digestion
Average COD, mg/1, Feed
After 10 days digestion
4.3
2.82
53
72
16.2
9.4
7.3
6.3
7.1
2,990
1,030
2,100
3,750
4,700
6,900
2,900
13,000
7,800
STP Standard Temperature and Pressure
DCH4 Methane
"C:N - Carbon-Nitrogen Ratio
Table 2. EXPECTED GAS YIELDS ON A PER ANIMAL BASIS
(adapted from Taiganides, 1974)
Wastes
Gas Produced
Cu ft/day
Methane
Percent
Heat Value
BTU/day
Swine
Cattle
Poultry
6.3
42.0
0.4
55-75
60-80
60-80
3,600
25,000
250
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Table 3. APPROXIMATE HIGHa HEAT VALUE OF FUELS (adapted from Fairbank, 1974)
Fuel
Producer Gas*5
Hydrogen
Carbon Monoxide
Water Gasc
Pyrolysis Gas^
Municipal
Feedlot
Bio-Gase
Coal Gas*
Methane
Natural Gas
Propane
Butane
Cattle Manure:
Air Dry
DM only
VS only
Hardwood
Softwood
Coal
Alcohol, Methyl
Alcohol, Ethyl
Dungoil
Diesel, #1
Kerosene
Gasoline
Fuel Oil, #2
0
Heat Value
BTU/lb BTU/gal.
23,861
21,591 91,547
21,221 102,032
5,000
6,730
9,100
7,100
9,000
13,000
11,500 63,700
16,700
15,000
19,600 135,250
19,830 134,100
20,300 124,100
20,150 133,000
BTU/ft3
157
270
316
322
375
500
620
680
994
1,050
2,516
3,280
958
Formula or Formulation Percent
CH4 cy^ co co2 H2 \2
2.5 .4 27 2.5 12 55
100
100
2 45 4 45 2
* * 3 * * *
24 10 17 22 27 *
60 35 * *
40 4 6 .5 46 1.5
100
92.6 .3 .5 2.2 3.6
C3»8
C4H10
(C33H48°12) + 18% to 52^ ash + moisture
(C33H48°12) + 18% to 52% ash
(C33H48°12)
CH40
C2H60
°2
.3
.5
*
*
.5
.3
operations or internal combustion engines.
Hot coal + blast of air (2C + N2 + 02 —• 2CO + N2)
°Hot coal + steam after heating w/air (C t H20 — CO + H2)
Farm Resource Science, Inc., Santa Ana, January 1974
eAlso called manure methane or swamp gas; derived from the anaerobic decomposition of organic matter
f
Destructive distillation of coal.
*Present in varying amounts.
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Table 4. PERFORMANCE PARAMETERS FOR ANAEROBIC DIGESTION OF LIVESTOCK WASTES
Adapted from Smith, 1975
Manure
Loading
>o
«J »0
<4-t
a
5- x
I I
Temperature Duration
°F °C Day
Dentention
Day
VS COD , . COD (NH, t NH/)-N Volatile Acids
Mixing Reduction Reduction Influent 3 4
% .
3 0 *J O
*J *J C
a C o ao
ig/1 as HAc
Alkalinity Gas Production Fraction as CH. pH Source
mg/1 as %
CaCO, „
3 « -d •-'-a
2* O C/l 0)
* S *Z
Jr"° "s
v >*i
>H B
Dairy bull
manure (froo
holding tanjc)0.24 3.8
Dairy cow
urine and
feces
0.24 3.8
0.202 3.1
0.176 2.8
90.5 32.5
90.6 43.6
74 23 37
95 35 20
10
15
26.3
16.6
X 19.4 9.33 - 45,200 206
X 17.7 13.2 - 68,270 376
X 10.4 - 1.00 - 1,240
X 48.3 - - -
216
177
<1,000
162
3,320 6.33 0.4 65.2 6.93 A
5,160 8.88 0.56 61.3 7.09 A
8,000 16.1 1.01 64 7.5 B
6.15 0.38 65 7.1 C
Beef manure
(concrete
floor)
Hog Urine
Hog manure
s craped
from solid
floor
O.lc 1.6
0.2C 3.2
0.07S 1.2
0.025 0.4
0.12 1.9
0.24 3.8
0.24 3.8
95 35
95 35
93 34 110
93 34 40
90.5 32.5
90.5 32.5
90.5 32.5
10
10
22
48
15
10
15
X 55.2 23.8 -
X 41.9 28.6 - -
X 47 - 1.32 - 1,300
X 43 - 1.32 - 1,200
X 60.9 54.6 - 35,000 594
X 44.2 35.5 - 46,000 730
X 59.2 41.8 - 70,000 1,010
100
100
1,500
1,200
200
1,080
290
1,500 13.7c>d 0.86c>d 58 6.7 D
2,050 17.7 l.l!C>d 57 6.8 D
6,800 19.6 1.23 59 • 7.4 I
6,800 23.5 1.47 50 7.4 E
4,440 11.1 0.69 60 7.14 A
6,330 13.2 0.83 58 7.17 A
7,130 12.2 0.76 59 7.27 A
Sheep urine
and feces
Fresh
poultry
manure
A
B
C
0.150 2.4
0.12 1.9
0.12 1.9
Grams et al .
Hart (1963)
Jeffrey et al.
95 35 13
90.5 32.5
90.5 32.5
(1971)
(1964)
20
10
15
X 38.0 - -
X 67.2 75.3 - 40,580 1,020
X 67.8 78.1 - 60,920 1,570
aLength of run at steady loading rate.
Detention time calculated from:
Total voluoe (or weight) of digester contents
95
350
175
9.7 0.61 63.5 7.3 C
7.28 0.45 58.0 7.2 A
8.56 0.53 57.8 7.35 A
0 Loehr § Agnew (1967}
E Taiganides (1963)
{or weight) added daily
Expressed on the basis of total not volatile solids
Calculations made by the author, using the original data.
-------
degree fed back to the feeder animals. The digested liquid exhausted from
the generator is estimated to contain 2% to 305% of the solid fraction or
about 2,880 Ibs of nitrogen daily for a 10,000 head unit.
As indicated in the above systems approach, there is a useable residual
product of the methane generation process. According to Sweeten (1974) this
residue is a "well-composed manure" amounting to one-third the raw manure
input. Another source (Anon., 1974a) indicates that the remaining sludges
from the process constitute approximately 50% of the volume of the solid
feed material. By comparison composted chicken manure has from 1.58% to 2%
nitrogen while the same manure digested in a bio-gas plant will analyze 6%
nitrogen (Singh, 1973). Thus, the residual sludge should have fertilizer
and soil conditioning qualities when applied to crop land; however, there
was not any indication as to the amount of residual salt levels in these
sludges.
Economics
Until recently, the cost of methane production by recovering bio-gas
from controlled anaerobic digestion processes has been very prohibitive.
In 1972, for example, Costigane (1972) concluded, after making an intensive
investigation into the theory and feasibility of anaerobic digestion, that
the most economical and efficient design presently available for methane
production and wastes stabilization "is not at present considered feasible
for animal waste treatment on a small farm due to the high initial equipment
costs." Tests conducted by Savery and Cruzan (1972) on an experimental
digester for the production of methane gas from chicken manure indicated
that a 60,000 chicken unit could supply sufficient quantities of methane to
be self-sufficient in its total electricity requirements. However, the costs
were six times that of its present supply. Smith (1973) concludes that
anaerobic digestion is only a partial stabilization process which must be
followed by additional, potentially expensive process; that increased han-
dling costs are due to increased volumes which are created by solids dilution;
and that costly management and supporting services are required to run an
anaerobic digester.
However, when considering the world energy situation and related needs
for renewable energy sources, bio-gasification of organic wastes is an impor-
tant possibility for consideration. Some preliminary estimates have been
made in consideration of this need. Fry (1973) reports that people with the
United States standard of living use 60 ft /day/person of natural gas (60,000
BTU). He further estimates that under optimal conditions, 10 pounds of
wastes would generate this amount of methane based on the production of
10 ft /lb of volatile solids destroyed. And according to estimates of
Solomon (19721, if all of the nation's animal wastes were anaerobically
digested, 10 ft of methane fuel could be produced annually. This is
nearly half of the current United States methane consumption. A more con-
servative estimate of from 10 to 20 percent of the current United States
natural gas consumption could be replaced by the anaerobic digestion of all
agricultural organic wastes (both wastes from crop production and animal
wastes) which could be economically collected was made by Wolf (1974).
12
-------
On process costs, Pfeffer (1973) estimates that the operating costs for
a digester ranges from $4.35 to $3054 per million BTU of gas generated.
Whereas, Boln (1971) presents a "conservative rule of thumb;" one ton of dry
organic matter produces 20,000 ft of methane worth about $3.40 at the 1971
well-head price of 17$ per thousand cu ft.
Methane cannot be liquified under normal temperatures (Lapp et. al 1975)
(Hansen 1976). This characteristic makes storage uneconimical due to the
large storage capacities required to store it in the gaseous form. Earth
and Hill (1975) suggest that the C02 which occupies one-third of the gas
volume be scrubbed by passing the gas through adilute albaline solution. The
nearby pure methane can then be utilized at approximately the same rate at
which it is produced. According to Hansen (1976) bio-gas should be used for
such low demand stationary uses as cooking, heating water and buildings, air
conditioning or stationary engines. The high compression required to store
enough bio-gas on a tractor for one hours operations creats a serious safety
hazzard.
EARTHWORM CASTINGS
Worm dirt (earthworm castings or feces) is the material which passes
through the gut of earthworms. The earthworm is very efficient at neutraliz-
ing or composting highly organic wastes. Fosgate and Babb (1972) intensively
cultivated earthworms on a media of cow manure. Worms require a media with
9%-15% protein content. The manure used contained about 14.25% protein and
required the addition of lime to maintain a neutral 7.0 pH. A raw feces to
live earthworm conversion ratio of 10:1 was obtained. The average mineral
composition of the cattle feces, earthworms, and earthworm feces on a dry
matter basis is presented in Table 5.
The earthworms, dried into a meal, were found to be very palatable to
cats. The earthworm dirt is a very good soil conditioner which only weighs
about 50% as much as normal potting soil.
Another investigator (Hancock, 1956) reported on the raising of worms on
a ration of peat moss, commercial laying mash, corn meal, and a small amount
of molasses. The compost produced by their excrement was harvested and fed
to broilers which grew to 3.5 Ibs in weight in 8 weeks. The other half of the
same flock, raised on regular commercial broiler feed, required 10 weeks to
reach three Ibs,
There have not been any studies of the use of "earthworm compost" as a
refeeding mechanism to animals other than broilers or of pollutional char-
acteristics of the process reported in the literature.
13
-------
Table 5. AVERAGE MINERAL COMPOSITION OF CATTLE FECES, EARTHWORMS,
AND EARTHWORM CASTINGS (DM BASIS) (Fosgate and Babb, 1972)
Source
Cow Feces
Earthworm
Earthworm Castings
N
2.36
9.31
2.98
P
0.72
0.90
0.32
K
0.73
0.88
0.40
Ca
1.43
0.54
1.20
Mg
0.55
0.19
0.36
14
-------
SECTION 5
THERMOCHEMICAL PROCESSES
Highly organic materials such as animal manure and other solid wastes can
be changed chemically by subjecting them to highly elevated temperatures. The
chemical transformation can be selectively controlled through regulation of
the atmospheric content and pressure. Such controlled heat induced chemical
changes are a result of thermochemical processing. Providing that favorable
economics exist, Whetstone (1973) reports thermochemical processing of manure
as the most acceptable alternative to land spreading.
Cow and/or buffalo chips provided the primary source of fuel to pioneer
settlers of the high plains of West Texas. These chips were burned to heat
houses and provide cooking heat. Wells et al. (1973) observed that feedlot
manure used directly as a fuel does not appear promising. His observation
was based on a preliminary experiment in which he rolled feedlot manure into
dried logs, "Blue Flame Buffalo Chips," which did not readily burn with a
flame but which smoldered to an ash giving off very little heat.
Incineration of animal wastes for the sole purpose of disposal is prac-
ticed on a very small scale. Davis et al. (1972) reported a manure weight
reduction of about 90% and a volume reduction of about 85% by incineration.
The economics of this process are not attractive because there is not any
economic return for the equipment, investment, maintenance, or operation costs
other than the intrinsic value of manure disposal. The processes discussed
herein utilize combustion of manure in one form or another and have as a
common demoninator the potential for recovery of a useable or saleable product
which will provide some economic return to the feeding operation.
PYROLYSIS
Pyrolysis, a common chemical process, is thermal decomposition that can
be achieved by heating organic materials in an inert atmosphere or by partial
combustion (Garner and Smith, 1973). The process equipment must include a
heat source, a pyrolysis or reaction chamber, and a system to separate product
gases, condensates, tars, chars, and ash. The process equipment may either
be designed to handle the feedstock on a batch basis or with a continuous flow
of feedstock. Pyrolysis has been used for several hundred years to make char-
coal and in more recent times to recover by-products such as methanol, acetic
acid, and turpentine (Loehr, 1974).
15
-------
White and Taiganides (1971) reported that product yields for batches of
swine, beef, dairy, and poultry manure were similar. Garner and Smith (1973)
pyrolyzed steer manure containing 80% moisture. They identified many oxygen-
ated and nitrogenous organic compounds, none of which were produced in quanti-
ties which were sufficient to economically justify separation. They reported
that the costs of pyrolysis for the disposal of manure was approximately $5.60
per ton and thus, not economically attractive.
Schlesinger et al (1972) reported the data presented in Table 6 for manure
pyrolyzed in a batch reactor designed for the testing of coal.
The value of the liquid pyrolysate from this process was placed at no more
than the current price of crude petroleum and coke oven tars. When compared
to simple incineration, Garner et al. (1972) concluded that their pyrolysis
process was uneconomical due to equipment and separation costs. The costs of
pre-drying was most uneconomical and accounted for the largest liability to
the project. The manure used was as produced or about 80% moisture. Their
economics did not consider dryer manure as cleaned from lots in more arid
regions of the country.
Whetstone (1973) warns that the yields for pyrolysis of manure are a com-
plex function of many variables. These variables include manure composition
and particle size, heating rates, maximum temperature, and pressure in the
pyrolysis chamber. For particular pyrolysis schemes, other factors may also
influence the product yields; among these are the purging of the reactor
chamber with gases or the allowing of liquid products to reflux back into
the pyrolysis chamber. For these reasons considerable judgement must be
exercised in drawing conclusions from published data for batch pyrolysis of
manure.
Continuous pyrolysis of manure is complicated by requirement of maintain-
ing stable, constant reactor heat and pressures while continuously feeding
manure through the reactor and at the same time recovering the products of
pyrolysis. Several methods have been developed to continuously pyrolyze such
feedstocks as municipal solid wastes, non-compostable wastes, oil shale, coal,
and other organic materials. While most of these processes could have appli-
cability for animal wastes, there has only been one continuous manure pyrolyzer
reported in detail. This pyrolyzer or retort as it is called employs air
injection to energize pyrolysis reactions in a moving bed (Massie and Parker,
1973). This retort is detailed in Figure 3. The feedstock enters the top of
the retort and the product char and ash is discharged through the bottom.
Counterflow circulation of gases serve to transport heat upward in the retort
to form manure drying and pyrolysis zones in the upper section of the retort.
Two gas injection cycles are employed. Air is injected to generate heat at
a combustion front which moves downward in the retort when the lower portion
of the retort is cold. The injected air is diluted with oxygen-free gas to
lower the temperatures at the combustion front, so that the ash in the manure
cannot fuse and form clinkers. When the combustion front nears the bottom
of the retort where the associated high temperatures might damage the grate,
air injection is stopped and only oxygen-free gas is injected. The oxygen-
free gas cools the lower portion of the retort and continues the pyrolysis
and drying of manure in the upper portion of the retort. When the lower half
of the retort has cooled, air injection is again resumed.
16
-------
Table 6. CHARACTERISTICS OF RAW PRODUCTS FROM THE PYROLYSIS OF MANURE
Batch Pyrolysis
Ultimate Analysis of Feed, Wt.
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Ash
Yields (per ton of wet feed)
Gas (Std. cubic feet)
Oil (bbl)
Waterphase (gal.)
Char (Ib)
A
0.
41.2
5.7
33.3
2.2
0.3
17.2
13,940
0.31
38.3
726
B
*
*
*
*
*
8.65
104. 4a
0.25
222
143
C
*
*
*
*
*
*
V-
38r
*
*
f
0.331
Continuous
Pyrolysis
D
*
*
*
*
*
22.0
16,610
0.96
89.5
526
Oil Hydrogasi-
Production fication Ammonia Synthesis Gas
E 5 F
20.5
2.5
14.5
1.3
0.5
15.1
*
2.6
*
*
G
35.4
4.2
23.5
0.7
0.2
36.0
.967°
0.0
.872°
40.68
H
35.4 35.
4.6 5.
30.1
* 2.
* 0.
25.6 23.
* 8,400
o
*
I
1-39.6
3-5.9
0.0
5-3.1
4-0.6
5-29.2
-15,000
.88e
93
J
42.6
5.5
23.7
2.8
0.5
24.9
790E
0.14
42
650
Cyclonic
Burner
K
27.6
3.76
21.48
2.32
0.5
44.30
16,208
1.0°
1,093
TCD-Char
L
23.82
3.80
*
1.85
*
*
*
*
*
*
Oil Composition, Vol.
Carbon
Hydrogen
Nitrogen
Su 1 fur
Oxygen
*
*
*
*
*
*
*
*
*
*
* *
* *
* *
* *
* *
78.6
9.5
4.2
0.37
7.3
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
it
*
Gas Composition, Vol. %
Oxygen
Nitrogen
Carbon dioxide
Carbon monoxide
Hydrogen
Methane
Ethylene
Ethane
Carbon
Water
Hydrogen Sulfide
0.0
0.0
24.5
18.0
27.5
22.7
0.0
0.0
7.3
0.0
0.0
0.0
7
37.2
16.7
16.4
15.5
0.4
1.7
*
*
*
4 1.72
19 49.83
18 14.06
18 17.72
30 10.2
h 3'°7
13h
*
0.0 *
0.0
0.0 *
*
*
*
*
*
*
*
*
*
*
*
0.0
0.0
33.5
0.7
11.3
42.1
0.0
12.4
0.0
0.0
0.0
0.0
0.0
16. 11
3.4
10.56
18.55
0.0
5.38
0.0
45.85
0.15
0.3-2.5
28.4-38.3
13.1-18.7
11.5-17.3
18.1-26.2
6.2-7.9
2.7-4.1
<=0.3
0.0
0.0
0.0
0.0
7.1
14.2
12.8
27.4
32.3
5.9
0.4
0.0
0.0
0.0
3.5
65.8
22.5
4.8
2.2
0.6
0.6
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Char, Wt. %
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Ash
49.4
0.4
0.4
1.1
0.3
48.4
*
*
*
*
*
*
63 *
* *
* *
* *
* *
36 40
*
*
*
*
*
*
*
*
*
*
*
*
44.1
1.6
0.0
0.0
0.0
54.2
32.0-41.2
0.3-1.6
*
2.0-2.5
*
36.7-53.9
*
*
*
*
*
21.5
21.54
1.07
*
1.42
*
76.40
30.07
1.49
*
0.0
*
*
Heatine Values
A
B
C
D
E
F
Feed, BTU/lb. (dry)
Gas, BTU/ft
Char, BTU/lb. (dry)
- Schlesinger et al. (1972)
- Garner and Smith (1973)
- White and Taiganides (1971)
- Massie and Parker (1973)
- Appell and Miller (1972)
- Appell et al. (1971)
7,110
450
7,290
G -
H -
I -
J -
K -
L -
4,200
11,000
Kiang et
* . 7,630
1,900J 123
3,000 6,390
al. (1973)
Feldman et al. (1973)
Halligan
et al. (1974)
Huffman and Halligan (1974-75)
Natour et
Mackenzie
al. (1975)
(1976)
*
* 1
*
A
,000+
*
4
*
* Not reported
a - Ibs/T of wet
b - mg/1
feed
c - moles/80 gr.
d - H2 + CO
e - bbl/ ton
of feed, oil
3.194-3.7391
4.132-5.5351
f -
g -
h -
i -
j -
plus waterphase
6,350
*
gr./gr. of
gr./80 gr.
5,604
2,011
total solids
feed
total combustibles and i
Kg ccl/Kg
per Ib of
total solids
*
*
lluminants
-------
Solid Waste
Gas
Drying
Pyrolysis
Oxygen Free Gas
Air
Pyrolyzed Waste
Figure 3. Continuous retort schematic(adapted from Massie and
Parker, 1973)
18
-------
Feasibility of this retort has been demonstrated in a six-inch pilot
model. Table 6 reports the yield of products from this retort. A major
difference in the list of observed pyrolysis products from the continuous
retort and that reported for batch pyrolysis of manure is the yield of liquid
organics. The continuous retort yielded about one barrel of oil per ton of
manure processed in contrast with the 0.3 barrel per ton reported for the
batch pyrolysis. These data show that manure pyrolyzed in the continuous
retort produces more oil per ton of manure than is reported for average
Colorado oil shale (20-30 gallons of oil per ton of oil shale). The increase
in oil yield over that of batch pyrolysis is due to the rapid removal of
pyrolysis products from the retort by the circulated gases.
Conceptual process flow sheets have been prepared for a commercial plant
using the Texas Tech University retort and costs estimated by Parker et al.
(1973), For a plant processing 2,000 tons per day of 30 percent moisture
manure an investment of 14.7 million dollars has been estimated. When credit
is taken for electric power generated and ammonium sulfate produced by this
plant, the annual income exceeds the operating expenses, including maintenance,
by $846,000 if the manure entering the plant be considered to have zero value.
If no credit is taken for oil and char produced, the cost of manure processing
is several dollars per ton with a 14 percent rate of return for industrial
economics and $1.70 per ton for municipal economics using the criteria from
Table 7.
Table 7. ECONOMIC CRITERIA FOR EVALUATION OF PROCESS COSTS
(Adapted from Parker et al., 1973)
Public Ownership
Economics
Private Ownership
Economics
Size (tons/day)
Project Life (yr)
Depreciation Schedule
Interest Rate
2,000
20
20 yr straight
line
6%
2,000
20
11 yr sum
digits
14%
of
(year end discount)
Income Tax
Fixed Capital Investment,
FCI
Maintenance
Salvage
Supervision
Payroll
Plant Overhead
Working Capital
Insurance and Local Taxes
0.0
48%
4.1 of maj or
equipment costs
4% of FCI/yr
5% of FCI
20% of labor
25%
50% of labor
5% of FCI
2% of FCI
19
-------
The preceding pyrolysis methods, with energizing by partial combustion
of the solids being pyrolyzed, result in pyrolysis gases which are diluted
with nitrogen and combustion gases. For a price, dilution with nitrogen can
be avoided by using oxygen instead of air to oxidize the fuel as has been
proposed for several coal pyrolysis and gasification methods. Cyclic opera-
tion of the pyrolysis processes can also be utilized to produce pyrolysis
gases not contaminated with nitrogen or combustion gases.
Other thermochemical processes to convert manure into selected gases,
liquid and solid fractions have been developed by controlling various condi-
tions of pyrolysis. For example the amount of carbon in the char can be con-
trolled by varying the pyrolysis reactor temperatures. A detailed description
of liquification to oil, gasification of synthesis gas, and hydrogasification
to methane manure processing schemes have been presented by Walawender et al.
(1973a). A detailed economic analysis of these processes has also been pre-
sented by Walawender et al. (1973b).
OIL PRODUCTION
The U.S. Bureau of Mines has developed a means to convert organic wastes
to low sulfur fuel by exposing them to CO and Na2CO_ as a catalyst at high
pressures and temperatures. Urban refuse and cellulosic wastes pyrolyzed at
temperatures between 250° and 400° C and at pressures of from 1,500 to 5,000
psi will yield about two barrels of low sulfur (0.1%) oil per ton of ash-free
feedstock. This conversion of organic matter to oil, water, and gas is about
90% efficient with the yield of oil usually near 40% (Appell et al., 1970).
Animal wastes conversions are essentially complete at 380° C in the absence
of solvents, but pressures of 5,000 to 6,000 psig are obtained because of
combined high steam and gas pressures generated with wet manures (Appell and
Miller, 1972). Bovine manure, which is not readily converted to oil at 250° C
as are other organic wastes, will produce highest conversion efficiencies at
380° C and high temperatures after pre-treatment with CO and steam. Catalysts
are not needed due to characteristically high calcium, sodium, and potassium
content of animal wastes (Appell et al., 1971). The composition of cattle
manure feedstock and the oil product is shown on Table 6. The composition of
product oil from cattle and chicken manure is shown in Table 8.
Walawender et al. (1973b) presented an economic evaluation of the manure
to oil process based on 1973 cost considerations. This evaluation was based
on a plant with a capacity to handle 4,300 tons of wet manure feedstock per
day. The analysis also considers that the process will produce one barrel
of oil per ton of wet manure rather than the two barrels estimated by Appell
et al. (1970). These estimates show a capital investment of $44,180,200
(Table 9) and a total product cost per pound of $0.0326 (Table 10). These
capital investment costs and total product costs have increased in the period
from 1973 to 1975; however, crude oil in the same period has increased from
$0.02 per pound to $0.037 per pound. Process economics, even with the increase
in crude oil prices, remain unattractive when attempting to encourage further
development and optimization of the process by the private sector.
20
-------
Table 8. COMPOSITION OF OIL FROM MANURE (Appell et al., 1971)
Manure
Bovine
Bovine (PE)b
Chicken
Temp.
(° C)
380
350
350
Reactor
Time
(hrs.)
0.3
1
1
Analysis (%)
C
78.9
79.7
75.4
H
9.5
9.5
9.7
M
4.2
3.2
6.8
S
0.37
0.56
0.26
oa
7.3
7.1
7.8
By difference
PE = Protein extracted
Table 9. ESTIMATED CAPITAL INVESTMENT FOR OIL PROCESS
(Walawender et al., 1973b)
Item
A. Direct Costs
1. Purchase Equipment (delivered)
2. Equipment Installation
3. Instrumentation and Controls (installed)
4. Piping (installed)
5. Electrical (installed)
6. Buildings
7- Yard Improvements
8. Service Facilities (installed)
9 . Land
TOTAL DIRECT PLANT COSTS
B. Indirect Costs
1. Engineering and Supervision
2. Construction Expenses
3. Contractor's Fee
4. Contingency
FIXED CAPITAL INVESTMENT
C. Working Capital
TOTAL CAPITAL INVESTMENT
Cost
$ 8,955,200
4,029,800
1,791,000
3,134,300
1,074,600
1,791,000
716,400
4,925,400
537,300
$26,955,000
$ 2,955,200
3,582,100
1,791,000
3,134,300
$38,417,600
5,762,600
$44,180,200
21
-------
Table 10. TOTAL PRODUCT COST ESTIMATE FOR OIL PROCESS
(Walawender et al., 1973b)
Item Cost
I. Manufacturing Cost $
A. Direct Production Costs
1. Raw Materials
Manure 1,413,200
Carbon Monoxide 4,842,000
2. Operating Labor 197,100
3. Direct Supervisory and clerical labor 29,600
4. Utilities 1,563,800
5. Maintenance and repairs 1,536,700
6. Operating supplies 192,100
7. Laboratory charges 19,700
B. Fixed Charges
1. Depreciation 3,841,800
2. Local Taxes 384,200
3. Insurance 384,200
C. Plant Overhead Costs 98,600
II. General Expenses
A. Administrative Costs 264,500
B. Distribution and Selling Costs 312,800
C. Research and Development Costs 469,100
D. Financing 88,400
ANNUAL TOTAL PRODUCTION COSTS* $15,657,800
TOTAL PRODUCTION COSTS PER POUND* $0.0326
* Basis: 4,282.5 tons/day wet manure feed, 330-day/year plant operation.
22
-------
GASIFICATION
By reacting cattle manure with hydrogen at gasification (Hydrane process,
Feldman et al., 1972) conditions, Kiang et al. (1973) showed that a suitable
synthetic natural gas (SNG) could be produced. The conditions of this pro-
cess called hydrogasification are shown in Table 11.
Table 11. SUMMARY OF REACTOR RESULTS FOR THE DIRECT HYDROGASIFICATION
OF CATTLE MANURE (adapted from Kiang et al., 1973)
Reactor Tempterature, °C
Initial press, psig*
Operating press, psig*
Solid charge, grams
Hydrogen charge, g-moles
Solid residue, grams
Carbon in charge, g-moles
Gas produced, g-moles
Carbon gasified, %
Water recovered, g-moles
550
150
1,630
80
0.562
40.6
2.363
0.967
40.4
0.872
* psig = pounds per square inch gauge
These data show that cattle manure is readily converted to pipeline gas
by hydrogasification at temperatures low enough to allow appreciable yields
of ethane. Synthetic Natural Gas with a heating value in excess of 1,000
BTU/scf can be produced without any need for methanation by hydrogasifying
the manure, shifting a low concentration CO to C0~, and scrubbing out the
CO,,. In addition, it was found that no tars or oils were produced from manure
hydrogasification in spite of the relatively low temperatures. An experiment
made by these researchers with cattle manure in a continuous free-fall dilute-
phase reactor indicated that the manure in such a reactor system is more
reactive than in the batch reactor because of the much higher rates and the
low concentration of particles in the dilute phase reactor. An analysis of
the manure feedstock and products from hydrogasification are presented in
Table 6.
Walawender et al. (1973b) have presented some basic economic analysis of
the hydrogasification process, Tablgs 12 and 13. The breakeven or total pro-
duct cost of $2.02 per MSCF (1 x 10 standard cubic feet) for the methane is
about four times greater than the sale price of methane at the time of release
of the above analysis. Thus the processing costs of the manure was $9.41 per
ton as produced.
Feldman et al. (1973) estimated North Slope gas at $1.00/106 BTU in 1973,
and reported U.S. natural gas consumption at 24 x 10 scf per year. The
results of their study to convert cattle manure to pipeline gas by direct
hydrogasification by the Hydrane Process (described in detail by Feldman et al,
(1972) showed that supplying cattle manure containing 52% moisture to an
23
-------
Table 12. ESTIMATED CAPITAL INVESTMENT FOR HYDROGASIFICATION PROCESS
(Walawender et al., 1973b)
Item Cost
I. Gasification System $
A. Direct Costs
1. Purchased Equipment (delivered) 1,269,500
2. Equipment Installation 571,300
3. Instrumentation and Controls (installed) 253,900
4. Piping (installed) 444,300
5. Electrical (installed) 152,300
6. Buildings 253,900
7. Yard Improvements 101,600
8. Service Facilities (installed) 698,200
9. Land 76,200
TOTAL DIRECT PLANT COST (Gasification System) 3,821,200
B. Indirect Costs
1. Engineering and supervision 418,900
2. Construction Expenses 507,800
3. Contractor's Fee 253,900
4. Contingency 444,300
FIXED CAPITAL INVESTMENT (Gasification System) 5,446,100
FIXED CAPITAL INVESTMENT (Separation System) 1,500,000
FIXED CAPITAL INVESTMENT (Entire Process) 6,946,100
C. Working Capital 1,041,900
TOTAL CAPITAL INVESTMENT $7,988,000
integrated pipeline gas plant yielded approximately 4.6 scf/lb of dry organic
solids of 1,000 BTU/scf gas or at 159 mm ton manure/yr about 1.46 trillion
scf/yr. This is about 5.8% of the total U.S. consumption or 24% of the U.S.
residential and commercial gas consumption. The Hydrane Process was origi-
nally developed by Bureau of Mines for transforming unpretreated coal to
pipeline gas.
Economic estimates for hydrogasification of 8,280 tons of wet manure/day
(690,000 Ib/hr manure feed rate)are presented in Tables 14 and 15.
24
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Table 13. TOTAL PRODUCT COST ESTIMATE FOR HYDROGASIFICATION PROCESS
(Walawender et al., 1973b)
Item Cost
I. Manufacturing Cost $
A. Direct Production Costs
1. Raw Materials
Manure 330,000
Hydrogen 1,557,100
2. Operating Labor 157,700
3. Direct supervisory and electrical labor 23,700
4. Utilities 412,800
5. Maintenance and repairs 347,300
6. Operating supplies 69,500
7. Laboratory charges 15,800
B. Fixed Charges
1. Depreciation 694,600
2: Local Taxes 69,500
3. Insurance 69,500
C. Plant Overhead Costs 78,900
II. General Expenses
A. Administrative Costs 79,300
B. Distribution and selling costs 82,600
C. Research and Development costs 123,800
D. Financing 16,000
ANNUAL TOTAL PRODUCT COST* $4,128,100
TOTAL PRODUCT COST PER MSCF* $2.02
*Basis: 1,000 tons/day wet manure feed, 330-day/year plant operation.
25
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Table 14. CAPITAL INVESTMENT SUMMARY FOR MANURE-TO-PIPELINE
GAS PLANT (adapted from Feldman et al., 1973)
Manure rate, Ib/hr 690,000 (design base)
Dryer 3,040,000
Hydrogasifier 1,326,750
Gasifier 2,273,000
Shift Converter 249,000
Gas Purification 6,562,000
Methanation 280,000
Oxygen Plant 4,812,500
Offsite Facilities 3,272,350
Contractors Overhead 1,686,350
plus profit
Interest during Construction 1,175,100
Total Working Capital 521,250
Total Capital Investment $25,198,280
Table 15. OPERATING COSTS, REVENUE REQUIREMENTS, AND GAS PRICES
FOR MANURE-TO-PIPELINE GAS PLANT (adapted from Feldman et al
1975) '
Manure Rate, Ib/hr 690,000 (design base)
Manure Cost 0.0
Other Direct Materials 100,520
Direct Operating Labor 722,700
Maintenance 654,470
Supplies 98,170
Supervision 72,270
Payroll Overhead 79,500
General Overhead 775,800
Depreciation 1}253,850
Local Taxes and Insurance 740,310
Contingencies 89,510
By-product Credit 0.0
Operating Expenses $4,564,900
20-yr avg price of gas, $/10 BTU $0.41
20-yr avg price of gas, $/MSCF* $4.10
* 1 scf = 1,000 BTU
26
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The present economics of the hydrogasification of manure by the Hydrane
Process have been summarized by Halligan and Sweazy (1972). Their conclusion
was that even though 27 ft of methane could be produced from the manure
excreted from each animal daily, the very high capital and operating costs
required for a plant to accomplish the conversion would not be economically
feasible. These researchers, however, offer a process with a potential pro-
duction of approximately 2.5 pounds of anhydrous ammonia from the excreta of
each feedlot animal daily. Thus, an ammonia synthesis to anhydrous ammonia
conversion plant located near a major Texas Panhandle feeding center could
obtain sufficient quantities of manure in a 15-mile radius to supply a 1,000
ton per day ammonia plant with each day's gas production. This would nearly
equal the 1972 West Texas ammonia fertilizer consumption (Anon:, 1973).
This process, developed at Texas Tech University (Herzog, 1973; Herzog
et al., 1973; and Halligan et al., 1974), utilizes a mixture of manure, air,
steam, and small stream of carbon dioxide which is fed into a fluidized-bed
reactor to produce ammonia synthesis gas. Figure 4 is a flow diagram of the
partial oxidation of manure to produce synthesis gas.- In the initial phase
of the process development a 4.1-cm diameter fluidized bed reactor was util-
ized, Figure 5. The synthesis gas was compatible with existing ammonia plant
technology and suitable for subsequent conversion to anhydrous ammonia. A
product analysis is presented in Table 6.
The H-:N2 ratios in the product gas as collected from the reactor were
all less than 1.5:1 which are below the optimum 3:1 desired for ammonia syn-
thesis gas. However, thermally reforming the gas with steam would produce
ultimate hydrogen from the reforming of the methane and ethylene. This
reforming would also purify the gas of hydrocarbons. Synthesis gas ratios
obtained before and after reforming are shown in Table 16.
The economics of recovering ammonia synthesis gas from manure were
reported by Wideman et al., (1974). A summary of the installed costs for
the major sections of the plant is given in Table 17. The reactor section
of the plant comprises the largest portion (42%) of the investment. This
is due largely to the size and number of reactors, as well as the need for
Table 16. SYNTHESIS GAS RATIOS OF THE PRODUCT GASES
(Halligan et al., 1974)
Ultimate H2:N2
Before reforming
After reforming - based
1 2
1.5 1.0
3.1 2.1
Run Number
3 4
1.0
2.5
1.1
2.9
5
1.4
2.9
6
1.1
,2.5
on gas analysis
27
-------
00
Char
Collector
Feed
Hopper
Reactor
Furnace
Water-cooled
Condenser
Furnace
Controller
Steam
Generator
Condensate Collection
Flasks
Temperature
Recorder
Figure 4. Partial oxidation of manure - flow diagram (Halligan et al., 1974)
-------
10.2 cm
10.7cm
3.1 cm
13.0cm
9.7cm
3.8cm
Top Plate
(0.25cm thick)
Flange
(0.95 cm thick)
Dip Tube
(1.3 cm OD
Incoloy Tubing)
Thermocouples
(0.32 cm00)
Reactor
( 4.1 cm Sch. 40
Incoloy 800 Pipe)
Entrance Section
Gas Inlet Tube
{1.3 cm OD
Incoloy Tubing)
Scale: Approximately 1/2 Scale
Figure 5. Reactor details (Halligan et al., 1974)
29
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Table 17. INSTALLED COST OF MAJOR EQUIPMENT
(adapted from Wideman et al., 1974)
Operating Pressure
(psig)
30
100
340
Total Investment
$31,887,110
Reactors and feeder 4,942,500
section
Desulfurization and 8,832,730
reforming*
$22,523,940
5,405,740
5,811,178
$14,150,240
6,013,850
3,636,610
Compressors and
boilers
Operating Costs
18,048,100
4,446,120
11,293,408
3,286,190
4,482,790
2,592,580
*Does not include catalysts
firebricking. The lock hopper feeders and solids dischargers themselves com-
prise nearly 35% of the total reactor costs. There is little option in this
section of the plant from a process design standpoint, but the investment can
be-decreased if the mass flux rate can be increased above the assumed 150 lb/
ft -hr.
The most convenient way to summarize costs associated with processing
the manure is to determine a value for the product gas for break even opera-
tion. This was done for several different assumed values for the cost of
manure. This cost is primarily a transportation cost, although the manure
itself may ultimately have some value as fertilizer.
The product value was determined using a discounted cash flow type calcu-
lation. The industrial environment and assumptions used are shown in Table 18.
The resulting costs are shown in Table 19 for a 10% interest rate. As can be
seen, the minimum cost for producing the gas is $10.47 per ton of equivalent
ammonia, or 13.5$ per MSCF of ultimate synthesis gas. This minimum cost occurs
if the manure costs nothing to deliver to the plant site. As this manure cost
increases, the cost of producing the gas goes up, as can be seen in Table 19.
Halligan and Sweazy (1972) have estimated a synthesis gas value of $12.50 per
ton of equivalent ammonia.
In terms of solid wastes disposal, the investment costs of the process
is $4,625 per daily ton of manure processed, but in terms of production, the
investment becomes $10,165 per daily equivalent ton of ammonia.
30
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TABLE 18. ECONOMIC CRITERIA (adapted from Wideman et al., 1974)
Size, tons NH /day 1,000
Project life, years 20
Depreciation Schedule, year sum of digits 11
Interest rate, % year-end discount 10, 14
Income tax, % 48
Fixed capital investment (FCI), % of major equipment costs 4.1
Maintenance, % of FCI/year 4
Salvage, % of FCI 5
Supervision, % of labor 20
Labor, dollars/operating man hour 5
Payroll, % of labor + supervision 25
Plant overhead, % of labor 50
Working capital, % of FCI 5
Table 19. COST OF SYNTHESIS GAS PRODUCTION*
(adapted from Wideman et al., 1974)
(340 psig Operating Pressure)
Manure Cost**
($/ton) $0.00 $1.50 $5.00
Synthesis gas cost per ton of
equivalent ammonia ($/ton) 10.47 13.77 17.06
Cost per MSCF of synthesis
gas ultimate ($/MSCF) .135 .177 .220
* Includes 10% discounted cash flow on investment
**Delivered to plant site
31
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The results of this basic evaluation of the process utilizing the small
bench scale reactor were sufficient for the researchers to conclude, "The
SGFM project has been shown to be technically, as well as economically, at-
tractive for additional research. For this reason, and the probability of
future curtailment of natural gas feedstock supplies, continued development
of the process is advisable" (Wideman et al0, 1974).
Walawender et al. (1973a) described the ammonia synthesis gas recovery
process in detail with material and energy balance equations utilized in
specifying the major items of equipment. Walawender et al. (1973b) also pre-
sent an economic evaluation of the process,, Their evaluation was based on
a design capacity of 1,100 tons of wet manure per day. The gaseous product
amounts to some eight million scf per day. No credit was assumed for the
char by-products of the process.
The estimated capital investment for the synthesis gas process is pre-
sented in Table 20. Total product cost estimates for the synthesis gas pro-
cess are presented in Table 21.
Table 20. ESTIMATED CAPITAL INVESTMENT FOR SNYTHESIS GAS PROCESS
(Walawender et al., 1973b)
Item Cost
A. Direct Costs $
1. Purchased Equipment (delivered) 629,700
2. Equipment Installation 220,400
3. Instrumentation and Controls (installed) 63,000
4. Piping (installed) 157,400
5. Electrical (installed) 56,700
6. Buildings 125,900
7. Yard Improvements 50,400
8. Service Facilities (installed) 251,900
9. Land 37,800
TOTAL DIRECT PLANT COST 1,593,200
B. Indirect Costs
1. Engineering and Supervision 207,800
2. Construction Expenses 188,900
3. Contractor's Fee 125,900
4. Contingency 220,400
FIXED CAPITAL INVESTMENT 2,336,200
C. Working Capital 350,400
TOTAL CAPITAL INVESTMENT $2,686,600
32
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Table 21. TOTAL PRODUCT COST ESTIMATED FOR SYNTHESIS GAS PROCESS
(Walawender et al., 1973b)
Item Cost
I. Manufacturing Cost $
A. Direct Production Costs
1. Raw Materials
Manure 360,000
2. Operating Labor 118,300
3. Direct Supervisory and Clerical Labor 17,800
4. Utilities 121,300
5. Maintenance and Repairs 116,800
6. Operating Supplies 23,400
7. Laboratory Charges 11,800
B. Fixed Charges
1. Depreciation 233,600
2. Local Taxes 23,400
3. Insurance 23,400
C. Plant Overhead Costs 59,200
II. General Expenses
A. Administrative Costs 37,900
B. Distribution and Selling Costs 24,300
C. Research and Development Costs 36,400
D. Financing 5,400
ANNUAL TOTAL PRODUCT COST* $1,212,900
TOTAL PRODUCT COST PER MSCF $0.458
* Basis: 1,090 tons/day wet manure feed, 330-day/year plant operation.
Processing costs amount to $3.37 per ton of wet manure. Assuming that
the gas product can be sold for $0.25/MSCF (the 1975 well-head price for
natural gas has surpassed this amount), the processing is reduced to $1.53
per ton of wet manure. The breakeven sales price for the gas is $0.458/MSCF.
The current breakeven price has increased by some undetermined factor due
to recent widespread inflationary, economic trends. Thus, present increases
in well-head gas prices are offset by increased equipment, construction,
and labor costs.
33
-------
The above processing costs can be reduced through the utilization of
the char to produce additional gas or used to reduce the quantity of purchased
utilities. Optimization of the process should also contribute to cost reduc-
tions. Presently anhydrous ammonia is generated from methane. Natural gas
reserves, the primary source of methane, have reached a critical level. In
view of this, the economics can be expected to become Very favorable in the
near future.
Another process design to produce ammonia synthesis gas from manure was
developed at Texas Tech University (Natour et al., 1975). A small scale air-
fired cyclonic burner was constructed and operated to partially oxidize pul-
verized cattle manure without external heat or added fuel. The effect of
increased reaction temperature, which varied from 1,110° F to 1,480° F,
showed that if sufficient heat transfer between entering and exiting streams
is achieved, and the product gas shifted and reformed, the projected ultimate
hydrogen yield will range from 7.2 to 12.8 scf/pound of ash-free dry manure.
Figure 6 is a flow diagram for the partial combustion of manure utilizing a
cyclonic burner. Product analysis are presented in Table 6.
The results of the preliminary studies involving the bench scale fluid-
ized bed reactor and the cyclonic burner to produce synthesis gas from cattle
manure were used to design a "mini-pilot" plant at Texas Tech University,
Figure 7 (Huffman, Halligan, and Peterson 1978). The plant, which is currently
being evaluated, was designed to optimize the synthesis gas from manure
production process. The reactor configuration was altered by placing an
expanded pre-heating chamber at the top such that manure being fed into the
reactor from the top would be pre-heated by heat radiated from the lower
fluidized bed portion of the reactor. Thus, in concept heat that would be
otherwise passed off with product gases would be utilized to lower the total
energy requirements of the system.
The composition of the product gases as a result of this design configura-
tion were unanticipated. The pre-heating chamber not only effectively raised
the temperature of the incoming feedstock but at the same time provided a
cooling chamber for the product gases which quenched the thermal transfor-
mation of the ethylene into methane. The resulting product gas, Table 6,
characteristically contains commercially significant amounts of ethylene
(Huffman, Halligan, and Peterson 1978).
The production of ethylene improves the economic feasibility of the
process. Table 22 is a preliminary evaluation of the economics of the syn-
thesis gas production process with consideration for the recovery of ethylene.
A combination of synthesis gas and ethylene production is the gasifi-
cation process most likely to provide an attractive profit margin while
reducing the animal wastes problem. Process economics could become even more
attractive after additional optimization at the demonstration plant level.
Many other solid wastes, such as cotton gin trash, grain cropping wastes,
municipal refuse, peanut hulls, etc., are being evaluated in the "mini-pilot"
model. Favorable data from these evaluations could result in the construc-
tion of plants near large metropolitan and farm centers. These locations
would provide manure disposal access for animal production facilities which
34
-------
Feed
Air
Air
Feeder
Air
•DX—-*
Propane
^Cyclonic Burner
, Heot
Exchanger
Solids Collectors
-fi—
To Vent
W.T.M.
Cooling Woter
Figure 6. Flow diagram for the partial combustion of manure utilizing a cyclonic
burner (adapted from Natour et al., 1975)
-------
Blower
Solids
Holder
Star Feeder
Sight Glass
Solids
Gas
Seperotor
Power Supply
Tor
Removal
Pressure
Control
Valve
Turbine
Meter
i
Condensote
Removal
VJ=3-»-
Primory
Solids
Collection
Ram
Figure 7. Syn-Gas-II flow schematic (Huffman, Halligan, and Peterson, 1978)
36
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Table 22. PRELIMINARY ETHYLENE PRODUCTION FROM MANURE ECONOMICS
(Huffman and Halliganjt
Item Cost
I. Reactor and Feed Section Costs* $ 6,000,000
II. Gas Recovery 22,000,000
A. Site Development
B. Working Capital
C. Engineering
D. Buildings
E. Fire Brick Design on Reactor
F. Downtime Contingencies
G. Process Water Treatment
TOTAL INVESTMENT TO BUILD PLANT IN 75 DOLLARS $28,000,000
III. Operating Costs**
A. 10-year 10% interest
B. Manure cost of 1.50/T
C. Labor and Supervision
D. Plant Overhead
E. Taxes, Utilities
TOTAL OPERATING COSTS $ 7,000,000
Annual Value of Ethylene*** $ 2,750,000
Annual return on $28,000,000 investment, (%)*** 9.47
T Personal Communication with W. J. Huffman and J. E. Halligan
Texas Tech University
2
* Reactor costs based on capacity of 150# manure/hr/ft .
** No char energy allowance or pollution control incentives.
*** Value of product and annual return on investment based on:
1. Number of cattle = 400,000 head one time capacity.
2. Tons of ash free manure = 1,200/day.
3. Total product gas yield = 48 scf/ton manure.
4. Pounds of ethylene per year = 74,100,000.
5. Pounds ethylene per pound of dry ash free manure = 0.094.
6. Ethylene yield is based on 20 scf of product gas/pound of dry
ash free manure at 6% ethylene in product gas.
7. Value of ethylene = $0.12/lb.
8. Taxes = 50% of product value.
37
-------
are much smaller than the large concentrations of animals now required to
exceed the economic break points.
CHAR AND CARBON RECOVERY
The basic products of most pyrolysis processes are tars, gases, aqueous
liquids, chars, and ash. The chars and ash are usually combined in the raw
product form. The ratio of tars to ash is usually a function of the amount
of soil mixed with the raw manure feedstock. Manures from soil or "dirt"
lots usually are very high in soil and subsequently ash content due to the
mixing actions of the trampling of manure and soil by the cattle or the
grazing of the cattle at available manure soil interfaces. Concrete based
lots may even have relatively high soil or ash content in manure generated by
animals which are fed rations which are contaminated by wind blown dust at or
before harvest.
Many researchers have suggested that the char could be used to supple-
ment heat energy used to maintain pyrolysis <, Others advocate the recycle of
the char back through the process to recover additional tars or gaseous
fractions. In both instances there is a certain percentage of residual ash
containing a concentrated form of salt equal to that quantity which was in
the original feedstock. Salt buildup in the wastes is one of the major
problems of the original concept of land disposal of animal wastes. Salts
are not changed or reduced in these reactions; therefore, there is a tendency
to concentrate salts per unit of volume in the reduced total volume of final
wastes which must ultimately be disposed. Thus, by necessity one will need
approximately the same acreage to dispose of these chars as was needed to
dispose of the original volume of manure. Landfills on dedicated sites are
conceivable as the volume of the char is considerably less than the volume of
manure throughout, so less land would be needed for this type of disposal.
However, problems concerning groundwater contamination could arise as a
result of landfilling chars in some geographical areas.
An alternative to land disposal and/or landfill of the char could be to
consume it in the manufacture of some product. Characteristically product(s)
should be so selected that a large amount of char could be used in their
manufactures with some financial return on the investment.
Char called TCD (treated cow dung) has been evaluated for use as a lamp
black substitue in ink, rubber, and paint; as a filler and carbon source in
charcoal briquettes; as a filler in hot pressed ceramic tiles; and as a
foaming agent in the fabrication of lightweight foamed glass (Mackenzie, 1976)
(Anon., 1975). As a lamp black substitute, the char should be free of ash and
corresponding grit. The chars tested were only marginally acceptable for ink
filler and pigments; however, rubber samples made from char lamp black sub-
stitutes tested satisfactorily. Charcoal briquettes made from the char had
burning characteristics comparable to compressed wood chip charcoal presently
on the market.
Chars with higher ash content were satisfactory as fillers.in paint and
ceramic tile, while the most promising use investigated in this study was the
manufacture of glass foam. This process utilizes two solid waste materials,
38
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scrap glass and char. TCD milled to a minus two hundred mesh particle size
is mixed with powdered scrap glass. This mixture is fired in a mold to a
temperature at which the glass softens. At these temperatures, the carbon in
the TCD carbonizes to CCL and creates small pores in the softened glass.
These small pores are trapped upon cooling and a foam like cellular structure
results. The light weight glass foam can be fabricated in a wide range of
sizes, shapes, densities, and appearances. This material has excellent
thermal, sound, and electrical insulative properties and is nonflammable,
light, strong, chemically resistant and durable (Mackenzie, 1974; Mackenzie,
1975). Fabricated of TCD-scrap glass foam insulation materials are estimated
to be competitive with commercially available foam glass products which are
fabricated from new glass and specially prepared chemical foaming agents.
Mackenzie (1976) also suggests that (1) tars condensed from the production
of TCD potentially are useable as a crude oil source, (2) the aqueous liquids
produced have a potential fertilizer value as they are very high in nitrogen,
and (3) gases produced could be used to supplement process heat requirements.
The characteristics of the char and other products of the UCLA process which
are being evaluated by Mackenzie are presented in Table 6.
An evaluation of the chemical and physical properties and potential uses
of chars produced by the Texas Tech synthesis gas process was presented by
Kara et al. (1975). The potential uses which Kara evaluated were using char
and ash as a primary fuel, a potassium fertilizer and a lime soil condition-
er, an adsorption media to remove synthetic color from water, a coagulant
aid, and an admixture in cement, concrete, or lime. The results of this
characterization and evaluation showed that potassium, sodium, calcium,
magnesium, phosphorus, silicon, chloride, and sulfate are the major consti-
tuents of the ash fraction. The specific gravity of this ash varied from
2.02 and 2.46 and the fusion temperatures ranged from 1,099° C to 1,288° C.
The water soluble content varied from 32% to 51% with potassium, sodium,
chloride, and sulfate being the major soluble constituents of the ash. There
was little variability in the physical and chemical characteristics of the
ash from two different feedlots. The char has a low heating value, is dif-
ficult to ignite, and produces a large quantity of refractory ash; thus, the
prospects of using char as a primary fuel are not encouraging. However, its
use as a supplemental fuel may be feasible.
Manure ash contains from 15.06% to 24.10% potassium, expressed as potash
(K^O), and from 6.02% to 6 ,,82% calcium, expressed as lime (CaO), indicating a
potential usefulness as a potassium fertilizer and a lime soil conditioner.
However, the high sodium content may render such applications infeasible.
The adsorption ability of char in removing synthetic color from water was
close to that of activated carbon. Ash was also found to have appreciable
color adsorbing capability.
The use of ash with aluminum sulfate in coagulation tests resulted in a
slight turbidity decrease relative to aluminum sulfate alone. The reduction
was not great enough, however, to warrant the use of ash as a coagulant aid.
The composition of manure ash and its high percentage of soluble components
indicate that its use as an admixture in cement, concrete, or lime may not be
feasible. The groundwater pollution potentials of char and ash are not
great; thus, they would seem quite conducive to disposal in a carefully
designed landfill.
39
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PORTABLE REACTORS
The discussion of thermochemical processes has been based on large fixed
site reactors. Knight (1974) proposes an alternative to a fixed facility
site. Figure 8 is an artists-concept of Knights proposed portable pyrolysis
unit. The truck mounted reactor would periodically make visits to feeders on
an established route converting their manure wastes into the various products
of pyrolysis for a minimal fee or payment depending upon the final economic
analysis in a working situation.
40
-------
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Legend
Loader
Waste receiving bin
Chopper
Dryer
Waste converter
Cyclone separator
Condenser
Char-oil mixer
Char storage
Oil storage
Draft fan
Gas engine
Generator
Gas burner
Figure 8. Portable waste conversion pyrolysis unit (adapted from Knight et al., 1974)
-------
SECTION 6
OTHER BY-PRODUCT RECOVERY SYSTEMS
COMPOST FUEL
After composting, manure is a clean, sulphur-free fuel resembling lignite
(Anon., 1974d and 1974e). According to one midwest inventor, the wastes from
a 60,000 head feedlot when composted into fuel could produce the energy value
of 109,440 barrels of oil (Anon., 1974d). The selling value of this fuel
would be $1,094,400 with oil at $10 per barrel. Thus, for each 1,000 head of
cattle, the compost-fuel derived from lot wastes is estimated at $18,240
(Anon., 1974e). Composting manure reduces moisture content, odors, pollution
potentials, and health hazards. The heat required by this process is pro-
duced by bacterial action. An average of from 15 to 28 BTUs are created for
each BTU expended in processing. Thus, fuel is produced for lower costs than
oil, propane, natural gas, or coal (Anon., 1974e).
HARDBOARD
Sloneker et al. (1972) report on a process which they have developed to
produce a hardboard from a fraction of manure. Animal wastes are fraction-
ated into (1) solubles, (2) solids suitable for refeeding, and (3) residue.
The residue is dispersed with hypochlorite solution. Fibrous material is
recovered by filtration and vacuum dried. Then the fibers are sprayed with
an aqueous resin, and mixed in the open until a moisture content of 11% and a
resin content of 6.36% is reached. This mixture is then placed into a mold,
heated to 250°-350° C, and pressed to 1,000 psi for 10 minutes to produce a
hardboard.
The hardboard is not as water resistent and does not have the board
strength of other commercial hardboards. The researchers concluded that the
product needs additional work to improve it, but that it is still promising.
42
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SECTION 7
SUMMARY
Several byproduct-recovery-from-animal-wastes schemes have been investi-
gated. None of the systems have been developed to a point where they could
be reduced to practice on a commercial scale. Many of the processes, however,
appear to be very promising and could, with additional optimization, provide
substantial monetary returns on initial investments. Many processes are
viable alternatives to the present land disposal of animal wastes and dis-
posal/treatment processes now being used for other highly organic solid
wastes.
One of the schemes which is receiving a lot of public attention in view
of the present energy "crunch" is anaerobic fermentation to produce methane.
This process, which is technically quite feasible, has been known for several
years and never reduced to commercial practice. Highly organic nitrogen-rich
livestock wastes must be diluted with water to prevent toxicity to the mi-
crobes which produce the gas. This dilution can double and triple,the volume
of wastes which must be handled after digestion. Other factors which are
deterrents to the economic feasibility of the process are:
1. Financial returns from the gas and/or electricity generated are not
ample to justify the capital equipment and construction costs.
2. Detention time of wastes in the generator ranges from 10-20 days.
The longer detention times which accumulate greater amounts of
manure not only increase methane production per unit of wastes but
also increase reactor size and operation costs.
3. Anaerobic digestion is only a partial waste stabilization process.
Therefore, additional stabilization must follow the methane produc-
tion step or the greater diluted volume of wastes must be handled
for disposal in the same manner as the original feedstock to the
process.
4. Methane to air ratios of from 1:7 to 1:2 are highly explosive, thus,
caution should be exercised in the design and placement of various
components of a system.
5. Microorganism communities within digesters can be eliminated by
contamination with toxic substances.
6. Methane must be compressed to at least 2,100 psi to have an equiva-
lent power to volume ratio as gasoline. Thus holding tanks are
very large and heavy. Automobiles, for example, are known to
utilize 5 to 15 cubic feet per mile. The fuel tank with a capacity
for the average traveling radius would weigh several hundred pounds.
43
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Even with all of these disadvantages, the process could have some
application for supplying a continuous power need or for introduction directly
into a methane transport pipeline.
The production of pipeline gases and oil like hydrocarbons from the
highly organic animal manures is by no means a proven process. Much work
still remains to be done to develop and optimize an economically feasible
conversion process. The state-of-the-art could have been significantly
advanced in this area were it not for drastic funding cuts to programs within
Federal agencies which were conducting this research (Anon., 1974f). These
cutbacks are all in view of recent energy shortages with resulting need for
Federally imposed energy legislation and the findings and recommendations of
the President's Water Pollution Control Advisory Board (Anon., 1971-72),
which states:
"The board believes that recycling animal wastes back onto the
land is the best practicable approach in most situations, particu-
larly for small operations, through the use of catchment basins,
lagooning systems, and/or solid waste handling techniques. There
are also other possible uses which should be given full consider-
ation. Testimony presented to the Board indicates that promising
possibilities exist in converting animal wastes into fuels, such
as oil or gas, building materials, dry fertilizer, tires, etc.,
and in recycling back into animal feeds.
Recommendation: That the Environmental Protection Agency give
high priority to funding for research and development projects
which may develop practicable and safe alternate uses for animal
wastes."
The U.S. Bureau of Mines (Anderson, 1972) reports an estimated two
billion tons of U.S. annual production of organic wastes of which 880 million
tons are moisture and ash free organic material which could be used to pro-
duce an approximated two barrels of oil per ton. The energy requirement to
accomplish this would be equivalent to 0.75 barrel of oil, leaving a net
production of 1.25 parrels per ton of dry organic material processed. Vaughn
(1971) reports that about four-fifths of the total annual solid waste pro-
duction in the U.S. is animal manure.
The thermochemical process which appears to be the most economically
attractive is ethylene production by the Texas Tech process. The economic
outlook for all of the thermochemical processes would appear to limit the use
of such systems to locations where large amounts of manure and other organic
wastes can be readily accumulated. Thus, location of conversion facilities
near large metropolitan areas could help alleviate solid municipal and domes-
tic waste problems while affording the smaller animal producer within an
economically feasible hauling distance an opportunity to dispose of his
manure wastes.
44
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50
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
i. REPORT NO.
EPA-600/2-79-142
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
RECOVERY OF BY-PRODUCTS FROM ANIMAL WASTES-
A LITERATURE REVIEW
5. REPORT DATE
August 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
R. Douglas Kreis
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
P. 0. Box 1198
Ada, Oklahoma 74820
10. PROGRAM ELEMENT NO.
1BB770
11. CONTRACT/GRANT NO.
In-House
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency - Ada, OK
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
State-of-the-Art - Current
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The primary purpose of this report was to identify and summarize by-product-from-
animal-wastes-recovery processes from the current literature. By-product recovery
processes are distinguishable from wastes reuse and recycle processes by the formation
of a chemically or physically changed product or by-product from the wastes as produced
Most of the schemes investigated were grouped into either biological or thermo-
chemical processes. Methane production, a biological process utilizing anaerobic
fermentation of the wastes, is receiving the greatest amount of popular and scientific
attention. The economics of methane storage is the strongest deterrent to the
development of this process for widespread application.
Thermochemical processes investigated include conversion to oil and oil-like tars;
anhydrous ammonia synthesis gas and ethylene; hydrogasification; manufacture of carbon
black, carbon black substitutes, and fillers and foaming agents in foam glass con-
struction materials; and other fuels and construction products.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Agricultural Wastes
Organic Wastes
Gasification
Materials Recovery
Carbon Black
Fuels
Ethylene
Plastics
Manure
Synthetic Natural Gas
Insulation Foam
43F, 68D, 71D,
71E, 71P, 89G,
97D, 97F, 970,
99D
13. DISTRIBUTION STATEMEN1
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
59
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
51
-US GOVERNMENT PRINTING OFFICE 1979 -657-060/5366
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