demonstration of biogas production using low moisture content

DEMONSTRATION OF BIOGAS PRODUCTION USING LOW MOISTURE CONTENT
DEMONSTRATION OF BIOGAS PRODUCTION USING
LOW MOISTURE CONTENT BEEF CATTLE MANURE
FINAL REPORT
Presented to:
Western Regional Biomass Energy Program
Grant No. 55008
Contract Date: July 7, 1998 to March 31, 2000
TABLE OF CONTENTS
Abstract
Executive Summary
Introduction
Literature Review
Objectives
Scope of Work
Investigator Profiles and Responsibilities
Principal Investigator:
Dr. David Parker
Box 60998
West Texas A&M University
Canyon, TX 79015
Phone: (806) 651-5281
Fax: (806) 651-2504
E-mail: dparker@mail.wtamu.edu
Materials and Methods
Results and Discussion
Conclusions and Suggestions
for Further Activities
Appendix A - Raw Data (in Microsoft Excel
97)
Co-Investigators:
Dr. Darren Williams, West Texas A&M University
Dr. N. Andy Cole, USDA-ARS, Bushland, TX
Dr. Brent Auvermann, TAES, Amarillo, TX
Mr. J. Shiloh Posey, Graduate Student, WTAMU
May 31, 2000
This research was supported by a Western Regional Biomass Energy Program Department of Energy
award (Award No. 55008). Such support does not constitute an endorsement by the Department of
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DEMONSTRATION OF BIOGAS PRODUCTION USING LOW MOISTURE CONTENT
Energy or the Western Regional Biomass Energy Program of the views expressed herein.
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DEMONSTRATION OF BIOGAS PRODUCTION USING LOW MOISTURE CONTENT
DEMONSTRATION OF BIOGAS PRODUCTION USING
LOW MOISTURE CONTENT BEEF CATTLE MANURE
ABSTRACT
A research and demonstration project was performed to evaluate biogas production at ambient temperatures
using beef cattle manure scraped from open lot feedyards. Laboratory experiments were conducted to measure
potential biogas production rates using beef cattle manure at 21° C (70° F). Manure with an initial volatile solids
content of 32.0% produced biogas at rates of 0.0046, 0.12, 0.14, 0.13, and 0.035 liters per gram VS at wet
basis moisture contents of 50, 60, 70, 80, and 95%, respectively. A field demonstration project was conducted
to determine feasibility of collecting biogas using "landfill-type" cells. Two 91m 3 cells were excavated in native
soil, lined on the top and bottom with EPDM geomembranes, and manure at a wet basis moisture content of
60% was placed within the cells. The first cell was loaded with manure in February, 1999, and began biogas
production on August 1, 1999. Biogas production ceased around October 23, 1999. During the 12 week period,
the first cell produced 1,500 m 3 (53,000 ft 3 ) of biogas with a maximum methane concentration of 52%. The
biogas production rate in the first cell was 0.10 L/g VS, which compares favorably to the laboratory results. The
second cell was loaded with manure (initial VS= 41.9%dry weight basis) in January, 2000, and has not
produced any biogas to date. This research and demonstration project demonstrated that biogas could be
produced in landfill cells using beef cattle manure scraped from open lots. However, further work is required
before biogas production with beef cattle manure will be feasible.
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DEMONSTRATION OF BIOGAS PRODUCTION USING LOW MOISTURE CONTENT
DEMONSTRATION OF BIOGAS PRODUCTION USING
LOW MOISTURE CONTENT BEEF CATTLE MANURE
EXECUTIVE SUMMARY
Beef cattle feedlots in the Texas panhandle produce more than 6 million beef cattle annually. The manure is
deposited in open-lots, and is removed every 6 to 12 months. Traditionally, this manure has gone directly to
land application following removal from the pens. At these beef cattle feedyards, annual manure production is
about 36 billion pounds of fresh manure, equating to about 1.3 billion pounds after drying on the pen surface for
6 to 12 months. This amount of manure represents a tremendous biogas energy potential should economically
methods be developed to harvest that energy. This research and demonstration project was performed to
evaluate biogas production at ambient temperatures using beef cattle manure scraped from open lot feedyards.
Three laboratory experiments were conducted to determine potential biogas production rates. In the first two
laboratory experiments, biogas was produced in collapsible low density polyethylene (LDPE) containers. The
permeability of the containers resulted in low biogas production rates and abnormal gas concentrations. The
experimental procedures were modified for the third experiment and the biogas was collected by water
displacement in Nalgene containers kept at 21° C (70° F). Manure in the third experiment had an initial volatile
solids (VS) content of 32.0% dry weight basis. Biogas production rates were 0.0046, 0.12, 0.14, 0.13, and
0.035 liters per gram VS at wet basis moisture contents of 50, 60, 70, 80, and 95%, respectively. Biogas
production rates were steady throughout the 8 months that biogas was produced.
A field demonstration project was conducted to determine feasibility of collecting biogas using "landfill-type"
cells. Two 91m 3 (3,200 ft 3 ) cells were excavated in the native soil to a depth of 6 feet. The cells were lined on
the top and bottom with EPDM geomembranes, and manure at a wet basis moisture content of 60% was
placed within the cells. The first cell was loaded with manure (initial VS=32.0% dry weight basis) in February,
1999, and began biogas production around August 1, 1999. Biogas production ceased around October 23,
1999. During the 12 week period, the first cell produced a total of about 1,500 m 3 (53,000 ft 3 ) of biogas with a
maximum methane concentration of 52%, for a biogas production rate of 0.10 liters per gram VS. The second
cell was loaded with manure (initial VS=41.9% dry weight basis) in January, 2000, and has not produced any
biogas to date.
This research and demonstration project demonstrated that biogas could be produced in landfill cells using beef
cattle manure scraped from open lots. The biogas production appears to be highly temperature dependent, as
biogas was produced for only 7 weeks out of the year. Thus, biogas production with beef cattle manure may not
be feasible unless the cells are heated so that biogas could be produced year-round. Further studies are
warranted to continue development of an economical method for biogas production from beef cattle manure
collected in open lots.
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INTRODUCTION
DEMONSTRATION OF BIOGAS PRODUCTION USING
LOW MOISTURE CONTENT BEEF CATTLE MANURE
INTRODUCTION
About 6.3 million beef cattle are fed each year in feedyards in the Texas Panhandle area (Figure 1). In addition,
more than 3.4 million hogs are grown in the same area. There are 70 feedyards in the area with capacities
greater than 20,000 cattle, with several lots as large as 50,000 to 85,000 head. About 36 billion pounds or 16
million metric tons of manure (wet basis) are produced at beef cattle feedyards alone (Parker et al., 1997). The
potential biogas energy production from this vast amount of manure would be immense if an economical
method of production was found.
Figure 1. Cattle Feeding Area Covering Twenty-Six Counties in Texas, Two
Counties in New Mexico, Three Counties in Oklahoma, and Three Counties in Kansas
Manure production and management at beef cattle feedlots differs from most dairies and swine operations. At
beef cattle feedlots, manure that is deposited on the ground is scraped and removed every 120 to 365 days, as
opposed to swine and dairy operations that scrape or remove manure as often as every day. As a result, beef
cattle manure contains more foreign matter (soil, rocks) and less volatile solids than swine or dairy manure.
These solids cause problems in conventional biogas digesters. A typical open-lot beef cattle feedyard is shown
in Figure 2.
Beef cattle manure has a much lower moisture content than dairy and swine waste because water is not added
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INTRODUCTION
during the waste management process. Because water is a precious commodity in the Texas High Plains, the
addition of large amounts of water to beef cattle manure for digestion is impractical.
Figure 2. A typical open-lot beef cattle feedyard in the Texas panhandle.
On August 4, 1997, a biomass workshop entitled "Livestock Waste Streams: Energy and Environment" was
held in Amarillo, Texas. The workshop was sponsored by the Western Regional Biomass Energy Program,
Texas Renewable Energy Industries Association, and West Texas A&M University’s Alternative Energy
Institute. The focus on the workshop was on producing energy from livestock manure. One of the research and
demonstration opportunities identified by participants at the workshop was to produce biogas from manure in a
landfill cell type arrangement. The demonstration project presented in this report was one of the ideas that
resulted from discussions among a group of experts involved in that workshop.
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LITERATURE REVIEW
DEMONSTRATION OF BIOGAS PRODUCTION USING
LOW MOISTURE CONTENT BEEF CATTLE MANURE
LITERATURE REVIEW
The development of alternative energy and fuel sources began well before 1970, but the interest in producing
biogas from manures peaked during that time because of rising prices in the fossil fuel market. Due to high cost,
high maintenance, and design problems, interest in biogas production at beef cattle feedyards declined. Recent
interest has surfaced in areas that deal with more than just the conservation of fossil fuels. These areas include
controlling odors and groundwater contamination.
Biogas is composed almost exclusively of methane and carbon dioxide with traces of H2 S, N 2 , H 2 and CO. The
energy value of biogas is typically 400-700 BTU/ft 3 as compared to 1,000 BTU/ft 3 for natural gas. The
breakdown of cattle manure in biogas is accomplished by three types of bacteria, 1) hydrolytic, 2) transitional,
and 3) methanogenic. Hydrolytic bacteria are utilized in the first steps of production by reducing large
macromolecules (proteins, fats, carbohydrates) into much smaller molecules such as amino acids, sugars,
acids, and alcohols. Transitional bacteria further reduce these molecules into acetic acid, H 2 and CO 2 . The final
step of breakdown is accomplished by methanogenic bacteria, which reduce the molecules into methane (CH 4 )
and carbon dioxide (CO 2 ) (Engler et al., 1995). Hansen et al. (1998) states that acetate-utilizing methanogens
are responsible for 70% of methane produced in a biogas reactor. Biogas production is also a temperaturedependent
process (Misra et al., 1992). The process takes place in either psychrophilic (

OBJECTIVES
OBJECTIVES
The objectives of this research and demonstration project were to 1) determine how moisture content affects
biogas production rates from beef cattle manure collected from open lots, and 2) evaluate the feasibility of
producing biogas using beef cattle manure in a low cost, low maintenance landfill-type cell.
SCOPE OF WORK
The scope of work, as outlined in the WRBEP Contract No. 55008 dated 7/1/98, consisted of the nine tasks
outlined below:
Task 1 Laboratory Closed-Cell Biogas Production Experiments
Task 2 Biogas and Product Evaluation for the Laboratory Closed-Cell Biogas
Experiments
Task 3 Construction of Anaerobic Landfill-Cell Digesters
Task 4 Add Manure to Cell One and Seal
Task 5 Monitor Biogas Production for Cell One
Task 6 Add Manure to Cell Two and Seal
Task 7 Monitor Biogas Production for Cells One and Two
Task 8 Evaluate the Data for Biogas Production for Cells One and Two
Task 9 Prepare Final Reports
INVESTIGATOR PROFILES AND RESPONSIBILITIES
This project was completed as a group effort of several scientists and one graduate student. Profiles of the
investigators and roles played by each individual are presented below.
Dr. David Parker is an agricultural engineer and assistant professor at West Texas A&M University in Canyon,
Texas. Dr. Parker has a 75% research, 25% teaching appointment and devotes his research time to animal
waste research. He also teaches graduate courses in agricultural waste management and environmental
statistics. Dr. Parker was responsible for overall management of this project, and for preparation of quarterly
and final reports. In addition, Dr. Parker was the thesis advisor for the graduate student working on the project.
Dr. Darren Williams is an assistant professor of chemistry at West Texas A&M University specializing in
instrumental analysis. Dr. Darren Williams was responsible for the analysis of the biogas samples, and served
on the graduate committee for the graduate student working on the project.
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OBJECTIVES
Dr. Brent Auvermann is an agricultural engineer and assistant professor employed by Texas A&M University in
Amarillo, Texas. Dr. Auvermann has a 35% research and 65% extension appointment. His duties include
performing research and technology transfer related to livestock manure management and protection of air and
water quality. Dr. Auvermann provided assistance and guidance throughout the project, assisted with data
evaluation and interpretation, and served on the graduate committee for the graduate student working on the
project.
Dr. Andy Cole is an animal scientist working at the USDA-ARS Conservation and Produciton Research
Laboratory in Bushland, Texas. Dr. Cole has a 100% research appointment in the area of animal waste
management. Dr. Cole provided assistance and guidance throughout the project, assisted with data evaluation
and interpretation, and served on the graduate committee for the graduate student working on the project.
Mr. J. Shiloh Posey is a M.S. graduate student in Biology at West Texas A&M University. Mr. Posey is originally
from Plainview, TX, and was responsible for supervising the construction of the biogas cells, daily monitoring of
the experiments and demonstration project, and preparation of a thesis on the project.
MATERIALS AND METHODS
This project consisted of three laboratory experiments and a field demonstration project. The laboratory
experiments were conducted in the Environmental Agriculture Lab at West Texas A&M University’s Kilgore
Research Center. The field demonstration project was conducted at the WTAMU Research Feedlot located 6
miles east of Canyon, TX.
Laboratory Experiment No.1
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OBJECTIVES
Figure 3. Low density polyethylene collapsible containers used in experiments 1 and 2.
Manure (120 g total, 50 g VS) was placed into 4-L low density polyethylene (LDPE) collapsible containers
(Figure 3) and water was added to obtain seven moisture contents of 12.9, 20, 30, 40, 50, 75% (wet weight
basis) with five replications for each moisture content. The manure as received from the commercial feedyard
had an initial moisture content of 12.9% (dry weight basis) and the initial VS content was 48.0% (dry weight
basis). Moisture content was determined by oven drying at 100 o C, and volatile solids (VS) was determined
using a muffle furnace at 500 o C (ASAE, 1999). The containers were filled with CO 2 , flattened and sealed to
remove oxygen. The containers were maintained at 21° C (70° F) throughout the experiment to simulate
psychrophilic temperature conditions. Biogas production was measured by immersing the containers in water
and calculating biogas volumes by displacement.
Laboratory Experiment No. 2
The second experiment was similar to the first, except that samples were kept at 35° C (95° F) to simulate
thermophilic temperature conditions. The treatments consisted of six moisture contents (35, 50, 57.5, 65, 72.5,
and 80% by weight), also with five replications for each. These samples were kept in a 1.3 m x 1.3 m x 0.67 m
deep plywood box which was equipped with a NuTone wall heater (model 9376N) and thermostat. After the
samples reached a stabilization point (70 days for Experiment 1 and 45 days for Experiment 2), they were
analyzed for CH 4 , CO 2 , N 2 , and other gases using a Hewlett Packard GCD 1800 GC/MS. Hydrogen sulfide was
analyzed using a Jerome 631-X (Arizona Instrument Corp., Phoenix, AZ) hydrogen sulfide meter.
Laboratory Experiment No. 3
Manure (VS=32.0%) at moisture contents of 50, 60, 70, 80, and 95% (wet weight basis) wase placed into 250
ml Erlenmeyer flasks equipped with rubber stoppers and plastic hoses (1/4" O.D. polyurethane-Cole Parmer
Instrument Company). Three replications of each were used. The 1000 ml Nalgene containers were filled with
water and inverted into containers filled to half volume with water. Ahose was inserted into each container, for a
total of fifteen samples. The total volume for each container was recorded over time. As each container filled
with gas, it was sealed, removed, and replaced by another Nalgene container. A schematic of the laboratory
apparatus used in Experiment 3 is shown in Figure 4.
Figure 4. Schematic of laboratory apparatus used in experiment 3.
Field Demonstration Project
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OBJECTIVES
The field phase of the experiment was conducted at West Texas A&M University’s Research Feedlot. Two
below ground "landfill" cells were constructed in Fall, 1998. The excavation was completed by Earthworks, Inc.
on September 23-25, 1998. The lower liner was installed in the two landfill-cell digesters on October 8-9, 1998.
Each cell measured 11 m x 11 m (34 ft x 34 ft) at ground level and was 2 m (6 ft) in depth with a 3 m x 3 m (10
ft x 10 ft) base. Each cell had a capacity of 91 m 3 (3,200 ft 3 ). A schematic of the landfill cells is shown in Figure
5.
Figure 5. Schematic of landfill-type biogas reacter.
Each cell was lined with an EPDM geosynthetic liner (Colorado Lining International, Parker, CO) on the bottom
and top (Figure 6). The first cell was filled with manure, saturated to 60% moisture content by weight, and
capped on February 12, 1999 (Figure 7). Initial volatile solids content of manure in the first cell was 32.0%. The
second cell was filled (60% moisture content by weight, initial VS=41.9%), and capped on January 5, 2000. A
gas collection apparatus was constructed of PVC pipe to collect gas samples at the top of each cell. Each cell
was equipped with a data logger (Starlogger Model 6004) and thermisters to monitor manure temperatures at
0.7 and 1.3 m above the bottom of each cell.
Each cell was capped by placing a single piece of EPDM geomembrane over the top of each cell and the
perimeter of the liner was buried. The gas was allowed to collect for several days, thus inflating the upper liner
into a dome. The volume of the dome was measured with surveying instruments.
To collect the biogas from the cells, a large plastic bag was attached to the exit port and was periodically tested
for methane content using a GT Land Surveyor portable methane analyzer (Gastech, Newark, CA).
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OBJECTIVES
Figure 6. Installing the EPDM geomembrane on the bottoms of the cells.
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OBJECTIVES
Figure 7. Loading manure into cell no. 1 using a front-end loader.
Statistical Analyses
Mean biogas production rates (L/g VS) were compared using LSD comparisons at a significant level of 0.05.
Statistical analyses were performed using the SPSS Version 10 software package.
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Results and Discussion
RESULTS AND DISCUSSION
Experiments 1 and 2
The gas volumes for Experiments 1 are plotted in Figures 8a – 8g. At 21° C, gas production was negligible at
moisture contents of 50% or less. The average biogas production rate at 75% moisture content was 0.067 L/g
VS (Table 1). At 35° C, average gas production was 0.0, 0.0041, 0.0061, 0.012, 0.018, and 0.025 L/g VS for
moisture contents of 35, 50, 57.5, 65, 72.5, and 80%, respectively (Table 2).
The average concentrations of N 2 , CO 2 , H 2 O, and CH 4 in the biogas produced in Experiment 1 are
summarized in Table 1. For Experiment 2, none of the average methane concentrations were above 5%, and
only 6 of the containers were above 2% methane content (Figures 9a-9f). In Experiment 1 there was a greater
percentage of CH 4 in the containers than in Experiment 2. All containers showed high concentrations of N 2 ,
which is not typical for biogas. Because these results were abnormal for biogas generation, the LDPE
containers were investigated to determine the cause of the atypical results.
The following gas permeabilities have been reported for LDPE (Nalgene, 1999):
MATERIAL
Water
PERMEABILITY
1.0-1.5g.mil/100in 2 /day
Nitrogen
180 cc mil/100 in 2 /day
Oxygen
500 cc mil/100in 2 /day
Carbon Dioxide
2700 cc mil/100in 2 /day
No permeability values were found for methane. However, three containers were filled with CO 2 , CH 4 , and air
and monitored for about two weeks. The container of CO 2 shrank to approximately half of the original volume,
the container of air did not change volume appreciably, and the container of CH 4 shrank 5-10%. This quick test
suggests that CO 2 produced in the biogas might leave the container more rapidly than the N 2 or O 2 could enter
the container. Because there was a several month time span between the completion of the experiment and the
time of analysis of the gas concentrations, it was reasoned that diffusion through the LDPE affected the original
biogas concentrations. Because significant O 2 probably entered the containers during the experiment, the
biogas production rates are questionable. For these reasons, a third experiment was performed using 1,000 ml
Nalgene containers that were less permeable to gas diffusion.
Experiment 3
The results of Experiment 3 are plotted in Figures 10a-10e.. As each container filled with gas, it was removed,
and sealed with a screw-on cap. Some of the samples were not analyzed immediately, and the results showed
increased N 2 content and very little or no CH 4 content (Table 3). These results appear to be the result of
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Results and Discussion
diffusion through the threads used to seal the cap onto the container. Samples analyzed immediately after
removal from the water had the highest methane contents.
Total biogas volumes for Experiment 3 were variable within the same moisture content (Figures 10a-10e and
Table 3). In an experiment comparing biogas production between dry and fresh dairy manure, Chen et al.
(1988) found that varying levels of methane were produced because of microbial variations. This is supported
by Hashimoto et al. (1981) who stated that the degree of contamination by inorganics also affect ultimate
methane yields (B 0 ). The biogas production volumes for Experiments 1 and 2 are significantly lower than
previously published values for beef cattle manure (Safley et al., 1992). Safley states that B 0 should be
approximately 0.33 m 3 /kg VS. As expected, production volumes increased as moisture content increased, with
minimal production below 40% moisture content for both Experiment 1 and Experiment 2. As shown in Table 1,
there were no statistically significant differences in mean biogas production rates among the first five moisture
contents, but mean biogas production rates were significantly higher for the two highest moisture contents for
Experiment 1.
Field Demonstration Project
The first cell began biogas production on August 1, 1999, and ceased quickly on October 23, 1999. During the
12 week period, the first cell produced a total of about 1,500 m 3 (53,000 ft 3 ) of biogas with a maximum
methane concentration of 52%. This was considerably less than was produced in the laboratory experiment 3,
thus we believe that all of the volatile solids have not been expended, and biogas production should occur
again during the summer 2000 as soon as the temperature is warm enough.
Biogas production volumes and methane concentrations are shown in Table 4 and plotted in Figure 11. A
photograph of the biogas cell when it was full of biogas is shown in Figure 12.
Shown in Figure 13 is the temperature of the manure within cell no. 1 since it was loaded in January, 1999.
Initially the manure temperature was about 25° C (77° F), but temperatures dropped rapidly during the first
month as the manure became anaerobic. Temperatures began rising during the summer months, a result of
warmer ambient temperatures, and peaked around the first of August at 22.4° C (72° F). The manure
temperature dropped below 15° C (59° F) in the middle of October and has remained below 15° C until the
present (May, 2000). The pH of the manure in cell 1 was tested immediately after cessation of biogas
production. The pH of the three samples was 7.26, 6.98, and 7.00.
The total volatile solids in cell 1 was 1.55 x 10 7 g. The total volume of biogas produced in cell 1 was 1.51x 10 6 L
for the 12 weeks of production, which equates to a biogas production rate of 0.10 L/g VS.
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Results and Discussion
Figure 8a. Experiment 1, Control Moisture.
Figure 8b. Experiment 1, 20% Moisture.
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Results and Discussion
Figure 8c. Experiment 1, 25% Moisture.
Figure 8d. Experiment 1, 30% Moisture.
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Results and Discussion
Figure 8e. Experiment 1, 40% Moisture.
Figure 8f. Experiment 1, 50% Moisture.
Figure 8g. Experiment 1, 75% Moisture.
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Results and Discussion
Figure 9a. Experiment 2, 35% Moisture.
Figure 9b. Experiment 2, 50% Moisture.
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Results and Discussion
Figure 9c. Experiment 2, 57.5% Moisture.
Figure 9d. Experiment 2, 65% Moisture.
Figure 9e. Experiment 2, 72.5% Moisture.
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Results and Discussion
Figure 9f. Experiment 2, 80% Moisture.
Figure 10a. Experiment 3, 50% Moisture.
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Results and Discussion
Figure 10b. Experiment 3, 60% Moisture.
Figure 10c. Experiment 3, 70% Moisture.
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Results and Discussion
Figure 10d. Experiment 3, 80% Moisture.
Figure 10e. Experiment 3, 95% Moisture.
Figure 11. Biogas production rates measured in cell no. 1.
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Results and Discussion
Figure 12. Photograph of cell no. 1 showing the full dome of biogas
produced from anaerobic digestion of beef cattle manure. The
dome holds about 71 m 3 (2,500 ft 3 ) of biogas when full.
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Results and Discussion
Figure 13. Temperature of manure in Cell No. 1.
Temperature was less than 15° C between 10/27/99 and 5/15/00.
Treatment (%
Moisture)
Table 1. Biogas production rates and other gas concentrations for
Experiment 1, conducted using LDPE containers at 21° C (70° F).
Biogas Production Rate Gas Concentrations (%)
Mean
(L/g VS)*
St. Dev.
Nitrogen
(N 2 ) %
Methane
(CH 4 ) %
Carbon Dioxide
( CO 2 ) %
Water
(H 2 O) %
Control
Moisture
20% Moisture
Content
25% Moisture
Content
30% Moisture
Content
40% Moisture
Content
50% Moisture
Content
75% Moisture
Content
1.28 E-03 a 7.155 E-04 84.5 0 13.5 2
1.28 E-03 a 7.155 E-04 86 0 12.5 2
1.28 E-03 a 7.155 E-04 79 0 18 3
9.60 E-04 a 1.431 E-03 83 .75 14.4 1.6
1.60 E-03 ab 2.263 E-03 76 6 16 2
3.52 E-03 b 7.155 E-04 68 14 16 2
3.87 E-02 c 2.629 E-03 61.5 20 15.7 2
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Results and Discussion
* Using LSD comparisons, mean biogas production rates with same letters are not significantly
different (α =0.05).
Table 2. Biogas production rates and other gas concentrations for Experiment 2,
conducted using LDPE containers at 35° C (95° F).
Treatment (%
Moisture)
Biogas Production Rate Gas Concentrations (%)
Mean (L/g
VS)*
St. Dev. Nitrogen (N 2 )
%
Methane
(CH 4 ) %
Carbon Dioxide
(CO 2 ) %
Water (H 2 O)
%
35% Moisture
Content
50% Moisture
Content
0.00 a 0..00 NA 4.5 NA NA
1.248 E-02 b 3.03 E-03 NA BD NA NA
57.5% Moisture
Content
65% Moisture
Content
1.920 E-02
bc
2.848 E-02
cd
4.80 E-03 NA BD NA NA
6.34 E-03 NA 3.14 NA NA
72.5% Moisture
Content
80% Moisture
Content
3.64 E-02 d 1.55 E-02 NA .23 NA NA
4.80 E-02 e 4.66 E-03 NA 2.97 NA NA
NA=not analyzed BD=below detection limit
* Using LSD comparisons, mean biogas production rates with same letters are not significantly
different (α =0.05).
Table 3. Biogas Production Rate and other gas concentrations for Experiment 3.
Treatment (%
Moisture)
Biogas Production Rate Mean Gas Concentrations (%)
Mean (L/g
VS) *
St. Dev. Nitrogen (N 2 )
%
Methane
(CH 4 ) %
Carbon Dioxide
(CO 2 ) %
Water (H 2 O)
%
50% Moisture
Content
60% Moisture
Content
70% Moisture
Content
80% Moisture
Content
4.57 E-03 a 3.98 E-03 67.85 6.57 23.6 2.47
1.15 E-01 b 3.97 E-02 7.68 58.93 28.45 4.96
1.45 E-01 b 3.19 E-02 10.7 60.16 27.02 2.12
1.33 E-01 b 8.83 E-03 11.67 52.48 32.85 3.0
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Results and Discussion
95% Moisture
Content
3.47 E-02 a 3.03 E-02 38.4 52.8 7.20 1.56
* Using LSD comparisons, mean biogas production rates with same letters are not significantly
different (α =0.05).
Table 4 Biogas Project Gas Production Log
Wed, February 17, 1999 4:00 PM Covered manure with membrane
Tue, August 3, 1999 10:00 AM Tent full first time
Thur, August 5, 1999 3:00 PM Opened Vent 40% CH 4
Fri, August 6, 1999 1:00 PM Plugged Vent
Tue, August 10, 1999 3:00 PM Opened Vent 50% CH 4
Wed, August 11, 1999 3:30 PM Plugged Vent
Sun, August 15, 1999 8:00 AM Opened Vent 50% CH 4
Sun, August 15, 1999 3:00 PM Plugged Vent
Wed, August 18, 1999 3:00 PM Opened Vent
Mon, August 23, 1999 2:00 PM Plugged Vent
Thurs Aug 26, 1999 3:00 PM Opened Vent
Tue Aug 31, 1999 3:00 PM Plugged Vent
Fri Sept. 3, 1999 1:00 PM Opened Vent 52% CH 4
Mon Sept 20 4:00 PM Plugged Vent
Sat Sept 25 9:00 AM Opened Vent
Wed Sept 29 2:00 PM Plugged Vent
Mon Oct 4 12:00 PM Opened Vent
Wed Oct 6, 1999 2:00 PM Plugged Vent
Mon Oct. 11, 1999 Opened Vent 49% CH 4
Wed Oct 13
Plugged Vent
Tue Oct 19 3:00 PM Opened Vent 52% CH 4
Mon Oct 23 1:00 PM Plugged Vent
No biogas produced between 10/23/99 and 5/15/2000
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Results and Discussion
Back
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Conclusions
CONCLUSIONS AND SUGGESTIONS FOR FURTHER ACTIVITIES
Beef cattle feedlots in the Texas panhandle produce more than 6 million beef cattle annually, and the manure
from these feedlots represents a tremendous biogas energy potential. This project utilized laboratory and field
experiments to evaluate biogas production from beef cattle manure scraped from open lots. The field project
evaluated using landfill-type cells for producing biogas from beef cattle manure. In laboratory experiments
where low density polyethylene (LDPE) containers were used as mini digesters, we discovered that the
containers were too permeable to gases to obtain representative biogas production rates. In modified
experiments, biogas production rates reached a maximum of 0.14 liters per gram VS at a wet basis moisture
contents of 70%, which is lower than published values of about 0.3 liters per gram VS.
In the field demonstration project, biogas was produced during a 12 week period in August through October. A
total of 1,500 m 3 of biogas was produced at a rate of 0.10 liters per gram VS. While the results are promising,
only producing biogas for 3 months out of the year severely limits the application of this method at beef cattle
feedyards. A heated digester would produce biogas year-round, however, additional studies and engineering
work are warranted to see if the landfill-cell method would be economically justifiable for use at beef cattle
feedyards.
REFERENCES
Angelidaki, I. and B.K. Ahring. 1994 Anaerobic thermophilic digestion of manure at different ammonia leads:
Effect of temperature. Water Research 28: 727-731.
ASAE, 1999. Uniform terminology for rural waste management. ASAE Standard S292.5. American Society of
Agricultural Engineers, St. Joseph, MI.
Engler, Cady R. and Marshall J. McFarland. 1997. Dairy manure digestion research and demonstration project.
In Proceedings of Workshop #1, Livestock Waste Streams: Energy and Environment. pp. 64-68. Texas
Renewable Energy Industries Association:Austin, TX.
Hansen, Kaare Hvid, Irini Angelidaki and Birgitte Kiger Ahring. 1998. Anaerobic digestion of swine manures:
inhibition by ammonia. Water Research 32:5-12.
Kottwitz, D.A. and D.D. Schulte. 1982. Tumble-mix anaerobic digestion of dry beef manure. ASAE Paper
Presented at the 1982 Winter Meeting, American Society of Agricultural Engineers, St. Joseph, MI.
Misra, Upama, Sonjay Singh, Amarika Singh, and G.N. Pandey. 1992. A new temperature controlled digester
for anaerobic digestion for biogas production. Energy Conservation Management 33:983-986.
Nalgene, 1999. Physical properties of Nalgene Labware, Internet Source.
Parker, D.B., B.W. Auvermann, B.A. Stewart and C.A. Robinson. 1997. Agricultural energy consumption,
http://www.westbioenergy.org/cattle/conclusions.htm (1 of 2) [3/26/2003 8:52:58 AM]

Conclusions
biomass generation, and livestock manure value in the Southern High Plains. In Proceedings of Workshop #1,
Livestock Waste Streams: Energy and Environment. Texas Renewable Energy Industries Association:Austin,
TX.
Parker, D.B. and R.E. Smith. 1997. A roundtable discussion on energy production from livestock wastes. In
Proceedings Livestock Waste Streams: Energy and Environment. Texas Renewable Energy Industries
Association. Austin, TX. In Press.
Schulte, D.D. 1997. Swine manure digestion systems. In Proceedings of Workshop #1, Livestock Waste
Streams: Energy and Environment. pp.. 44-51. Texas Renewable Energy Industries Association:Austin, TX.
SERI. 1995. Anaerobic digestion data base: Guide for operation and data analysis. Biomass Program Office,
Solar Energy Research Institute. Golden, CO.
SPS. 1996. Cattle-feeding Capitol of the World - 1996 Fed Cattle Survey. Southwestern Public Service
Company, Amarillo, TX.
Back
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75% Moisture 50% Moisture 40% Moisture 30% Moisture 25% Moisture 20% Moisture Control Moisture
Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS
0 0.4 0 0 0 0.48 0 0 0 0.48 0 0 0 0.56 0 0 0 0.48 0 0 0 0.48 0 0 0 0.4 0 0
45 1.2 0.8 0.016 45 0.64 0.16 0.0032 45 0.48 0 0 45 0.56 0 0 45 0.56 0.08 0.0016 45 0.56 0.08 0.0016 45 0.48 0.08 0.0016
55 2.32 1.92 0.0384 55 0.64 0.16 0.0032 55 0.48 0 0 55 0.56 0 0 55 0.56 0.08 0.0016 55 0.56 0.08 0.0016 55 0.48 0.08 0.0016
70 2.4 2 0.04 70 0.64 0.16 0.0032 70 0.48 0 0 70 0.56 0 0 70 0.56 0.08 0.0016 70 0.56 0.08 0.0016 70 0.48 0.08 0.0016
0 0.4 0 0 0 0.4 0 0 0 0.56 0 0 0 0.48 0 0 0 0.48 0 0 0 0.48 0 0 0 0.4 0 0
45 1.04 0.64 0.0128 45 0.64 0.24 0.0048 45 0.56 0 0 45 0.56 0.08 0.0016 45 0.56 0.08 0.0016 45 0.56 0.08 0.0016 45 0.48 0.08 0.0016
55 1.92 1.52 0.0304 55 0.64 0.24 0.0048 55 0.56 0 0 55 0.56 0.08 0.0016 55 0.56 0.08 0.0016 55 0.56 0.08 0.0016 55 0.48 0.08 0.0016
70 2.24 1.84 0.0368 70 0.64 0.24 0.0048 70 0.56 0 0 70 0.56 0.08 0.0016 70 0.56 0.08 0.0016 70 0.56 0.08 0.0016 70 0.48 0.08 0.0016
0 0.4 0 0 0 0.48 0 0 0 0.4 0 0 0 0.56 0 0 0 0.48 0 0 0 0.48 0 0 0 0.4 0 0
45 1.04 0.64 0.0128 45 0.64 0.16 0.0032 45 0.64 0.24 0.0048 45 0.56 0 0 45 0.56 0.08 0.0016 45 0.56 0.08 0.0016 45 0.48 0.08 0.0016
55 1.84 1.44 0.0288 55 0.64 0.16 0.0032 55 0.64 0.24 0.0048 55 0.56 0 0 55 0.56 0.08 0.0016 55 0.56 0.08 0.0016 55 0.48 0.08 0.0016
70 2.16 1.76 0.0352 70 0.64 0.16 0.0032 70 0.64 0.24 0.0048 70 0.56 0 0 70 0.56 0.08 0.0016 70 0.56 0.08 0.0016 70 0.48 0.08 0.0016
0 0.4 0 0 0 0.48 0 0 0 0.56 0 0 0 0.56 0 0 0 0.48 0 0 0 0.48 0 0 0 0.4 0 0
45 1.04 0.64 0.0128 45 0.64 0.16 0.0032 45 0.56 0 0 45 0.56 0 0 45 0.56 0.08 0.0016 45 0.56 0.08 0.0016 45 0.4 0 0
55 2.08 1.68 0.0336 55 0.64 0.16 0.0032 55 0.56 0 0 55 0.56 0 0 55 0.56 0.08 0.0016 55 0.56 0.08 0.0016 55 0.4 0 0
70 2.4 2 0.04 70 0.64 0.16 0.0032 70 0.56 0 0 70 0.56 0 0 70 0.56 0.08 0.0016 70 0.56 0.08 0.0016 70 0.4 0 0
0 0.4 0 0 0 0.4 0 0 0 0.4 0 0 0 0.48 0 0 0 0.56 0 0 0 0.56 0 0 0 0.4 0 0
45 1.2 0.8 0.016 45 0.56 0.16 0.0032 45 0.56 0.16 0.0032 45 0.64 0.16 0.0032 45 0.56 0 0 45 0.56 0 0 45 0.48 0.08 0.0016
55 2 1.6 0.032 55 0.56 0.16 0.0032 55 0.56 0.16 0.0032 55 0.64 0.16 0.0032 55 0.56 0 0 55 0.56 0 0 55 0.48 0.08 0.0016
70 2.48 2.08 0.0416 70 0.56 0.16 0.0032 70 0.56 0.16 0.0032 70 0.64 0.16 0.0032 70 0.56 0 0 70 0.56 0 0 70 0.48 0.08 0.0016
Mean 0.0214 0.0026 Mean 0.0012 0.0007 Mean 0.0010 0.0010 Mean 0.0010
St. Dev. 0.0159 0.0017 St.Dev. 0.0019 0.0012 St. Dev. 0.0008 0.0008 St. Dev. 0.0008
0.006
40% Moisture
0.005
Production (L/g VS)
0.004
0.003
0.002
0.001
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
0
0 20 40 60 80
Time (days)
0.06
75% Moisture
0.006
25% Moisture
Production (L/g VS)
0.05
0.04
0.03
0.02
Rep 1
Rep 2
0.01
Rep 3
Rep 4
0
0 20
Time
40
(days)
60 80
Rep 5
Production (L/g VS)
0.006
0.005
0.004
0.003
0.002
0.001
0
30% Moisture
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/g VS)
0.005
0.004
0.003
0.002
0.001
0
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/g VS)
0.006
50% Moisture
0.005
0.004
0.003
0.002
Rep 1
Rep 2
0.001
Rep 3
0
Rep 4
0 20 40 60 80Rep 5
Time (days)
Production (L/g VS)
0.006
0.005
0.004
0.003
0.002
0.001
0
20% Moisture
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/g VS)
0.006
0.005
0.004
0.003
0.002
0.001
0
Control Moisture
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5

35% Moisture 50% Moisture 57.5% Moisture 65% Moisture 72.5% Moisture 80% Moisture
Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS Time (days) Volume (L) Vol. (t=0) (t=0)/50gVS
0 0.48 0 0 0 0.56 0 0 0 0.48 0 0 0 0.48 0 0 0 0.64 0 0 0 0.64 0 0
7 0.48 0 0 7 0.56 0 0 7 0.48 0 0 7 0.48 0 0 7 0.64 0 0 7 0.64 0 0
14 0.48 0 0 14 0.56 0 0 14 0.48 0 0 14 0.56 0.08 0.0016 14 0.72 0.08 0.0016 14 1.36 0.72 0.0144
21 0.48 0 0 21 0.56 0 0 21 0.48 0 0 21 1.04 0.56 0.0112 21 1.6 0.96 0.0192 21 2.72 2.08 0.0416
28 0.48 0 0 28 0.72 0.16 0.0032 28 0.96 0.48 0.0096 28 1.28 0.8 0.016 28 2.4 1.76 0.0352 28 2.88 2.24 0.0448
35 0.48 0 0 35 1.04 0.48 0.0096 35 1.04 0.56 0.0112 35 1.68 1.2 0.024 35 2.56 1.92 0.0384 35 3.04 2.4 0.048
44 0.48 0 0 44 1.04 0.48 0.0096 44 1.04 0.56 0.0112 44 2.08 1.6 0.032 44 2.72 2.08 0.0416 44 3.04 2.4 0.048
0 0.48 0 0 0 0.56 0 0 0 0.56 0 0 0 0.48 0 0 0 0.64 0 0 0 0.72 0 0
7 0.48 0 0 7 0.56 0 0 7 0.56 0 0 7 0.56 0.08 0.0016 7 0.64 0 0 7 0.72 0 0
14 0.48 0 0 14 0.56 0 0 14 0.56 0 0 14 0.64 0.16 0.0032 14 0.8 0.16 0.0032 14 1.6 0.88 0.0176
21 0.48 0 0 21 0.56 0 0 21 0.56 0 0 21 1.04 0.56 0.0112 21 1.2 0.56 0.0112 21 2.72 2 0.04
28 0.48 0 0 28 0.8 0.24 0.0048 28 1.28 0.72 0.0144 28 1.12 0.64 0.0128 28 1.2 0.56 0.0112 28 2.8 2.08 0.0416
35 0.48 0 0 35 1.04 0.48 0.0096 35 1.6 1.04 0.0208 35 1.36 0.88 0.0176 35 1.2 0.56 0.0112 35 2.88 2.16 0.0432
44 0.48 0 0 44 1.04 0.48 0.0096 44 1.6 1.04 0.0208 44 1.52 1.04 0.0208 44 1.2 0.56 0.0112 44 3.04 2.32 0.0464
0 0.64 0 0 0 0.52 0 0 0 0.56 0 0 0 0.48 0 0 0 0.64 0 0 0 0.72 0 0
7 0.64 0 0 7 0.52 0 0 7 0.56 0 0 7 0.48 0 0 7 0.64 0 0 7 0.8 0.08 0.0016
14 0.64 0 0 14 0.52 0 0 14 0.56 0 0 14 0.64 0.16 0.0032 14 0.8 0.16 0.0032 14 1.04 0.32 0.0064
21 0.64 0 0 21 0.52 0 0 21 0.56 0 0 21 1.04 0.56 0.0112 21 2 1.36 0.0272 21 2.56 1.84 0.0368
28 0.64 0 0 28 0.8 0.28 0.0056 28 0.88 0.32 0.0064 28 1.2 0.72 0.0144 28 2.48 1.84 0.0368 28 2.96 2.24 0.0448
35 0.64 0 0 35 1.12 0.6 0.012 35 1.44 0.88 0.0176 35 1.52 1.04 0.0208 35 2.56 1.92 0.0384 35 3.44 2.72 0.0544
44 0.64 0 0 44 1.12 0.6 0.012 44 1.76 1.2 0.024 44 1.6 1.12 0.0224 44 2.56 1.92 0.0384 44 3.52 2.8 0.056
0 0.4 0 0 0 0.48 0 0 0 0.56 0 0 0 0.4 0 0 0 0.64 0 0 0 0.64 0 0
7 0.4 0 0 7 0.48 0 0 7 0.56 0 0 7 0.48 0.08 0.0016 7 0.64 0 0 7 0.64 0 0
14 0.4 0 0 14 0.48 0 0 14 0.56 0 0 14 0.48 0.08 0.0016 14 0.64 0 0 14 0.8 0.16 0.0032
21 0.4 0 0 21 0.48 0 0 21 0.56 0 0 21 0.88 0.48 0.0096 21 1.44 0.8 0.016 21 1.92 1.28 0.0256
28 0.4 0 0 28 0.8 0.32 0.0064 28 0.8 0.24 0.0048 28 1.12 0.72 0.0144 28 2.56 1.92 0.0384 28 2.32 1.68 0.0336
35 0.4 0 0 35 1.28 0.8 0.016 35 1.6 1.04 0.0208 35 1.84 1.44 0.0288 35 3.2 2.56 0.0512 35 2.88 2.24 0.0448
44 0.4 0 0 44 1.28 0.8 0.016 44 1.6 1.04 0.0208 44 2.08 1.68 0.0336 44 3.28 2.64 0.0528 44 2.88 2.24 0.0448
0 0.48 0 0 0 0.44 0 0 0 0.56 0 0 0 0.4 0 0 0 0.56 0 0 0 0.64 0 0
7 0.48 0 0 7 0.44 0 0 7 0.56 0 0 7 0.48 0.08 0.0016 7 0.56 0 0 7 0.72 0.08 0.0016
14 0.48 0 0 14 0.44 0 0 14 0.56 0 0 14 0.48 0.08 0.0016 14 0.56 0 0 14 0.72 0.08 0.0016
21 0.48 0 0 21 0.44 0 0 21 0.56 0 0 21 0.8 0.4 0.008 21 1.44 0.88 0.0176 21 1.36 0.72 0.0144
28 0.48 0 0 28 0.64 0.2 0.004 28 0.72 0.16 0.0032 28 1.44 1.04 0.0208 28 2.4 1.84 0.0368 28 2.4 1.76 0.0352
35 0.48 0 0 35 0.96 0.52 0.0104 35 1.04 0.48 0.0096 35 1.92 1.52 0.0304 35 2.64 2.08 0.0416 35 2.88 2.24 0.0448
44 0.48 0 0 44 1.2 0.76 0.0152 44 1.52 0.96 0.0192 44 2.08 1.68 0.0336 44 2.64 2.08 0.0416 44 2.88 2.24 0.0448
Mean 0.0000 0.0041 Mean 0.0061 0.0117 Mean 0.0178 0.0251
St. Dev. 0.0000 0.0055 St. Dev. 0.0084 0.0113 St. Dev. 0.0184 0.0209
0.06
57.5% Moisture Experiment 2
0.06
35% Moisture Experiment 2
0.05
Production (L/gVS)
0.05
0.04
0.03
0.02
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/gVS)
0.04
0.03
0.02
0.01
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
0.01
0
0 20 40 60 80
Time (days)
0
0 20 40 60 80
Time (days)
0.06
65% Moisture Experiment 2
Production (L/gVS)
0.06
0.05
0.04
0.03
0.02
50% Moisture Experiment 2
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/gVS)
0.05
0.04
0.03
0.02
0.01
0
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
0.01
0
0 20 40 60 80
Time (days)

Experiment 3
50%Moisture 60% Moisture 70% Moisture 80% Moisture 95% Moisture
Time (days) Vol (t=0) (L) (t=0)/21.9gVS Time (days) Vol (t=0) (L) (t=0)/20.7gVS Time (days) Vol (t=0) (L) (t=0)/15.4gVS Time (days) Vol (t=0) (L) (t=0)/11.6gVS Time (days) Vol (t=0) (L) (t=0)/2.5gVS
0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000
46 0.0800 0.0037 46 0.0200 0.0010 46 0.0100 0.0006 46 0.0200 0.0017 46 0.1100 0.0440
57 0.1000 0.0046 57 0.0200 0.0010 57 0.0200 0.0013 57 0.0200 0.0017 57 0.1300 0.0520
66 0.1000 0.0046 66 0.0200 0.0010 66 0.1300 0.0084 66 0.0200 0.0017 66 0.1400 0.0560
80 0.1000 0.0046 80 0.0200 0.0010 80 0.4400 0.0286 80 0.0200 0.0017 80 0.1400 0.0560
92 0.1000 0.0046 92 0.0200 0.0010 92 0.9000 0.0584 92 0.0200 0.0017 92 0.1400 0.0560
104 0.1000 0.0046 104 0.0400 0.0019 104 1.1600 0.0753 104 0.0900 0.0078 104 0.1400 0.0560
113 0.1000 0.0046 113 0.0400 0.0019 113 1.2000 0.0779 113 0.1400 0.0121 113 0.1400 0.0560
125 0.1400 0.0064 125 0.0400 0.0019 125 1.3600 0.0883 125 0.1400 0.0121 125 0.1400 0.0560
134 0.1400 0.0064 134 0.1000 0.0048 134 1.5000 0.0974 134 0.1600 0.0138 134 0.1400 0.0560
139 0.1400 0.0064 139 0.1200 0.0058 139 1.5400 0.1000 139 0.3000 0.0259 139 0.1400 0.0560
143 0.1600 0.0073 143 0.1600 0.0077 143 1.6000 0.1039 143 0.4400 0.0379 143 0.1400 0.0560
155 0.1600 0.0073 155 0.2600 0.0126 155 1.6400 0.1065 155 0.5800 0.0500 155 0.1400 0.0560
161 0.1600 0.0073 161 0.3600 0.0174 161 1.6800 0.1091 161 0.6000 0.0517 161 0.1400 0.0560
182 0.1600 0.0073 182 0.4200 0.0203 182 1.9000 0.1234 182 0.7800 0.0672 182 0.1400 0.0560
196 0.1600 0.0073 196 0.7200 0.0348 196 1.9800 0.1286 196 0.8600 0.0741 196 0.1400 0.0560
206 0.1600 0.0073 206 0.8600 0.0415 206 2.1800 0.1416 206 1.0200 0.0879 206 0.1400 0.0560
218 0.1600 0.0073 218 1.0600 0.0512 218 2.3000 0.1494 218 1.1600 0.1000 218 0.1400 0.0560
232 0.1600 0.0073 232 1.2600 0.0609 232 2.4800 0.1610 232 1.3000 0.1121 232 0.1400 0.0560
246 0.1600 0.0073 246 1.6600 0.0802 246 2.7000 0.1753 246 1.5200 0.1310 246 0.1400 0.0560
0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000
46 0.0500 0.0023 46 0.0100 0.0005 46 0.0400 0.0026 46 0.0000 0.0000 46 0.0400 0.0160
57 0.0500 0.0023 57 0.0100 0.0005 57 0.0600 0.0039 57 0.0300 0.0026 57 0.0600 0.0240
66 0.0500 0.0023 66 0.0200 0.0010 66 0.0700 0.0045 66 0.2600 0.0224 66 0.0700 0.0280
80 0.0500 0.0023 80 0.1800 0.0087 80 0.1000 0.0065 80 0.5800 0.0500 80 0.1000 0.0400
92 0.0600 0.0027 92 0.5200 0.0251 92 0.1800 0.0117 92 0.7600 0.0655 92 0.1000 0.0400
104 0.0600 0.0027 104 1.0000 0.0483 104 0.3800 0.0247 104 0.7800 0.0672 104 0.1000 0.0400
113 0.0600 0.0027 113 1.0100 0.0488 113 0.5600 0.0364 113 0.8200 0.0707 113 0.1000 0.0400
125 0.1200 0.0055 125 1.2700 0.0614 125 0.8000 0.0519 125 0.9200 0.0793 125 0.1000 0.0400
134 0.1400 0.0064 134 1.3900 0.0671 134 0.8600 0.0558 134 1.0200 0.0879 134 0.1000 0.0400
139 0.1400 0.0064 139 1.4700 0.0710 139 1.1200 0.0727 139 1.0600 0.0914 139 0.1000 0.0400
143 0.1400 0.0064 143 1.5300 0.0739 143 1.1800 0.0766 143 1.0600 0.0914 143 0.1000 0.0400
155 0.1400 0.0064 155 1.5700 0.0758 155 1.1800 0.0766 155 1.1600 0.1000 155 0.1200 0.0480
161 0.1400 0.0064 161 1.6300 0.0787 161 1.2600 0.0818 161 1.2200 0.1052 161 0.1200 0.0480
182 0.1400 0.0064 182 1.9300 0.0932 182 1.5200 0.0987 182 1.3200 0.1138 182 0.1200 0.0480
196 0.1400 0.0064 196 2.7300 0.1319 196 1.5600 0.1013 196 1.3600 0.1172 196 0.1200 0.0480
206 0.1400 0.0064 206 2.9500 0.1425 206 1.6200 0.1052 206 1.3800 0.1190 206 0.1200 0.0480
218 0.1400 0.0064 218 3.1100 0.1502 218 1.8200 0.1182 218 1.4400 0.1241 218 0.1200 0.0480
232 0.1400 0.0064 232 3.1900 0.1541 232 2.0000 0.1299 232 1.5200 0.1310 232 0.1200 0.0480
246 0.1400 0.0064 246 3.2700 0.1580 246 2.2600 0.1468 246 1.6600 0.1431 246 0.1200 0.0480
0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000 0 0.0000 0.0000
46 0.0000 0.0000 46 0.0100 0.0005 46 0.0000 0.0000 46 0.0700 0.0060 46 0.0000 0.0000
57 0.0000 0.0000 57 0.0100 0.0005 57 0.2000 0.0130 57 0.3000 0.0259 57 0.0000 0.0000
66 0.0000 0.0000 66 0.0200 0.0010 66 0.1100 0.0071 66 0.5000 0.0431 66 0.0000 0.0000
80 0.0000 0.0000 80 0.0200 0.0010 80 0.1400 0.0091 80 0.7400 0.0638 80 0.0000 0.0000
92 0.0000 0.0000 92 0.0200 0.0010 92 0.4600 0.0299 92 0.8000 0.0690 92 0.0000 0.0000
104 0.0000 0.0000 104 0.0400 0.0019 104 0.6200 0.0403 104 0.8400 0.0724 104 0.0000 0.0000
113 0.0000 0.0000 113 0.0600 0.0029 113 0.6800 0.0442 113 0.8400 0.0724 113 0.0000 0.0000
125 0.0000 0.0000 125 0.1800 0.0087 125 0.8200 0.0532 125 0.9600 0.0828 125 0.0000 0.0000
134 0.0000 0.0000 134 0.2600 0.0126 134 0.8400 0.0545 134 1.0000 0.0862 134 0.0000 0.0000
139 0.0000 0.0000 139 0.3200 0.0155 139 0.8600 0.0558 139 1.0400 0.0897 139 0.0000 0.0000
143 0.0000 0.0000 143 0.3700 0.0179 143 0.8600 0.0558 143 1.0400 0.0897 143 0.0000 0.0000
155 0.0000 0.0000 155 0.6300 0.0304 155 0.9000 0.0584 155 1.1000 0.0948 155 0.0000 0.0000
161 0.0000 0.0000 161 0.8600 0.0415 161 0.9400 0.0610 161 1.1600 0.1000 161 0.0000 0.0000
182 0.0000 0.0000 182 1.3200 0.0638 182 1.1200 0.0727 182 1.2600 0.1086 182 0.0000 0.0000
196 0.0000 0.0000 196 1.4400 0.0696 196 1.1400 0.0740 196 1.2800 0.1103 196 0.0000 0.0000
206 0.0000 0.0000 206 1.6200 0.0783 206 1.2400 0.0805 206 1.3000 0.1121 206 0.0000 0.0000
218 0.0000 0.0000 218 1.7200 0.0831 218 1.4200 0.0922 218 1.3200 0.1138 218 0.0000 0.0000
232 0.0000 0.0000 232 2.0400 0.0986 232 1.5200 0.0987 232 1.4200 0.1224 232 0.0000 0.0000
246 0.0000 0.0000 246 2.1800 0.1053 246 1.7200 0.1117 246 1.4600 0.1259 246 0.0000 0.0000
Mean 0.0035 0.0395 Mean 0.0659 0.0660 Mean 0.0303
St. Dev. 0.0030 0.0456 St. Dev. 0.0478 0.0446 St. Dev. 0.0246
0.06
80% Moisture Experiment 2
0.2500
50% Moisture Experiment 3
Production (L/gVS)
0.05
0.04
0.03
0.02
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/g VS)
0.2000
0.1500
0.1000
0.0500
Rep 1
Rep 2
Rep 3
0.01
0
0 20 40 60 80
Time (days)
0.0000
0 50 100 150 200 250 300
Time (days)
0.06
80% Moisture Experiment 2
Production (L/gVS)
0.06
0.05
0.04
0.03
0.02
0.01
72.5% Moisture Experiment 2
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
Production (L/gVS)
0.05
0.04
0.03
0.02
0.01
0
0 20 40 60 80
Time (days)
Rep 1
Rep 2
Rep 3
Rep 4
Rep 5
0
0 20 40 60 80
Time (days)

Volatile Solids (dry weight basis) Volatile Solids Daily Biogas Production for Field Experiment Pit No. I
Experiment 1 Pit II Time (days) Production ft. 3 Production m 3
1 2 3 4 5 Avg. 1 2 3 4 5 Avg. 7/28/99 0 0
45% 49.20% 48.00% 49% 48.80% 48.00% 31.50% 42.60% 43.80% 45.30% 46.50% 41.94% 7/31/99 625 17.72
8/1/99 625 17.72
Experiment 2 8/2/99 625 17.72
1 2 3 4 5 Avg. 8/3/99 625 17.72
44% 45.30% 46.50% 32% 42.60% 41.94% Field Experiment Data 8/6/99 625 17.72
Avg. Moisture Content of Manure in Pit II: 14.32% 8/7/99 625 17.72
Experiment 3 8/8/99 625 17.72
1 2 3 4 5 Avg. Desired Moisture Content of Manure/Water in Pit II: 60-65% 8/9/99 625 17.72
30.62% 32.99% 32.02% 32.12% 32.32% 32.01% 8/10/99 625 17.72
Density of Manure: .673g/cm cu. 8/12/99 625 17.72
Pit I 8/13/99 625 17.72
1 2 3 4 5 Avg. Weight of Water: 62.4 lbs./ ft. cu. 8/14/99 625 17.72
30.62% 32.99% 32.02% 32.12% 32.32% 32.01% 8/15/99 625 17.72
Weight of Manure: .673 x 62.4 = 42 lbs./ ft. cu. 8/15/99 833 23.61
Field Experiment Data 8/16/99 833 23.61
Avg. Moisture Content of Manure in Pit I: 20% Total Available Volume of Pit II: 3,200 ft. cu. 8/17/99 833 23.61
8/18/99 833 23.61
Desired Moisture Content of Manure/Water in Pit I: 60-65% Total Wet Weight of Manure in Pit II: 3,200 x 42 = 134,000 lbs. 8/23/99 833 23.61
8/24/99 833 23.61
Density of Manure: .673g/cm cu. Total Dry Weight of Solids in Pit II: 134,000 lbs x .1432 = 114,811lbs 8/25/99 833 23.61
8/26/99 833 23.61
Weight of Water: 62.4 lbs./ ft. cu. Total Weight of Volatile Solids in Pit II: 114,811 x 41.94% = 48,151 lbs 8/31/99 833 23.61
9/1/99 833 23.61
Weight of Manure: .673 x 62.4 = 42 lbs./ ft. cu. Grams of Voltatile Solids = 48,151 lbs / 2.2(lbs/Kg) = 21,887 Kg x 1000 = 21,887,000 g 9/2/99 833 23.61
9/3/99 833 23.61
Total Available Volume of Pit I: 3,200 ft. cu. 9/20/99 833 23.61
9/21/99 500 14.17
Total Wet Weight of Manure in Pit I: 3,200 x 42 = 134,000 lbs. 9/22/99 500 14.17
9/23/99 500 14.17
Total Dry Weight of Solids in Pit I: 134,000 lbs x .20 = 107,000lbs 9/24/99 500 14.17
9/25/99 500 14.17
Total Weight of Volatile Solids in Pit I: 107,000 x 32.01% = 34,250 lbs 9/29/99 500 14.17
9/30/99 500 14.17
Grams of Voltatile Solids = 34,250 lbs / 2.2(lbs/Kg) = 15,569 Kg x 1000 = 15,569,000 g 10/1/99 500 14.17
10/2/99 500 14.17
Total biogas Production for Pit I: 25,000 ft. cu. 10/3/99 500 14.17
10/4/99 500 14.17
35.28 ft. cu. = 1 m cu. 10/6/99 500 14.17
10/7/99 500 14.17
25,000 ft. cu. / 35.28 = 708.6 m cu. 10/8/99 500 14.17
10/9/99 500 14.17
1,000 L = 1 m cu. 708.6 x 1,000 = 708,600 L 10/10/99 500 14.17
10/11/99 500 14.17
708,600 L / 20,400,000 VS = .03474 L / g VS 10/13/99 500 14.17
g
10/14/99 416 11.79
10/15/99 416 11.79
10/16/99 416 11.79
10/17/99 416 11.79
10/18/99 416 11.79
10/19/99 416 11.79
10/23/99 0 0.00
0.2500
60% Moisture Experiment 3
0.2500
80% Moisture Experiment 3
Production (L/g VS)
0.2000
0.1500
0.1000
0.0500
Rep 1
Rep 2
Rep 3
Production (L/g VS)
0.2000
0.1500
0.1000
0.0500
Rep 1
Rep 2
Rep 3
25
22.5
Field Experiment (Pit 1)
0.0000
Production (L/g VS)
0.2500
0.2000
0.1500
0.1000
0.0500
0 50 100 150 200 250 300
Time (days)
70% Moisture Experiment 3
Rep 1
Rep 2
Rep 3
0.0000
Production (L/g VS)
0.2500
0.2000
0.1500
0.1000
0.0500
0 50 100 150 200 250 300
Time (days)
95% Moisture Experiment 3
Rep 1
Rep 2
Rep 3
Production (m cu. / day)
20
17.5
15
12.5
10
7.5
5
2.5
0
7/19/99 8/8/99 8/28/99 9/17/99 10/7/99 10/27/99 11/16/99
Time (days)
0.0000
0 50 100 150 200 250 300
Time (days)
0.0000
0 50 100 150 200 250 300
Time (days)