05-11-2012, 05:49 PM
DEMONSTRATION OF BIOGAS PRODUCTION USING LOW MOISTURE CONTENT BEEF CATTLE MANURE
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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 91m3 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 m3 (53,000 ft3) 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.
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.
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.
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.