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
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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http://www.westbioenergy.org/cattle/execsumm.html [3/26/2003 8:52:51 AM]