Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: 7/18/1999
Publication Date: N/A
Technical Abstract: Two laboratory experiments were completed, and a field demonstration project is currently underway to evaluate biogas production from beef cattle manure collected from open-lot pens. Experiment 1 was conducted at 21 deg C and Experiment 2 was conducted at 35 deg C. Collapsible 4 L low density polyethylene (LDPE) containers were filled with 120 g of manure (50 g VS) and water, the containers were flattened, and the air was displaced. For Experiment 1, water was added to obtain wet weight basis moisture contents (MCs) of 13% (control), 20, 25, 30, 40, 50, and 75%. For Experiment 2, MCs of 35, 50, 57.5, 65, 72.5, and 80% were used. In Experiment 1, biogas production was minimal after 70 days at moisture contents of 50% or less. At the 75% moisture content, the average biogas production was 1.92 L/container. In Experiment 2, the average biogas production after 45 days was 0.00, 0.61, 0.94, 1.42, 1.84, and 2.40 L/container for moisture contents of 35, 50, 57.5, 65, 72.5, and 80%, respectively. Biogas production began after seven days for the 80% MC, after 14 days for the 72.5 and 65% MCs, and after 21 days for the 57.5 and 50% MCs. Gas at the completion of the experiments contained 62 to 85% N2. The permeability of the LDPE containers may be high enough to allow diffusion of gases into and out of the container. In comparison to water, the containers have a relatively high permeability to CO2 and moderate to low permeability to CH4 and O2. In the field demonstration project, feedyard manure and water (60% moisture content) were placed into a 91 m**3 landfill cell that was lined and capped with EPDM geomembrane. No appreciable amount of biogas has been produced in the past three months.