Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Biogas production at beef cattle feedlots is hard to justify because of the large amounts of dilution water required and the high cost to design and operate conventional water-based digestion systems. Laboratory and field experiments were conducted to determine the feasibility of producing biogas using "dry" aged beef cattle manure scraped from open-lot feedyards. Biogas production rates were measured at 21C in the laboratory at four total solids contents using a water displacement technique. Biogas yields were 0.180, 0.210, 0.190 and 0.005 L per gram volatile solids (VS) at solids contents of 20, 30, 40 and 50 percent, respectively. Biogas was produced steadily for 300 days before declining and eventually ceasing after 450 days. The biogas contained 52 to 60 percent methane. A field demonstration project was conducted to produce biogas using geomembrane-lined digesters. Two 90 m3 digesters excavated in native soil to a depth of 1.8 m were lined on top and bottom with ethylene propylene diene monomer (EPDM) geomembranes. Digester 1 was loaded with manure (solids content 40 percent) in February, 1999. Biogas was produced during the first summer for 12 weeks beginning August 1, 1999, and during the second summer for 13 weeks beginning July 14, 2000. Digester 1 produced 1,510 m3 of biogas the first summer and 920 m3 the second summer, with a typical methane concentration of 52 percent. Total biogas yield over the two summers was 0.16 L/g VS in digester 1. Digester 2 was loaded with manure (solids content 50 percent) in January, 2000, and produced less than 5 m3 of biogas. This research demonstrates that biogas can be produced in below-ground digesters using aged beef cattle manure if the solids content is less than or equal to 40 percent, but that year-round biogas production is not feasible unless the digesters are heated or insulated.