Methane Generation from Cattle Residue at a Dirt Feedlot. Final Report

摘要

In order to investigate the feasibility of producing fuel gas and an energy-intensive refeed product from dirt feedlot residues by anaerobic fermentation, the Department of Energy awarded Hamilton Standard a contract to operate the Hamilton Standard mobile processing unit at the Monfort of Colorado Kuner feedlot. During the test program a stable fermentation was achieved utilizing aged feedlot pen residue after a sufficient adaption period was provided. Methane yields varied considerably as a function of feedstock source; as low as 1.3 cubic feet per pound of volatile solids from the feedlot stockpile, and as high as 3.5 cubic feet from one of the feedlot pens. Average yield from all pens was 2.5 cubic feed of methane per pound of volatile solids processed. The fermentor liquid effluent and dewatered effluent were acceptable to cattle as a feed ingredient and were used to provide one-half the daily supplemental protein for two groups of twenty steers each. Weight gains and feed conversion were nearly the same as for cattle fed the normal ration. Data from the test program were used to evaluate the economics of producing fuel gas at a large dirt feedlot. A preliminary design for a full scale system to produce unscrubbed fuel gas for the Monfort Kuner feedlot was developed, from which capital and operating costs were estimated. The production cost of fuel gas was then established as a function of byproduct credit given to the fermentor residue as a refeed product. With zero credit, gas can be produced at $6.30 per million Btu. When a credit is assigned to the refeed product based on the cost of urea as a protein source, the production cost falls to $2.70 per million Btu. When a credit is assigned to the refeed product based on the cost of cottonseed meal as a protein source, the production cost is -$21, indicating that the system produces a net income from the value of the refeed product. (ERA citation 06:002133)