Thermophilic, Anaerobic Fermentation of Beef Cattle Residue

摘要

The research being conducted at the U.S. Meat Animal Research Center to convert livestock manure into methane and a high protein feed ingredient by thermophilic anaerobic fermentation is summarized. The pilot-scale fermentor is 5.7 m exp 3 with a working volume of 5.1 or 5.4 m exp 3 depending on the retention time. The fermentor was operated at 55 exp 0 C; and 20, 12, 6, and 4 days' retention times at loading rates of 3.4, 5.2, 11.4, and 15 kg VS/m exp 3 /day, respectively. The results showed that the total solids, volatile solids and COD reduction decreased as the retention time decreased; the fixed solids and total nitrogen were not lost during fermentation; and the total gas and methane production rate increased as the retention time decreased. High protein biomass from the fermentation was recovered through centrifugation and by direct incorporation into the ration. Feeding trials using dried centrifuge cake showed that the digestibility of dry matter, organic matter, and nitrogen tended to decrease slightly as the amount of centrifuge cake in the ration increased. An economic assessment was performed on a hypothetical, thermophilic, anaerobic fermentation system for a 10,000-head beef feedlot. The assessment showed that the capitalized investment costs ranged from $85 to $131/head, and the annual costs ranged from $29 to $39/head/yr, depending on the type of biomass recovery system used. (ERA citation 04:032911)