Performance of a pilot-scale, thermophilic, anaerobic fermenter treating cattle waste

Abstract Start-up and steady-state operation of a pilot-scale, thermophilic, anaerobic fermenter is described. The fermenter was operated at: temperatures of 45, 50 and 55°C; hydraulic retention times (HRT) ranging from 4 to 12 days; mixed continuously or for 2 h/day; and fed once/day or 22 times/day. No difference in methane (CH 4 ) production rate was observed when the fermenter was mixed 2 h/day versus continuously. CH 4 production rate was about 10% higher when the fermenter was fed the same loading rate 22 times/day compared to once/day. The highest CH 4 production rate achieved by the fermenter was 4.7 m 3 CH 4 /m 3 fermenter·day. This is the highest rate reported in the literature for fermentation of livestock waste and about four times higher than other pilot- or full-scale systems fermenting livestock waste. Performance of the pilot-scale fermenter was predicted using a previously reported kinetic equation. The mean ratio of predicted to experimental CH 4 production rates was 0.99 with a standard deviation of 0.10.