Psychrophilic dry anaerobic digestion of dairy cow feces: Long-term operation

摘要

This paper reports experimental results which demonstrate psychrophilic dry anaerobic digestion of cow feces during long-term operation in sequence batch reactor. Cow feces (13-16% total solids) has been anaerobically digested in 12 successive cycles (252 days) at 21 days treatment cycle length (TCL) and temperature of 20 ℃ using psychrotrophic anaerobic mixed culture. An average specific methane yield (SMY) of 184.9 ± 24.0, 189.9 ± 27.3, and 222 ± 27.7 _NL CH_4 kg~(-1) of VS fed has been achieved at an organic loading rate of 3.0, 4.0, and 5.0 gTCOD kg~(-1) inoculum d~(-1) and TCL of 21 days, respectively. The corresponding substrate to inoculum ratio (SIR) was 0.39 ± 0.06, 0.48 ± .02, 0.53 ± 0.05, respectively. Average methane production rate of 10 ± 1.4 _NL CH_4 kg~(-1) VS fed d~(-1) has been obtained. The low concentration of volatile fatty acids indicated that hydrolysis was the reaction limiting step.