2-PHASE ANAEROBIC FERMENTATION OF LIQUID SWINE WASTE TO METHANE

Two-phase anaerobic digestion of liquid swine manure was developed with options for single-cell protein (SCP) or methane production. In the acidogenic phase at 2-4 days retention time and 2.5-7.0% dry matter (DM) concentration, 8-46% of the volatile solids was solubilized. Maximum reactor capacity was 3.86 g/l at 7.0% DM concentration, but optimal operation was achieved at 4.5% DM concentration at 4 days retention time. The 2nd methanogenic phase was operated continuously and had a maximum specific methane production rate of 0.70 l/l day at 12 days retention time. With recirculation, the rate was 1.16 l/l day at 8.5 days retention time with 52.7% conversion of organic matter. Maximum digestibility was 66% of the lignin free organic matter.