Study on biogas production from pig manure wastewater by microbial electrosynthesis at sub-psychrophilic conditions

Abstract

In colder regions, relatively low temperatures results in low microbial activity and low biogas production in anaerobic digestion. This study investigated if microbial electrosynthesis system (MES) can enhance biogas production from pig manure wastewater under sub-psychrophilic conditions (20 °C). Results showed that the applied voltage of MES (0.4 V and 0.8 V) significantly increased the biogas production and COD removal rate. Biogas production and COD removal rate increased most when the voltage reached 0.8 V (34.77 %, 26.67 %), and decreased when the voltage was 1.2 V. Low voltage (≤ 0.8 V) did not significantly alter the microbial structure, but higher voltage (1.2 V) resulted in a significant decrease in Clostridium and Methanosarcina. Coenzyme F420, NADH, as indicators for methanogenic efficiency, showed the highest fluorescence intensity at 0.8 V and decreased at 1.2 V. Results indicated that the improvement of gas production was mainly due to the improvement of key enzymes rather than the shift of microbial structure. The information provided will be useful to improve the efficiency of biogas production.