Influence of applied voltage on bioelectrochemical enhancement of biomethanation for low-rank coal and microbial community distribution.

The performance of peat biomethanation was investigated in bioelectrochemical anaerobic digestion at different applied voltages, and compared to conventional anaerobic digestion. The methane yield was stabilized at 16 mL/g peat in the conventional anaerobic digestion. However, in the bioelectrochemical anaerobic digestion, the methane yield was significantly increased to 264 mL/g peat at the applied voltage of 4 V, followed by 1 V, 2 V, 0.5 V and 0 V. The bioelectrochemical system could enrich more electroactive microorganisms on the electrode, as well as in the bulk solution, and further improve the direct interspecies electron transfer for methane production. The 16S rRNA analysis showed a significant increase in the abundance of specific microorganisms in the bulk solution, including Firmicutes phylum and Proteobacteria phylum, in addition to a gradual increase in acetoclastic methanogenesis with an increase in applied voltage. These results provide a solution to turn low-rank coal into a new alternative energy.