Increasing methane production from coal under the application of an electric field system by enriching microorganisms on electrode

The functional microbial community, especially the electrode microorganisms, are crucial for the increment of biomethane production from coal by the application of an electric field. In this paper, the effect of electrode microorganisms on methane production from coal was investigated. They were enriched using the electrically domesticated flora (EF) and the primitive flora (PF) under 1.2 V, respectively. The methane production in EF and PF increased significantly by up to 22.75% and 40.02% compared with the nonenriched group (NF), suggesting that the enrichment of electrode microorganisms is an effective approach to enhance methane production from coal. When methane production ended, both the microbial community on electrode and in culture solution changed significantly. The proportions of such electroactive bacteria as Desulfovibrio and Thermincola on electrode in PF were 222.14% and 15466.67%, respectively higher than those in NF, while the proportion of fermentative bacterium Ramlibacter in EF increased by 979.42%. The bacterial richness and diversity in the culture solution decreased distinctly in EF and PF, revealing that the functional bacteria were transferred from culture solution to electrode in the effect of electric field. Fourier transform infrared spectrometer results verified that the degradation of 4,5-adjacent aromatic H deformation and C-O in coal were mainly promoted. And the enrichment of electrode microorganisms led to the accumulation of ketones and acids and the consumption of esters as revealed by gas chromatography-mass spectrometry. These findings indicated that methane production was enhanced by enriching electroactive and fermentative microbes on electrode which further improved coal biodegradation. It also provided a new way to further increase methane production from coal and promoted the application of bioelectrochemical system in microbially enhanced coalbed methane.