Enhanced coal biomethanation by microbial electrolysis and graphene in the anaerobic digestion

Abstract

The combination of microbial electrolytic cells and conductive materials can effectively promote direct interspecies electron transfer (DIET) to increase methane production, which has great potential for enhanced anaerobic degradation of organic matter. A single-chamber microbial electrolytic cell containing graphene was constructed using long-flame coal as a substrate. The results showed that the external electric field and graphene increased the abundance of hydrolytic bacteria (Paraclostridium, Sedimentibacter) and hydrogen-producing acetogenic bacteria (Anaerovorax) in the AD system. The consumption rate of alkanes, volatile fatty acids and alcohols was accelerated, which provided sufficient nutrients for methanogens and increased biomethane production by 53.1 %. The abundance of related genes involved in the carbon dioxide reduction pathway was significantly increased. The abundance of pilA gene involved in electron transport in the AD system increased by 153.7 %, and the abundance of electroactive microorganisms Geobacter and Methanosarcina capable of DIET increased significantly, which further promoted coal biomethanation.