Methanol metabolism and archaeal community changes in a bioelectrochemical anaerobic digestion sequencing batch reactor with copper-coated graphite cathode

[Display omitted] •BEAD-SBRCu produced methanol from food waste increasing methylotrophic methanogens.•BEAD-SBRCu removed COD and produced methane with no pH decrease at high OLR.•Methanol is converted to methane by hydrogenotrophic and methylotrophic methanogens. In this study, the metabolism of methanol and changes in an archaeal community were examined in a bioelectrochemical anaerobic digestion sequencing batch reactor with a copper-coated graphite cathode (BEAD-SBRCu). Copper-coated graphite cathode produced methanol from food waste. The BEAD-SBRCu showed higher methanol removal and methane production than those of the anaerobic digestion (AD)-SBR. The methane production and pH of the BEAD-SBRCu were stable even under a high organic loading rate (OLR). The hydrogenotrophic methanogens increased from 32.2 to 60.0%, and the hydrogen-dependent methylotrophic methanogens increased from 19.5 to 37.7% in the bulk of BEAD-SBRCu at high OLR. Where methanol was directly injected as a single substrate into the BEAD-SBRCu, the main metabolism of methane production was hydrogenotrophic methanogenesis using carbon dioxide and hydrogen released by the oxidation of methanol on the anode through bioelectrochemical reactions.