Screening of pure cultures for their efficiency to convert electricity and CO2 into methane

Abstract

The demand for defossilization and decarbonization resulting from the climate crisis and the lack of storable renewable energy has brought biomethane back into focus. Methanogenic microorganisms can be used to convert renewable energy into biomethane. In a pressurized H-cell reactor, we demonstrate the electroactivity of four different methanogenic archaea under conditions of direct and indirect electromethanogenesis. The cathodes were adjusted to a potential of −300 mV (direct electromethanogenesis) and − 700 mV (indirect electromethanogenesis) relative to a standard hydrogen electrode. At −300 mV, no significant methane formation was observed in all four cultures. At a potential of −700 mV, Methanococcus maripaludis achieved an average daily methane production rate of 61 mmol/m2 per day. The highest methane concentration of 199.4 mmol/m2 and the highest coulombic efficiency of 74.0 % were reached within 72 h by Methanococcus maripaludis.