Investigation of the mechanisms for bioelectrochemical methane production

Abstract

The methane producing microbial electrolysis cell (MEC) is a recently discovered technology that is able to convert CO2 into methane using an energy source and electrochemically active micro-organisms as catalyst. Previous lab scale studies have shown reasonable methane production rates with high energy efficiencies for different cathode potentials. However, for further improvement of the design of the MEC, the exact processes that are occurring at the bio-cathode need to be unraveled. This study describes the possible methane production routes in two MECs at different cathode potentials. The results presented here suggest that mixed cultures are able to accept electrons directly for methane formation and indirectly via the intermediates H2 and acetate at a cathode potential of -0.7V. At this cathode potential, methane was produced at production rates up to 7.6 ml CH4/L reactor per day with cathodic electron efficiencies that reached up to 99%.