Biogas-Upgrading of Anaerobic Digestion Effluent CO2 into CH4 Using a Microbial Electrosynthesis Cell

Abstract

Upgrading anaerobic digestion (AD) biogas has been highlighted to secure an alternative renewable energy source. The CO2 content of AD effluent is over 40%, thus it is necessary to separate and/or increase CH4 content up to 95%. This study examines a microbial electrosynthesis (MES) to directly convert CO2 into CH4 by cathode attached cell. The MES with −1.0V (vs. Ag/AgCl) applied cathodic potential presented a maximum rate of 10.55L CH4/ m2 cat/ day and achieve 96% of final CH4 content. The next-generation sequencing indicates the most methanogens attached to the cathode surface rather than suspension. These results suggest that cathode attached cells play a major role in the biogas-upgrading of CO2 into CH4 in the MES system.