Influence of ion exchange membrane types on microbial electrosynthesis performance and biomethane production

Microbial electrosynthesis (MES) utilizes electrical current to convert CO₂ into various products via electroactive microbial activity at the cathode. Methane production in MES relies on methanogens within the cathode biofilm and is influenced by various factors including the type of ion exchange membrane, which plays a critical role but remains underexplored, particularly regarding ion transport mechanisms. This study examined methane production in MES reactors equipped with cation exchange membranes (CEM-MES) and anion exchange membranes (AEM-MES) at cathodic potentials of -1.0 to -1.2 V (vs. Ag/AgCl). AEM-MES produced 10.1 times more methane than CEM-MES. Despite elevated catholyte pH and greater pH imbalances in AEM-MES, methane production was primarily governed by H₂ production rate rather than pH imbalance. The microbial community of cathode biofilm was significantly influenced by membrane type, with Methanobacterium prevailing in AEM-MES, correlating with reactor performance. AEM-MES demonstrated enhanced methane production, particularly at cathodic potentials that minimized hydrogen evolution.