Anaerobic Process Intensification via Electro-methanogenesis − Advancing Biogas Upgradation through CO2 Utilization

Abstract

This study investigates the enhancement of anaerobic processes through electro-methanogenesis (EM), focusing on biogas upgrading and in situ CO2 utilization. The effects of applied potential (AP), closed circuit (CC), open circuit (OC), and control (C; without electrode) conditions were evaluated in electro-methanogenic bioreactors operated at 30 °C and 48 °C. Using stainless-steel electrodes, eight reactor configurations were compared. Results showed that mesophilic conditions (48 °C) yielded higher biogas and methane production efficiencies than ambient conditions (30 °C). Among the electrode configurations, the AP condition achieved the highest biogas production, followed by CC, OC, and control. The integration of electrochemical conditions with elevated temperatures significantly improved the calorific value of the biogas, achieving a 1.6–2.08-fold increase. The R8/EMAP/48 condition demonstrated the highest methane equivalent utilization, with CH4 as the primary electron sink. In situ and external potentials enhanced bacterial metabolic activity and facilitated mediated interspecies electron transfer through soluble redox-active molecules such as quinones and NADH. This approach effectively overcomes the thermodynamic limitations of conventional anaerobic digestion, providing a method for increasing methane production by enhancing in situ electron flux while also supporting targeted decarbonization by upgrading the biogas energy value.