Membrane aeration as an energy-efficient method for supplying oxygen to microbial fuel cells

An active supply of oxygen will help with electricity generation in microbial fuel cells (MFCs). Although air-cathode MFCs have been developed to eliminate aeration, the MFCs with active aeration could have their niches in system scaling up and/or removal of certain contaminants that require oxygen in the cathode. In this study, an alternative aeration method based on a gas-transfer membrane has been investigated for MFC applications, in comparison with diffused aeration. The membrane-aerated microbial fuel cell (MAMFC) achieves a maximum coulombic efficiency (CE) of 55.4%, a current density of 17.3 A m^-3 and COD removal efficiency of >61%. The CE of the MAMFC is higher than that of the diffused aeration MFC (DAMFC), indicating a higher conversion efficiency of substrate to electricity with membrane aeration. At the similar dissolved oxygen level of 6.61 mg O₂ L^-1, the MAMFC requires an energy input of 0.05 kW h m^-3, significantly lower than 1.76 kW h m^-3 by the DAMFC. Although both MFCs have negative energy balances under the testing conditions, the MAMFC could theoretically save 588-3485% of energy compared with the DAMFC. This study demonstrates that membrane aeration could be an energy efficient method for providing an active oxygen supply for MFC applications.