Operating strategies to improve performance and coulombic efficiency by selecting electrogens over methanogens in microbial fuel cells

The suppression of methanogens affects the performance of Microbial Fuel Cells (MFCs), but its degree of importance is application dependent. In terms of Coulombic Efficiency (CE), avoiding methanogenesis is essential for MFC type volatile fatty acid (VFA) sensors but less critical for scaled-up MFCs removing COD from real wastewater. To study the suppression of methanogenesis, different H-type MFCs were enriched with acetate, propionate and butyrate. These reactors were operated under different open ciruit (OC) and closed circuit (CC) regimes. During OC operation, significant CH4 was produced but was inhibited when anodic media was replaced and operated in CC. The archeal communities on the electrode and in solution were compared after different OC/CC regimes, and clearly indicated the shift of some dominant species from electrode to the solution phase during OC operation. The results indicate gradual inhibition of methanogenesis during OC/CC operation and also complete inhibition after starving the MFC for a period of time.