Integrating the independent granular charge carriers into microbial fuel cell: From performance to mechanism analysis

Abstract

The mutual benefits between electroactive bacteria (EAB) and non-EAB promote bioenergy recovery in microbial fuel cell (MFC), while competition between functional and non-functional bacteria on electrodes hinders further performance improvement. Introducing non-electrode conductive carriers into MFC may reduce contact resistance and alleviate interspecies competition. In this study, three-dimensional spherical biochar (BC) granules as independent microbial and charge carriers are introduced into anode chamber of an MFC without direct contact with the electrode (carbon cloth, CC) creating CC-BC-MFC. CC-BC-MFC achieves superior power density of 15 ± 1.4 W m−3 compared to CC-MFC (12 ± 1.4 W m−3) and CC/BC-MFC (10 ± 1.2 W m−3, where BC directly contacts CC). Higher effluent quality highlights the outstanding contribution of adequate biomass in effective containment treatment. Smaller internal resistance and higher coulombic efficiency are obtained in CC-BC-MFC by relieving microbial competition at anode. Syntrophic growth between Geobacter (69.4 %) and Methanosarcina (98 %) is established on BC in CC-BC-MFC, with high expression of Geobacter-associated pili genes and acetotrophic and CO2-reducing methanogenic genes associated with methanogens. Therefore, incorporating BC as flexible and independent charge carriers can reduce internal resistance, provide adequate habitat, alleviate microbial competition at anode, and offer a feasible strategy for MFC in wastewater treatment.