Recent advances in biochar-integrated microbial fuel cells for energy recovery and environmental remediation

Abstract

Microbial fuel cells (MFCs) have attracted increasing attention as sustainable technologies capable of simultaneously treating wastewater and generating bioelectricity. However, their widespread implementation remains constrained by relatively low power output and the high cost of electrode materials and catalysts. In recent years, significant advances have been made in the development and application of biochar as a renewable, low-cost, and tunable functional material in MFCs. This review critically examines recent advances in biochar-integrated MFCs, focusing on the relationships between biochar properties, microbial interactions, electron transfer mechanisms, and catalytic activity. The roles of biochar as anode, cathode, and separator materials are evaluated, together with its application in environmental MFC systems such as sediment, plant/soil, and constructed wetland configurations. Techno-economic analyses suggest that biochar-based electrodes can substantially reduce material and electrode costs compared with conventional carbon and noble-metal-based materials, while life cycle assessments highlight their potential contribution to carbon sequestration and circular bioeconomy strategies. Nevertheless, critical challenges persist, including inherent variability in biochar physicochemical properties, long-term electrode fouling and structural degradation, scalability limitations, and environmental risks from metal leaching in chemically modified biochars. Addressing these barriers through integrated, multiscale design strategies spanning material synthesis, reactor engineering, and microbial community optimization will be essential for translating biochar-integrated MFC technologies into scalable and sustainable solutions.