From Olive Waste to Bioelectricity: Integrated Substrate Recovery and Biochar Cathode Engineering for Advanced Microbial Fuel Cells

The increasing demand for sustainable energy and efficient wastewater treatment has driven interest in single-chamber microbial fuel cells (SCMFCs) as integrated systems for bioelectricity generation and waste remediation. This study evaluates untreated agro-industrial byproduct olive mill wastewater (OMW) as a substrate in SCMFCs. It investigates the performance of activated biochar derived from olive pomace coated on stainless-steel mesh (ACB/SSM) as a low-cost cathode material. A synthetic media was used as a control. Electrochemical performance was assessed using voltage profiles, polarization analysis, power density, chemical oxygen demand (COD%) removal, and coulombic efficiency (CE%). The synthetic media achieved higher peak voltage (0.647 ± 0.026 V) and power density (46.05 mW m−2), whereas OMW showed more stable voltage output and lower internal resistance. OMW exhibited superior initial COD removal (74%) and a gradual increase in CE% up to 63% over successive cycles. In contrast, synthetic media exhibited a consistent COD% of 64%; its CE% removal improved to 61%. These results demonstrate that, despite lower peak power, OMW provides a more stable and sustainable substrate for long-term SCMFC operation. The use of waste-derived biochar cathodes further enhances system feasibility by reducing cost and supporting circular economy principles. This study highlights the potential of OMW-based SCMFCs as a practical approach for simultaneous wastewater treatment and renewable energy recovery.