Performance evaluation of POME-based microbial fuel cells: treatment efficiency, power generation, and electron loss pathways

Palm oil mill effluent (POME) represents a major environmental burden due to its exceptionally high organic load and complex pollutant profile. Microbial fuel cells (MFCs) offer a distinctive waste-to-energy platform capable of simultaneously treating POME while recovering electrical energy through microbial metabolism. This study evaluates the performance of POME-fed MFCs across three interrelated dimensions: wastewater treatment efficiency, electrochemical energy recovery, and electron loss mechanisms that constrain system performance. Reported chemical oxygen demand (COD) removal efficiencies range from approximately 40% to over 90%, with the highest values typically achieved in hybrid configurations incorporating sorptive or redox-active materials. Power densities span several orders of magnitude, from below 2 mW m⁻² to above 600 mW m⁻² under highly optimized laboratory conditions; however, most POME-fed systems operate within a much narrower and more practically relevant range of roughly 10–500 mW m⁻², reflecting substrate complexity, mass-transfer limitations, and competing microbial pathways. Coulombic efficiencies (CE) are generally low, commonly below 50%, indicating that a substantial fraction of substrate-derived electrons is diverted to methanogenesis, aerobic respiration, biomass synthesis, and other non-electrogenic sinks rather than current generation. Collectively, the available evidence demonstrates that while POME-MFCs can achieve substantial organic removal, sustained electrical output remains constrained by fundamental biological and electrochemical trade-offs, underscoring the need for integrated reactor design, microbial management, and process control to improve practical viability.