A Comparative Study of Microbial Fuel Cells and Microbial Electrolysis Cells for Bioenergy Production from Palm Oil Mill Effluent§.

Research background: The increasing environmental concerns due to fossil fuel consumption and industrial wastewater pollution necessitate sustainable solutions for bioenergy production and wastewater treatment. Palm oil mill effluent (POME), a high-strength industrial wastewater, poses significant environmental challenges. Microbial electrolysis cells (MEC) and microbial fuel cells (MFC) offer promising avenues for bioenergy recovery from such wastewaters.

Experimental approach: Dual-chamber H-type reactors equipped with proton exchange membranes were used to separately evaluate the performance of MEC and MFC in the production of bioenergy from POME. Hydrogen production and chemical oxygen demand (COD) removal in MECs were evaluated at different applied voltages and influent COD expressed as oxygen concentrations, while in MFCs the effect of external resistance on power output and COD reduction was investigated. Response surface methodology (RSM) was used to optimise these operational parameters for maximum bioenergy recovery and efficient wastewater treatment.

Results and conclusions: The results showed that the efficiency of hydrogen production and COD removal in MECs were maximised at low influent COD value and low voltage supply. The MEC effectively produced hydrogen and treated industrial wastewater, while the MFC successfully produced electricity and reduced COD. Field emission scanning electron microscopy confirmed the formation of biofilms on the electrodes, indicating active microbial communities involved in the production of bioenergy. A trade-off between power density and COD removal efficiency in MFCs was observed, with medium resistance values yielding maximum power output. The integration of MEC and MFC showed potential for treating high-strength industrial wastewater like POME, offering a greener and more energy-efficient approach.

Novelty and scientific contribution: This study demonstrates the potential feasibility of integrating MEC and MFC technologies for simultaneous bioenergy production and wastewater treatment from POME. It extends the knowledge in biochemical engineering by optimising operational conditions for improved bioenergy recovery and highlights the role of microbial communities in bioelectrochemical systems. The results form a basis for future research on sustainable bioenergy production and contribute to efforts towards environmental sustainability.