Microbial electrolysis cells and microbial fuel cells for biohydrogen production: current advances and emerging challenges

Microbial fuel cells (MFC) and microbial electrolysis cells (MEC) are developing as sustainable power source technologies that can be utilized for feasible wastewater treatment and hydrogen production. Hydrogen gas has immense potential as an ecologically adequate energy carrier for vehicles. MFC is bioelectrochemical process that utilize microorganism as the impetuses to oxidize organic and inorganic matter and create electricity, whereas MEC are a reactor for biohydrogen production by combining MFC and electrolysis. MEC and MFC have been the cleanest, eco-friendly, and efficient method for biohydrogen production. The basic mechanism and thermodynamic principles involved in the production of hydrogen have been discussed in brief. Effective factors influencing H2 production such as microbial population, electrodes, membrane, and substrate were elaborated and recent advances in the factors have been explored for the better understanding of developing MFC and MEC technology-based hydrogen generation. This review completes a brief outline of topical advances in the MFC, MEC setup, and different operational parameters which influencing hydrogen production (ionic strength, applied voltage, organic loading, and hydraulic retention time). The review describes the current challenges involved in the technology used and provides effective future perspectives for overcoming the limitations.