Microbial aided electrolysis cells (MEC), also called bio-electrochemically assisted microbial reactor (BEAMR), use electro-hydrogenesis to directly con­vert biodegradable material into H2 by applying external voltages in fuel cells in an anaerobic microenvironment [116, 117]. The supplemented voltage helps to decompose acetate spontaneously under standard conditions [116, 118]. Based on a thermodynamic analysis the addition of greater than 0.11 V to that generated by bacteria (-0.3 V) will yield H2 gas at the cathode, but voltages of -0.2 V are needed because of electrode over-potentials [116]. This process, referred to as electro­hydrogenesis, provides a route for extending H2 production past the endothermic barrier imposed by the microbial formation of fermentation end products, such as acetic acid [116]. Microbial electrolysis makes it possible to generate H2 utilizing effluents generated from acidogenic fermentation and opens the possibility of using diluted organic matter varying in composition, such as wastewater, for H2 produc­tion [119]. Membrane-less continuous flow microbial electrolysis cell (MEC) with a gas-phase cathode was also used to produce H2 [119].