Although H2 produced from dark fermentation process is considered as a viable alternative fuel and energy carrier of the future, H2 storage, purification, low pro­duction rates and the requirements of separate fuel cell systems for the generation of energy (electricity) are some of the inherent limitations. Alternatively, the microbial fuel cell (MFC) facilitates in situ conversion of energy in the form of bioelectricity from wastewater treatment by dark fermentation [111, 147-158]. MFC is a hybrid bio-electrochemical system, which converts the substrate directly into electricity by the oxidation of organic matter in the presence of bacteria (bio-catalyst) at ambi­ent temperature/pressure [155, 156]. The potential developed between the bacterial metabolic activity [reduction reaction generating electrons (e-) and protons (H+)] and electron acceptor conditions separated by a membrane manifests bioelectricity generation. In an acidogenic microenvironment, single and dual chambered MFC systems were evaluated for the production of bioelectricity using various types of wastewater viz., chemical wastewater, designed synthetic wastewater, domes­tic sewage and vegetable waste employing mixed cultures as anodic biocatalysts [147-158] (Table 7). The higher activity of intracellular e — carriers which will help in the translocation of e — from bacteria to the outside of the cell might be the rea­son for higher current generation observed under acidic pH operation [156]. Apart

from power generation, the MFC also demonstrated an enhanced substrate degrada­tion rate along with good color and total dissolved solid (TDS) removal efficiency compared to conventional anaerobic treatment [156]. MFCs can also utilize acid — rich carbon effluents generated from acidogenic processes as primary substrate for bioelectricity generation along with additional treatment efficiency.