Bioelectrochemical systems: Sustainable bio-energy powerhouses.

Bioelectrochemical systems comprise of several types of cells, from basic microbial fuel cells (MFC) to photosynthetic MFCs and from plant MFCs to biophotovoltaics. All these cells employ bio entities at anode to produce bioenergy by catalysing organic substrates while some systems convert solar irradiation to energy. The current review epitomizes the above-mentioned fuel cell systems and elucidates their electrical performances. Microbial fuel cells have advantages over conventional fuel cells in terms of being sustainable whilst producing impressive power efficiencies without any net carbon emissions. They can be utilized for several environmentally friendly applications including wastewater treatment and bio-hydrogen generation, apart from producing clean and green electricity. Multifarious heterotrophic and autotrophic microbes and plants have been studied for their potential as imperative components of fuel cell technology. MFCs also display some interesting applications, such as integration of plant MFCs into architecture to produce "green" cities. Biophotovoltaic technology is the current hot cake in this field, which aspires to achieve significant electrical efficiencies by light-induced water splitting mechanisms. Furthermore, the utilization of BPVs in space renders it a technology for the future. Compared with other fuel cell systems, this technology is still in its inception and requires further efforts to endeavour its use on commercial or industrial level.