Plant microbial fuel cells: A promising biosystems engineering

Conversion of waste to energy via a biological process establishes microbial fuel cells (MFC) as a prominent source of sustainable energy. MFC has been investigated for bioelectricity production through organic degradation of wastewater by microbial consortium. The potential of MFC applications in biosensors, desalination and hydrogen gas production has been explored. Many descendants of an MFC have been developed in recent years based upon the configurations, structures and purposes such as sediment MFC, mud MFC, soil MFC, constructed wetland MFC, photosynthetic MFC and biovolt-photogalvanic MFC. A plant microbial fuel cell (PMFC) is a promising modification of MFC that exercises the unique plant-microbe relationship at the rhizosphere region of a plant and converts solar energy into bioelectricity. In-situ bioelectricity and biomass production, rather than the supply of external substrates, make this technology different from traditional MFCs. Thus, designing and understanding PMFCs should be viewed from a biosystems engineering perspective rather than only through MFC methodology. Plant-microbe harmony at the soil interface, driven by rhizodeposition coupled with efficient engineering, ultimately directs towards its real applications. Thus, this paper reviews three main paradigms. Firstly, effects of plants in PMFC via rhizodeposition and photosynthetic activity are explored. Secondly, the role of microbes driven by soil physiochemical and biological characteristics are shown. Thirdly, the engineering aspects involved in designing an efficient configuration are revealed and an attempt is made to interpret the PMFC with biosystems principles. Furthermore, an overview of a PMFC system is done, along with the future perspectives and challenges.