Microbial Fuel Cell and Associated Novel Derived Systems as Bifunctional Technologies to Produce Green Energy and Pollutant-Free Water

Global energy security and water scarcity are currently two major challenges facing society. Many new strategies and technologies have been developed to address these issues; however, most can only partially solve a single one. Therefore, microbial fuel cells (MFCs) and associated novel technologies have emerged as sustainable, bifunctional solutions for treating various wastewater streams while generating renewable electrical energy through the biochemical oxidation of organic substrates. The basic configuration of an MFC comprises anodic and cathodic chambers, an external electrical circuit, ion-exchange membranes, organic substrates, and electrogenic bacteria. Biological fuel cells are inherently multidisciplinary systems whose performance depends on several biotic and abiotic parameters, with bacterial electrogenic metabolism as the driving force. In this review paper, the most important factors affecting MFC performance and the common equations employed to determine bioelectrochemical efficiency are described. A major highlight is the analysis and comparison of recently proposed MFC-derived hybrid technologies: microbial electrolysis cells (MECs), microbial desalination cells (MDCs), plant microbial fuel cells (PMFCs), and constructed wetland MFCs (CW-MFCs) for treating wastewater and soil pollutants while enhancing the recovery of green energy. Novel configurations, basic biochemistry, and a brief history of bioelectrochemistry are also reported. In addition, this review aims to compare the applications, fundamentals, basic configuration, and limitations of each biological fuel cell. Based on a comprehensive analysis, the challenges, opportunities, economics, and scaling-up possibilities of each MFC-derived technology are reported. Since biological oxidation in the anodic chamber and reduction at the cathode surface are the basis of all fuel cells, there are characteristic challenges that must be addressed: enhancing power output, increasing pollutant degradation and scalability, reducing construction and operational costs, and ensuring long-term stabilization. MFCs and the associated derived systems appear suitable for converting residual organic matter into green energy, even at a pilot scale; however, to improve scalability and reduce power costs, further research is still needed.