Upscaling feasibility of a graphite-based truncated conical microbial fuel cell for bioelectrogenesis through organic wastewater treatment

Energy generation from bioelectrochemical techniques: Concepts, reactor configurations and modeling approaches

The process industries play a significant role in boosting the economy of any nation. However, poor management in several industries has been posing worrisome threats to an environment that was previously immaculate. As a result, the untreated waste and wastewater discarded by many industries contain abundant organic matter and other toxic chemicals. It is more likely that they disrupt the proper functioning of the water bodies by perturbing the sustenance of many species of flora and fauna occupying the different trophic levels. The simultaneous threats to human health and the environment, as well as the global energy problem, have encouraged a number of nations to work on the development of renewable energy sources. Hence, bioelectrochemical systems (BESs) have attracted the attention of several stakeholders throughout the world on many counts. The bioelectricity generated from BESs has been recognized as a clean fuel. Besides, this technology has advantages such as the direct conversion of substrate to electricity, and efficient operation at ambient and even low temperatures. An overview of the BESs, its important operating parameters, bioremediation of industrial waste and wastewaters, biodegradation kinetics, and artificial neural network (ANN) modeling to describe substrate removal/elimination and energy production of the BESs are discussed. When considering the potential for use in the industrial sector, certain technical issues of BES design and the principal microorganisms/biocatalysts involved in the degradation of waste are also highlighted in this review.

Carbon nanotubes encapsulating FeS2 micropolyhedrons as an anode electrocatalyst for improving the power generation of microbial fuel cells

The low power density originating from poor electroactive bacteria (EAB) adhesion and sluggish extracellular electron transfer (EET) at the anode interface, is a major impediment preventing the practical implementation of microbial fuel cells (MFCs). Tailoring the surface properties of anodes is an effective and powerful strategy for addressing this issue. In this study, we successfully fabricated an efficient anode electrocatalyst, consisting of carbon nanotubes encapsulating iron disulfide (FeS2@CNT) micropolyhedrons, using simple hydrothermal and freeze-drying methods, which not only strengthened the anode interaction with EAB but also promoted the EET process at the anode interface. As expected, the MFCs with a FeS2@CNT anode yielded an outstanding power density of 1914 mWm-2 at a current density of 4350 mA m-2, which significantly exceeded those of pure CNT (1096.2mW m-2, 2703.3 mA m-2) and carbon cloth (426.8mWm-2, 965.6 mA m-2) anodes. The high-power output can be attributed to the synergistic effect between FeS2 and CNTs, endowing the anode with biocompatibility for biofilm adhesion and colonization, nutrient diffusion, and the presence of abundant Fe and S active sites for EET mediation. Owing to the low cost, facile fabrication process, and excellent electrocatalytic performance toward the redox reactions in biofilms, the synthesized FeS2@CNT electrocatalyst is a promising material for high-performance and cost-effective MFCs with commercial applications.

Progress in microbial fuel cell technology for wastewater treatment and energy harvesting

The global energy crisis has stimulated the development of various forms of green energy technology such as microbial fuel cells (MFCs) that can be applied synergistically and simultaneously toward wastewater treatment and bioenergy generation. This is because electricigens in wastewater can act as catalysts for destroying organic pollutants to produce bioelectricity through bacterial metabolism. In this review, the factors affecting energy production are discussed to help optimize MFC processes with respect to design (e.g., single, double, stacked, up-flow, sediment, photosynthetic, and microbial electrolysis cells) and operational conditions/parameters (e.g., cell potential, microorganisms, substrate (in wastewater), pH, temperature, salinity, external resistance, and shear stress). The significance of electron transfer mechanisms and microbial metabolism is also described to pursue the maximum generation of power by MFCs. Technically, the generation of power by MFCs is still a significant challenge for real-world applications due to the difficulties in balancing between harvesting efficiency and upscaling of the system. This review summarizes various techniques used for MFC-based energy harvesting systems. This study aims to help narrow such gaps in their practical applications. Further, it is also expected to give insights into the upscaling of MFC technology while assisting environmental scientists to gain a better understanding on this energy harvesting approach.