• Energy Research

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.

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.

In this research, efforts were put to demonstrate synergistic interactions between bioenergy generation and wastewater treatment. The extent of such synergistic effect was assessed against wastewater effluents released from the beverage industry through the operation of a membrane-less truncated conical (TC) microbial fuel cell (MFC). A graphite-based reactor was operated for five cycles in batch mode using beverage industry wastewater as an organic substrate. Maximum bioelectricity produced on the fifth operating cycle corresponded to a voltage of 338 mV and a power of 1.14 mW at 100 Ω. The MFC recorded a higher substrate degradation rate (0.84 kg of chemical oxygen demand [COD]/m3-day) accompanied by the development of an electroactive biofilm and polarization behavior (e.g., a reduction in internal resistance from 323 Ω to 197 Ω over five operation cycles). Cyclic voltammetry showed a maximum performance of the biofilm during the fifth cycle (through its enrichment) as interpreted by oxidation and reduction currents of 2.48 and -2.21 mA, respectively. The performance of the proposed MFC was superior to other designs reported previously in both effluent treatment and bioenergy generation. A maximum treatment efficiency of 84.4% (in 385 h) was seen at an organic load (COD) of 3500 mg/L with the specific power yield (0.504 W/Kg of substrate (COD) removal) and volumetric power yield (15.03 W/m3). Our experimental studies support that the proposed system could be upscaled to realize the commercial operation.

In this research, efforts were put to demonstrate synergistic interactions between bioenergy generation and wastewater treatment. The extent of such synergistic effect was assessed against wastewater effluents released from the beverage industry through the operation of a membrane-less truncated conical (TC) microbial fuel cell (MFC). A graphite-based reactor was operated for five cycles in batch mode using beverage industry wastewater as an organic substrate. Maximum bioelectricity produced on the fifth operating cycle corresponded to a voltage of 338 mV and a power of 1.14 mW at 100 Ω. The MFC recorded a higher substrate degradation rate (0.84 kg of chemical oxygen demand [COD]/m3-day) accompanied by the development of an electroactive biofilm and polarization behavior (e.g., a reduction in internal resistance from 323 Ω to 197 Ω over five operation cycles). Cyclic voltammetry showed a maximum performance of the biofilm during the fifth cycle (through its enrichment) as interpreted by oxidation and reduction currents of 2.48 and -2.21 mA, respectively. The performance of the proposed MFC was superior to other designs reported previously in both effluent treatment and bioenergy generation. A maximum treatment efficiency of 84.4% (in 385 h) was seen at an organic load (COD) of 3500 mg/L with the specific power yield (0.504 W/Kg of substrate (COD) removal) and volumetric power yield (15.03 W/m3). Our experimental studies support that the proposed system could be upscaled to realize the commercial operation.