The microbial electrolysis cell (MEC) is an emerging technology for bioenergy production using organic wastewater. Normally, a preassimilated bio-anode is utilized by the MEC to break down the organic content, but the formation and assimilation of microbial community at the anode surface is a time-consuming process. This study utilized a novel unassimilated Ni-foam anode for the first time in solar-powered MEC for bioenergy production. Synthetic dairy manure wastewater (SDMW) was used both as substrate and an inoculum in the solarpowered tubular MEC. The impacts of the exposed surface area of the bio-anode on bioenergy production were evaluated by utilizing two different separation techniques (rate-limited bio-anode -MEC and fully exposed bio-anode -MEC). The former technique achieves a maximum methane production rate of 30.35 ± 0.03 mL/L, 14.2% more than that achieved by the later mentioned technique (26.4 ± 0.05 mL/L). Hydrogen production was approximately 800 ± 5 mm 3 in both experimentations. The maximum generated current in the rate limited bioanode -MEC was 35.5 mA. Scanning electron microscope images confirmed the formation of rod-shaped along with round-shaped microbial communities on the anode surface, and, interestingly, round-shaped bacteria were also grown on the cathode surface. The bioenergy (H 2 and CH 4 ) produced using SDMW within first 13 days of operation, along with the formation of a microbial community, was a significant success in this area and has opened up many research opportunities for producing instant bioenergy from organic waste.

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Summary Microbial electrolysis cells (MECs) are one of the most promising innovation amongst bio‐electrochemical systems for biohydrogen production. A wide variety of wastewaters and organic wastes that is, sodium acetate, glucose, glycerol, domestic wastewater, sugar industries effluent, food processing wastewater, industrial wastewater, etc. can be utilized as substrates in MEC. The objective of this comprehensive review is to study the effects of reactor configuration, electrode materials, and substrates on the maximum hydrogen production rate (HPR) and columbic efficiency (CE) of the MEC system. The obtained results were summarized based on reactor configuration, substrate concentration, electrodes, applied voltage, HPR, and CE. Despite this significant progress, MEC technology still requires substantial developments to be recognized as a commercially viable technology. At the end of this review, the most promising future perspectives were also discussed which could be the appealing solutions for various problems associated with MEC technology. This review supports energy engineers and researchers to analyze the performance of various MECs for future assistance in research.

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