Evaluating the use of unassimilated bio-anode with different exposed surface areas for bioenergy production using solar-powered microbial electrolysis cell

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 solar-powered 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 mm³ in both experimentations. The maximum generated current in the rate limited bio-anode – 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 (H₂ and CH₄) 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.