Valorization of mixed blackwater/agricultural wastes for bioelectricity and biohydrogen production: A microbial treatment pathway

The management of wastewater and agricultural wastes has been limited by the separate treatment processes, which exacerbate pollution and contribute to climate change through greenhouse gas emissions. Given the energy demands and financial burdens of traditional treatment facilities, there is a pressing need for technologies that can concurrently treat solid waste and generate energy. This study aimed to evaluate the feasibility of producing bioelectricity and biohydrogen through the microbial treatment of blackwater and agricultural waste using a dual-chamber Microbial Fuel Cell (MFC). The research focused on identifying optimal feedstock ratios and pH conditions, accompanied by biochemical assays to characterize the microbial community involved. The predominant microorganisms identified included <i>Escherichia coli</i>, <i>Salmonella</i> spp., and <i>Pseudomonas aeruginosa</i>, among others. The highest open circuit voltage achieved was 1090 mV at a hydraulic retention time (HRT) of 6 days. Maximum removal efficiencies for Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) were 90.87 % and 76.67 %, respectively, with a Columbic efficiency of 40.17 %. The peak power density measured was 345 mW/m², and the highest hydrogen yield was 483 ppm/s. The optimal feedstock ratio was found to be 3:1:1 (300 g cassava peel, 100 g banana peel, and 100 g tomato waste), with ideal pH conditions at 9.35. This study underscores the potential for generating bioelectricity and biohydrogen from the microbial treatment of mixed blackwater and agricultural wastes in a single system, eliminating the need for separate treatment and the use of external energy source. The work contributes to the advancement of environmental engineering and management, bioenergy, microbial fuel cell, and affordable and clean energy.