Hydrogen Production in Microbial Electrolysis Cell and Valorization of Reactor Effluent for Algal Biomass

To counter energy scarcity and geopolitical tensions, sustainable fuels are the need of the hour. The current study has explored a noble combination of hydrogen production in a single-chambered microbial electrolysis cell and then its reactor effluent was used for algal biomass production to promote maximum resource recovery. A heat-pretreated sugarcane bagasse fed MEC resulted in 2.1 ± 0.02 m³ of hydrogen/m³/day at an applied voltage of 0.8 V, with a coulombic efficiency of 57.6 ± 0.5 % and an electrical energy efficiency of 70.16 ± 2%. A high current density of 48 A/m² due to effective biofilm and a corresponding COD removal efficiency of 69.1 ± 2% were reported, and hydrogen production rates (HPR) for the MEC were reported as 1.85 ± 0.02 m³/m²/d on the basis of cathode surface area. Further, the MEC reactor digestate was separated in solid and liquid digestate fractions, supplied to the algal growth batch reactor, and resulted in significant biomass growth. The solid feed digestate residue produced a biomass productivity of 0.95 g/L, and liquid feed digestate filtrate produced a biomass productivity of 0.65 g/L of dry algal biomass. The study proposes maximum energy extraction and reactor digestate valorization for a circular economy and a sustainable environment.