Integrating Microbial Electrolysis Cell with Dark Fermentation to Enable Biohydrogen Production from Waste Corn Stover

Biological hydrogen production is a promising route for converting lignocellulosic waste biomass into energy. Dark fermentation (DF) can efficiently convert recalcitrant biomass into hydrogen gas, but its yield is thermodynamically limited, resulting in limited hydrogen recovery coupled with the production of a fermentation effluent rich in residual organics that need to be removed from solution. Microbial electrolysis cells (MECs) can convert these residual compounds into hydrogen, enhancing overall yield while limiting downstream treatment. Here, we integrated DF with a bench-scale MEC (100 cm2), enabling stable hydrogen production from corn stover. The integrated DF-MEC achieved a maximum hydrogen yield of 5.0 mol H2/mol saccharide and a hydrogen production rate of 3.45 L/L-d. The MEC delivered high current density (up to 12.6 +- 0.5 A/m2) and hydrogen productivity (28.6 +- 1.9 L/L-d) with unamended fermentation effluent, comparable to or exceeding smaller-scale MECs previously reported. Anodic Coulombic efficiencies of up to 75% were achieved, demonstrating efficient conversion of fermentation-derived organics into hydrogen. Overall, the integrated DF-MEC system significantly increased hydrogen recovery (5.0 mol H2/mol saccharide) compared to DF alone (2.0 mol H2/mol saccharide), highlighting the advantage of coupling biological fermentation with bioelectrochemical conversion. Our results establish an integrated DF-MEC platform as a practical approach for intensifying hydrogen recovery from lignocellulosic waste streams while simultaneously polishing fermentation effluents through coupling biological fermentation with bioelectrochemical conversion.