Integrating dark fermentation and electrohydrogenesis for enhanced biohydrogen production from food waste

Abstract

Biohydrogen production from food waste offers a sustainable and carbon-neutral alternative to fossil fuels. However, its large-scale application is limited by the rapid hydrolysis of biodegradable organics, resulting in the accumulation of inhibitory byproducts such as ammonia and volatile fatty acids (VFAs), especially lactic acid. These compounds suppress hydrogen-producing bacteria and reduce system efficiency. Integrating dark fermentation (DF) with microbial electrolysis cells (MECs) has emerged as a promising approach to overcome these limitations by converting residual organics into additional hydrogen via electrohydrogenesis. Optimization of operational parameters such as pH, hydraulic retention time (HRT), and organic loading rate (OLR) further enhances hydrogen yield by minimizing VFA accumulation and improving system stability. Integrated DF–MEC systems have achieved hydrogen yields of up to 1608.6 ± 266.2 mL H₂ per g COD consumed and COD removal efficiencies of 78.5 ± 5.7%. Heat pretreatment and the use of genetically engineered microbial strains have been shown to further enhance hydrogen production. Engineered strains have delivered hydrogen yields ranging from 0.47 to 1.88 mol H₂ per mol glucose. MEC integration has also demonstrated a 30–40% increase in hydrogen production compared to standalone DF systems. The digestate from lactate-driven DF, enriched with VFAs such as acetate and lactate, provides an excellent substrate for MECs, thereby enhancing electrohydrogenesis. Despite high initial capital costs, the long-term benefits, such as waste valorization, greenhouse gas reduction, and renewable energy recovery, make the DF–MEC system a viable and scalable solution for sustainable hydrogen production from food waste.