Mesophilic Dark Fermentation of Food Waste for Biohydrogen Production in a Mixed Batch Reactor

Biohydrogen is considered a promising biofuel of strategic interest characterized by high energy content per mass unit, easiness in producing electricity through fuel cells, a process that produces water as the only by- product. Among the bioprocesses aimed at biohydrogen production, dark fermentation is gaining a worldwide interest for being both environmental friendly and relatively efficient. In this perspective, food waste represents a good substrate for biohydrogen production through dark fermentation, being made of biodegradable organic matter and nutrients essential for the growth of microorganisms driving this process. In this study, biohydrogen production through a mesophilic batch dark fermentation (37 °C) was performed. The effect of the progressive adaption of the inoculum on the food waste feedstock was evaluated. Both the liquid and the gas phases produced during the incubation were analyzed. Microbial biomass, pH, biogas volume and composition were also monitored. Biohydrogen yields increased with progressive inoculum acclimation to the food waste, reaching about 35 mL/gVSFW in 3 days of dark fermentation, with an average biohydrogen in the biogas produced of 55 %, corresponding to a theoretical energy recovery of about 34 kWh for 1 ton of food waste.