Fermentative biohydrogen production from a novel combination of vermicompost as inoculum and mild heat-pretreated fruit and vegetable waste

This study reports for the first time on biohydrogen production by dark fermentation using a novel combination of mild heat-pretreated fruit and vegetable waste (FVW) as raw material and vermicompost as an economical source of hydrogen-producing bacteria. A suspension rich in reducing sugars obtained from FVW was used at different initial concentrations (5 to 25 g reducing sugars/L) during the bioprocess conducted in batch reactors at mesophilic temperature of 35 °C. The use of a mild heat-pretreated substrate and the consequent elimination of the natural microbiota present in the FVW led to higher hydrogen production than the control. Clostridium species, hydrogen-producing bacteria via butyric acid fermentation pathway, were the dominant microorganisms in the bioprocess. Hydrogen production, volumetric hydrogen production rate, and pretreated substrate degradation efficiency (63.0 mL/g VS, 372.6 mL/L/d, and 50% BOD5, respectively) obtained in the experiments performed with the highest substrate concentration demonstrated that the developed bioprocess was promising simultaneously leading to high hydrogen contents in biogas and high substrate removal efficiencies.