Effect of inoculum to substrate ratio (ISR) on hydrogen production through dark fermentation of food waste

The objective of the present study is to evaluate the influence of the inoculum to substrate ratio (ISR) on hydrogen production through dark fermentation of food waste (FW). Batch tests were performed adopting ISR values ranging between 0.05 and 0.25 g VSINOCULUM/g VSSUBSTRATE under mesophilic conditions (39°C) and adopting a pH set-point value of 6.5. Activated sludge was used as inoculum without any pre-treatment aimed at harvesting specific hydrogenogenic biomass. The obtained results underlined that an appropriate choice of the ISR was essential in order to increase H2 yield, to decrease lag phase duration and to maximize the mass of FW treated in the reactor. The best performance in terms of H2 yield (88.8 Nl H2/kg VSFW) was observed at ISR = 0.14 g VS INOCULUM/g VS SUBSTRATE.