Effect of pH value on biohydrogen production from food waste

In the present study we tried to fill some existing gaps in the knowledge of fermentative H2 production from food waste. Fractions of municipal solid waste such as food waste (FW) and the broader mixture of materials known as organic fraction of municipal solid waste (OFMSW, basically FW combined with non-recoverable paper residues) may represent relatively inexpensive and suitable sources of biodegradable organic matter for H2 production, mainly due to their high carbohydrate content and wide availability. The main issues dealt with in the present study include: i) evaluating the influence of the operating pH on fermentative H2 production from FW and defining the optimal pH range, ii) comparing the H2 yield with or without external inoculum addition, iii) evaluating the effect of thermal pre-treatment of the inoculum on process kinetics and overall H2 production. Several batch fermentation tests were carried out on FW samples, by systematically varying the operating pH, the addition of an external inoculum and its pre-treatment. The different pH values adopted in the batch tests exerted a remarkable influence on H2 yield, clearly showing that adequate pH control is one of the key factors for significant H2 production to be achieved. The best performance was observed at pH = 6.5 for all the batch tests performed. In particular, by fixing the pH value at 6.5, using a thermal pretreated activated sludge and optimizing the F/M ratio a specific H2 production of 120 Nl H2/kg VS was obtained.