Two-Phase Anaerobic Digestion of Food Wastes for Hydrogen and Methane Production

Food waste is successfully treated by anaerobic digestion process, where the organic matter is converted into methane. On the other hand, food waste bioprocessing to produce hydrogen has been only recently implemented, wherein a number of expensive pretreatment techniques have been proven. This chapter describes the recent studies on hydrogen and methane production from food waste using a dark fermentation reactor coupled with anaerobic digestion at thermophilic temperature. The use of external chemicals to control the pH was avoided, but sludge recirculation from the methanogenic reactor to the dark fermentation was exploited to maintain the system in an optimal pH range for production of a gas mixture with the typical composition of enriched methane. Ammonia accumulation and variation was observed during 1 year of process monitoring and was finally elaborated with a chemometric analysis tool, giving back useful results to be implemented in an automatic process control based on correlation between ammonia, conductivity and alkalinity.