OFMSW Fermentation with Different Inocula and Its Effects on Methane Production

Purpose Thermodynamically, lactic acid and ethanol allow the best energy recovery among all common metabolites for methane production. The main objective of this work was to favor the fermentation of OFMSW for better lactic acid and ethanol production. Methods As a first step, OFMSW was fermented using two different inocula: Yeast (Saccharomyces cerevisiae) and anaerobic granular sludge from a UASB wastewater treatment plant. The naturally occurring microorganisms in OFMSW were always present and active. The second step was the methanization of digestates from the previously mentioned fermentations. Results OFMSW fermentation with NOM and anaerobic granular sludge + NOM mainly produced lactic acid; yeast fermentation produced ethanol, lactic acid, and volatile fatty acids. Methane production from the fermentation digestates increased with decreasing substrate concentration, and higher methane production was obtained with the digestate from NOM fermentation. Higher concentrations of propionic and butyric acids were observed for higher digestate concentrations from yeast and NOM after 30-day methanization. Conclusion Every one of the fermented digestates produced more methane than unfermented OFMSW. Methane produced from unfermented OFMSW was not inhibited as propionic, and butyric acid concentrations were the lowest of all four cases.