Psychrophilic anaerobic digestion of semi-dry mixed municipal food waste: For North American context

Treating municipal organic solid wastes economically is a challenge, predominantly in cold and high-altitude regions, where the temperature can be below 20 degrees C. The aim of this research was to improve the anaerobic digestion (AD) of food waste (FW) with or without animal manure in a low-cost psychrophilic anaerobic digestion in sequencing batch reactor (PADSBR) at 20 degrees C. Feed solid content was varied from 37% to 13%, mainly to validate the stability of digestion process suitable for different scenarios and OLR was increased from 0.8 to a maximum of 4.2 kg VS/m(3) d. Results showed that methane production from FW mixture was feasible at low-temperature and specific methane yield of 0.401 +/- 0.01 m(3) CH4/kg VSfed was observed even at high OLR. When loading rates applied to bioreactors were increased by 225%, methane conversion rates decreased only by 10%, while maintaining the operational stability (e.g. no foaming, no acidification). Methane content was constantly in the range of 64-69%, which shows the quality of biogas is excellent and remained almost steady. The results suggest that PAD SBR at 20 degrees C is comparatively efficient in saving the heat energy and at the same time obtains the CH4 values close to mesophilic/thermophilic conditions. This concept is particularly vital for cold countries facing energy constrains. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.