Energy Recovery from Food Industry Sludge through Anaerobic Digestion

Abstract

Sludge generated in three Portuguese food processing companies - chestnut, dairy and fruit-cereal – were anaerobically digested, over 77-day experimental time, under batch mode and mesophilic conditions of temperature, to assess the anaerobic digestion process applicability to the energetic valorisation of these organic material surpluses. The biogas production of 106-144 mL (STP conditions) and the methane content of 61-72% indicate that all tested sludge reserve an energetic potential through anaerobic process. Comparatively, the sludge digestion from the fruit-cereal processing industry provided the largest volume of biogas, while the milk-yogurt reached the highest methane yield amount (209 L CH4 kg-1 VSinfluent). Anaerobic digestion is an alternative process that, according to the obtained results, can advantageously contribute to solving the problem of excess sludge in the food industry by converting it into a digestate for agricultural purposes and an energy carrier vector (biogas/methane).