Recovering Bioenergy from Municipal Organic Wastes Through Anaerobic Co-Digestion

Abstract

Gainesville Regional Utility is investigating the feasibility of anaerobic digestion to reduce municipal organic waste accumulation, mitigate greenhouse gas emissions, and produce biogas as a renewable energy source. Since biogas generation from food waste can be unpredictable due to its variable composition, the objective of this study was to see how co-digestion of different ratios of food waste to wastewater biosolids would impact biomethane production and digestate quality. A biomethane potential test was carried out on four conditions with varying food waste to wastewater biosolids ratios, 0:100, 10:90, 30:70, and 50:50. The inoculum was collected from a bench scale digester from the UF Agricultural and Biological Engineering department and the wastewater biosolids were collected from three wastewater treatment plants in Gainesville, Florida. The food waste substrate was a prepared mixture. After 18 days of digestion, the average specific methane production of each condition (0%, 10%, 30%, and 50% food waste) was 147, 175, 240, and 336 mL/g VS added, respectively. Methane production increased as the ratio of food waste increased. The highest methane production was observed at the 50:50 ratio. This work demonstrated that adding food waste to wastewater biosolids can improve anaerobic digestion performance and provide greater energy recovery as methane.