Field performance of small scale anaerobic digesters treating food waste

Abstract

Internationally, it has been reported to have over 30 million small scale anaerobic digesters. Despite the large number of existing small scale anaerobic digesters and a growing interest in food waste digestion, there has been a paucity of research regarding low cost digester's performance. This paper aims to provide a snap shot of the performances of small scale digesters treating food waste exclusively. The performance of six small scale digesters, ranging from 1m3 to 25m3 were recorded and analysed. Results showed consistently high substrate degradation ranging from 92.5% to 97.5% COD with daily methane production ranging between 0.25m3/kg VS and 0.46m3/kg VS. Composition of biogas analyzed yielded between 63.1%–66.8% CH4 and between 27.4%–33.3% CO2. Results also revealed a negative linear correlation between gas production and % total solids and a positive linear correlation between gas production and the organic loading rate. While small scale digesters can effectively degrade food waste; the total dependency on digester for their gas requirements is unlikely and alternative fuel source is required.