Field performance of small scale anaerobic digesters treating food waste

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 1 m3 to 25 m3 were recorded and analysed. Results showed consistently high substrate degradation ranging from 92.5% to 97.5% COD with daily methane production ranging between 0.25 m3/kg VS and 0.46 m3/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.

► Five operating anaerobic digesters fed exclusively with food waste were monitored.
► Substrate degradation ranged between 92.5% and 97.5% chemical oxygen demand.
► Daily methane production ranging between 0.25 and 0.46 m3/kg VS.
► Negative linear correlation between gas production and %TS.
► Positive linear correlation between gas production and organic loading rate.