Assessing the variability in biomethane production from the organic fraction of municipal solid waste in batch and continuous operation

This paper examines the variability in biomethane potential from the organic fraction of municipal solid waste depending on source of origin. Eight organic waste streams were examined for biochemical methane potential (BMP). Specific methane yields of between 274 and 368mL CH₄ gVS^-1 for household waste and 491-535mL CH₄ gVS^-1 for commercial waste were achieved. Inclusion of garden waste reduced methane yields. A continuous trial on commercial food waste produced an average of 560±29mL CH₄ gVS^-1 at a moderate organic loading rate (OLR) of 2kg VS m^-3day^-1 with a hydraulic retention time (HRT) of 30days. Raising the OLR to 4kg VS m^-3day^-1 led to a reduction in specific methane yield. The low carbon to nitrogen (C:N) ratio of commercial food waste (14.4) led to process instability due to total ammonia nitrogen levels in excess of 7000mgL^-1 towards the end of the trial.