Study of the performance of a thermophilic biological methanation system

Abstract

This study investigated the operation of ex-situ biological methanation at two thermophilic temperatures (55°C and 65°C). Methane composition of 85-88% was obtained and volumetric productivities of 0.45 and 0.4LCH₄/Lreactor were observed at 55°C and 65°C after 24h respectively. It is postulated that at 55°C the process operated as a mixed culture as the residual organic substrates in the starting inoculum were still available. These were consumed prior to the assessment at 65°C; thus the methanogens were now dependent on gaseous substrates CO₂ and H₂. The experiment was repeated at 65°C with fresh inoculum (a mixed culture); methane composition and volumetric productivity of 92% and 0.46LCH₄/Lreactor were achieved in 24h. Methanothermobacter species represent likely and resilient candidates for thermophilic biogas upgrading.

Keywords: Biogas; Biological methanation; Methanogenic archaea; Power to gas; Volatile fatty acids.