Kinetic analysis of the key stages of low temperature methanogenesis

A simple method was derived to analyze the kinetics of low temperature substrate degradation by microbial consortia of forest, tundra, or prairie soils, leaf litter and pond silt. Some limitations of the method are discussed. This method originated from a generalized model of anaerobic digestion developed earlier. Hydrolysis, acetogenesis and acetoclastic methanogenesis were analyzed during conversion of endogenous organic matter, mixture of hydrogen and carbon dioxide (H2/CO2), and volatile fatty acids. Generally, the Contois equation was applied to describe hydrolysis kinetics of endogenous material, while Monod kinetics was used to describe acetogenesis and methanogenesis stages, but the approximations of Contois and Monod equations were used also in the special cases. The kinetic coefficients of hydrolytic, homoacetogenic and acetoclastic methanogenic bacteria were determined at low and moderate temperatures and the effect of temperature was investigated. At the extremely low temperature of 6°C the model’s maximum specific growth rate of acetoclastic methanogens differs not so much (0.011–0.022 day−1) for tundra soil, pond silt, cattle and pig manure. The rate constants increase substantially at higher temperature.