Modelling low-temperature methane production from cattle manure by an acclimated microbial community

The modified model of anaerobic digestion suggested earlier was used to describe a low temperature methanogenesis during a batch cattle-manure digestion by an acclimated microbial community investigated by Kotsyurbenko et al. (1993). The model showed that the pH inhibition of acetoclastic methanogens and propionate-consuming syntrophs is significant in explanation of the long-term constant values of acetate and propionate concentrations in spite of an appreciable rate of methanogenesis. A low rate of acetate production during acidogenesis as well as propionate and butyrate degradation at 6°C is compensated by a low rate of acetate consumption during acetoclastic methanogenesis. The system dynamics was described well by two alternative microbial pathways with or without participation of homoacetogenic bacteria. The corresponding kinetic coefficients were evaluated. The independent experimental data during a low-temperature cattle manure digestion without inoculation were used for the model verification. It was shown that a dominance of homoacetogenic bacteria over hydrogen-consuming methanogens needs to be considered to describe the hydrogen, methane, VFA and pH time-profiles.