Psychrophilic anaerobic digestion of screened dairy manure

Psychrophilic (12°C) anaerobic digestion in a laboratory scale (4 l) fixed-film reactor fed with screened dairy manure was successfully attained from a mesophilic fixed-film reactor. Within an operational period of $\text{2}\text{1}\text{2}$ month, methane production rate of 0.27 l CH₄ l⁻¹ day⁻¹ obtained at 1 day hydraulic retention time. The highest methane production rate was 0.30 l CH₄ l⁻¹ day⁻¹ at a loading rate of 28.7 g VS l⁻¹ day⁻¹ at 1 day hydraulic retention time. This study indicates that fixed-film reactor can handle a sudden change of temperature without stopping gas production, and also a high loading rate and short hydraulic retention time with no signs of process instability.