A comprehensive literature review was conducted on psychrophilic anaerobic digestion and design of anaerobic digesters for treating animal manures. Anaerobic digestion of caged layer manure was studied in the laboratory at low temperatures (14–23°C). The digesters were operated to determine combinations of temperature and loading rate that gave acceptable methane yield. Acceptable methane yield was obtained for loading rates ranging between 0·15 kg VS/m day and 0·57 kg VS/m3 day for temperatures of 14°C and 23°C, respectively. The resulting data along with that taken from similar tests documented in the literature was found to approximate the van't Hoff-Arrhenius equation. This equation is then suggested as a technique for determining suitable loading rates for psychrophilic digesters based on data for digesters operated at higher temperatures.