Methane production from cattle waste in laboratory reactors at 40 degrees and 60 degrees C after solid-liquid separation.

Whole dairy waste and liquid effluent separated from the same waste with a solid-liquid separator were fermented at mesophilic and thermophilic temperatures. Chemical analyses of the two materials were similar. Methane production was superior in thermophilic reactors. With subtrates adjusted to 4.1% volatile solids, average methane production at 60 degrees C (166 ml/g volatile solids fed to reactors at 3- and 6-day retention time) was as efficient as the 40 degrees C (162 ml/g at 5- and 10-day retention times). Thermophilic reactors produced 1.67 liter methane/liter reactor per day as compared to .93 liter for mesophilic reactors. Efficiency of methanogenesis was no greater for whole waste than for separated effluent. Production of methane for the two substrates averaged over retention times and temperatures was 156 ml/g volatile solids fed to reactor for whole waste and 173 ml/g for separated effluent.