Anaerobic slurry co-digestion of poultry manure and straw: effect of organic loading and temperature

In order to obtain basic design criteria for anaerobic digestion of a mixture of poultry manure and wheat straw, theeffects of different temperatures and organic loading rates on the biogas yield and methane contents wereevaluated. since poultry manure is a poor substrate, in term of the availability of the nutrients, externalsupplementation of carbon has to be regularly performed, in order to achieve a stable and efficient process. thecomplete-mix, pilot-scale digester with working volume of 70 l was used. the digestion operated at 25°c, 30°c and35°c with organic loading rates of 1.0, 2.0, 2.5, 3.0, 3.5 and 4.0 kg volatile solid/m3d and a hrt of 15 days. at atemperature of 35°c, the methane yield was increased by 43% compared to 25°c. anaerobic co-digestion appearedfeasible with a loading rate of 3.0 kg vs/m3d at 35°c. at this state, the specific methane yield was calculated about0.12 m3/kg vs with a methane content of 53–70.2% in the biogas. the volatile solid (vs) removal was 72%. as aresult of volatile fatty acid accumulation and decrease in ph, when the loading rate was less than 1 or greater than4 kg vs/m3d, the process was inhibited or overloaded, respectively. both the lower and higher loading ratesresulted in a decline in the methane yield.