Effects of high-temperature isochoric pre-treatment on the methane yields of cattle, pig and chicken manure.

Cattle manure, dewatered pig manure and chicken manure were pre-treated in a high-temperature reactor under isochoric conditions for 15 min at temperatures between 100 and 225 degrees C with 25 degrees C intervals to study the effect on their methane yield. After 27 days of batch incubation, cattle manure showed a significant improvement in its biochemical methane potential (BMP) of 13% at 175 degrees C and 21% at 200 degrees C. Pig manure showed improvements at temperatures of 125 degrees C and above, with a maximum 29% increase in yield at 200 degrees C. The BMP of chicken manure was reduced by 18% at 225 degrees C, but at lower temperatures there were no significant changes. It was found that this method of pre-treatment could be feasible if sufficient surplus energy was available or if the energy used in the pre-treatment could be recovered.