Abstract
The objective of the present study was to investigate the running cost of methane fermentation by reducing urinary nitrogen excretion in pigs. Using slurry with reduced nitrogen excretion from growing-finishing pigs fed a reduced crude protein (CP) diet with apple pomace (CP : 11.6%), mesophilic methane fermentation was conducted to determine fermentation efficiency and the characteristics of the effluent. Concentrations of nitrogen and ammonia in the slurry from pigs fed a low CP diet with apple pomace were less (respectively, 13% and 34%) than those in the slurry from pigs fed the standard diet (CP : 15.3%). For the effluent from methane fermentation, the concentrations of nitrogen and ammonia for pigs fed a low CP diet were less (9% and 26%, respectively) than those for pigs fed the standard diet. By feeding a low CP diet with apple pomace, the volume of gas production from methane fermentation was 1.3 times greater than that from the standard diet. Composition of H2S in fermentation gas from a low CP diet with apple pomace was reduced 80% compared to that from a standard diet.
In conclusion, gas energy from mesophilic methane fermentation was 1.3 times greater from a low CP diet with apple pomace than with a standard diet. The cost of removing H2S can be decreased 70% when a low CP diet with apple pomace is used compared to the standard diet.
