Biogas production from pig manure fed Opuntia robusta diets.

This study was conducted with the aim to evaluated biogas production from swine manure of fattening pig fed 0, 5, 10 or 15% of Opuntia robusta (dry matter basis). Sun dried swine manure was stored in 20-L containers during 45 d. Biogas production was measured for 4 days in 1-L digesters at 32 °C, 48 digesters were used (12 by treatment), every day the material of the collector bags was extracted and was consider biogas if that was flammable. Volume of flammable gas, flame time and burning temperature were recorded daily. During the experimental periods gas production was different (P<0.001); 0% diet produced (963 ml day-1), 5% OR produced biogas (567 ml day-1); 10% OR diet produced (623 ml day-1) and 15% OR diet (170 ml day-1). Flame time showed similar trend with the volume with adjusted media of 19, 13, 17 and 4 seconds for 0, 5, 10 or 15% OR diets. Flame temperature was similar (P=0.64) 660°C when gas was flammable. The sun dried swine manure from Opuntia robusta diets reduces the biogas production, therefore OR’s manure could have less environmental impact than control diet manure for a faster degradation rate during the drying period.