Effects of levels of tropical rice husk-derived biochar in diet-based high rice straw on in vitro methane production and rumen fermentation

This study was conducted to evaluate effects of biochar levels in diets on in vitro methane emission and rumen fermentation. Biochar, produced from rice husk, pyrolysis at 700 °C, was supplemented in diets at 0, 1, 3, 5, and 7% (dry matter (DM) basis). Total gas, methane production, dry matter (DM) and organic matter (OM) digestibility, pH, and NH 3 -N concentration were measured at 4, 24, and 48 h after incubation. Results showed that total gas and methane emission of diets with biochar was lower than that of the diet without biochar. Methane production decreased linearly ( P < 0.01) with increasing biochar levels. DM and OM digestibility, as well as NH 3 -N concentration of diets with 1 or 3% biochar, was similar to the diet without biochar. When the dietary biochar level was increased up to 5 or 7% in diets, OM and DM digestibility and NH 3 -N concentration decreased significantly compared to the diet without biochar ( P < 0.01). Our findings implicated that supplementing 3% biochar (DM basis) to the diet is recommended to reduce methane production.