Effects of Biochar Produced From Tropical Rice Straw, Corncob and Bamboo Tree at Different Processing Temperatures on in Vitro Rumen Fermentation and Methane Production

This study aimed to evaluate the effects of biochar produced from tropical biomass resources (rice straw, corncob and bamboo) at different processing temperatures (300, 500 and 700 o C) on in vitro rumen fermentation and methane production. Treatments were arranged as a 3x3 factorial with three biomass resources and three biochar processing temperatures. Added biochar occupied 3% of the substrate (DM basic). 250 mg of the air-dried substrate was incubated in 120 ml bottles, which contained 25 ml of mixed rumen fluid and buffer mineral solution. Total gas and methane production, in vitro digestibility of DM, OM, and in vitro rumen fermentation characteristics were determined at three-time points: 4, 24 and 48 hours of the incubation. Results showed that biomass resources and processing temperatures affected gas production at 4, 24 and 48 hours of the incubation (P < 0.02). Interactions between biomass resources and processing temperatures affected gas production at 4 hours (P = 0.06) and 24 hours (P = 0.001). Biomass resources and processing temperatures affected methane production at different time points of the incubation, except the effect of biomass resources at 24 hours (P = 0.406). Increased processing temperature from 300 to 700 o C reduced gas and methane production (P < 0.05). Biomass resources affected OM digestibility after 4 and 24 hours of incubation. Processing temperatures and their interaction with biomass resources affected OM digestibility after 48 hours of incubation (P < 0.001). NH 3 -N concentrations at 24 and 48h were highest for corncob, then rice straw, and lowest for bamboo tree derived biochar (P < 0.05 ) . Increased processing temperatures resulted in higher NH 3 -N concentrations at 24 and 48 hours of incubation (P < 0.05). To mitigate methane production, biomass resources and processing temperatures should be considered when utilising biochar as feed additive in ruminant diets.