Pre-treatment of sugarcane bagasse with a combination of sodium hydroxide and lime for improving the ruminal degradability: optimization of process parameters using response surface methodology

A three-factor, three-level, face-centred cubic design was adopted to investigate the effect of three pre-treatment parameters, namely sodium hydroxide-to-dry biomass ratio [0.00, 0.05, and 0.10 (w/w)], lime-to-dry biomass ratio [0.00, 0.05, and 0.10 (w/w)] and residence reaction time (24, 96, and 168 h), at moderate temperature (21°C) on 24-h cumulative gas production (GP24) and delignification, as the response variables. Under the optimal pre-treatment conditions of NaOH-to-dry biomass ratio of 0.09 (w/w), lime-to-dry biomass ratio of 0.09 (w/w) and residence time of 160.3 h, the model predicted 151.6 mL gas/g organic matter (OM) versus the experimental value of 147.2 mL gas/g OM. Under the optimal conditions of NaOH-to-dry biomass ratio of 0.10 (w/w), lime-to-dry biomass ratio of 0.08 (w/w) and residence time of 156.8 h, sugarcane bagasse (SCB) was maximally delignified by 41.2%, whereas the model predicted 43.6% delignification. Under the optimal conditions determined for GP24, the neutral detergent fibre degradability of the pre-treated biomass after 24 and 48 h was 37.2 and 56.3%, respectively, a 1.90-fold and 1.58-fold over the untreated biomass, respectively. Overall, it was found that combined alkali treatment at optimal conditions effectively enhanced the ruminal degradability of SCB.