Two-stage fractionation of sugarcane bagasse by autohydrolysis and glycerol organosolv delignification in a lignocellulosic biorefinery concept

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Bioethanol production from lignocellulose biomass offers a solution to current environmental challenges caused by fossil fuel energy resources, while satisfying the biorefinery concept. In this study, two-stage fractionation (autohydrolysis (AH) followed by glycerol organosolv delignification (GOD)) of sugarcane bagasse (SCB) was studied as a function of temperature, time, glycerol content and liquid-to-solid (LSR) ratio using experimental designs. The effect of three different AH pretreatment severities on delignification extents (DE) of the solid fractions were also evaluated. Scanning electron microscopy was used to examine the changes in the surface of SCB pretreated by AH. Energy balances of four fractionation conditions were estimated, and the use of pure and crude glycerol in GOD was evaluated based on DE and lignin contents. A DE of ∼64% was obtained at 210.3°C, 40min, LSR of 6.5 (v/w) and 80% (v/v) pure glycerol for GOD of SCB pretreated by AH at 175.8°C, 49min and LSR of 5.3 (v/w), which resulted in an energetic profitability (EP) of 141.48MJ/kgSCB. The use of crude glycerol at 80% (v/v) under the same process conditions optimized for pure glycerol also proved to be feasible (DE of ∼64% and EP of 142.67MJ/kgSCB), widening the possibilities for its direct use in GOD of SCB pretreated by AH in a 2G bioethanol integrated plant.