Sustainable biorefinery for cascade fractionation of moso bamboo into furfural, glucan oligomers and less-condensed lignin

Abstract

The sustainability and profitability of biorefineries depend on the efficient utilization of all lignocellulosic components. Therefore, developing an integrated pretreatment process that facilitates efficient fractionation and targeted valorization is essential to ensure the viability of future biorefinery systems. Here, we present an integrated fractionation strategy that efficiently separates all major lignocellulosic components and converts them into a variety of valuable products. Specifically, an ultra-low concentration of p-toluenesulfonic acid (p-TsOH) selectively depolymerizes hemicellulose to xylose at a high yield (93.86%), while preserving cellulose and lignin. The resulting xylose hydrolysate is directly mixed with methyl isobutyl ketone (MIBK) to form a biphasic system, in which the Lewis acid AlCl₃ cooperates with p-TsOH to dehydrate xylose into furfural with a yield of 93.14 mol%. The p-TsOH treated solids are subsequently subjected to mild hydrolysis in an acidified LiBr molten salt hydrate (MSH) system, yielding glucan oligomers at 76.34% and recovering lignin with a yield of 79.64%. Spectral analysis shows lignin enriched in less-condensed moieties (Hibbert's ketones, benzodioxane), favouring downstream valorization. Glucan oligomers are isolated by antisolvent precipitation. A screening environmental assessment based on the experimentally validated mass balance (100 kg bamboo feed) indicates a low fresh-material demand and manageable energy use: fresh PMI (process mass intensity, chemicals make-up only) ≈0.28 kg kg⁻¹ combined products; E-factor ≈0.30 kg kg⁻¹ (excluding water); and an energy intensity of ≈27.9 MJ kg⁻¹ (≈1.39 kg CO₂e per kg, assuming natural gas heating). This approach thus offers a practical and environmentally credible route to co-produce furfural, glucan oligomers, and structurally favourable lignin from lignocellulosic biomass.