Tailored low-waste integrated biorefinery via hydrothermal-organosolv pretreatment for multiple bio-based products:...

Lignocellulosic biomass is a renewable carbon source with strong potential to partially replace fossil resources. However, its valorization into high-value products remains constrained by technical, economic, and environmental challenges. Fractionation is therefore a critical step in biorefinery design to enable efficient utilization of cellulose, hemicellulose, and lignin. This study developed a sequential hydrothermal (HT)-Organosolv fractionation process of rice straw. The strategy produces fermentable sugars, xylooligosaccharides (XOS) and lignin co-products for industrial applications. Under optimized conditions, the process achieved an XOS production of 18.82 g/L, and a fermentable sugar yield of 618.6 g/kg biomass, with an enzymatic hydrolysis efficiency of 94.2%. Simultaneously, the organosolv step facilitated effective lignin recovery. The extracted lignin retained its characteristic aromatic structure (H/G/S units), highlighting its potential as a bioactive co-product for further valorization. The process demonstrated an energy efficiency of 724.3 g fermentable sugars per kWh, while E-factor was in a range of 0.09-0.12. In addition, a techno-economic assessment was conducted for multiple product pathways, including lactic acid, xylooligosaccharides, and organosolv lignin. Overall, the integration of HT and organosolv pretreatments improve sugar yield, enables lignin recovery, reduce energy demand, and minimize waste, offering a promising approach for sustainable lignocellulosic biorefineries.