Valorization of White Lupin Straw Through Mild Dilute Acid Hydrothermal Treatment: A Sustainable Route for Monosaccharide and 5-Hydroxymethylfurfural Production

This study investigates the potential use of white lupine straw (WLS), an underutilized agricultural by-product, as a raw material to produce valuable biochemicals such as monosaccharides and 5-hydroxymethylfurfural (5-HMF) through hydrothermal pretreatment. The aim was to optimize mild reaction conditions to maximize the recovery of these products while minimizing degradation. The hydrothermal treatment of WLS in subcritical water with trace amounts of sulfuric acid was performed, followed by a two-step approach to evaluate the yields of hemicellulose and 5-HMF. The highest monosaccharide yield (163 g/kg) was achieved at temperatures between 174 and 181 °C and a holding time of 7–14 min, while the 5-HMF production was 139.9 g/kg at 199–203 °C and after 0.5–4.5 min. These results suggest that optimal 5-HMF production also increases the remaining solid residue. This study highlights the feasibility of WLS as a sustainable, low-cost biomass resource. It highlights the balance between temperature and time to maximize valuable product yields. The results contribute to advancing biorefinery processes by demonstrating that WLS can be effectively converted into bioethanol precursors and industrial chemicals, supporting circular bioeconomy principles and providing an environmentally friendly alternative to burning crop residues.