Deep eutectic solvent-assisted lignocellulose fractionation for integrated biorefineries: process performance,...

Deep eutectic solvents (DESs) have gained attention as tunable media for fractionating lignocellulosic biomass into cellulose-rich solids, hemicellulose-derived streams, and recoverable lignin. This review examines acidic, neutral, alkaline, amino-acid-based, ternary, cosolvent-assisted, physically intensified, hydrothermal, and enzyme-integrated DES systems using a common biorefinery framework. The analysis considers fractionation effectiveness, product-stream quality, process intensity, downstream compatibility, and implementation readiness. Particular attention is given to the effects of DES composition, acidity, polarity, viscosity, water content, feedstock structure, lignin quality, enzyme compatibility, solvent recovery, and process integration. Recent studies show that ternary, alkaline, ethanol-assisted, hydrothermal, ultrasound-assisted, and one-pot systems can improve fractionation and downstream conversion. However, many studies still rely on high solvent loading and extensive washing and provide incomplete hemicellulose and lignin balances. Information on inhibitor formation, changes in solvent composition during reuse, scale-up, techno-economic performance, and life-cycle impacts also remains limited. DES-assisted fractionation should therefore be evaluated as a potentially sustainable biorefinery strategy whose performance depends on solvent recovery, energy and water demand, product quality, and process integration. Future studies should emphasize high-solids processing, standardized lignin-quality assessment, complete mass and energy balances, solvent maintenance during reuse, and combined techno-economic and life-cycle evaluation.