@article{Niu2026, 
author = {Yuwei Niu and Lixin Jia and Yanbin Cui and Fuqing Xu},
title = {Recent advances in deep eutectic solvent pretreatment of agricultural and forestry wastes and its sustainability},
year = {2026},
journal = {Transactions of the Chinese Society of Agricultural Engineering},
volume = {42},
number = {15},
pages = {11-24},
keywords = {agricultural and forestry wastes, deep eutectic solvents, lignocellulosic biomass, techno-economic analysis, life cycle assessment},
url = {https://www.sciopen.com/article/10.11975/j.issn.1002-6819.202603251},
doi = {10.11975/j.issn.1002-6819.202603251},
abstract = {Agricultural and forestry wastes, such as crop straw, corn cobs, nutshells, and forestry residues, represented abundant and renewable lignocellulosic resources for the production of bioenergy, platform chemicals, and functional materials. However, their efficient valorization was restricted by the intrinsic recalcitrance of lignocellulose. Cellulose was embedded in hemicellulose and lignin matrices, and these three major components were stabilized by hydrogen bonding, van der Waals interactions, and covalent linkages. This structure reduced polysaccharide accessibility, limited lignin fractionation, and increased the difficulty of subsequent conversion processes. Therefore, efficient and sustainable pretreatment remained a key step for improving the resource recovery efficiency of agricultural and forestry wastes. Deep eutectic solvents (DESs) were increasingly investigated as green and tunable solvents for lignocellulosic biomass (LCB) pretreatment. Compared with conventional pretreatment methods, DESs showed potential advantages in selective lignin dissolution, polysaccharide enrichment, and preservation of reactive lignin structures. These characteristics made DES pretreatment suitable for LCB fractionation and downstream valorization. Nevertheless, the sustainability of DES pretreatment could not be determined only by delignification efficiency, sugar yield, or the green characteristics of individual solvent components. Instead, it depended on LCB feedstock characteristics, DES composition, solvent dosage, residue behavior, recovery efficiency, downstream valorization routes, and system boundaries. In this review, recent progress in DES pretreatment of agricultural and forestry wastes was summarized. Firstly, the resource characteristics of typical agricultural and forestry wastes and the structural barriers limiting lignocellulose conversion were introduced. The mechanisms of component fractionation and structural regulation by DESs were discussed, with particular attention to preferential lignin dissolution, polysaccharide enrichment, and improvement in conversion accessibility. Secondly, the downstream valorization routes of DES-pretreated fractions, together with their advantages and limitations, were reviewed. Biological conversion, chemical catalytic conversion, and material preparation were identified as the three main downstream valorization routes. The reviewed studies indicated that single low-value, fuel-oriented routes were often insufficient to fully support the economic advantage of DES pretreatment. In contrast, multi-product biorefinery strategies and whole-component utilization were more favorable for distributing pretreatment and separation costs and for improving overall process value. Thirdly, the sustainability of DES pretreatment was evaluated from the perspectives of DES component renewability, environmental safety, solvent recovery, and system-level economic and environmental performance. DESs prepared from renewable acids, alcohols, amino acids, and sugars showed potential for reducing environmental burdens. However, the advantages of DES pretreatment were strongly affected by DES residues, their effects on downstream conversion and receiving environments, target products, and solvent recovery levels. Residual DESs could affect downstream biological conversion processes, such as enzymatic hydrolysis, fermentation, and anaerobic digestion, as well as wastewater treatment, air emissions, and soil exposure. Therefore, their toxicity and biodegradability needed to be discussed within specific exposure pathways. Solvent recovery was identified as a critical factor for engineering application. Antisolvent precipitation, liquid–liquid extraction, membrane separation, and other recovery strategies showed different product selectivity, energy requirements, and recycling stability. Finally, recent techno-economic analysis (TEA) and life cycle assessment (LCA) studies were reviewed. The results showed that the economic and environmental performance of DES pretreatment varied markedly with the evaluation benchmark, system boundary, solvent recycling assumptions, and downstream product portfolio. Clear definitions of processing scale or evaluation scenario were essential for TEA, whereas the definition of a functional unit was critical for LCA. Overall, the sustainability advantages of DES pretreatment were conditional rather than intrinsic. Future research should focus on agricultural and forestry waste-derived DESs, low-energy and high-solid-loading pretreatment technologies, stable solvent recycling, and standardized full-chain TEA and LCA frameworks, which would support the engineering application of DES pretreatment in sustainable biomass refining.}
}