Deep eutectic solvent pretreatment for cellulose extraction from agricultural residues

Agricultural residues represent an abundant yet underutilized resource for sustainable cellulose production in Indonesia. In this study, sugarcane bagasse, banana pseudostems, and corn cobs, three widely available Indonesian agricultural residues, were pretreated using a choline chloride-citric acid deep eutectic solvent (DES) and directly compared with conventional NaOH pretreatment under identical conditions. DES pretreatment produced cellulose-rich solids with cellulose contents of up to 41 % for sugarcane bagasse, 30 % for banana pseudostems, and 26 % for corn cobs, while effectively reducing lignin-related functional groups as confirmed by FTIR analysis and morphological changes observed by SEM-EDX. Compared to NaOH, DES generally induced more pronounced surface fibrillation and porosity. Recycling experiments revealed that DES pretreatment performance gradually declined upon successive reuse, correlating with increased solvent viscosity and pH drift. However, a gradual decline in pretreatment performance was observed during DES recycling, indicating that further optimization is needed to maintain efficiency across multiple cycles. These results demonstrate the potential of choline chloride-citric acid DES as a pretreatment strategy for valorizing underutilized agricultural residues in Indonesia, while highlighting recyclability-related limitations that require further optimization.