A Data-Driven Semi-Quantitative Framework for Comparative Screening and Tiering of Cellulose Nanocrystal Isolation Pathways: Implications for Process Assessment and Future Optimization.

Cellulose nanocrystals (CNCs) are lignocellulose-derived nanomaterials valued across multiple industries due to their low toxicity and density, high mechanical strength and surface area, biodegradability, and potential as renewable alternatives to fossil-based materials. However, CNC isolation remains highly variable, with no structured framework for comparing processing routes according to their integrated operational burden, defined here as the combined relative Labor, Waste, and Cost scores assigned to the reported processing conditions. This study presents a literature-derived, semi-quantitative Scoring and Tiering framework for comparing CNC isolation processes and their main stages (alkaline treatment, bleaching, and acid hydrolysis), based on the relative operational burden reported across 140 studies. The burden was assessed across Labor, Waste, and Cost categories. The proposed framework enables comparison at process, stage, and category levels. The Waste category contributed most strongly to the calculated scores, whereas Labor contributed less. Bleaching showed the greatest variability, while alkaline treatments were more standardized. The proposed framework provides a transparent, literature-derived, semi-quantitative tool for structured screening, comparison, and prioritization of CNC isolation pathways based on their relative operational burden. Its Tiers are intended as comparative indicators rather than absolute measures of sustainability, scalability, or industrial performance. Future laboratory- and pilot-scale validation incorporating feedstock variability, standardized process-balance data, and integration of the Process Tier with CNC quality metrics could enable a more comprehensive evaluation of CNC isolation pathways.