Eco-design of cellulose nanocrystals through ESCAPE method at lab-scale

Cellulose nanocrystals (CNC) are produced mainly following top-down procedures by cleaving the hierarchical structure of cellulose. Herein, we investigate and compare, at lab scale, two different processes for CNC production: the standard one, based on acidic treatment by H₂SO₄, and an alternative approach involving an oxalic acid/choline chloride deep eutectic solvent (DES), with the aim of both verifying the allegedly "greener" impact of the latter protocol and of identifying those critical steps to intervene on for an appropriate process eco-design. CNC from both methods were produced and characterized in terms of chemical composition, surface charge, and morphology. At the same time, the sustainability of the lab-scale processes was evaluated using the "ESCAPE" tool. Considering the different energy mixes provided by two European countries (Italy and France), sustainability was assessed in terms of embodied energy (EE) and carbon footprint (CF). The DES-based process was found to be more sustainable due to its shorter purification time and higher mass recovery. These findings allowed to identify the most impactful steps in the synthesis processes, namely purification phases and water consumption. Targeted improvements of these steps reduced the overall environmental impact with minimal effect on the final chemical and physical properties of the materials.