Green Processes for Chitin and Chitosan Production from Insects: Current State, Challenges, and Opportunities.

Chitin and chitosan are valuable biopolymers with various applications, ranging from food to pharmaceuticals. Traditionally sourced from crustaceans, the rising demand for chitin/chitosan, paired with the development of the insect sector, has led to the exploration of insect biomass and its byproducts as a potential source. Conventional processes rely on hazardous chemicals, raising environmental concerns. This critical review evaluates emerging "greener" approaches, including biological methods, green solvents, and advanced processing techniques, for chitin/chitosan production from insect-derived materials such as exuviae and cocoons. Two systematic evaluations are included: (1) a cross-comparison of chitin and chitosan yields across insect life stages and byproducts (e.g., up to 35.7% chitin from black soldier fly (BSF) larval exoskeletons can be obtained) and (2) a stepwise sustainability assessment of over 30 extraction workflows reported across 16 studies. While many are labeled as green, only a few, such as bromelain, lactic acid fermentations, or NADES-based processes, demonstrated fully green extraction up to the chitin stage. No study achieved a fully green conversion to chitosan, and green workflows typically required materials with low fat content and minimal pretreatment. These findings will be useful to identify opportunities and underscore the need to refine greener methods, improve yields, reduce impurities, and enable industrial-scale production, while sustainability data need to be generated.