Multipurpose cellulose nanofiber/chitosan/black soldier fly oil bioplastic films toward functional, biodegradable, and sustainable packaging

The valorization of industrial and insect-derived biomass into functional materials offers a sustainable alternative to petrochemical-based polymers. In this study, bio-based composite films were developed by integrating cellulose nanofibers (CNF) from paper waste with chitosan (CS) and black soldier fly larvae oil (BSFL), using citric acid as a green crosslinking agent. A stable system was achieved through assisted dispersion of the hydrophobic oil phase, followed by structural consolidation within the CNF/CS network during film casting, where BSFL oil is incorporated as a physically dispersed phase rather than participating in covalent crosslinking. Structural and thermal analyses reveal a progressive transition toward a more amorphous and constrained polymer network, with the crystallinity index decreasing from 59% (CNF) to 38% (CNF/CS) and 24% (CNF/CS/BSFL), alongside an increase in glass transition temperature to approximately 340 °C, indicating restricted chain mobility arising from combined crosslinking and physical confinement effects. The optimized films exhibited a tensile strength of 52.2 MPa and reduced swelling behavior (<50%), demonstrating enhanced mechanical integrity and water resistance, while maintaining high transparency (86.17%) with moderate haze (53.27%). These improvements translated into practical performance, where net-style packaging prototypes extended the shelf life of grapes and tomatoes to 20–21 days, outperforming conventional plastic packaging. This work highlights a cooperative structure–property relationship and presents a scalable strategy for converting waste-derived resources into engineered biocomposites for sustainable packaging applications.