ZnCl₂-induced fiber swelling for synergistic manufacturing of adhesive-free straw-chitin biocomposites: Performance and life cycle assessment.

Developing high-performance adhesive-free composite boards from agricultural solid waste is of critical significance for the high-value valorization of lignocellulosic biomass and the sustainable fabrication of eco-friendly advanced materials. To address the inherent limitation of low raw material utilization efficiency caused by conventional destructive pretreatments, this study innovatively fabricated biomass-based mineralized composite boards using wheat straw-a representative agricultural lignocellulosic waste-via a multi-step synergistic modification strategy. The tailored protocol involved dilute acid pretreatment for selective hemicellulose removal and lignin-cellulose skeleton exposure, TEMPO-mediated partial lignin oxidation for in-situ adhesion/filler functionalities, ZnCl₂ immersion for fiber swelling and hydrogen bond dissociation, chitin compounding, and mild wet hot-pressing for multi-component interfacial recombination. A rigorous cradle-to-gate life cycle analysis (LCA) quantitatively evaluated the process environmental footprint. Experimental results demonstrated that the strategy constructed a robust 3D cross-linked network via lignin thermal condensation and acid-catalyzed chitin-cellulose amidation, significantly enhancing mechanical properties (124.03% higher bending strength to 41.94 MPa, moderate 16.95% tensile strength gain to 13.84 MPa), water resistance (78.61% lower absorption to 26.58%), and flame retardancy. LCA identified hot-pressing and dilute acid pretreatment as primary environmental impact sources. This work provides profound scientific insights and practical technical guidance for high-value straw waste utilization and green fabrication of high-performance adhesive-free biomass composite boards.