From agroforestry wastes to high-performance cellulose nanofiber aerogels: mechanisms, engineering strategies, and building energy-saving applications

The accelerating demand for building energy conservation and carbon reduction has intensified global interest in high-performance and sustainable thermal insulation materials. Aerogels, characterized by ultra-low thermal conductivity and lightweight porous structures, have emerged as promising candidates for next-generation green building applications. Among them, cellulose nanofiber (CNF) aerogels derived from abundant agroforestry biomass wastes offer a renewable and low-carbon alternative with significant technological potential. This review systematically examines the extraction pathways and resource diversity of CNFs sourced from agroforestry residues, clarifies the key processes and underlying principles governing CNF aerogel fabrication, and synthesizes recent advancements in mechanical reinforcement and flame-retardant engineering. The thermal-insulation mechanisms of CNF aerogels are analyzed from structural and physicochemical perspectives, followed by an overview of emerging CNF-based insulation products, such as aerogel panels, transparent aerogel glass, and flexible insulation fabrics, toward practical deployment. By integrating material fundamentals with engineering strategies and product development, this work provides comprehensive guidelines for converting agroforestry wastes into high-performance CNF aerogels and evaluates their industrial prospects as innovative insulation solutions for energy-efficient buildings.