Recent progress in wood-based polymer composites toward cleaner production and circular material systems

Wood–polymer composites (WPCs), which are formed by embedding natural fillers such as wood flour (WF), lignin, and bamboo into polymer matrices, have gained increasing attention as eco-friendly alternatives to conventional synthetic materials. Their appeal lies in the combination of renewable components, their cost-effectiveness, and the ability to tailor their mechanical properties through careful formulation and processing. However, the widespread adoption of WPCs is limited by challenges such as moisture sensitivity, poor interfacial bonding between the hydrophilic fillers and the hydrophobic polymers, and degradation of the structural integrity at high filler loadings. This review comprises insights from over 200 peer-reviewed studies published in the past decade and focuses on two critical aspects, namely enhancement of the mechanical performances of WPCs and their optimization for targeted applications. Key advancements include control of the filler morphology, chemical surface treatments, the integration of hybrid nanofillers, and matrix modifications that improve the interfacial adhesion and stress transfer properties. In addition, the effects of different processing technologies, including extrusion, injection molding, compression molding, and additive manufacturing, are examined with respect to the composite structure, anisotropy, and scalability. This review also highlights the evolving scope of WPC applications that range from conventional sectors, such as the construction and automotive sectors, to advanced uses, such as flame-retardant and electrically conductive composites, transparent wood structures, and bio-based adhesives. By mapping recent developments in material design, processing, and end-use functionality, this review provides a comprehensive roadmap for the future research and industrial advancement of WPCs within circular and sustainable material systems.