Bamboo and Palm Kernel Shell Reinforcements in Sustainable Composites: Processing, Structure–property Relations and Hybrid-Design Priorities

Abstract

Bamboo-derived fibres and particles and palm kernel shell particles are increasingly investigated as reinforcements for lower-impact composite materials. Their appeal arises from renewable or residual biomass origins, low density, local availability in many tropical production regions and the possibility of displacing a proportion of mineral filler or synthetic reinforcement. Bio-origin alone, however, does not establish environmental superiority, nor does it guarantee reliable engineering performance. This critical narrative review evaluates the constituent characteristics, processing routes, interfacial mechanisms, property trade-offs, sustainability claims and scale-up requirements of bamboo- and palm-kernel-shell-reinforced composites, with particular attention to the still limited evidence for combined bamboo–palm kernel shell systems. Literature published from 1998 to 29 May 2026 was identified through scholarly metadata, open-access indexing and broad scholarly web searches, supplemented by citation chaining. Evidence was appraised for methodological transparency, comparability, relevance and consistency rather than pooled statistically. The most defensible conclusion is that performance depends less on the nominal biofiller identity than on reinforcement morphology, moisture condition, surface chemistry, particle-size distribution, dispersion, fibre orientation, loading, matrix selection and process-induced porosity. Bamboo fibres can provide directional crack bridging and stiffness, whereas palm kernel shell particles can contribute hardness, packing and dimensional constraint; these functions are potentially complementary but remain insufficiently validated in direct hybrid studies. Alkali treatment, compatibilisation and hierarchical interfacial modification can improve stress transfer, yet excessive treatment may damage bamboo fibres, increase processing burdens or obscure the environmental advantage. Moisture uptake, property scatter, inconsistent feedstock characterisation and limited long-term ageing data remain major barriers. Sustainability assessments are weakened by narrow cradle-to-gate boundaries and omission of drying, chemical treatment, matrix production, service life and end-of-life scenarios. Progress therefore requires factorial mixture designs, standardised feedstock reporting, durability-led testing, process-scale validation and comparative life-cycle assessment. Bamboo and palm kernel shell reinforcements are credible components of sustainable composite strategies, but their value is conditional on disciplined materials engineering and transparent system-level accounting.