Natural fiber-based materials for additive manufacturing: A comprehensive review of materials, processing challenges, and sustainable applications

The increasing demand for environmentally responsible manufacturing practices has intensified research on natural fiber-reinforced composites for additive manufacturing (AM). Natural fibers such as hemp, flax, jute, sisal, bamboo, and cellulose-based derivatives offer attractive benefits, including low density, renewability, biodegradability, and reduced environmental footprint. This review provides an integrated assessment of natural fiber feedstocks, preprocessing techniques, fiber–matrix compatibility strategies, and their suitability across major AM technologies. The article critically examines processing challenges related to moisture sensitivity, thermal degradation, inconsistent fiber morphology, and interfacial adhesion, alongside mitigation strategies such as alkali treatment, silane coupling, plasma modification, and optimized extrusion conditions. A comparative discussion of AM techniques—including FDM, DIW, SLA, DLP, powder bed fusion, and bioprinting—is presented with emphasis on material compatibility, printability, and mechanical performance. Reported mechanical improvements in natural fiber composites include up to 615% increases in tensile strength for cationized hemp fibers, 84% increases for CNF-reinforced PLA, and 5–6-fold improvements in impact resistance for continuous cotton fiber composites. Sustainability pathways, including recyclability, circular economy integration, carbon sequestration potential, and end-of-life biodegradability, are also highlighted. The review identifies key research gaps such as the lack of standardization in fiber preparation, limited understanding of rheology–printability correlations, and insufficient life cycle assessments. Overall, natural fiber-based materials demonstrate strong potential to replace conventional synthetic polymer composites in AM, particularly for lightweight structural, biomedical, consumer product, and packaging applications.