A review on the use of agricultural and animal byproducts in polymer composites: a sustainable approach to materials reinforcement

Abstract The increasing need for eco-friendly replacements to synthetic materials has motivated wide research into polymer biocomposites reinforced with natural byproducts. This review investigates the use of agricultural wastes and animal byproducts, specifically rice husk (RH) and cow bone particles (CBP), as reinforcements in polymer matrices for sustainable material development. RH, rich in silica, enhances thermal stability and stiffness, while CBP, primarily composed of calcium phosphate and collagen, improves toughness, bioactivity, and mechanical strength. The review summarizes recent studies on both single and hybrid composites, signifying that RH-CBP hybrid systems can offer synergetic enhancements in flame resistance, strength, thermal behavior, and biodegradability. These hybrid biocomposites find applications in automotive parts, structural panels, packaging materials, biomedical, and consumer goods. Comparative assessments reveal that, despite challenges such as moisture absorption and dispersion, bio-fillers are a cost-effective and eco-friendly substitute to traditional synthetic fibers, meeting the increasing need for sustainable materials. The paper also highlights research gaps, specifically in optimizing hybrid bio-fillers ratios, certifying durability under diverse environmental settings, and providing standardized processing techniques, stressing the need for further research into hybridization strategies for multifunctional applications.