Extraction and Characterization of <i>Opuntia ficus-indica</i> Fibrous Networks from Agricultural Waste for Sustainable Biocomposites

With increasing interest in the recovery of agricultural waste for circular solutions, this study investigates Opuntia ficus-indica agricultural waste as a sustainable, low-cost source of reinforcement fibers for biocomposites. Opuntia ficus-indica cladodes contain a complex three-dimensional hierarchical network of fibers that have biologically evolved to provide mechanical support against bending stresses. Instead of relying on single-fiber performance, these fibrous networks offer planar reinforcement through structural configuration. Fibrous networks were obtained from Opuntia ficus-indica cladodes via two extraction techniques. The comparison between water retting and solid–liquid extraction highlights relevant trade-offs between fiber quality and processing efficiency. Water retting requires significantly longer processing times but produces fibers with higher crystallinity and lower residual parenchyma content. In contrast, solid–liquid extraction substantially reduces extraction time (up to 90%), offering potential advantages in operational efficiency and scalability; however, incomplete removal of non-fibrous tissue can compromise fiber quality and composite compatibility. Older cladodes yield fibrous networks with ideal characteristics for natural fibers intended for biocomposite applications. Further work will explore the mechanical properties of the fibrous networks obtained via water retting of old cladodes and surface treatments to improve the interfacial adhesion between the fibrous networks and polymer matrix.