From Bioresource Waste to Biocomposite: Modifying Posidonia Oceanica Fibers for Sustainable Biocomposites

The urgent need for sustainable material alternatives has accelerated interest in biobased composites. This study investigates Posidonia oceanica (PO) waste fibers, an abundant yet underutilized lignocellulosic marine resource, as reinforcement in fully biobased composites. To enhance fiber performance, surface modifications were conducted using sodium hydroxide, succinic acid, malonic acid, and pectinase enzyme via conventional, ultrasonic, and microwave-assisted methods. Among these, ultrasonic-assisted treatments with succinic acid and pectinase produced the most significant improvements. Succinic acid-treated fibers exhibited a tensile strength of 145.69 MPa, a modulus of 4376 MPa, and elongation of 9.46%, while pectinase-treated fibers achieved the highest tensile strength (220.52 MPa), modulus (5927 MPa), and elongation (12.53%). Characterization techniques (FTIR, SEM, DSC) confirmed increased surface roughness and functional group exposure, while finite element analysis revealed improved stress distribution and mechanical behavior. These findings highlight the potential of modified PO fibers as sustainable reinforcements for lightweight, high-performance composites in automotive, aerospace, and construction applications, contributing to marine biomass valorization and circular material strategies.