Upcycling algal biomass into biodegradable materials: Enhancing structural properties and performance through hydrophobic modifications

Abstract

This study presents a sustainable approach for valorizing algal residual biomass (ARB) through its incorporation into PLA/PBAT bioplastic blends. The acetylated ARB demonstrated multifunctional properties, serving as both a nucleating agent (increasing relative crystallinity from 12.77 % to 32.30 % in PLA/PBAT 30/70 blends) and a compatibilizer (high-temperature tanδ peak vanished in PLA/PBAT 70/30 blends). Mechanical testing revealed ARB's unique plasticizing effect, particularly in PLA/PBAT (30/70) blends where it induced yield behavior and plastic deformation, increasing elongation at break from 7.24 % to 7.97 % with 25 % ARB content. The optimal 20 % ARB formulation achieved a balanced tensile strength of 6.24 MPa with 7.82 % elongation, while flexural modulus decreased from 1106.92 MPa to 200 MPa in PLA-rich blends, indicating significant system softening. Thermal analysis showed enhanced stability and improved crystallization behavior. The composites maintained excellent biodegradability (17.71 %/8 weeks) with no phytotoxicity, while reducing material costs by 14.13 %. Comparative analysis positioned ARB composites as superior to starch-based bioplastics, suggesting their potential as sustainable alternatives in bio-based plastic formulations. This work provides a practical pathway for developing cost-effective, eco-friendly bio-composites with tunable mechanical properties through ARB incorporation.