PBAT/PLA bio-composites reinforced with four lignocellulosic industrial wastes: A comparative study of thermo-mechanical behavior

This study presents a comprehensive investigation of biodegradable bio-composites based on a commercial PBAT/PLA blend reinforced with 30 wt% of four lignocellulosic agri-food industrial wastes, namely beer spent grain (BSG), olive pomace (OP), coffee silverskin (CSS), and mandarin pomace (MP). The aim is to valorize organic residues while improving the functional performance of biopolymers for sustainable applications. Findings show that all fillers maintained thermal stability up to 240◦C and were compatible with the processing temperature (160◦C) for PBAT/PLA. ECO-CSS and ECO-BSG exhibited slightly better thermal stability due to their filler lignin-rich composition, which increased melt viscosity. OP and MP fillers contain oils and pectin, which reduce viscosity, improving flow and processability. All fillers enhanced the stiffness and tensile strength of pure PBAT/PLA, compromising its deformability. CSS leads to the most pronounced stiffening, increasing the modulus from ~79 MPa (neat PBAT/PLA) to ~260 MPa, approximately three times higher, while reducing deformation by 48 times. OP fillers cause less stiffening (1.26 times) and slightly better deformation with 22 times lower value. Notably, the measured particle sizes and shape differences among fillers did not directly affect the thermo-mechanical responses; instead, the property profiles were primarily governed by the chemical features of fillers. Overall, these results highlight the potential of agri-food wastes as effective bioplastic fillers for producing biocomposites with tunable stiffness and deformability.