Valorization of Oil Press Residues in Starch-Based Biocomposites for Sustainable Wood Substitution

The growing interest in sustainable materials has stimulated interest in biodegradable biocomposites produced from renewable and industrial by-product resources. In this study, the feasibility of replacing wood particles with nigella, rapeseed, and evening primrose pomace residues in modified thermoplastic starch (MS)-based composites was investigated. Composite boards were manufactured using lignocellulosic filler containing wood substituted by untreated pomace at different substitution levels (30%, 65%, and 100%) and matrix ratios (30% and 40%). Mechanical performance, surface roughness, wettability, and water stability were evaluated. Pomace content was the dominant factor affecting MOR, and contact angle. Increasing wood substitution reduced the MOR. Intermediate levels of nigella substitution reduced surface roughness. Rapeseed and evening primrose residues improved resistance to water-induced disintegration at higher substitution levels, whereas composites containing nigella residues remained highly susceptible to degradation during soaking. The results demonstrate that unmodified oil press residues can serve as alternative lignocellulosic fillers in starch-based biocomposites and provide a promising route for valorization of agro-industrial by-products.