Dual valorization of rice and potato byproducts into nanostructured additives and starch matrices for thermoplastic starch bioplastics

Agrifood industries generate large rice and potato byproducts that remain underutilized. This work demonstrates the dual valorization of complementary rice- and potato-processing side-streams within a single material platform, converting lignocellulosic residues into nanostructured additives and starch-rich byproducts into thermoplastic starch (TPS) matrices. Rice husks and potato peels were subjected to single-step or sequential purification to obtain nanoadditives, enabling systematic comparison between high-yield simplified processing and enhanced structural refinement. Potato washing slurries, rice dust, and rejected colored rice were directly processed into TPS via thermomechanical mixing followed by compression molding. Nanoadditives were incorporated at 10 wt% relative to the starch-rich matrix as reinforcing agents. Single-step purification achieved higher yields (up to 27% for potato peels and 43% for rice husks), whereas sequential purification increased nanoadditive crystallinity and thermal stability. Incorporation into TPS films increased tensile strength and Young's modulus by up to 177% and 522%, respectively, while elongation at break ranged from 12% to 49%, depending on matrix-filler combination. Surface water contact angle increased by up to 132%, and water vapor permeability decreased by up to 25%. These findings highlight the trade-off between material recovery and structural refinement, providing design insights for the development of fully side-stream-derived TPS composites with tailored mechanical and barrier performance.