From Waste to Nano: Unlocking Vegetable Residues for Sustainable Nanotechnology

Abstract

Conventional nanoparticle synthesis has significantly advanced nanotechnology but often relies on hazardous chemicals, toxic solvents, and energy-intensive processes, raising environmental and health concerns. Consequently, green synthesis has emerged as a sustainable alternative that utilizes renewable biological resources as natural reducing and stabilizing agents. Among these resources, vegetable-processing residues are increasingly recognized as valuable feedstocks owing to their abundance and rich phytochemical composition. Peels, stems, seeds, pomace and other residues contain phenolics, flavonoids, proteins, polysaccharides, reducing sugars, and related metabolites that mediate nanoparticle reduction, nucleation, capping, and stabilization. These phytochemical constituents have enabled the eco-friendly synthesis of Ag, Au, Fe/iron-oxide, zinc oxide, copper oxide and other nanomaterials while simultaneously promoting waste valorization within a circular bioeconomy. Importantly, variations in feedstock chemistry influence nanoparticle size, morphology, stability, and functional performance, establishing a direct feedstock-process-property relationship. Waste-derived nanoparticles have demonstrated promising antimicrobial, catalytic, photocatalytic, sensing, and pollutant-remediation capabilities, with growing applications in food, agriculture, and biomedicine. This review critically examines vegetable residues as functional nano-feedstocks, highlighting their biochemical drivers, synthesis mechanisms, process determinants, characterization strategies, major nanoparticle classes, and emerging applications. It also discusses challenges associated with feedstock heterogeneity, reproducibility, biosafety, sustainability, and industrial scale-up, emphasizing that standardized feedstocks, mechanism-guided synthesis, and application-specific validation are essential for translating vegetable-waste nanotechnology into reliable and scalable sustainable technologies.