Sustainable materials and renewable energy from orange peel waste: A critical analysis

The global transition toward a circular bioeconomy has repositioned orange peel waste (OPW) from an undervalued agricultural byproduct to a versatile precursor for potential technological applications. This paper provides a critical evaluation of scholarly advancements disseminated between 2020 and 2026, focusing on the transformation of citrus residues into advanced nanomaterials, environmental remediation agents, and energy storage systems. Through innovative thermochemical and green synthesis pathways, OPW-derived materials have demonstrated promising functional performance in laboratory settings. Quantitative synthesis reveals that engineered adsorbents achieve maximum sequestration capacities for aqueous pollutants exceeding 190 mg/g, with removal efficiencies frequently surpassing 95%. In the field of nanotechnology, citrus-mediated synthesis has successfully produced nanoparticles with dimensions typically ranging from 20 nm to 100 nm, exhibiting antioxidant scavenging activities as high as 90%. Furthermore, OPW-derived hard carbons have demonstrated competitive laboratory-scale specific capacities for ion batteries and supercapacitors in the range of 330 mAh/g to 550 F/g, while specialized catalytic systems have yielded hydrogen production rates approaching 2800 micromol/g·h, establishing a foundational baseline for future development. Despite these impressive laboratory-scale achievements, the transition to industrial application remains hindered by challenges regarding process scalability, feedstock heterogeneity, and long-term operational stability. This paper critiques the underlying mechanisms of material functionalization and proposes a strategic roadmap for future research, emphasizing the integration of artificial intelligence and cascading biorefinery models. Ultimately, the valorization of orange peel waste offers a potential solution for simultaneous waste mitigation and sustainable resource recovery, providing a path for further investigation into resilient industrial development.