Citrus by-product valorization: Integrating extraction technologies, sustainability assessment, and techno-economic perspectives

The valorization of citrus by-products has attracted increasing attention as a strategy to recover bioactive compounds and promote sustainable biorefinery development. However, current literature remains fragmented, particularly due to the lack of integration between extraction technologies, sustainability assessment tools, and process engineering criteria. Most studies focus on isolated aspects, such as extraction efficiency or specific techniques, without providing a comprehensive framework to support technology selection and industrial implementation. This review critically evaluates conventional and emerging extraction technologies, including ultrasound-, microwave-, supercritical fluid-, pressurized liquid-, and gas-expanded liquid-based systems, applied to citrus residues. Special attention is given to solvent systems, process intensification strategies, and their impact on extraction performance and scalability. Furthermore, this work integrates sustainability and techno-economic perspectives by discussing the combined application of Life Cycle Assessment (LCA), Techno-Economic Analysis (TEA), and green chemistry metrics. A multi-criteria evaluation framework is proposed, incorporating parameters such as Technology Readiness Level (TRL), energy demand, solvent intensity, and compatibility with biorefinery concepts. By bridging the gap between laboratory-scale research and industrial implementation, this review provides a structured and decision-oriented perspective for the development of sustainable citrus biorefineries.