Green add-in of agricultural wastes through NADES-based ultrasound and microwave extraction methods: Optimization and greenness assessment

Abstract

The increasing volume of agricultural wastes presents both an environmental burden and a potential resource for circular economy applications. Green extraction technologies offer a viable route to recover valuable bioactive compounds from these residues while reducing reliance on hazardous solvents and energy-intensive processes. This review examines recent developments in Natural Deep Eutectic Solvents (NADES) coupled with Ultrasound-Assisted Extraction (UAE) and Microwave-Assisted Extraction (MAE), with particular focus on their combined contributions to efficiency, selectivity, and process sustainability. The mechanistic roles of cavitation-driven cell disruption and dielectric heating are discussed in relation to mass transfer enhancement and solvent–matrix interactions. Optimization strategies, including Taguchi designs, response surface methodology, artificial neural networks, and multi-response desirability models, are evaluated for their effectiveness in refining extraction conditions. Greenness assessment tools such as Analytical Greenness (AGREE), Green Analytical Procedure Index (GAPI), and the Analytical Eco-Scale are also reviewed to highlight inconsistencies in current sustainability evaluations and to identify opportunities for more comprehensive benchmarking. By integrating solvent innovation, process intensification, and environmental metrics, this review situates NADES-based UAE/MAE as emerging platforms for the valorization of agricultural wastes within a sustainable circular economy framework. Key research gaps and future directions are identified, including the need for standardized greenness metrics, improved understanding of synergistic mechanisms, and assessment of solvent recyclability for future scale-up.