Ultrasound-assisted extraction with deep eutectic solvents for valorization of agro-food waste: A sustainable and eco-friendly approach.

The growing need for innovative, sustainable, and eco-friendly solutions worldwide has intensified efforts to valorize agro-food waste, which is generated in vast quantities worldwide and is rich in valuable substances with diverse industrial applications. Conventional extraction methods using organic solvents have long been employed for this purpose, but their significant drawbacks highlight the need for alternative approaches. This review explores the application of non-thermal ultrasound-assisted extraction (UAE) with deep eutectic solvents (DESs) for extracting valuable substances from agro-food waste. It critically examines recent innovations in the UAE with DESs, including mechanisms, applications to agro-food waste, limitations, and aspects of safety, sustainability, and scalability. The key findings indicate that UAE with DESs outperforms conventional and other novel extraction techniques for agro-food waste valorization. This approach offers significant benefits, such as enhanced extraction efficiency, high-quality extracts, reduced processing time and energy consumption, biodegradability, low toxicity, and the reusability and tunability of DESs, all of which align with eco-friendly practices. While identifying a single best DES is challenging due to their varying extraction efficiencies with different waste materials, but optimal ultrasonication parameters commonly reported in the literature include 300-400 W power, 30 min extraction time, 40 °C temperature, and a solid-to-solvent ratio (SSR) of 1:30 g/mL to achieve high extraction efficiency. Future studies should investigate a wider range of plant and animal-based waste, optimize ultrasonic parameters and DES compositions, explore combinative extraction methods, enhance compound purification and solvent recovery, and assess industrial scalability through TEA, LCA, safety testing, and regulatory alignment.