From vineyard waste to high-value products: Educational laboratory experiences integrating green analytical chemistry and biorefinery concepts

The wine industry generates significant amounts of waste, including grape pomace and vine pruning residue, which are underutilized feedstocks whose valorization offers a strategic opportunity for sustainable process development and circular processes. Within this framework, two attractive laboratory practices were designed as part of a University Extension Course at University of Vigo (Campus of Ourense), with the aim of introducing participants to biorefinery concepts and green analytical chemistry through the efficient utilization of wine industry residues. The first practice explored the acid-catalyzed conversion of fructose to 5-hydroxymethylfurfural using both a commercial fructose solution and an aqueous extract of white grape pomace containing fructose, applying microwave-assisted treatment at 150 °C and different reaction times. The second activity evaluated the controlled release of paracetamol (as a model drug) from an alkali lignin-based hydrogel, used as a representative system for vine pruning lignin valorization. In both cases, UV–Vis spectrophotometry was employed for analytical determination. A satisfaction survey completed by 8 participants revealed high scores across all evaluation criteria, including theoretical content, clarity and quality of teaching, interactivity, and design of the laboratory experiments. Overall, the proposed activities provided an effective pedagogical strategy for fostering competencies in sustainability and circular bioeconomy across different educational levels, while facilitating the acquisition of knowledge in chemistry, technology, and mathematics and the development of key skills for future professional practice.