Spanish University Develops Efficient Method to Extract Coffee Ground Oil for Biodiesel

Researchers at the Universitat Rovira i Virgili (URV) in Spain have created a fast extraction process that recovers about 90 % of the oil contained in spent coffee grounds. The method uses n‑hexane at 45 °C for 60 minutes with a solvent‑to‑dry‑residue ratio of 35 mL g⁻¹, yielding oil with only 0.3 % impurities, far cleaner than the traditional Soxhlet technique (≈4 % impurities). Coffee waste worldwide amounts to roughly 6 million tonnes per year, and the grounds contain about 15 % lipids rich in linoleic and palmitic acids, making them suitable as a feedstock for biodiesel. The remaining biomass retains its cellulose, hemicellulose and lignin, allowing further conversion into other bio‑based chemicals. The findings were published in the journal *Biomass and Bioenergy* and highlight a scalable, lower‑energy route for turning a common kitchen waste into renewable fuel and valuable materials.