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The Politecnico di Milano, coordinator of the WORLD—Waste Oils RecycLe and Development project, proposes an innovative, circular and sustainable process to turn used vegetable oil into a valuable resource.

The study was in RSC Sustainability and was rewarded for its originality by being featured on the cover.

The goal of the WORLD project is to optimize waste vegetable oil treatment processes while improving the quality of end products, reducing waste and fostering European independence in the supply of critical raw materials.

In fact, vegetable oil is used widely around the world, and cooking and food preservation generate an enormous amount of waste oil. Around 4 million metric tons of used vegetable oil are produced in Europe each year, representing just 4% of the total global amount of this abundant, widespread product. If not properly disposed of, this waste can lead to significant environmental impacts.

The WORLD project proposes to recycle used vegetable oil, yielding innovative materials used as bio-lubricants, air purification devices and fine chemical components from petroleum-free precursors. These applications are presented as a supply chain parallel to their well-known use in the production of biodiesel, although this is limited by law to 10% and concerns only the purest fraction of the waste.

In addition to economic and technological benefits, the project has a strong social and environmental impact: raising awareness of correct waste oil collection can reduce public costs related to incorrect disposal and prevent environmental damage.

In addition, a life cycle analysis (LCA) will be conducted to assess the best strategies to minimize ecological, economic and social impacts by adopting a zero waste approach.

"We started by observing that the waste vegetable oil recycling industry is currently based on simple decantation and filtration processes, without adequate scientific optimization. We therefore analyzed two alternative techniques: bentonite treatment and water washing to improve their efficiency and reduce their environmental impact," explains Andrea Mele from the "G. Natta" Department of Chemistry, Materials and Chemical Engineering at the Politecnico di Milano.

"Through an experimental approach based on the design of experiments (DoE) methodology and multivariate statistical analysis, we optimized key parameters such as temperature, pH, bentonite concentration and oil-to-water ratio," continues Alberto Mannu, who recently transferred from the Politecnico di Milano to the Department of Mechanical and Industrial Engineering at the University of Brescia.

"The results showed that washing with water at 75°C and pH 6 guarantees the best performance in terms of yield, productivity and environmental sustainability, minimizing the production of waste and the carbon impacts of the process."

Today, thanks to the WORLD project, a mathematical model developed using the collected data yields predictions of equivalent CO₂ emissions according to operating conditions, providing the recycling industry with a practical tool for optimizing processes in line with environmental certification standards.

This scientifically validated approach marks a step forward in the transition towards a more efficient and sustainable circular economy. It forms part of the key principles of green chemistry, opens new prospects for sustainability and efficiency, and is highly competitive from a technical/economic perspective in models of the circular economy.