Cooking oil can be transformed into biodiesel through a process called transesterification. In this process, the oil is combined with an alcohol, such as methanol, and a catalyst, such as sodium hydroxide or potassium hydroxide, in the presence of heat. The chemical reaction that occurs breaks down the oil into its constituent parts: glycerol and fatty acid esters. The esters are then separated from the glycerol and purified to produce biodiesel. The glycerol can be used for other purposes, such as soap-making or as an animal feed supplement.

Turning cooking oil into biodiesel has several environmental and economic benefits. Biodiesel is a renewable, cleaner-burning fuel that can be used in place of traditional diesel fuel. It produces lower emissions of harmful pollutants, such as particulate matter and carbon monoxide, and can reduce greenhouse gas emissions compared to fossil fuels. Additionally, using waste cooking oil for biodiesel production reduces the amount of oil that ends up in landfills or is illegally dumped, helping to prevent environmental damage. Furthermore, biodiesel production from waste oil can create local jobs and reduce dependence on imported petroleum products.