Waste cooking oil is the leftover oil that remains after cooking food. It is commonly generated in households and restaurants when frying or sautéing. This oil can become a problem if not disposed of properly, as it can clog drains and harm the environment. Instead of throwing it away, waste cooking oil can be recycled. It can be converted into biodiesel, a renewable energy source that can power vehicles. Additionally, some companies collect waste cooking oil to use in animal feed or for making soaps and candles, promoting sustainability and reducing waste.