Used Cooking Oil is a term used in the food industry. It means that certain fats and oils were used to cook food, and afterward, they are recycled, or reused, by some firms to make new food products. The fats and oils are collected as garbage, and after some processing, they can be reused as a raw material to make new food products.

In the restaurant industry, used cooking oil is commonly referred to as brown grease. It is the byproduct of frying foods in commercial deep fryers. The oil is collected and then processed into biodiesel and other products.

According to the National Renewable Energy Laboratory, recycling used cooking oil reduces greenhouse gas emissions by more than 80% when compared with petroleum-based diesel fuels.

The Used Cooking Oil Collection Act was enacted in California in 2003 in order to encourage the collection of used cooking oil for recycling purposes. The act requires all businesses that generate used cooking oil to contact a certified used cooking oil collector or transporter to remove the waste from their premises.