Biodiesel is a renewable fuel made from vegetable oils, animal fats, or recycled cooking grease. It is a cleaner-burning alternative to traditional diesel fuel, with lower emissions of harmful pollutants such as carbon monoxide and particulate matter. Biodiesel is also biodegradable and non-toxic, making it a safer option for the environment. It can be used in existing diesel engines without any modifications, and it has similar performance characteristics to petroleum-based diesel fuel. Biodiesel is a sustainable and environmentally friendly choice for powering vehicles and machinery, reducing dependence on fossil fuels and helping to combat climate change. The physical and chemical properties of biodiesel vary depending on its source and production method. The US National Biodiesel Board defines "biodiesel" as a mono-alkyl ester.