Biodiesel fuel is a renewable, biodegradable fuel that can be manufactured domestically from vegetable oils, animal fats, or recycled restaurant grease. It is a form of diesel fuel that is typically made by chemically reacting lipids such as animal fat (tallow) with an alcohol and a catalyst to produce long-chain fatty acid esters. Biodiesel is a drop-in biofuel, meaning it is compatible with existing diesel engines and distribution infrastructure. However, it is usually blended with petrodiesel (typically to less than 10%) since most engines cannot run on pure biodiesel without modification. Biodiesel blends can also be used as heating oil.

Some key characteristics of biodiesel fuel include:

• Renewable: Biodiesel is a renewable fuel that can be manufactured domestically from a variety of sources.
• Biodegradable: Biodiesel is biodegradable and non-toxic, making it a more environmentally friendly alternative to petroleum-based diesel fuel.
• Physical properties: Biodiesels physical properties are similar to those of petroleum diesel, but its performance in cold weather depends on the blend of biodiesel, the feedstock, and the petroleum diesel characteristics.
• Production: Biodiesel is commonly produced by the transesterification of vegetable oil or animal fat feedstock, and other non-edible raw materials such as frying oil.

There are many benefits to using biodiesel fuel, including its renewable nature, biodegradability, and potential to reduce dependence on foreign oil. Biodiesel is also a cleaner-burning fuel than petroleum diesel, with lower emissions of particulate matter, carbon monoxide, and hydrocarbons.