Biodiesel and renewable diesel are biomass-based biofuels
Biomass-based diesel fuels used as petroleum distillate fuel oil (diesel fuel and heating oil) include biodiesel and renewable diesel. They are both called biomass-based diesel fuels because they are mostly produced for use in diesel engines, but they can also be used as heating fuels. Both fuels are made from biomass or materials derived from biomass, but they differ in how they are produced and in their physical properties. Biodiesel meets the American Society for Testing and Materials (ASTM) specification ASTM D6751 and is approved for blending with petroleum distillate/diesel. Renewable diesel meets ASTM D975 specification for petroleum diesel, and it does not require blending with petroleum diesel for its use. Both fuels qualify for meeting the biofuels consumption levels required by the U.S. Renewable Fuel Standard Program.
Biodiesel is produced through transesterification
Biodiesel is produced through transesterification—a chemical process that converts fats and oils into fatty acid methyl esters (FAME). Approximately 100 pounds of oil or fat are reacted with 10 pounds of a short-chain alcohol (usually methanol) in the presence of a catalyst (usually sodium hydroxide or potassium hydroxide) to form 100 pounds of biodiesel and 10 pounds of glycerin (or glycerol). Glycerin is a sugar commonly used in the manufacture of pharmaceuticals and cosmetics.
Biodiesel is made from a variety of materials
Biodiesel can be made from nearly any feedstock (raw material) that contains adequate free fatty acids. Most of U.S. biodiesel production uses raw vegetable oils, used cooking oils, yellow grease, and animal fats as feedstocks for transesterification. Vegetable oils are the main feedstocks for U.S. biodiesel production. Other feedstocks for biodiesel production include waste animal fats from processing plants and used/recycled cooking oil and yellow grease from restaurants.
Vegetable oil in a bottle
Rapeseed oil, sunflower oil, and palm oil are major feedstocks for biodiesel production in other countries. Algae is also a potential source for biodiesel production. Algae contain fat pockets that help keep them afloat. This fat can be collected and processed into biodiesel.
Biodiesel is mostly used as an additive to petroleum diesel
Biodiesel is most often added to (blended) with petroleum distillate/diesel in ratios of 2% (referred to as B2), 5% (B5), or 20% (B20). It is called biodiesel because it is mostly used in diesel engines. Pure biodiesel (B100) can also be used in many applications. Petroleum diesel fuel tanks and equipment can also store and transport biodiesel. Learn more about use of biodiesel made from different feedstocks. Biodiesel blends may also be used as heating oil.
History of biodiesel
Before petroleum diesel fuel became popular, Rudolf Diesel, the inventor of the diesel engine in 1897, experimented with using vegetable oil (biodiesel) as fuel. Until 2001, the United States consumed only small amounts of biodiesel. Since then, U.S. biodiesel production and consumption have increased substantially, largely because of the availability of various government incentives and requirements to produce, sell, and use biodiesel including the Renewable Fuel Standard Program.
In 2019, the United States produced about 41 million barrels (1.7 billion gallons) of B100, imported about 4 million barrels (168 million gallons), exported about 2.7 million barrels (114 million gallons), and consumed about 43 million barrels (1.8 billion gallons) nearly all as blends with petroleum diesel.
Last updated: June 22, 2020