What does biodiesel mean?
Biodiesel is a renewable fuel designed for use in diesel engines, produced from biological sources such as vegetable oils, animal fats, or recycled cooking grease through a process called transesterification. Unlike petroleum diesel, which is refined from crude oil, biodiesel comes from plant or animal matter, making it biodegradable, non-toxic, and capable of reducing net carbon emissions when burned. It is rarely used pure; instead, it is commonly sold as a blend with conventional diesel — B20, a mix of twenty percent biodiesel and eighty percent petroleum diesel, is one of the most widespread formulations. The word entered common usage in the late twentieth century as concern over fossil fuels and climate change grew, and it now appears routinely in discussions of energy policy, agriculture, transportation, and environmental science. Its connotations are generally positive, evoking sustainability and local energy production, though critics note questions about land use and food-crop competition. For anyone reading about alternative fuels, 'biodiesel' is an essential term to understand.
nounA renewable fuel for diesel engines, made from vegetable oils, animal fats, or recycled cooking grease, typically blended with conventional petroleum diesel.
- A renewable, biodegradable fuel for compression-ignition (diesel) engines, produced from vegetable oils, animal fats, or recycled greases via transesterification, usually sold as a blend with petroleum diesel (e.g. B20).
"The city converted its entire bus fleet to run on biodiesel made from recycled restaurant oil."
"The farm powers its tractors with biodiesel pressed from its own rapeseed crop."
"Because it is biodegradable and non-toxic, biodiesel spills pose far less environmental risk than petroleum diesel."
Rarely pluralized; the plural appears mainly in technical contexts distinguishing different grades or feedstock-specific varieties of the fuel.
"Regulators test various biodiesels to confirm they meet ASTM quality standards."
Rudolf Diesel designed his original 1900 engine to run on peanut oil — so in a sense, biodiesel came before 'diesel' fuel did.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of biodiesel
Biodiesel is a modern English compound formed from 'bio-', borrowed from Greek 'bios' meaning 'life', combined with 'diesel', itself derived from Rudolf Diesel, the German engineer who patented the compression-ignition engine in the 1890s and famously demonstrated one running on peanut oil at the 1900 World's Fair. The compound arose in the late twentieth century alongside other 'bio-' coinages such as biofuel and biomass, reflecting growing interest in fuels of biological rather than fossil origin. It shares its 'bio-' element with words like biology, biography, and biodegradable.
How biodiesel is actually used
Biodiesel is an uncountable mass noun in most contexts; it is neutral to slightly positive in connotation, associated with sustainability and green energy. It is standard in technical, regulatory, and environmental writing.
Easily confused with biodiesel
Renewable diesel is chemically identical to petroleum diesel and produced by hydrotreating, whereas biodiesel is a fatty acid methyl ester that is typically blended with conventional diesel.
Ethanol is an alcohol-based biofuel used in gasoline (petrol) engines, while biodiesel is an oil- or fat-derived fuel for diesel engines.