With all the talk of biofuels swirling around, things can get a bit confusing. So we’ve put together this handy glossary for your reference. Now you can pontificate at cocktail parties with the best of ‘em.

And just to keep you awake (yeah, we remember second grade too), we’ve included some explanatory videos thanks to the good folks at Current TV. Look! Real people using and talking about biofuels! See, it’s not all just a journalistic fantasy.

Got more terms to suggest? Add them in Gristmill.



Biodiesel: A fuel derived from biological sources that can be used in diesel engines instead of petroleum-derived diesel. Through the process of transesterification, the triglycerides in the biologically derived oils are separated from the glycerin, creating a clean-burning, renewable fuel.

Christina in Taos, N.M., talks about running her truck on biodiesel. (1:45)

Biofuel: A fuel made from renewable biological sources. Biofuels include ethanol, methanol, and biodiesel. Biofuel sources include, but are not limited to: corn, soybeans, flaxseed, rapeseed, sugarcane, palm oil, raw sewage, food scraps, animal parts, and rice.

Biomass: Plant material such as wood, grains, agricultural waste, and vegetation that can be used as an energy source.

Biomass to liquid (BTL): The process of converting biomass to liquid fuels. Hmm, that seems painfully obvious when you write it out.

Butanol: Though generally produced from fossil fuels, this four-carbon alcohol can also be produced through bacterial fermentation of alcohol.

Carbon dioxide (CO2): A product of combustion that acts as a greenhouse gas in the Earth’s atmosphere, trapping heat and contributing to climate change.

Carbon monoxide (CO): A lethal gas produced by incomplete combustion of carbon-containing fuels in internal combustion engines. It is colorless, odorless, and tasteless. (As in flavorless, we mean, though it’s also been known to tell a bad joke or two.)

Carbon sink: A geographical area whose vegetation and/or soil soaks up significant carbon dioxide from the atmosphere. Such areas, typically in tropical regions, are increasingly being sacrificed for energy crop production.

Diesel engine: Named for the German engineer Rudolph Diesel, this internal-combustion, compression-ignition engine works by heating fuels and causing them to ignite. It can use either petroleum or bio-derived fuel.

Diesel fuel: A distillate of fuel oil that has been historically derived from petroleum for use in internal combustion engines. Can also be derived from plant and animal sources.

Diesel, Rudolph: German inventor famed for fashioning the diesel engine, which made its debut at the 1900 World’s Fair. He initially intended for his machine to run on vegetable-derived fuels, with the hope that farmers would be able to grow their own fuel sources.

Direct-injection engine: A diesel engine in which fuel is injected directly into the cylinder. Wow, that’s another one that seems painfully obvious when you write it out. Most of the newer models are “turbo direct injection,” which sounds significantly more complicated, not to mention badass.

E85: An alcohol fuel mixture containing 85 percent ethanol and 15 percent gasoline by volume, and the current alternative fuel of choice of the U.S. government.

Emissions: Substances discharged into the air during combustion, e.g., all that stuff that comes out of your car.

Energy balance: The difference between the energy produced by a fuel and the energy required to obtain it through agricultural processes, drilling, refining, and transportation.

Energy crops: Agricultural crops grown specifically for their energy value.

Energy-efficiency ratio: A number representing the energy stored in a fuel as compared to the energy required to produce, process, transport, and distribute that fuel.

Ethanol: A fuel produced from the fermentation of sugars in carbohydrates, derived from agricultural crops like corn and grains, wood, or animal wastes. It has a perfume-like smell and is the same as the intoxicating component of alcoholic beverages — meaning, yes, if you drank enough of it before it was denatured or mixed with gasoline, you could get drunk. That’s why friends don’t let friends drink fuel ethanol.

Feedstock: The biomass used in the creation of a particular biofuel (e.g., corn or sugarcane for ethanol, soybeans or rapeseed for biodiesel).

Flexible-fuel vehicle (or “flex-fuel” vehicle) : A vehicle that can run alternately on two or more sources of fuel. This includes cars capable of running on gasoline and gasoline/ethanol mixtures, as well as cars that can run on both gasoline and natural gas.

Fossil fuel: A fuel derived from the long-ago-dead-and-buried remains of organic life on Earth — e.g., dinosaurs — that is generally considered non-renewable. The use of these fuels contributes to pollution and is widely considered a factor in global climate change.

Gasification: A chemical or heat process used to convert carbonaceous material — coal, petroleum, biomass — into its gaseous components, carbon monoxide and hydrogen.

Gas to liquid (GTL): The process of refining natural gas and other hydrocarbons into longer-chain hydrocarbons, which can be used to convert gaseous waste products into fuels.

Gel point: The point at which a liquid fuel cools to the consistency of petroleum jelly.

Genetically modified organism (GMO): An organism whose genetic material has been modified through recombinant DNA technology, altering the phenotype of the organism to meet desired specifications. What, you don’t know what a phenotype is?

Greasecar: A diesel-powered automobile rigged post-production to run on used vegetable oil.

Hannah, Daryl: An elite assassin in Kill Bill and a religious fundamentalist in Steel Magnolias, this actress also makes a Splash with her veggie-powered El Camino.

Hydrocarbon: A chemical compound that contains a carbon backbone with hydrogen atoms attached to that backbone. What we refer to as petroleum is actually liquid, geologically extracted hydrocarbons, and gaseous geologic hydrocarbons are what we know as natural gas.

Indirect-injection engine: An older model of diesel engine in which fuel is injected into a pre-chamber, partly combusted, and then sent to the fuel-injection chamber.

M85: An alcohol fuel mixture containing 85 percent methanol and 15 percent gasoline by volume. Methanol is typically made from natural gas, but can also be derived from the fermentation of biomass.

Mercedes, diesel-powered, vintage 1970s-’80s: “It” car for greasecar enthusiasts (people who modify their diesel cars to run on vegetable oil). Also big in the grassroots biodiesel community.

Methanol: A fuel typically derived from natural gas, but which can be produced from the fermentation of sugars in biomass.

Modified/unmodified diesel engine: Traditional diesel engines must be modified to heat the oil before it reaches the fuel injectors in order to handle straight vegetable oil. Modified, any diesel engine can run on veggie oil. Without modification, the oil must first be converted to biodiesel.

Nelson, Willie: Herb-touting, veggie-oil-loving outlaw country legend who in 2005 founded BioWillie to market biodiesel to truck stops around the country.

Nitrogen oxides: Products of combustion that contribute to the formation of smog and ozone.

Particulate emissions: Tiny particles of a solid or liquid suspended in a gas, or the fine particles of carbonaceous soot and other organic molecules discharged into the air during combustion.

Straight vegetable oil (SVO): Any vegetable oil that has not been optimized through the process of transesterification. Using this type of veggie oil in your diesel automobile requires an engine modification that heats the oil before it reaches the fuel injectors — otherwise, the veggie oil gets all gummed up in cold weather. Essentially, once your vehicle is modified, you could just grab a bottle of canola oil at your local grocer, dump it in, and be good to go.

An L.A. mechanic explains the difference between biodiesel and SVO. (3:18)

Transesterification: The chemical process in which an alcohol reacts with the triglycerides in vegetable oil or animal fats, separating the glycerin and producing biodiesel.

Viscosity: The ability of a liquid to flow. The higher the viscosity, the slower the liquid flows.

Waste vegetable oil (WVO): Grease from the nearest fryer which is filtered (‘cuz chunks of potatoes and fish don’t so much lube the chambers) and used in modified diesel engines, or converted to biodiesel through the process of transesterification and used in any ol’ diesel car.

Young, Neil: Canadian singer/songwriter with a heart of gold and a soft spot for biodiesel, which he uses to power his tour bus.