Glossary

Use this comprehensive glossary to define terms commonly used in the alternative fuels and advanced vehicles industry. If you have questions about specific technologies or fuels, contact the Technical Response Service at 1-800-254-6735.

Click on the appropriate letter.

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ASTM International

A nonprofit organization that develops and delivers international standards. ASTM standards, test methods, specifications, and procedures are recognized as definitive guidelines for fuel quality.

Advanced Technology Vehicles

A vehicle that combines new engine, power, or drivetrain systems to significantly improve fuel economy. This includes hybrid power systems and fuel cells, as well as some specialized electric vehicles.

Alternative Fuel Vehicles

A dedicated, flexible fuel, or dual-fuel vehicle designed to operate on at least one alternative fuel.

Alternative Fuels

The Energy Policy Act of 1992 defines an alternative fuel as:

  • Biodiesel (B100)
  • Natural gas and liquid fuels domestically produced from natural gas
  • Propane (liquefied petroleum gas)
  • Electricity
  • Hydrogen
  • Blends of 85% or more of methanol, denatured ethanol, and other alcohols with gasoline or other fuels
  • Methanol, denatured ethanol, and other alcohols
  • Coal-derived, domestically produced liquid fuels
  • Fuels (other than alcohol) derived from biological materials
  • P-Series fuels

Anaerobic Digestion

Anaerobic digestion is series of processes in which microorganisms break down biodegradable material in the absence of oxygen.

Autoignition Temperature

The lowest temperature at which a flammable gas vapor will ignite spontaneously, without a source of ignition, after several minutes of exposure to sources of heat.

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Biochemical

Chemical reactions in living organisms.

Biochemical Conversion

Using enzymes and catalysts to change biological substances chemically to produce energy products. An example is digestion of organic wastes or sewage by microorganisms to produce methane.

Biomass

Plant matter such as trees, grasses, agricultural residue, algae, and other biological material.

Blender Pump

A fuel dispenser that draws fuel from two separate storage tanks and can dispense preprogrammed blends of those two fuels.

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Cetane Number

Cetane number relates to the fuels susceptibility to self-ignite. The higher the cetane number, the greater the fuel's tendency to self-ignite.

Clean Air Act Amendments of 1990

Amendments to the Clean Air Act of 1970 creating two gasoline standards to reduce vehicle emissions in highly polluted cities by requiring gasoline to contain cleaner-burning additives, such as ethanol.

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E85

A high-level gasoline-ethanol blend containing 51% to 83% ethanol, depending on geography and season.

Electric Grid

An interconnected system that maintains an instantaneous balance between supply and demand (generation and load) while moving electricity from generation source to customer.

Electricity

Electric current used as a power source. Electricity can be produced from a variety of feedstocks, including oil, coal, nuclear, hydro, natural gas, wind, and solar.

Emission Control Technologies

Equipment used in diesel-powered vehicles to reduce exhaust emissions, such as particulate matter and nitrogen oxides. New engines and vehicles can be designed with these technologies, and used engines can be retrofitted to use this equipment.

Energy Policy Act of 1992

Passed by Congress to enhance U.S. energy security by requiring federal, state, and alternative fuel provider fleets to implement petroleum-reduction measures. Learn more about EPAct Transportation Regulatory Activities.

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Feedstocks

Any material converted to another form of fuel or energy product. An example is using cornstarch to produce ethanol.

Flash Point

The minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid.

Flow Improvers

A chemical used in fuel to reduce friction and increase performance.

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Gasoline Gallon Equivalent

The amount of fuel it takes to equal the energy content of one liquid gallon of gasoline.

Gross Vehicle Weight Rating

The maximum weight of a vehicle, including curb weight (the weight of the vehicle on its own) and payload (the weight of cargo).

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Higher Heating Value

The heating value is the amount of heat released during the combustion of a specific substance, usually a fuel or food. The higher heating value is determined by bringing all the products of combustion back to the original pre-combustion temperature, condensing any water vapor generated. This value assumes the entire water component is liquid in the products of combustion and that heat can be used.

Higher Lubricity

The ability to reduce friction—usually in fuel pumps and fuel injectors.

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Incremental Price

The additional price of an alternative fuel vehicle over a similar conventional vehicle.

Internal Combustion Engine

A conventional vehicle motor that burns fossil fuel in a chamber in the presence of air.

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Kilowatt Hours

A measurement for electricity use.

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Legacy Chargers

Legacy electric charging systems such as inductive paddles. Learn more about types of chargers.

Lower Heating Value

The heating value is the amount of heat released during the combustion of a specific substance, usually a fuel or food. The lower heating value is determined by subtracting the heat of vaporization of water from the higher heating value for a particular substance, treating any water as a vapor.

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Negative Energy Balance

When producing a fuel takes more energy than the amount of energy the fuel provides.

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Oxygenate

A cleaner-burning additive in a fuel—usually containing hydrogen, carbon, and oxygen. Examples are ethers and alchohols, such as ethanol and methanol.

Oxygenated Fuels

Fuels blended with an additive—usually ether or ethanol—to increase oxygen content, allowing more-thorough combustion for reduced carbon monoxide emissions.

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Passenger-Miles per Gallon

Pmpg is the vehicle miles per gallon multiplied by the number of passengers traveling in the vehicle.

Positive Energy Balance

When producing a fuel takes less energy than the amount of energy the fuel provides.

Pump Octane Number

This number represents the ability of a fuel to resist knocking when ignited in the cylinder of an internal-combustion engine. The number here is the average of the research octane number and motor octane number.

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Regenerative Braking

A feature of hybrid and plug-in electric vehicles that captures energy normally lost during braking by using the electric motor as a generator and storing the captured energy in the battery.

Renewable Fuels Standard

A regulation created under the Energy Policy Act of 2005 and implemented by the U.S. Environmental Protection Agency to ensure transportation fuel sold in the United States contains a minimum volume of renewable fuel.

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Selective catalytic reduction

Selective catalytic reduction (SCR) is a means of converting nitrogen oxides (NOx) into nitrogen (N2) and water (H20). This is done using a reductant, such as urea or ammonia, and a catalyst.

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Tailpipe Emissions

Emissions produced through fuel combustion during a vehicle's operation.

Tallow

Animal fat that can be used to produce biodiesel.

Technical Response Service

For assistance with technical questions about alternative fuels and advanced vehicles, email the Technical Response Service at technicalresponse@icfi.com or call 1-800-254-6735.

Thermochemical

Heat and pressure-based chemical reactions that produce energy. Through gasification (heating biomass by partial oxidation to produce synthesis gas) and pyrolysis (heating biomass in the absence of oxygen to produce liquid oil), biomass feedstocks can be converted to alcohol and hydrocarbon fuels, chemicals, and power.

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Vehicle Categories

A system of classifying vehicles (e.g., passenger cars, commercial vehicles, trailers, off-road vehicles, and special-purpose vehicles).

Vehicle Weight Class

The size of vehicles. Includes light-duty, medium-duty, and heavy-duty vehicles based on their gross vehicle weight rating (the weight of a vehicle on its own plus the weight of cargo).

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Yellow Grease

Second-hand cooking oil that can be used to produce biodiesel.