Light Duty Vehicles
Automobiles and trucks having a gross vehicle weight rating of less than 8,500 pounds.
Liquefied Natural Gas (LNG)
Natural gas that has been refrigerated to temperatures at which it exists in a liquid state.
Liquefied Petroleum Gases (LPG)
Propane, propylene, normal butane, butylene, isobutane, and isobutylene produced at refineries or natural gas processing plants (includes plants that fractionate raw natural gas plant liquids).
Lower Heating Value (LHV)
The Btu content per unit of fuel excluding the heat from the condensation of water vapor in the fuel.
A fuel containing a mixture of 85 percent methanol and 15 percent gasoline.
100 percent (neat) methanol.
The simplest of the hydrocarbons and the chief constituent of natural gas. Methane, a gas at normal temperatures and pressures, boils at -263 degrees Fahrenheit.
A colorless liquid with essentially no odor and very little taste. The simplest alcohol, it boils at 64.7 degrees Celsius. It is miscible with water and most organic liquids (including gasoline) and is extremely flammable, burning with a nearly invisible blue flame. Methanol is produced commercially by the catalyzed reaction of hydrogen and carbon monoxide. It was formerly derived from the destructive distillation of wood, which caused it to be known as wood alcohol.
Methyl Tertiary Butyl Ether (MTBE), (CH3)3COCH3
A colorless, flammable, liquid oxygenated hydrocarbon that contains 18.15 percent oxygen and has a boiling point of 55.2 degrees Celsius. It is a fuel oxygenate produced by reacting methanol with isobutylene.
Motor Gasoline Blending of Oxygenates
Blending of gasoline and oxygenates under the Environmental Protection Agency’s “Substantially Similar” Interpretive Rule (56 FR [February 11, 1991]).
A mixture of hydrocarbon compounds and small quantities of various nonhydrocarbons existing in the gaseous phase or in solution with crude oil in natural underground reservoirs at reservoir conditions. The primary constituent compound is CH4.
Gas coming from wells also can contain significant amounts of ethane, propane, butanes, and pentanes, and widely varying amounts of carbon dioxide and nitrogen. Pipeline-quality natural gas has had most, but not all natural gas liquids and other contaminants removed. On board a vehicle, it is stored under high pressure at 2,500 to 3,600 pounds per square inch (psi). A gallon of natural gas at 2,000 psi contains about 20,000 Btu; at 3,600 psi, a gallon contains about 30,000 Btu.
Neat Alcohol Fuels
Straight alcohol (not blended with gasoline) that may be either in the form of ethanol or methanol. Ethanol, as a neat alcohol fuel, does not need to be at 200 proof; therefore, it is often used at 180 to 190 proof (90 to 95 percent). Most methanol fuels are not strictly “neat,” since 5 to 10 percent gasoline is usually blended in to improve its operational efficiency.
Nitrogen Oxides (NOx)
Air-polluting gases contained in automobile emissions, which are regulated by the Environmental Protection Agency. They comprise colorless nitrous oxide (N2O) (otherwise known as dinitrogen monoxide, or as the anaesthetic “laughing gas”), colorless nitric oxide (NO), and the reddish-brown-colored nitrogen dioxide (NO2). Nitric oxide is very unstable, and on exposure to air it is readily converted to nitrogen dioxide, which has an irritating odor and is very poisonous. Nitrogen dioxide contributes to the brownish layer in the atmospheric pollution over some metropolitan areas. Other nitrogen oxides of less significance are nitrogen tetroxide (N2O4) and nitrogen pentoxide (N2O5). Nitrogen oxides are sometimes collectively referred to as “NOx” where “x” represents any proportion of oxygen to nitrogen.
A region that exceeds minimum acceptable National Ambient Air Quality Standards (NAAQS) for one or more criteria pollutants, in high population density areas, in accordance with the U.S. Census Bureau population statistics. Such regions (areas) are required to seek modifications to their State Implementation Plans, setting forth a reasonable timetable using means (approved by the Environmental Protection Agency) to achieve attainment of NAAQS by a certain date. Under the Clean Air Act, if a nonattainment area fails to attain NAAQS, the Environmental Protection Agency may superimpose a Federal Implementation Plan with stricter requirements or impose fines, construction bans, or cutoffs in Federal grant revenues until the area achieves applicable NAAQS.