Glossary

Acid stabilization:
A circumstance where the pH of the waste mixture in an animal manure management system is maintained near 7.0, optimal conditions for methane production.

Aerobic bacteria:

Microorganisms living, active, or occurring only in the presence of oxygen.

Aerobic decomposition:

The breakdown of a molecule into simpler molecules or atoms by microorganisms under favorable conditions of oxygenation.

Aerosols:
Airborne particles.

Afforestation:
Planting of new forests on lands that have not been recently forested.

Agglomeration:
The clustering of disparate elements.

Airshed:
An area or region defined by settlement patterns or geology that results in discrete atmospheric conditions.

Albedo:
The fraction of incident light or electromagnetic radiation that is reflected by a surface or body. See planetary albedo.

Anaerobes:
Organisms that live and are active only in the absence of oxygen.

Anaerobic bacteria:
Microorganisms living, active, or occurring only in the absence of oxygen.

Anaerobic decomposition:
The breakdown of molecules into simpler molecules or atoms by microorganisms that can survive in the partial or complete absence of oxygen.

Anaerobic lagoon:
A liquid-based manure management system, characterized by waste residing in water to a depth of at least six feet for a period ranging between 30 and 200 days.

Anode:
A positive electrode, as in a battery, radio tube, etc.

Anthracite:
A hard, black, lustrous coal containing a high percentage of fixed carbon and a low percentage of volatile matter. Often referred to as hard coal.

Anthropogenic:
Human made. Usually used in the context of emissions that are produced as the result of human activities.

API Gravity:
A scale expressing the density of petroleum products as established by the American Petroleum Institute.

Asphalt:
A dark-brown to black cement-like material obtained by petroleum processing, containing bitumens as the predominant constituents. Includes crude asphalt as well as the following finished products: cements, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalts.

Associated gas:
Natural gas found mixed with crude oil in underground reservoirs, released as a byproduct of oil production.

Aviation gasoline:
All special grades of gasoline for use in aviation reciprocating engines. Excludes blending components, which are blended or compounded into finished aviation gasoline.

Balancing item:
A measurement of the difference between the reported amount of natural gas produced and the reported amount consumed.

Biofuels:
Organic materials, such as wood, waste, and alcohol fuels, burned for energy purposes.

Biogas:
The gas produced from the anaerobic decomposition of organic material in a landfill.

Biogenic:
Produced by the actions of living organisms.

Biomass:
Materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, crops, grasses, tree litter, roots, and animals and animal waste.

Biosphere:
The portion of the Earth and its atmosphere that can support life. The part of the global carbon cycle that includes living organisms and biogenic organic matter.

Bituminous coal:
A dense, black, soft coal, often with well-defined bands of bright and dull material. The most common coal, with moisture content usually less than 20 percent. Used for generating electricity, making coke, and space heating.

BOD5:
The biochemical oxygen demand of wastewater during decomposition occurring over a 5-day period. A measure of the organic content of wastewater.

Bromofluorocarbons (halons):
Inert, nontoxic chemicals that have at least one bromine atom in their chemical makeup. They evaporate without leaving a residue and are used in fire extinguishing systems, especially for large computer installations.

Bunker fuel:
Fuel supplied to ships and aircraft in international transportation, irrespective of the flag of the carrier, consisting primarily of residual fuel oil for ships and distillate and jet fuel oils for aircraft.

Calcination:
A process in which a material is heated to a high temperature without fusing, so that hydrates, carbonates, or other compounds are decomposed and the volatile material is expelled.

Calcium sulfate:
A white crystalline salt, insoluble in water. Used in Keene's cement, in pigments, as a paper filler, and as a drying agent.

Calcium sulfite:
A white powder, soluble in dilute sulfuric acid. Used in the sulfite process for the manufacture of wood pulp.

Capital stock:
Property, plant and equipment used in the production, processing and distribution of energy resources.

Carbon black:
An amorphous form of carbon, produced commercially by thermal or oxidative decomposition of hydrocarbons and used principally in rubber goods, pigments, and printer's ink.

Carbon budget:
The balance of the exchanges (incomes and losses) of carbon between carbon reservoirs (e.g., atmosphere and biosphere) in the carbon cycle.

Carbon cycle:
All carbon reservoirs and exchanges of carbon from reservoir to reservoir by various chemical, physical, geological, and biological processes. Usually thought of as a series of the four main reservoirs of carbon interconnected by pathways of exchange. The four reservoirs, regions of the Earth in which carbon behaves in a systematic manner, are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). Each of these global reservoirs may be subdivided into smaller pools, ranging in size from individual communities or ecosystems to the total of all living organisms (biota).

Carbon dioxide:
A colorless, odorless, non-poisonous gas that is a normal part of the ambient air. Carbon dioxide is a product of fossil-fuel combustion. Although CO2 does not directly impair human health, it is a greenhouse gas that traps the earth's heat and contributes to the potential for global warming.

Carbon dioxide equivalent:
The concentration of carbon dioxide that would cause the same amount of radiative forcing as a given mixture of carbon dioxide and other greenhouse gases. Carbon dioxide equivalents are generally computed by multiplying the amount (in kilograms) of the gas of interest (for example, methane) by its estimated global warming potential. Some analysts (and this report) use "carbon equivalent units" for convenience, defined as carbon dioxide equivalents multiplied by the carbon content of carbon dioxide (i.e., 12/44).

Carbon flux:
See carbon budget.

Carbon sink:
A reservoir that absorbs or takes up released carbon from another part of the carbon cycle. Vegetation and soils are common carbon sinks.

Catalytic converter:
A device containing a catalyst for converting automobile exhaust into mostly harmless products.

Cesspool:
An underground reservoir for liquid waste, typically household sewage.

Chlorofluorocarbons (CFCs):
A family of inert, nontoxic, easily liquefied chemicals used in refrigeration, air conditioning, packaging, and insulation, or as solvents or aerosol propellants.

Climate:
The average course or condition of the weather over a period of years as exhibited by temperature, humidity, wind velocity, and precipitation.

Clinker:
Powdered cement, produced by heating a properly proportioned mixture of finely ground raw materials (calcium carbonate, silica, alumina, and iron oxide) in a kiln to a temperature of about 2,700oF.

Cloud condensation nuclei:
Aerosol particles that provide a platform for the condensation of water vapor, resulting in clouds with higher droplet concentrations and increased albedo.

Coal coke:
A hard, porous product made by baking bituminous coal in ovens at temperatures as high as 2,000oF. Used both as a fuel and as a reducing agent in blast furnaces. The term "coal coke" is used instead of "coke" to distinguish it from petroleum coke.

Coalbed methane:
Methane produced from coalbeds in the same way that natural gas is produced from other strata. See "methane."

Combustion:
Chemical oxidation accompanied by the generation of light and heat.

Combustion chamber:
An enclosed vessel in which chemical oxidation of fuel occurs.

Cracking:
The refining process of breaking down the larger, heavier, and more complex hydrocarbon molecules into simpler and lighter molecules.

Criteria pollutant:
A pollutant determined to be hazardous to human health and regulated under EPA's National Ambient Air Quality Standards. The 1970 amendments to the Clean Air Act require EPA to describe the health and welfare impacts of a pollutant as the "criteria" for inclusion in the regulatory regime.

Crop residue:
Organic residue remaining after the harvesting and processing of a crop.

Cultivar:
A horticulturally or agriculturally derived variety of a plant.

Deforestation:
The removal of forest stands.

Degasification system:
The methods employed for removing methane from a coal seam that could not otherwise be removed by standard ventilation fans and thus would pose a substantial hazard to coal miners. These systems may be used prior to mining or during mining activities.

Degradable organic carbon:
The portion of organic carbon, present in such solid waste as paper, food waste, and yard waste, that is susceptible to biochemical decomposition.

Desulfurization:
The removal of sulfur, as from molten metals, petroleum oil, or flue gases.

Diffusive transport:
The process by which particles of liquids or gases move from an area of higher concentration to an area of lower concentration.

Distillate fuel:
A general classification for the petroleum fractions produced in conventional distillation operations. Included are products known as No. 1, No. 2, and No. 4 fuel oils and No. 1, No. 2, and No. 4 diesel fuels. Used primarily for space heating, on- and off-highway diesel engine fuel (including railroad engine fuel and fuel for agricultural machinery), and electric power generation.

Efflux:
An outward flow.

Electrical generating capacity:
The full-load continuous power rating of electrical generating facilities, generators, prime movers, or other electric equipment (individually or collectively).

EMCON Methane Generation Model:
A model for estimating the production of methane from municipal solid waste landfills.

Emissions:
Anthropogenic (human-caused) releases of greenhouse gases to the atmosphere (e.g., the release of carbon dioxide during fuel combustion).

Emissions coefficient/factor:
A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g., pounds of carbon dioxide emitted per barrel of fossil fuel consumed).

Enteric fermentation:
A digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal.

Eructation:
An act or instance of belching.

Ethyl tertiary butyl ether (ETBE):
A colorless, flammable, oxygenated hydrocarbon blend stock.

Ethylene:
An olefinic hydrocarbon recovered from refinery or petrochemical processes.

Ethylene dichloride:
A colorless, oily liquid used as a solvent and fumigant for organic synthesis, and for ore flotation.

Facultative bacteria:
Bacteria that grow equally well under aerobic and anaerobic conditions.

Flange:
A rib or a rim for strength, for guiding, or for attachment to another object (e.g., on a pipe).

Flared natural gas:
Natural gas burned in flares on the well site or at gas processing plants.

Flatus:
Gas generated in the intestines or the stomach of an animal.

Flue gas desulfurization:
Equipment used to remove sulfur oxides from the combustion gases of a boiler plant before discharge to the atmosphere. Also referred to as scrubbers. Chemicals such as lime are used as scrubbing media.

Fluidized-bed combustion:
A method of burning particulate fuel, such as coal, in which the amount of air required for combustion far exceeds that found in conventional burners. The fuel particles are continually fed into a bed of mineral ash in the proportions of 1 part fuel to 200 parts ash, while a flow of air passes up through the bed, causing it to act like a turbulent fluid.

Flux material:
A substance used to promote fusion, e.g., of metals or minerals.

Fodder:
Coarse food for domestic livestock.

Forestomach:
See rumen.

Fossil fuel:
Any naturally occurring organic fuel formed in the Earth's crust, such as petroleum, coal, or natural gas.

Fuel cycle:
The entire set of sequential processes or stages involved in the utilization of fuel, including extraction, transformation, transportation, and combustion. Emissions generally occur at each stage of the fuel cycle.

Fugitive emissions:
Unintended leaks of gas from the processing, transmission, and/or transportation of fossil fuels.

Gasification:
A method for exploiting poor-quality coal and thin coal seams by burning the coal in place to produce combustible gas that can be collected and burned to generate power or processed into chemicals and fuels.

Gate station:
Location where the pressure of natural gas being transferred from the transmission system to the distribution system is lowered for transport through small diameter, low pressure pipelines.

Geothermal:
Pertaining to heat within the Earth.

Global warming potential (GWP):
The instantaneous radiative forcing that results from the addition of 1 kilogram of a gas to the atmosphere, relative to that of 1 kilogram of carbon dioxide.

Greenhouse effect:
A popular term used to describe the roles of water vapor, carbon dioxide, and other gases in keeping the Earth's surface warmer than it would otherwise be. These radiatively active gases are relatively transparent to incoming shortwave radiation, but are relatively opaque to outgoing longwave radiation. The latter radiation, which would otherwise escape to space, is trapped by greenhouse gases within the lower levels of the atmosphere. The subsequent re-radiation of some of the energy back to the Earth maintains higher surface temperatures than would occur if the gases were absent. There is concern that increasing concentrations of greenhouse gases, including carbon dioxide, methane, and chlorofluorocarbons, may enhance the greenhouse effect and cause global warming.

Greenhouse gases:
Those gases, such as water vapor, carbon dioxide, tropospheric ozone, nitrous oxide, and methane, that are transparent to solar radiation but opaque to longwave radiation, thus preventing longwave radiation energy from leaving the atmosphere. The net effect is a trapping of absorbed radiation and a tendency to warm the planet's surface.

Gross gas withdrawal:
The full-volume of compounds extracted at the wellhead, including nonhydrocarbon gases and natural gas plant liquids.

Gypsum:
The most common sulfate mineral. Used in wallboard.

Halogenated substances:
A volatile compound containing halogens, such as chlorine, fluorine or bromine.

Halons:
See bromofluorocarbons.

Heating degree-day:
The number of degrees per day that the average daily temperature is below 65 degrees Fahrenheit.

Herbivore:
A plant-eating animal.

Hydrocarbon:
An organic chemical compound of hydrogen and carbon in either gaseous, liquid, or solid phase. The molecular structure of hydrocarbon compounds varies from the simple (e.g., methane, a constituent of natural gas) to the very heavy and very complex.

Hydrochlorofluorocarbons (HCFCs):
Chemicals composed of one or more carbon atoms and varying numbers of hydrogen, chlorine, and fluorine atoms.

Hydrofluorocarbons (HFCs):
Chemicals composed of one or two carbon atoms and varying numbers of hydrogen and fluorine atoms.

Hydroxyl radical (OH):
An important chemical scavenger of many trace gases in the atmosphere that are greenhouse gases. Atmospheric concentrations of OH affect the atmospheric lifetimes of greenhouse gases, their abundance, and, ultimately, the effect they have on climate.

Intergovernmental Panel on Climate Change (IPCC):
A panel established jointly in 1988 by the World Meteorological Organization and the United Nations Environment Program to assess the scientific information relating to climate change and to formulate realistic response strategies.

Jet fuel:
Kerosene- and naphtha-type fuels for jet engines. Kerosene-type jet fuel is a kerosene-quality product used primarily for commercial turbojet and turboprop aircraft engines. Naphtha-type jet fuel is a fuel in the heavy naphtha range used primarily for military turbojet and turboprop aircraft engines.

Kerosene:
A petroleum distillate that has a maximum distillation temperature of 401oF at the 10-percent recovery point, a final boiling point of 572oF, and a minimum flash point of 100oF. Used in space heaters, cookstoves, and water heaters, and suitable for use as an illuminant when burned in wick lamps.

Ketone-alcohol (cyclohexanol):
An oily, colorless, hygroscopic liquid with a camphor-like odor. Used in soapmaking, dry cleaning, plasticizers, insecticides, and germicides.

Leachate:
A liquid produced as water percolates through wastes, collecting contaminants.

Lignite:
A brownish-black coal of low rank with high inherent moisture and volatile matter content, used almost exclusively for electric power generation. Also referred to as brown coal.

Liquefied petroleum gases (LPG):
Ethane, ethylene, propane, propylene, normal butane, butylene, and isobutane produced at refineries or natural gas processing plants, including plants that fractionate new natural gas plant liquids.

Lubricant:
A substance used to reduce friction between bearing surfaces or as a process material, either incorporated into other materials used as aids in manufacturing processes or as carriers of other materials. Petroleum lubricants may be produced either from distillates or residues. Other substances may be added to impart or improve useful properties. Does not include byproducts of lubricating oil from solvent extraction or tars derived from de-asphalting. Lubricants include all grades of lubricating oils from spindle oil to cylinder oil and those used in greases. Lubricant categories are paraffinic and naphthenic.

Methane:
A hydrocarbon gas (CH4) that is the principal constituent of natural gas.

Methanogens:
Bacteria that synthesize methane, requiring completely anaerobic conditions for growth.

Methanol:
A light alcohol that can be used for gasoline blending. See oxygenate.

Methanotrophs:
Bacteria that use methane as food and oxidize it into carbon dioxide.

Methyl chloroform (trichloroethane):
An industrial chemical (CH3CCl3) used as a solvent, aerosol propellant, and pesticide and for metal degreasing.

Methyl tertiary butyl ether (MTBE):
A colorless, flammable, liquid oxygenated hydrocarbon containing 18.15 percent oxygen.

Methylene chloride:
A colorless liquid, nonexplosive and practically nonflammable. Used as a refrigerant in centrifugal compressors, a solvent for organic materials, and a component in nonflammable paint removers.

Mole:
The quantity of a compound or element that has a weight in grams numerically equal to its molecular weight. Also referred to as gram molecule or gram molecular weight.

Montreal Protocol:
The Montreal Protocol on Substances that Deplete the Ozone Layer (1987). An international agreement, signed by most of the industrialized nations, to substantially reduce the use of chlorofluorocarbons (CFCs). Signed in January 1989, the original document called for a 50-percent reduction in CFC use by 1992 relative to 1986 levels. The subsequent London Agreement called for a complete elimination of CFC use by 2000. The Copenhagen Agreement, which called for a complete phaseout by January 1, 1996, was implemented by the U.S. Environmental Protection Agency.

Motor gasoline:
A complex mixture of relatively volatile hydrocarbons, with or without small quantities of additives, obtained by blending appropriate refinery streams to form a fuel suitable for use in spark-ignition engines. Motor gasoline includes both leaded and unleaded grades of finished gasoline, blending components, and gasohol.

Multiple cropping:
A system of growing several crops on the same field in one year.

Municipal solid waste:
Residential solid waste and some nonhazardous commercial, institutional, and industrial wastes.

Naphtha:
A generic term applied to a petroleum fraction with an approximate boiling range between 122 and 400oF.

Natural gas:
A mixture of hydrocarbons and small quantities of various nonhydrocarbons in the gaseous phase or in solution with crude oil in natural underground reservoirs.

Natural gas liquids (NGLs):
Those hydrocarbons in natural gas that are separated as liquids from the gas. Includes natural gas plant liquids and lease condensate.

Natural gas, pipeline quality:
A mixture of hydrocarbon compounds existing in the gaseous phase with sufficient energy content, generally above 900 Btu, and a small enough share of impurities for transport through commercial gas pipelines and sale to end-users.

Nitrogen oxides (NOx):
Compounds of nitrogen and oxygen produced by the burning of fossil fuels.

Nitrous oxide:
A colorless gas, naturally occurring in the atmosphere, with the formula N2O.

Nonmethane volatile organic compounds (NMVOCs):
Organic compounds, other than methane, that participate in atmospheric photochemical reactions.

Octane:
A flammable liquid hydrocarbon found in petroleum. Used as a standard to measure the anti-knock properties of motor fuel.

Oil reservoir:
An underground pool of liquid consisting of hydrocarbons, sulfur, oxygen, and nitrogen trapped within a geological formation and protected from evaporation by the overlying mineral strata.

Organic content:
The share of a substance that is of animal or plant origin.

Organic waste:
Waste material of animal or plant origin.

Oxidize:
To chemically transform a substance by combining it with oxygen.

Oxygenate:
A substance which, when added to gasoline, increases the amount of oxygen in that gasoline blend. Includes fuel ethanol, methanol, and methyl tertiary butyl ether (MTBE).

Ozone:
A molecule made up of three atoms of oxygen. Occurs naturally in the stratosphere and provides a protective layer shielding the Earth from harmful ultraviolet radiation. In the troposphere, it is a chemical oxidant, a greenhouse gas, and a major component of photochemical smog.

Ozone precursors:
Chemical compounds, such as carbon monoxide, methane, nonmethane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone.

Paraffinic hydrocarbons:
Straight-chain hydrocarbon compounds with the general formula CnH2n+2.

Perfluorocarbons (PFCs):
Chemicals composed of one or two carbon atoms and four to six fluorine atoms, containing no chlorine. PFCs have no commercial uses and are emitted as a byproduct of aluminum smelting.

Perfluoromethane:
A compound (CF4) emitted as a byproduct of aluminum smelting.

Petrochemical feedstock:
Feedstock derived from petroleum, used principally for the manufacture of chemicals, synthetic rubber, and a variety of plastics. The categories reported are naphthas (endpoint less than 401oF) and other oils (endpoint equal to or greater than 401oF).

Petroleum:
Hydrocarbon mixtures, including crude oil, lease condensate, natural gas, products of natural gas processing plants, refined products, semifinished products, and blending materials.

Petroleum coke:
A residue that is the final product of the condensation process in cracking.

Photosynthesis:
The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll, with sunlight as the energy source. Carbon is sequestered and oxygen and water vapor are released in the process.

Pig iron:
Crude, high-carbon iron produced by reduction of iron ore in a blast furnace.

Pipeline, distribution:
A pipeline that conveys gas from a transmission pipeline to its ultimate consumer.

Pipeline, gathering:
A pipeline that conveys gas from a production well/field to a gas processing plant or transmission pipeline for eventual delivery to end-use consumers.

Pipeline, transmission:
A pipeline that conveys gas from a region where it is produced to a region where it is to be distributed.

Planetary albedo:
The fraction of incident solar radiation that is reflected by the Earth-atmosphere system and returned to space, mostly by backscatter from clouds in the atmosphere.

Pneumatic device:
A device moved or worked by air pressure.

Polystyrene:
A polymer of styrene that is a rigid, transparent thermoplastic with good physical and electrical insulating properties, used in molded products, foams, and sheet materials.

Polyvinyl chloride (PVC):
A polymer of vinyl chloride. Tasteless. odorless, insoluble in most organic solvents. A member of the family vinyl resin, used in soft flexible films for food packaging and in molded rigid products, such as pipes, fibers, upholstery, and bristles.

Post-mining emissions:
Emissions of methane from coal occurring after the coal has been mined, during transport or pulverization.

Radiative forcing:
The extent to which emitting a greenhouse gas into the atmosphere raises global average temperature.

Radiatively active gases:
Gases that absorb incoming solar radiation or outgoing infrared radiation, affecting the vertical temperature profile of the atmosphere.

Ratoon crop:
A crop cultivated from the shoots of a perennial plant.

Redox potential:
A measurement of the state of oxidation of a system.

Reflectivity:
The ratio of the energy carried by a wave after reflection from a surface to its energy before reflection.

Reforestation:
Replanting of forests on lands that have recently been harvested.

Reformulated gasoline:
Gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations promulgated by the U.S. Environmental Protection Agency under Section 211K of the Clean Air Act.

Renewable energy:
Energy obtained from sources that are essentially inexhaustible (unlike, for example, the fossil fuels, of which there is a finite supply). Renewable sources of energy include wood, waste, geothermal, wind, photovoltaic, and solar thermal energy.

Residual fuel oil:
The heavier oils that remain after the distillate fuel oils and lighter hydrocarbons are distilled away in refinery operations and that conform to ASTM Specifications D396 and D975. Included are No. 5, a residual fuel oil of medium viscosity; Navy Special, for use in steam-powered vessels in government service and in shore power plants; and No. 6, which includes Bunker C fuel oil and is used for commercial and industrial heating, electricity generation, and to power ships. Imports of residual fuel oil include imported crude oil burned as fuel.

Rumen:
The large first compartment of the stomach of certain animals in which cellulose is broken down by the action of bacteria.

Sample:
A set of measurements or outcomes selected from a given population.

Sequestration:
The fixation of atmospheric carbon dioxide in a carbon sink through biological or physical processes, such as photosynthesis.

Septic tank:
A tank in which the solid matter of continuously flowing sewage is disintegrated by bacteria.

Sinter:
A chemical sedimentary rock deposited by precipitation from mineral waters, especially siliceous sinter and calcareous sinter.

Sodium silicate:
A grey-white powder soluble in alkali and water, insoluble in alcohol and acid. Used to fireproof textiles, in petroleum refining and corrugated paperboard manufacture, and as an egg preservative. Also referred to as liquid gas, silicate of soda, sodium metasilicate, soluble glass, and water glass.

Sodium tripolyphosphate:
A white powder used for water softening and as a food additive and texturizer.

Stabilization lagoon:
A shallow artificial pond used for the treatment of wastewater. Treatment includes removal of solid material through sedimentation, the decomposition of organic material by bacteria, and the removal of nutrients by algae.

Still gas:
Any form or mixture of gases produced in refineries by distillation, cracking, reforming, and other processes. Principal constituents are methane, ethane, ethylene, normal butane, butylene, propane, propylene, etc. Used as a refinery fuel and as a petrochemical feedstock.

Stratosphere:
The region of the upper atmosphere extending from the tropopause (8 to 15 kilometers altitude) to about 50 kilometers. Its thermal structure, which is determined by its radiation balance, is generally very stable with low humidity.

Stripper well:
A well that produces 60 million cubic feet of gas per day or less for a period of three consecutive months while producing at its maximum flow rate.

Styrene:
A colorless, toxic liquid with a strong aromatic aroma. Insoluble in water, soluble in alcohol and ether; polymerizes rapidly; can become explosive. Used to make polymers and copolymers, polystyrene plastics, and rubber.

Subbituminous coal:
A dull, black coal of rank intermediate between lignite and bituminous coal.

Sulfur dioxide:
A toxic, irritating, colorless gas soluble in water, alcohol, and ether. Used as a chemical intermediate, in paper pulping and ore refining, and as a solvent.

Sulfur hexafluoride:
A colorless gas soluble in alcohol and ether, slightly soluble in water. Used as a dielectric in electronics.

Sulfur oxides (SOx):
Compounds containing sulfur and oxygen, such as sulfur dioxide (SO2) and sulfur trioxide (SO3).

Tertiary amyl methyl ether (TAME):
An oxygenate blend stock formed by the catalytic etherification of isoamylene with methanol.

Troposphere:
The inner layer of the atmosphere below about 15 kilometers, within which there is normally a steady decrease of temperature with increasing altitude. Nearly all clouds form and weather conditions manifest themselves within this region. Its thermal structure is caused primarily by the heating of the Earth's surface by solar radiation, followed by heat transfer through turbulent mixing and convection.

Uncertainty:
A measure used to quantify the plausible maximum and minimum values for emissions from any source, given the biases inherent in the methods used to calculate a point estimate and known sources of error.

Vapor displacement:
The release of vapors that had previously occupied space above liquid fuels stored in tanks. These releases occur when tanks are emptied and filled.

Ventilation system:
A method for reducing methane concentrations in coal mines to non-explosive levels by blowing air across the mine face and using large exhaust fans to remove methane while mining operations proceed.

Volatile organic compounds (VOCs):
Organic compounds that participate in atmospheric photochemical reactions.

Volatile solids:
A solid material that is readily decomposable at relatively low temperatures.

Waste flow:
Quantity of a waste stream generated by an activity.

Wastewater:
Water that has been used and contains dissolved or suspended waste materials.

Wastewater, domestic and commercial:
Wastewater (sewage) produced by domestic and commercial establishments.

Wastewater, industrial:
Wastewater produced by industrial processes.

Water vapor:
Water in a vaporous form, especially when below boiling temperature and diffused (e.g., in the atmosphere).

Waxes:
Solid or semisolid materials derived from petroleum distillates or residues. Light-colored, more or less translucent crystalline masses, slightly greasy to the touch, consisting of a mixture of solid hydrocarbons in

which the paraffin series predominates. Included are all marketable waxes, whether crude scale or fully refined. Used primarily as industrial coating for surface protection.

Weanling system:
A cattle management system that places calves on feed starting at 165 days of age and continues until the animals have reached slaughter weight.

Wellhead:
The top of, or a structure built over, a well.

Wetlands:
Areas regularly saturated by surface or groundwater and subsequently characterized by a prevalence of vegetation adapted for life in saturated-soil conditions.

Wood energy:
Wood and wood products used as fuel, including roundwood (cordwood), limbwood, wood chips, bark, sawdust, forest residues, and charcoal.

Yearling system:
A cattle management system that includes a stocker period from 165 days of age to 425 days of age followed by a 140-day feedlot period.

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File last modified: 10/21/97
Energy Information Administration/Emissions of Greenhouse Gases in the United States 1996
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