Alkali-Silicate Reactivity: The reaction between the alkalies (sodium and potassium) in Portland cement with certain siliceous rocks and minerals, such as opaline chert, strained quartz, and acidic volcanic glass, present in some aggregates; the products of the reaction can cause abnormal expansion and cracking of concrete in service. Class F fly ash is used in concrete to reduce the occurrence of alkali-silica reactivity.
Air Pollution: One or more chemicals or substances in high enough concentrations in the air to harm humans, other animals, vegetation, or materials. Such chemicals or physical conditions (such as excess heat or noise) are called air pollutants.
Asphalt: A dark-brown-to-black cement-like material containing bitumen as the predominant constituent. It is obtained by petroleum processing. The definition includes crude asphalt as well as the following finished products: cements, fluxes, the asphalt content of emulsions (exclusive of water), and petroleum distillates blended with asphalt to make cutback asphalt.
Autoclaved Aerated Concrete (AAC): AAC is a lightweight concrete with no course aggregate that is produced by mixing Portland cement, lime, aluminum powder, and water with a large proportion of a silica-rich material such as sand or fly ash. Fly ash can be as much as 75% of the material by weight. AAC combines relatively low thermal conductivity with mechanical properties sufficient for may load-bearing applications. It is also known as autoclaved cellular concrete (ACC) and porous concrete.
Beneficial Uses: The use of byproducts in such a manner that the material serves a beneficial function, while not adversely impacting human health or the environment. Beneficial uses of byproducts include construction applications (e.g., brick and concrete products, road bed, blasting grit, wall board, insulation, roofing materials), agricultural applications (e.g., as a substitute for lime) and other applications (e.g., absorbents, filter media, paints, plastics and metals manufacture, snow and ice control, waste stabilization).
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.
British Thermal Unit (BTU): The quantity of heat required to raise the temperature of one pound of water one degree of Fahrenheit at or near 39.2 degrees Fahrenheit.
Brown Power/Energy: Electricity generated from the combustion of nonrenewable fossil fuels (coal, oil, or natural gas) which generates significant amounts of greenhouse gases.
By-Product or byproduct: A secondary or incidental product deriving from a manufacturing process, a chemical reaction or a biochemical pathway, and is not the primary product or service being produced. A by-product can be useful and marketable, or it can have a negative ecological impact.
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 carbon dioxide does not directly impair human health, it is a greenhouse gas that traps (i.e., infrared) radiation and contributes to the potential for global warming.
Carbon Dioxide (CO2): The greenhouse gas whose concentration is being most affected directly by human activities. CO2 also serves as the reference to compare all other greenhouse gases. The major source of CO2 emissions is fossil fuel combustion. Atmospheric concentrations of CO2 have been increasing at a rate of about 0.5 percent per year and are now about 30% above pre-industrial levels. 
Carbon Dioxide Equivalent: A metric measure used to compare the emissions of various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCDE).” The carbon dioxide equivalent for a gas is derived by multiplying the tons of the bas by the associated GWP.
MMTCDE = (million metric tons of a gas) * (GWP of the gas)
Carbon Footprint: A measure of the amount of greenhouse gases emitted because of one’s activities. These can be tracked at global, state, or local levels as well as by companies and individuals. For greenhouse gases other than carbon, the effect of the emissions is translated into a measure called a “carbon equivalent”. A “carbon footprint” includes all the greenhouse gases.
Carbon Footprint: It measures total amount of greenhouse gas emissions released into the environment. Greenhouse gas emissions from all sources are summed up and changed into units of CO2 equivalent which is used to standardize greenhouse gas emissions and help make comparisons from different time periods and across industries. Carbon emissions are usually measured in metric tons per year (1 metric ton equals 2205 lbs).
Carbon Offset: Actions to reduce or avoid greenhouse gas (GHG) emissions in one location in order to “offset” GHG emissions occurring in a second location. As carbon dioxide is the most important GHG by volume, completely offsetting carbon dioxide emissions produces a result that is often described as “carbon neutral.”
Carbon Trading: A trading system for countries, companies and individuals designed to offset carbon emissions from one activity with another, whereby those who cannot meet their emissions goals may purchase credits from those who surpass their goals.
Cement Clinker: The fused particles or pellets produced from the sintering or burning zone (2200º F to 2700º F) of a rotary kiln in the cement manufacturing process. Raw materials (limestone, shale, iron ore, sand) are proportioned and ground to a powder and blended before being processed through the rotary kiln.
Certification: is the formal process of assessing and approving the performance level of a LEED constructed building.
Chemical Reaction: Interaction between chemicals in which there is a change in the chemical composition of the elements or compounds involved.
Clean Water Act: Federal legislation passed in 1972 and amended in 1976 that requires the EPA to set maximum pollutant levels for each known contaminant in U.S. surface waters and authorizes the EPA to regulate industrial discharge in order to meet those standards.
Coal: Formed from plant and animal matter that has been subjected to geologic heat and pressure, and transformed over millions of years into hard black solids. Because coal is a readily available resource in the United States, coal power plants provide about half of the nation’s electricity. However, coal-fired power plants generally cause more pollution per unit of electricity than any other fuel. Coal is considered nonrenewable because it cannot be replenished on a human time frame. 
Coal Combustion Products (CCPs): Residues from coal burning, including bottom ash, fly ash, boiler slag, and flu gas desulfurization materials (FGD), which can be used beneficially. (The use of the term “coal combustion products” in this document does not change the legal definition of solid waste as defined in RCRA 42 U.S.C. 6903(27).
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund): Federal legislation passed in 1980 that established a tax on the petroleum and chemical industries to fund cleanup of hazardous waste sites, as well as establishing EPA authority to assign responsibility for that cleanup to the polluters or purchasers of contaminated land.
Concrete: A construction material consisting primarily of aggregates, Portland cement, and water. Certain coal ashes can be used as a replacement for a portion of the Portland cement.
Construction and Demolition (C&D) Debris: Includes waste and recyclables generated from construction, renovation, and demolition or deconstruction of pre-existing structures. Land clearing debris including soil, vegetation, rocks, etc. are not to be included.
Contaminant: An unwanted airborne constituent that may reduce acceptability of the air.
Combustion: Chemical oxidation accompanied by the generation of light and heat.
Emission: Any gas, particle or vapor release into the environment from a commercial, industrial, or residential source including smokestacks, chimneys, and motor vehicles.
Engineered Application: Use of a byproduct that has been specifically designed and engineered (for example, a road design that incorporates appropriate run-off control and provides adequate strength for the required use).
Exhaust Air: The air removed from a space and discharged to outside the building by means of mechanical or natural ventilation systems.
Feedstock: The raw material used in manufacturing a product, such as the oil or gas used to make plastic.
Fill: Material such as dirt, gravel, or coal ash used to build up an area of land.
Flowable Fill: A fill material that flows like a liquid, is self-leveling, requires no compaction
or vibration to achieve maximum density, hardens to a predetermined strength, and is sometimes used as a controlled low-strength material.
Flue Gas Desulfurization Materials (FGD): The materials created during the process of removing gaseous sulfur dioxide from boiler exhaust gas. FGD materials often are used as a replacement for gypsum in wallboard.
Fluidized Bed Combustion (FBC): Process for burning coal more efficiently, cleanly, and cheaply. A stream of hot air is used to suspend a mixture of powdered coal and limestone during combustion. About 90 to 98 percent of the sulfur dioxide produced during combustion is removed by reaction with limestone to produce solid calcium sulfate.
Fossil Fuels: A general term for buried combustible geologic deposits or organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth’ crust over hundreds of millions of years. The popularity of these fuels is largely due to their low cost. Fossil fuels come in three major forms – coal, oil, and natural gas. Because fossil fuels are a finite resource and cannot be replenished once they are extracted and burned, they are not considered renewable.
Fossil Fuel Combustion: Burning of coal, oil (including gasoline), or natural gas. This burning, usually to generate energy, releases carbon dioxide, as well as combustion by products that can include unburned hydrocarbons, methane, and carbon monoxide. Carbon monoxide, methane, and many of the unburned hydrocarbons slowly oxidize into carbon dioxide in the atmosphere. Common sources of fossil fuel combustion include cars and electric utilities.
Global Warming: An increase in the near surface temperature of the Earth. Global warming is most often used to refer to the warming predicted to occur as a result of increased emissions of greenhouse gases. Scientists generally agree that the Earth’s surface has warmed by about 1 degree F in the past 140 years.
Global Warming Potential: The index used to translate the level of emission of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. Global warming potentials (GWPs) are calculated as the ratio of the radiative forcing that would result from the emissions of one kilogram of a greenhouse gas to that from emission of one kilogram of carbon dioxide over a period of time (usually 100 years).
Green Building: A comprehensive process of design and construction that employs techniques to minimize adverse environmental impacts and reduce the energy consumption of a building, while contributing to the health and productivity of its occupants, a common metric for evaluating green buildings is the LEED (Leadership in Energy and Environmental Design) certification.
Greenhouse Effect: The trapping of heat within the Earth’s atmosphere by greenhouse gases such as CO2, which is necessary to keep the plant at a temperature warm enough to sustain life, but becomes dangerous when greenhouse gases produced by humans cause the effect to intensify and push the global temperature to a high level.
Greenhouse Gas: Any gas including carbon dioxide, methane, and nitrous oxide that contributes to the greenhouse effect. 
Green Power: Electricity that is generated from renewable energy sources. Green power products can include electricity generated exclusively from renewable resources or, more frequently, electricity produced from a combination of fossil and renewable resources. Also known as “blended” products, these products typically have lower prices than 100% renewable products. Customers who take advantage of these options usually pay a premium for having some of all of their electricity produced from renewable sources.
Industrial Waste: Undesired materials created from an industrial operation; may be liquid, sludge, solid, or hazardous waste.
Infrared Radition:  The heat energy that is emitted from all solids, liquids, and gases. In the context of the greenhouse issue, the term refers to the heat energy emitted by the Earth's surface and its atmosphere. Greenhouse gases strongly absorb this radiation in the Earth's atmosphere, and radiate some back towards the surface, creating the greenhouse effect.
Landfill: A method for disposing of solid wastes by burying them in layers of earth.
Leachate: The liquid, including any suspended components in the liquid, that has percolated through or drained from a pile or cell of solid materials; the liquid stream that issues from a pile or cell of solid materials and that contains water, dissolved solids, and decomposition products of the solids.
LEED Certification: an acronym for Leadership in Energy and Environmental Design sponsored by the United States Green Building Council that creates standards for developing high performance, sustainable buildings. 
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.
Maximum Contaminant Level (MCL): The highest level of a contaminant that is allowed in drinking water.
Metric Ton: Common International measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 pounds or 1.1 short tons.
Nitrogen Oxides (NOx): Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced, for example, by the combustion of fossil fuels in vehicles and electric power plants. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), impair visibility, and have health consequences; they are considered pollutants.

Nitrous Oxide (N2O): A powerful greenhouse gas with a global warming potential most recently evaluated at 310. Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

Non-renewable Resource: a natural resource that is unable to be regenerated or renewed fully and without loss of quality once it is used, i.e., fossil fuels or minerals.
Organic Compound: Molecule that contains atoms of the element carbon, usually combined with itself and with atoms of one or more other element such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, or fluorine.
Ozone: Ozone (O3) is an important greenhouse gas found in both the stratosphere and the troposphere (lowest region of the atmosphere). In the stratosphere, ozone provides a protective layer shielding the Earth from ultraviolet radiation and subsequent harmful health effects on humans and the environment. In the troposphere, oxygen molecules in ozone combine with other chemicals and gases (oxidization) to cause smog.
Ozone Depletion: Stratospheric ozone is necessary to filter out harmful radiation from the sun. Scientists have linked depletion of stratospheric to increased incidence of skin cancer and other disorders and environmental degradation. Under international convention and national laws, governments are prohibiting the production, use, and release of ozone-depleting substances.
Ozone Layer: Begins approximately 15 kilometers above the earth and thins to an almost negligible amount at about 50 kilometers, shielding the Earth from harmful ultraviolet radiation from the Sun. The highest natural concentration of ozone (approximately 10 parts per million by volume) occurs in the stratosphere at approximately 25 kilometers above Earth. The stratospheric ozone concentration changes throughout the year as stratospheric circulation changes with the seasons. Natural events such as volcanoes and solar flares can produce changes in ozone concentration, but man-made changes are of the greatest concern.
Particulate Matter: Microscopic particles, both solids and droplets, that can remain suspended in the air for some time. PM is generated by natural processes, human activities, and reactions between air pollutants. Dust, pollen, soot, smoke, and ammonia droplets are examples of PM. Fine particulate matter is one of the main components of smog.
Point Source: A single identifiable source that discharges pollutants into the environment.
Pollution: A change in the physical, chemical, or biological characteristics of the air, water, or soil that can affect the health, survival, or activities of humans in an unwanted way. Some expand the term to include harmful effects on all forms of life.
Polymers: Any molecule chain made up from repeated elements, for example, plastics and adhesives.
Portland Cement: A hydraulic cement made by heating a mixture of limestone and clay containing oxides of calcium, aluminum, iron, and silicon in a kiln and pulverizing the resulting clinker. Common name for commercial cement.
Pozzolanic Properties: The phenomenon of strength development that occurs when lime and certain aluminosilicates react at ambient temperatures in the presence of water.
Ppb: Parts per billion.
Ppm: Parts per million.
Radiation: Energy emitted in the form of electromagnetic waves. Radiation has differing characteristics depending upon the wavelength. Because the radiation from the Sun is relatively energetic, it has a short wavelength (ultra-violet, visible, and near infrared) while energy radiated from the Earth's surface and the atmosphere has a longer wavelength (e.g., infrared radiation) because the Earth is cooler than the Sun.
Recycled Material: A material that would otherwise be destined for disposal but is diverted or separated from the waste stream, reintroduced as material feed-stock and processed into marketed end-products.
Renewable: A renewable product can be grown or naturally replenished or cleansed at a rate that exceeds human depletion of the resource.
Renewable Energy: Energy derived from non-fossil fuel resources (such as solar, wind, or geothermal energy) that can be replenished in full without a loss of quality, separate from sustainable energy because of emissions or other unsustainable impacts of the process of creating renewable energy.
Short Ton: Common measurement for a ton in the United States. A short ton is equal to 2,000 pounds or .907 metric tons.
Subbituminous Coal: A dull, black coal of rank intermediate between lignite and bituminous coal.
Sulfur Dioxide (SO2): A compound composed of one sulfur and two oxygen molecules. Sulfur dioxide emitted into the atmosphere through natural and anthropogenic processes is changed in a complex series of chemical reactions in the atmosphere to sulfate aerosols. These aerosols are believed to result in negative radiative forcing (i.e., tending to cool the Earth's surface) and do result in acid deposition (e.g., acid rain).
Sustainable: The condition of being able to meet the needs of present generations without compromising those needs for future generations. Achieving a balance among extraction and renewal and environmental inputs and outputs, as to cause no overall net environmental burden or deficit. To be truly sustainable, a human community must not decrease biodiversity, must not consumer resources faster than they are renewed, must recycle and reuse virtually all materials, and rely primarily on the resources of its own region.
Trace Element: An element present in extremely small quantities. In coal ash, trace elements are typically metals.