Glossary of Terms

Additionality—Additionality is a process that identifies Carbon Offset projects that would not have been built without the financial incentive provided by a functioning voluntary carbon market. Projects are deemed “additional” when the financial incentive provided by the sale of voluntary carbon offsets is verified to be a key factor in moving the project forward. Additionality is the cornerstone of verified Carbon Offset projects, since it provides consumer confidence that their purchase helped make the project happen. It is important to note that carbon offset verification standards use different tests to determine additionality. For more information on additionality tests, visit the Verified Carbon Standard, Climate Action Reserve, The Gold Standard or American Carbon Registry. Additionality is a complex topic—for more information, read the in-depth paper on Additionality found on the GHG Institute website.

Accountability—A concept of ethics and governance that obliges an entity to report, explain and be answerable for resulting consequences.

Agriculture Methane Capture Carbon Offsets—Agricultural operations, such as those in the dairy industry, result in methane emissions from animal waste. Sites may capture and flare the methane, which converts it into much less potent carbon dioxide. The methane gas may also be collected and scrubbed for use as biogas to produce energy, sometimes replacing natural gas or other fuel oils used for heating or energy production. The greenhouse gas (GHG) value is a function of converting the methane into carbon dioxide, which traps less heat in the atmosphere than methane.

Anaerobic Digestion—Biogas recovery systems use a process called anaerobic digestion where bacteria break down manure in an oxygen-free environment. One of the natural products of anaerobic digestion is biogas, which typically contains between 60 to 70 percent methane, 30 to 40 percent carbon dioxide and trace amounts of other gases. See Biogas. Source: U.S. Environmental Protection Agency

Biodiesel—A diesel fuel alternative made from vegetable oil or fats.

Bioethenol—Bioethenol is ethanol derived from the fermentation of plant matter (such as corn, switchgrass, grains or sugarcane).

Biofuels—Fuel generated from living matter.

Biogas—Biogas is an energy resource produced by capturing methane through a process called anaerobic digestion. Methane can come from any facility in which plant or animal matter is decomposing. Biogas renewable energy projects are most commonly operated on dairy farms that capture methane and convert it into energy that can be used to replace other fuels such as natural gas (commonly used for heating buildings).

Biomass—Biomass comes from raw materials such as sugar cane, wood residue or soybeans. In order to produce energy from Biomass, the organic matter must be burned in some way. Therefore the production of energy from biomass releases carbon dioxide into the air—unlike the use of other renewable energy sources such as solar or wind.

Campus Clean Energy Carbon Offsets—Institutions of higher-education across the U.S. are engaged in reducing their greenhouse gas (GHG) emissions through a variety of strategies including energy efficiency upgrades, on-site renewable energy and behavior change to reduce energy use. Carbon Offsets from this sector follow a performance-based approach and result from measured year-over-year improvements in energy use from either an entire campus or an individual certified green building located on campus.


Cap and Trade—Cap and trade is a market-based approach to change behavior and achieve environmental goals. Here is how it works:

  • The government sets an overall emission target, called a “cap” that applies to covered entities.
  • The “cap” is the sum of all allowed emissions from all of an entity’s facilities.
  • Once the cap is set and the covered entities have been specified, tradable emissions allowances (rights to emit) are distributed.
  • Each allowance authorizes the release of a specified amount of GHG emissions, generally one ton of CO2e.
  • The total number of allowances is equivalent to the overall emissions cap (e.g. if a cap of 1mm tons of emissions is set, 1mm one ton allowances will be issued).
  • Covered entities must submit allowances equivalent to the level of emissions for which they are responsible at the end of each of the program’s compliance periods.
  • For example AB-32 in California allows forestry based offsets to count toward the cap, but not renewable energy based offsets. Each compliance system will have its own parameters regarding offsets. Source: The Pew Center on Global Climate Change “Benefits of Cap and Trade” white paper.

    Carbon Dioxide—Carbon dioxide (or CO2) is a naturally occurring gas as well as a by-product of burning fossil fuels and biomass, or from land-use changes and other industrial processes. It is the principal human-caused greenhouse gas that affects the Earth's radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore has a global warming potential of 1. Source: U.S. Environmental Protection Agency


    Carbon Dioxide Equivalent—Carbon Dioxide Equivalent (or CO2e) is a measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as "million metric tons of carbon dioxide equivalents (MMTCO2Eq)." The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by the associated GWP. MMTCO2Eq = (million metric tons of a gas) * (GWP of the gas) Source: U.S. Environmental Protection Agency

    Carbon Emissions—When greenhouse gases are released into the atmosphere they are more generally referred to as “carbon emissions” because all greenhouse gases are calculated and measured in carbon dioxide equivalents. Carbon dioxide equivalent provides the standard unit of measure for greenhouse gases.

    Carbon Footprint—A carbon footprint is the total amount of greenhouse gases that are emitted into the atmosphere each year by a person, family, building, organization or company. A person’s carbon footprint includes greenhouse gas emissions from fuel that an individual burns directly, such as by heating a home or riding in a car. It also includes greenhouse gases that come from producing the goods or services that the individual uses, including emissions from power plants that make electricity, factories that make products and landfills where trash is sent. Source: U.S. Environmental Protection Agency

    Carbon Offset—One Carbon Offset represents a quantity of greenhouse gas (GHG) emissions reductions, measured in units (metric tons) of carbon dioxide equivalent (CO2e) that occur as a result of a discrete project. The emissions reductions from that project can be sold to enable the purchaser/owner to claim those GHG reductions as their own. These reductions can then be used to reduce, or offset, any GHG emissions for which the purchaser is responsible.

    Climate Change—Climate change refers to any significant change in the measures of climate lasting for an extended period of time. In other words, climate change includes major changes in temperature, precipitation or wind patterns that occur over several decades or longer. Source: U.S. Environmental Protection Agency

    Corporate Social Responsibility—Organizational self-regulation whereby an organization measures and ensures it is operating with current ethical, legal, environmental and international standards and norms.

    Cradle-to-Cradle—The life cycle of a product that can be reused and recycled without loss of material integrity.

    Cradle-to-Grave—The life cycle of a product from generation to disposal.

    Emissions—The release of a substance (usually a gas when referring to the subject of climate change) into the atmosphere. Source: U.S. Environmental Protection Agency

    Energy Recovery—The process of utilizing the energy released from a resource recovery process (e.g. gasification) for another purpose (to generate steam, fuel or electricity).

    Environmental Footprint—An environmental footprint is similar to a carbon footprint but includes impacts on the environment beyond gas emissions. For example, evaluating a person, family, building, organization or company environmental footprint may include considering impacts on water resources, the amount of non-recycled waste, extraction of natural resources and other factors to evaluate the entire environmental footprint.

    Forestry Carbon Offsets—Healthy forests absorb and hold carbon dioxide emissions produced from other sources and are an important source of greenhouse gas (GHG) sequestration. Carbon offsets from forestry may be created through a variety of strategies including: avoided deforestation and permanent land conservation, reforestation and replanting activities and improved forest management and stewardship in working forests where harvesting occurs.

    Forest Stewardship Council—The Forest Stewardship Council (FSC) is a nonprofit organization established to promote responsible forest management. FSC also evaluates and certifies the sustainability of forest products.

    Geothermal Energy—Geothermal energy is the natural thermal energy that is generated and stored in the Earth.

    Global Warming—The recent and ongoing global average increase in temperature near the Earth’s surface. Source: U.S. Environmental Protection Agency

    Global Warming Potential—A measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide. Source: U.S. Environmental Protection Agency

    Grasslands Conservation Carbon Offsets—Similar to forestry, native grasses and other vegetation provide a natural source of greenhouse gas (GHG) absorption and sequestration. Carbon Offsets from this category focus on maintaining native plant life through permanent land conservation and avoided conversion for commercial development or agriculture.

    Green Building Council—The U.S. Green Building Council (USGBC) is a 501(c)(3) nonprofit organization committed to a prosperous and sustainable future for the nation through cost-efficient and energy-saving green buildings. USGBC works toward its mission of market transformation through its LEED® green building program, robust educational offerings, a nationwide network of chapters and affiliates, the annual Greenbuild International Conference & Expo, and advocacy in support of public policy that encourages and enables green buildings and communities.

    Green Guides—The Federal Trade Commission (FTC) has produced Green Guides to advise businesses in making environmental claims about their organization or the products they produce to comply with truth-in-advertising principles. Learn more or download the latest Green Guides

    Greenhouse Effect—The greenhouse effect is the trapping and build-up of heat in the atmosphere near the Earth’s surface. Some of the heat flowing back toward space from the Earth's surface is absorbed by water vapor, carbon dioxide, ozone and several other gases in the atmosphere and then re-radiated back toward the Earth’s surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase. Source: U.S. Environmental Protection Agency

    Greenhouse Gas (GHG)—A greenhouse gas is any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride. Source: U.S. Environmental Protection Agency

    Greenwashing—The deceptive or misleading use of advertising and marketing to overstate an organizations’ environmental or sustainable practices.

    Kyoto Protocol—Reached in 1997, a protocol to the United Nations Framework Convention on Climate Change that commits ratifying governments to achieve quantified targets to reduce greenhouse gas emissions.

    Landfill Gas Extraction Carbon Offsets—Unregulated landfill operations may collect and convert the methane emissions occurring as solid wastes break down at their facility over time. Methane gas may be flared and converted to carbon dioxide in order to significantly reduce its greenhouse gas (GHG) potency. The methane gas may also be collected and scrubbed for use as biogas to produce energy, sometimes replacing natural gas or other fuel oils used for heating or energy production. The GHG value is a function of converting the methane into carbon dioxide, which traps less heat in the atmosphere than methane.

    Landfill-Gas-to-Energy—Landfill-gas-to-energy (LFGTE) projects capture methane gas for electricity and heat, turning a potent greenhouse gas (GHG) into a beneficial source of renewable energy.

    Life Cycle Analysis (LCA)—The evaluation of the environmental impacts of a product or service over the course of its lifetime in order to identify and reduce net impacts.

    LEED®—LEED® stands for Leadership in Energy and Environmental Design. LEED® is an environmental rating and certification system for residential and commercial buildings from the U.S. Green Building Council. LEED® provides benchmarks for the design, construction and operation of a property and covers site makeup, building materials, water and energy efficiency as well as indoor environmental quality. It also provides certification for people who demonstrate an understanding of green building practices.

    Methane—An odorless flammable gas that is the main constituent of natural gas and the simplest of the alkane series of hydrocarbons.

    Natural Gas—A gaseous fossil fuel that occurs naturally underground and consists of methane and other hydrocarbons.

    Naturally Occurring Methane Capture Carbon Offsets—Methane emissions may occur from land areas where coal or other high concentrations of un-extracted fossil fuels are present underground, resulting in a naturally occurring source of GHG emissions. Methane gas may be flared and converted to carbon dioxide in order to significantly reduce its greenhouse gas (GHG) potency. The methane gas may also be collected and scrubbed for use as biogas to produce energy, sometimes replacing natural gas or other fuel oils used for heating or energy production. The GHG value is a function of converting the methane into carbon dioxide, which traps less heat in the atmosphere than methane.

    Photovoltaic—The conversion of light into an electric current.

    Photovoltaic (PV) System—A PV system is a system that includes solar panel cells that convert energy from the sun into direct current electricity.

    Radiative Forcing—At high altitudes, the effect of greenhouse gases is considerably different than on the ground level. Aircraft also emit water vapor during flight which can cause the formation of ice clouds, called contrails. Where contrails persist, cirrus clouds begin to form which have an additional impact on global warming. Clouds can have a double effect on radiation: they warm the earth by reducing the amount of radiation from the earth that escapes into space but also cool the earth by reflecting the sun's rays back into space. However, contrails lead to a net warming factor, which is estimated to be 2.7 times the normal effect (IPCC, 1999). SOURCE:

    Refrigerant Leak Prevention Carbon Offsets—This type of project quantifies the greenhouse gas (GHG) emission reductions generated by reducing hydroflourocarbon (HFC) refrigerant leaks commonly found in commercial refrigeration systems. Rather than rely on annual equipment inspection for leak detection, this strategy utilizes automated infrared detection systems to identify issues when they occur and allows for immediate response. This results in a significant reduction in HFC emissions escaping through refrigerant equipment failure. Like methane, HFCs are a far more potent greenhouse gas (greater warming potential) than carbon dioxide, so it’s essential to prevent their release into the atmosphere.

    Renewable Energy—Renewable Energy is defined as energy that is derived from natural resources (such as sunlight, wind, water flow, geothermal heat, etc.) and whose supply is naturally replenished.

    Renewable Energy Certificates (RECs)—A Renewable Energy Certificate, or REC, is a tradable, legal mechanism that represents the environmental benefits associated with one megawatt-hour of electricity generated from a renewable energy resource. These certificates may be sold and traded and the owner of the REC can legally claim to have purchased renewable energy. RECs incentivize the production of renewable energy by providing a source of revenue to electricity generated from renewable sources.

    Renewable Energy Production Carbon Offsets—Renewable energy facilities, such as wind or solar, generate Carbon Offsets through displacing fossil fuel-based electricity production sources within the power grid. The greenhouse gas (GHG) value of this activity depends on the composition of the electricity mix within the grid region where the renewable energy facility is located.

    Solar Energy—The conversion of light into an electric current.

    Sustainability—Sustainability may be defined as meeting the needs of present generations without compromising the ability of future generations to meet their needs. Source: U.S. Green Building Council

    Sustainability is a way of working and living that balances immediate needs for commerce, living, habitation, food, transportation, energy and entertainment with future needs for these resources and systems as well as the liveliness and support of nature, natural resources and future generations.

    Sustainability addresses human and natural systems (such as social justice, social values, biodiversity, ecosystem services and lifecycle food chains) as well as economic systems (such as market viability, profit and returns) in order to meet needs and desires without endangering the viability of future generations or endeavors. Source: Natural Capitalism

    Sustainable—A method of using a particular resource such that the resource is not permanently damaged and can continue to be used.

    Transportation Efficiency Carbon Offsets—Carbon Offsets from the transportation sector primarily focus on reducing emissions resulting from gasoline or diesel fuel used in fleet trucking operations. The two key strategies include truck idle reduction (where not required by law) such as with a truck-stop electrification project and efficiency upgrades to trucking equipment in order to improve fuel economy above prevailing regulated standards. In each case, reduced fuel consumption results in a reduction of greenhouse gas (GHG) emissions attributable to the strategy deployed.

    Triple Bottom Line—How some organizations measure the economic, social and environmental performance of a project. Also known as “people, planet, profit” or “the three pillars.”

    Water Footprint—The volume of water used by an entity (both directly and indirectly).

    Water Restoration Certificates® (WRCs)—Water Restoration Certificates® (WRCs) were created by BEF in 2008. One WRC is equal to 1,000 gallons of in-stream flow restored to a critically dewatered stream, river, or wetland. Organizations can use WRCs to balance or restore their water usage (or water footprint) gallon-for-gallon.

    Wind Energy—Also called “wind power,” wind energy is electrical power generated from a wind turbine.