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Greenhouse Gas Accounting


A variety of greenhouse gas (GHG) accounting protocols are available for reporting emissions, such as the World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD) GHG Protocol Corporate Standardnon government site opens in new window.

For federal agencies, see the White House Council on Environmental Quality (CEQ) GHG Guidanceopens in new window and the Federal Comprehensive Annual Energy Reporting Requirementsopens in new window from the Department of Energy's Federal Energy Management Program (FEMP).

Emission Scope

For accounting purposes, GHGs are divided into 3 standard categories, or "scopes":

  • Scope 1 Direct (Onsite) Emissions
    • Stationary fuel combustion – boilers, emergency generators, on-site heat and power production
    • Mobile combustion – vehicles and mobile equipment
    • Fugitive emissions – refrigerants, on-site landfills and wastewater treatment, electrical equipment/switchgears
    • Process emissions – cement production
  • Scope 2 Indirect Emissions
    • Electricity – U.S. EPA eGRIDopens in new window provides emission factors to convert electric energy purchases into GHG emissions
    • Purchased steam, hot water, and chilled water – depends on provider fuel use
    • Combined Heat and Power
  • Scope 3 Indirect Emissions
    • Transmission and Distribution (T&D) – losses from off-site purchases of electricity, steam, hot water, and chilled water
    • Business travel – ground transportation and air travel
    • Commuter travel
    • Contracted wastewater – wastewater treatment plants and septic
    • Contracted waste – landfill emissions and incineration
Graphic showing Scope 1, 2, and 3 emission examples that match the text above.
Types of Greenhouse Gas Emissions
Source: U.S. EPAopens in new window
How to Calculate Emissions
Step 1: Calculate the emissions from each GHG
Activity x Emission Factor (Tons GHG/activity unit) = Emissions (Tons GHG)

Activities such as burning fossil fuels release several types of gases into the atmosphere. The amount of each gas released per unit of the activity (e.g., ton of coal burned) is referred to as an "emission factor". These can be calculated from direct measurement, measured carbon or energy content of the fuel, or based on the chemical formula. See the EPA GHG Emission Factors Hubopens in new window for an "easy-to-use set of default emission factors".

Step 2: Calculate CO2 equivalents (CO2e) for each GHG and sum overall emissions
Emissions x Global Warming Potential (GWP) = Total Emissions (Tons CO2e)

Each protocol will have recommended factors for global warming potential in order to convert all emissions into a single unit (CO2e) that can be summed across all GHG. The table below includes several common values.


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Related Topics


Climate Change

Climate change refers to significant and lasting alteration of climatic patterns (e.g., temperature, precipitation, wind). It may result from: natural factors, such as changes in the sun's intensity or slow changes in the Earth's orbit around the sun; natural processes within the climate system (e.g. changes in ocean circulation); and human activities that change the atmosphere's composition (e.g., through burning fossil fuels) and the land surface (e.g., deforestation, reforestation, urbanization, desertification). During the 20th century, human activities released large amounts of carbon dioxide and other greenhouses gasses into the atmosphere, resulting in an increase in the rate of climate change.

EPA | Climate Changeopens in new window

Greenhouse Gases

Gases that trap heat in the earth’s atmosphere are called greenhouse gases. Examples of greenhouse gases include carbon dioxidenon government site opens in new window, methane, and chlorofluorocarbons. The primary source of carbon dioxide emissions is the combustion of fossil fuels for energy.

EPA | Greenhouse Gas (GHG) Emissionsopens in new window

FEMP | Annual Greenhouse Gas and Sustainability Data Reportopens in new window

Greenhouse Gases (GHG)

A range of human activities cause the release of greenhouse gases into the atmosphere (e.g., the release of carbon dioxide during fuel combustion). These gasses can damage or be trapped in the earth’s atmospheric layers, contributing to global climate change.

EPA | Greenhouse Gas (GHG) Emissionsopens in new window

Scope 1 Greenhouse Gases

Direct greenhouse gas emissions from sources that are owned or controlled by the Federal agency.

Sustainability.gov | Federal Greenhouse Gas Accounting and Reporting Guidanceopens in new window

Scope 2 Greenhouse Gases

Direct greenhouse gas emissions resulting from the generation of electricity, heat, or steam purchased by a Federal agency.

Sustainability.gov | Federal Greenhouse Gas Accounting and Reporting Guidanceopens in new window

Scope 3 Greenhouse Gases

Greenhouse gas emissions from sources not owned or directly controlled by a Federal agency but related to agency activities, such as vendor supply chains, delivery services, and employee travel and commuting.

Sustainability.gov | Federal Greenhouse Gas Accounting and Reporting Guidanceopens in new window

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