Introduction to Emission Factors

Module 2 breaks down the basics of how scope 3 emissions are estimated. We will cover the importance of emission factors and the different methods associated with measuring them. By completing this module, you will:

• Gain a high-level understanding of emission calculations
• Learn how organizations can account for their emissions based on the business data they have available
• Understand how organizations can automate the calculation process through software.

The estimated time to complete is 15 min.

Terms to Know

• Emission Factors - Representative values that attempt to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant.
• Global Warming Potential (GWP) - A GWP indicates the relative heat-trapping ability of a given GHG compared to one unit of carbon dioxide. For example, methane is 28 times more potent than carbon dioxide over 100 years.
• Calculation Methods - The mathematical formulas used to calculate the carbon footprint associated with a business activity, as determined by the Greenhouse Gas Protocol (GHGP) and Partnership for Carbon Accounting Financials (PCAF).
• Partnership for Carbon Accounting Financials (PCAF) - The Partnership for Carbon Accounting Financials (PCAF) is a global partnership of financial institutions that work together to develop and implement a harmonized approach to assess and disclose the greenhouse gas (GHG) emissions associated with their loans and investments. These are known as financed emissions.
• Materiality - The quality of being relevant or significant. In sustainability reporting, materiality refers to the significance or importance of an issue, impact, or aspect within an organization’s sustainability strategy, reporting, and decision-making.

Introduction to Emission Factors

Once an organization has determined which Scope 3 emission categories (upstream or downstream) are material to its footprint, the next step is to quantify those emissions. This is done by converting business activity data into emissions data using emission factors.

What is an emission factor?

The U.S. Environmental Protection Agency (EPA) defines an emission factor (EF) as:

“A representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant.”

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In simple terms, an emission factor answers the question:
How much greenhouse gas is emitted per unit of activity?

How emission factors are used

Emission factors are applied to business activity data, which represents any measurable activity that results in greenhouse gas emissions.

Common examples include:

Business activity data

• Gallons of fuel combusted
• Tonnes of waste landfilled
• Kilowatt-hours (kWh) of electricity consumed

Corresponding emission factors

• kg CO₂ emitted per gallon of fuel combusted
• kg CH₄ emitted per tonne of waste landfilled
• kg CO₂ emitted per kWh of electricity consumed

To calculate emissions, organizations simply multiply the activity data by the appropriate emission factor:

Activity data × Emission factor = GHG emissions

This calculation is the basic building block of carbon accounting and applies across Scope 1, Scope 2, and Scope 3 emissions.

Why emission factors matter

Emission factors play a critical role in determining the accuracy and credibility of emissions calculations. The choice of emission factor influences:

• The precision of emissions estimates
• Comparability across reporting periods
• Alignment with standards and disclosure requirements

Because of this, emission factors that are open-source, transparent, and regularly updated are generally preferred. Emission factor sets published by government agencies, academic institutions, and reputable research organizations are widely used and trusted.

Governments, researchers, and private organizations regularly update emission factors to reflect changes in energy systems, technologies, and scientific understanding. Selecting appropriate and up-to-date emission factors is therefore an essential step in building a reliable greenhouse gas inventory.

Lesson takeaway

Emission factors connect real-world business activities to greenhouse gas emissions. By applying the right emission factors to activity data, organizations can quantify their emissions consistently and transparently, forming the foundation for accurate carbon accounting and informed climate decision-making.