Emissions Factors - A Guide to GHG Accounting, Reporting, and Best Practices

Introduction: Why Emission Factors Are Important for Businesses

At a time when regulatory and market requirements are increasing, companies must account for their GHG emissions accurately and transparently. A key tool for this is emission factors —simple yet powerful coefficients that convert activity data (e.g., energy sold, fuel consumption, production volume) into greenhouse gas emissions (CO₂ equivalents).  

Emissions factors are relevant not only for internal climate strategies and reduction targets, but also for official external reporting, particularly when companies are required to disclose their carbon footprint in the context of ESRS E1 (Climate Change) or the GHG Protocol Corporate Standard. They are also used for Scope 1, Scope 2, and Scope 3 emissions to ensure transparency regarding direct and indirect emissions.  

What Are Emission Factors? – Definition & Mechanics

An emission factor is a numerical value that indicates how much greenhouse gas (in kg, t CO₂e, etc.) is released during a specific activity. This value is typically a statistically determined average that can be expressed in units such as:

• kg CO₂e per liter of fuel
• kg CO₂e per kWh of electricity
• kg CO₂e per kilometer driven
  

In GHG Protocol terminology, an emission factor is used to convert activity data into emission values:

Emissionen = Aktivitätsdaten × Emissionsfaktor × Global Warming Potential (GWP)  

This means that, depending on the activity—such as the burning of fossil fuels or electricity consumption—there are specific standardized factors that can be used to calculate CO₂ emissions.  

Regulatory and Methodological Context

The GHG Protocol as a global standard

The Greenhouse Gas Protocol (GHG Protocol) is the most widely used international standard for greenhouse gas accounting for organizations and products. It not only defines methods for collecting and calculating emissions, but also provides guidelines and tools for using emission factors —for example, for stationary energy, purchased electricity, or mobile combustion.  

The GHG Protocol Corporate Standard recommends calculating direct (Scope 1) and indirect (Scope 2) emissions using standardized emission factors. Companies should use data that is as accurate as possible —and, if necessary, rely on local, sector-specific, or country-specific factors.  

Link to EU reporting

In the context of EU regulations, such as ESRS E1 on climate change, emission factors are used to consistently incorporate CO₂ emissions into sustainability reports. This supports the concept of double materiality—that is, both a company’s environmental impact and the resulting financial risks. The use of standardized emission factors enhances the transparency, comparability, and verifiability of the disclosed information.  

Examples & Sources of Emission Factors

Germany: UBA Emission Factors

The German Federal Environment Agency (UBA) provides a list of emission factors for greenhouse gas accounting by organizations, which is updated regularly. These factors cover fuels, transportation, and other sectors and are available for download in Excel format.  

In addition, the UBA publishes a so-called Handbook of Emission Factors (HBEFA) for the transportation sector—a recognized reference work containing emission factors for passenger cars, trucks, and other vehicle categories.  

U.S. EPA – GHG Emission Factors Hub

The U.S. Environmental Protection Agency (EPA) also maintains a GHG Emission Factors Hub, which provides standardized emission factors for various sectors and activities (e.g., electricity generation, mobile combustion).  

Application in business practice

In practice, emission factors are used in various ways:

• Scope 1 emissions: direct emissions from company-owned sources (e.g., boilers, vehicles) calculated as fuel consumption multiplied by a factor.
• Scope 2 emissions: indirect emissions from purchased energy, such as electricity, which are accounted for using different emission factors depending on the region.
• Scope 3 emissions: additional indirect emissions along the value chain, for which proprietary factors derived from supplier or logistics data are sometimes used.
  

Depending on the availability of data, companies can use default factors (e.g., from UBA lists) or rely on company-specific factors if more precise measurements are available.  

Challenges & Recommendations

Common challenges

• Data quality: Activity data is often inconsistent or difficult to obtain.
• Regional differences: Emissions intensity varies significantly by energy source and region.
• Scope 3 complexity: Many indirect emissions require company-specific or sector-specific factors.
  

Our recommendation

• Use official data sources such as the UBA, EPA, and IPCC whenever possible.
• Data aggregation systems should be designed to accurately attribute emissions to specific groups.
• Always document the sources and assumptions underlying the emission factors used to ensure traceability.

FAQ – Frequently Asked Questions About Emission Factors

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