Understanding Emission Factors: A Key to Accurate Carbon Accounting

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Introduction: Emission Factors in Carbon Accounting

Emission factors […] relate the amounts of greenhouse gases emitted by a business to a set amount of activity performed by that business. GHG Protocol

In carbon accounting, companies assess how many emissions are produced by each activity within their operations. They tackle topics ranging from business travel to purchased heat and electricity.

All these activities vary widely, use different measurement units, and can generate different types of greenhouse gases (GHG). That is where emission factors come in.

What Are Emission Factors and What Are They Used For?

At their simplest, emission factors are coefficients used in carbon accounting to make data comparable. Emission factors represent the amount of greenhouse gases emitted per unit of activity or material consumed.

They have three main uses:

  1. Standardizing Emissions Data: Convert all GHGs produced by an activity into a weight of CO2e (CO2 equivalent) per activity unit, such as tons of CO2e per kilometer traveled by car.
  2. Estimating Emissions: Allow for multiple possible estimations of emissions from the same activity.
  3. Comparing Activities: Make the carbon impact of different activities comparable.

Emission Factors Practical Example

Emission factors are valuable for the flexibility they provide to users. Using car emissions as an example, a user has various options to estimate emissions, including the following combinations:

  • Kilometres traveled, fuel type, and vehicle type.
  • Fuel consumed, fuel type, and vehicle type.
  • Vehicle fuel use efficiency and fuel consumed.

An additional option for trucks and vans is:

  • Distance traveled, vehicle type (van or truck), and mass transported.

This flexibility illustrates how emission factors can be tailored to different scenarios and their ease of use.

To provide even more flexibility, two types of emission factors have been developed: activity-based emission factors and spend-based emission factors. Activity-based emission factors are considered the most precise but require more data. Spend-based emission factors allow users to estimate emissions from financial data, which is often more accessible.

How To Use Emission Factors

Since emission factors are coefficients, they can be applied using simple multiplication. For activity-based emission factors, the formula is:

<aside> 💡 Emissions = activity × activity emission factor

</aside>

Spend-based emission factors use a similar approach:

<aside> 💡 Emissions = spending × spend emission factor

</aside>

Using the EPA’s emission factor database, an actual formula for car emissions based on fuel type and consumption would look like this:

<aside> 💡 Emissions = 100 liters × 2.91 kgCO₂/liter = 291 kgCO₂ or 0.291 tCO2e

</aside>

The Best Emission Factor Databases

Multiple organisations now offer emission factor databases, varying in user-friendliness and comprehensiveness. Some of the most notable ones include:

Country-Specific Databases:

International Databases:

Private Databases:

We will soon post a comparative guide to help you find the best emission factor database for your needs.

Considerations for Choosing an Emission Factor Database:

Data Fit: Ensure the database offers emission factors that match the data you can collect (spend-based or activity-based data).

Location Dependency: Emission factors can vary by location. Choosing a database specific to your geography ensures you get the emission factors in the correct units.

Time fit: Emission factors change over time as efforts to achieve Net Zero emissions progress. Ensure the database is regularly updated.

Beyond Emission Factors

It’s important to understand that an emission factor is just an estimation using data and assumptions from studies. Climate Partner

How can this be overcome? By using primary data!

The GHG Protocol recommends that businesses use custom values whenever possible. These custom values can be gathered through Lifecycle Analysis (LCA).

LCA projects determine the GHG or carbon equivalent emissions associated with specific materials, products, or services. Each LCA is specific to a company, as operations can vary significantly.

Check our LCA post to learn more! (Coming soon, in the meantime, take a look at the Ecoinvent database for LCAs.)

Let us know what you thought about this introduction to emission factors or if you have any issues accessing those databases!

See you soon on greengency

Cheers,

Alec

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