Each emission calculation always requires a coefficient called "Emission factor" that expresses the average emission rate of a given source, relative to units of activity or process/processes.
Usually, an emission factor is given in the form kgCO2e, so the kilograms of carbon dioxide equivalents. Other units of mass can be expressed as well (e.g. grams or pounds). The term ‘carbon dioxide equivalent’ is a standardised measure for expressing all greenhouse gases (GHGs) in a single unit, based on their differential Global Warming Potentials (GWP). For example, methane’s GWP100 is 28, which means that one kilogram of methane is 28 kgCO2e over a 100-year period (IPCC, 2018).
Why are there different Emission Factors?
As emission factors relate to the specific activities associated with generating those emissions, they can greatly vary for different geographic regions and timeframes. For example, in the case of electricity, the value of the emission factor will be higher in countries with more fossil fuels for electricity production than in those with more renewable energy.
As science evolves, Emission Factors improve in terms of accuracy and precision over time. This might have an effect on the emission values that you see in your dashboards. We’re providing Release Notes for each improvement so you’re always up to date on what’s happening!
But emission factors are average values, isn't this a problem?
As emission factors are deduced by using various statistical methods and assumptions, some levels of uncertainty exist that vary across data points. Be assured that we use the most accurate values that have been published.
What can you do to decrease the levels of uncertainties in the emissions calculations even further?
The most important lever for you is providing as accurate data as possible and minimising the use of national averages.
How do we use emission factors?
As recommended by the GHG Protocol, we use the activity data you provide and match it with the relevant emission factors to estimate the total emissions of each activity.
Our main sources for the emission factors are the national-level emission factor databases reported to the IPCC, nation-specific peer-reviewed scientific research articles, established databases and renowned studies such as those by the Umweltbundesamt (UBA). Only in instances where data on local emission factors are not available, or for business cases where international or regional data is more relevant, do we use the emission factors at the regional level (e.g. EU).
We constantly review and update our emission factor repository to provide you with the most accurate emissions estimates possible.
Please review our Release Notes for more details.