Choosing the correct emission factor is perhaps the most challenging step in calculating one's carbon footprint. How do I know which emission factors I should use? How do I select the correct emission factor? We summarized in one writing everything you should know about choosing an emission factor and the differences between the factors.

What is the emission factor?

The emission factor describes how much emissions have been generated from producing a product or service. Choosing the correct emission factor is essential for calculating your carbon footprint. Selecting the wrong factor affects the result of the calculation and distorts the outcome, affecting the monitoring of emissions and reporting reliability.

After all, calculating your carbon footprint is relatively easy. It is a multiplication where the company's so-called activity data is multiplied by emission factors. Activity data include fuel and electricity consumption data and purchases of raw materials needed for production.

Which emission factors should I use?

Emissions calculations should always be based on standards, and standards recommend primarily using primary data, i.e., data from suppliers of products and services. If supplier-specific coefficients are not available, secondary data, i.e., reliable databases and scientific publications, can be used.

Emission factors should also be up-to-date. For example, energy emission factors have changed significantly in recent years as the share of renewable energy in the energy system has increased. This is also reflected in the emission factors for various products and services which use energy in their production. Therefore, the carbon footprint calculations of products and services need to be updated at regular intervals, which is often also in the calculator's interest, especially in calculating emissions from energy-intensive products, services, and companies.

How do I choose the correct emission factor?

Depending on the method used, the emission factors can be very different. For example, emissions from electricity consumption can be calculated based on market and location. Emission factors for Finland's average electricity production and procurement can be found in several reliable sources, including the Finnish Energy Agency, Motiva, and Statistics Finland. Electricity companies must also provide their customers with information on the origin of the electricity they sell and the emissions from its production. More and more companies are also offering electricity produced from renewable energy sources, with an emission factor of 0 g / kWh.

However, renewable electricity is not entirely emission-free, as emissions are generated at the beginning of the life cycle. These types of emissions are, for example, emissions during the production and transport of fuels or emissions from the construction of a wind farm. According to the guidelines, these so-called upstream emissions must also be considered. In Finland, data on these emissions are limited, and energy companies do not yet take these emissions into account, with a few exceptions.

Emissions can be of either fossil or biogenic origin. Emission factors can be either production-stage, cradle-to-gate, or lifecycle (cradle-to-grave) factors. On the other hand, the emission factor can only include carbon dioxide (CO2) or other greenhouse gas emissions, in which case we speak of carbon dioxide equivalent (CO2e). Different emission factors are useful in different situations: it depends on the purpose of the calculation and the system boundary, which factor is used in each case.

When selecting emission factors for emission calculation, it is not advisable to choose the first emission factor found on the Internet but to pay attention to the source's reliability, age, and type of the emission factor, in addition to the goal of the calculation. For more information on choosing the correct emission factor, see the Greenhouse Gas Protocol standards. And you can always turn to emission calculation professionals!