This subsection details what an emission factor is, how to choose or develop them from available information, and gives some examples of [database](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/appendices/appendix-2-examples-of-emission-factor-databases) (DB) of emission factors.
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As a reminder, emissions from each emission source of the organisation are estimated as follows:
Emission from a source = [Activity data](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.2-method-for-collecting-activity-data) x [emission factor](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.3-method-for-selecting-emission-factors) = [result](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.5-emission-profile) ± [higher](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.4-method-for-estimating-uncertainties)
{% endhint %}
## Emission factors
The [emissions quantification method](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.1-method-for-quantifying-emissions) involves defining emission factors (EFs) that convert an organisation's activity data into tCO2e. These EFs represent the average amount of GHG emitted per reference unit. They do not measure GHG emissions, but estimate them. They typically take the following form:
{% hint style="info" %}
EF apricot, pitted, raw = 0.88 kgCO2e/kg (source: Agribalyse®)
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By multiplying this EF by the number of kilograms of pitted raw apricots consumed by an organisation, it will obtain the GHG emissions associated with that consumption. EFs are therefore essential to carbon accounting, but must be handled with care.
Indeed, EFs are developed from assumptions and the resulting studies. An EF covers a specific temporal, geographic and technical boundary. For example, emission factors for the average French electricity mix apply only to France and vary by year. Therefore, one must always ensure to choose the EF best suited to the situation.
## Selection of emission factors
Not all EFs are of equal quality, so they must be carefully chosen to achieve **accurate**. In general, the broader the scope an EF covers, the less precise it is, and vice versa.
Thus, when choosing EFs, the organisation shall:
* Choose or develop EFs of the best possible quality, in accordance with the different criteria set out above.
* Document and retain all EFs used, including in particular their source, units and the[higher ](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.4-method-for-estimating-uncertainties)associated (all characteristics), related documents (DB documentation, sources used, etc.) and any other information deemed relevant, to ensure these emission factors are traceable and comparable from year to year.
* Balance efforts: Searching for or developing a very precise EF for an emission source is often resource-intensive. It is important to carefully select EFs for significant emission sources. Focusing on action and reduction of significant emissions is the core of Bilan Carbone®.
### Data collection matrix
This documentation of emission factors is carried out alongside documentation on the activity data used, notably by recording all this information within the [data collection matrix](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4.2-method-for-collecting-activity-data#matrice-de-collecte-des-donnees), which allows assigning the AD and the corresponding EFs.
## The different types of emission factors
The different scenarios an organisation will encounter when selecting emission factors are detailed below.
### EFs from databases
A number of EFs are available in databases (DBs), some of which are [listed in the following section](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/appendices/appendix-2-examples-of-emission-factor-databases).
:mag\_right: *The reference database for France is the* [*Base Empreinte®*](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/appendices/appendix-2-examples-of-emission-factor-databases) *of the Agency for the Environment and Energy Management (*[*ADEME, French Public Agency for Ecological Transition*](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/glossary#a)*).*
Here are a number of elements to consider, which the organisation must take into account in order to choose the best possible EF in a DB. These **selection elements** may be the responsibility of the organisation or of the DB (but the organisation is responsible for its choice of DB). When several EFs are available for the same emission source, the organisation shall refer to these elements to adjudicate.
Figure 4.3: Elements for selecting emission factors in a database.
🌐 [*English version*](https://abc-transitionbascarbone.fr/wp-content/uploads/2025/11/Elements-to-consider.png) *of this image.*
### EFs developed by the organisation
In the case where no EF is available for the emission source considered, or to improve the precision or representativeness of an EF, the organisation may:
* Approximate this emission source to another similar emission source. This degrades the representativeness of the EF and will result in less precise quantification. The organisation shall therefore use a [higher](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4-accounting/4.4-method-for-estimating-uncertainties/4.4.2-how-should-they-be-determined) higher than that of the chosen similar EF.
* Develop its own emission factor for the emission source considered.
To develop an emission factor, the organisation shall carry out a relevant life cycle assessment (LCA) and use the "Climate Change" indicator. Note that it is necessary to follow the methodological recommendations for creating EFs of the DB most used by the organisation in order to maintain homogeneity among the EFs used.
Following the LCA, the emission factor will a priori be as representative and precise as possible, because specific to the organisation's emission source. Uncertainty arising from the LCA shall be associated with the resulting EF.
If this is not possible, the organisation may develop its own EF from, for example, the different raw materials used to create the product (via their respective EFs) or from the carbon accounting of the product's manufacturer. In the case of a product requiring machining, manufacturing or assembly phases, the organisation may increase the EFs of the different raw materials by a certain percentage to account for additional emissions related to these phases. In all cases, it will be necessary to assign a high uncertainty rate to this EF.
### EFs in spend-based ratios
Some EFs are expressed as values in kgCO2e/k€ spent, which are notably [offered by several DBs](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/appendices/appendix-2-examples-of-emission-factor-databases). They are called "[Spend-based emission factors](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/glossary#ratios-monetaires)", or "Non-specific spend-based ratios".
While they have the advantage of being usable for data easily accessible by the organisation (the [accounting activity data](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/4.2-method-for-collecting-activity-data#les-donnees-dactivite-comptables) from the organisation's standard accounting), these EFs have two major drawbacks in carbon accounting:
* There are very few of them, and they are derived from averages across many products, and are therefore associated with very high uncertainties. They are also sensitive to[inflation](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/glossary#i) and not always representative of the activity. For example, the spend-based ratio "land transport" in kgCO2e/k€ can be used for any land vehicle in the same way, whereas cost is not representative of differences in GHG emissions from one vehicle to another.
* They do not allow tracking the impact of actions from one assessment to another. With an assessment calculated from spend-based ratios, the only decarbonisation lever becomes reducing the amount of the expenditure. Yet responsible purchasing policies (local, sustainable purchases) are often more expensive, which will lead to an increase in the assessment if such purchases are accounted for via spend-based EFs.
An organisation can create its own spend-based ratio, for example from the carbon accounting of its stakeholders. These EFs are called "[Specific spend-based emission factors](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/glossary#ratios-monetaires-specifiques)". However, even if the associated uncertainties are low (spend-based ratio developed specifically for an emission source), this does not allow fine management of actions, because the only decarbonisation lever becomes reducing the amount of the expenditure.
It is therefore strongly recommended to **not use EFs** "Spend-based ratios". These EFs may optionally be used for the following emission sources:
* Use of service activities and intellectual services (lawyers, consulting, etc.), but the organisation shall develop "Specific spend-based ratio" EFs during its maturity progression.
* Non-significant emission sources, and where data are difficult to access (example: small office supplies). The organisation shall nonetheless phase out spend-based ratios for these emission sources during its maturity progression.
In the event the organisation uses spend-based ratios, it may [adjust](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/appendices/appendix-1-main-accounting-principles-of-bilan-carbone-r) these spend-based ratios according to the inflation that applies to its purchases or rentals of goods and services.
## Requirements related to the selection of emission factors
Here are different requirements to be achieved in terms of EF selection for each of the 3 [maturity levels](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/1-framework-for-the-approach/1.1-define-your-bilan-carbone-r-maturity-level).
Beginner level: criterion L1
The share of emissions calculated via emission factors in spend-based ratios (specific and non-specific) shall be reported. It is recommended not to calculate more than 30% of the total assessment emissions via spend-based ratios.
The use of non-specific spend-based ratios must be justified. In the case of non-significant categories or service provisions, the use of these spend-based ratios is tolerated by default.
The organisation shall build a robust documentation process that will improve the selection of emission factors for future Bilan Carbone® exercises. If carried out precisely, the data collection matrix may become an integral part of this documentation.
Intermediate level: criterion L2
The use of spend-based ratios shall progressively decrease, notably through the calculation of specific spend-based ratios for the organisation's partners, service providers or suppliers. The emission factors used shall become more refined as the organisation increases its maturity on carbon issues.
The share of emissions calculated via emission factors in spend-based ratios (specific and non-specific) shall be reported.
It is recommended not to calculate more than 20% of the total assessment emissions via specific spend-based ratios.
The use of non-specific spend-based ratios must be justified. Ideally, any non-specific spend-based ratio is excluded. It is recommended not to calculate more than 10% of the total assessment emissions via non-specific spend-based ratios: any excess must be the subject of a detailed justification.
The organisation shall build a robust documentation process that will improve the selection of emission factors for future Bilan Carbone® exercises. If carried out precisely, the data collection matrix may become an integral part of this documentation.
Advanced level: criterion L3
The use of spend-based ratios shall continue to decrease, notably through the calculation of specific spend-based ratios for the organisation's partners, service providers or suppliers. The emission factors used shall become more refined as the organisation increases its maturity on carbon issues.
The share of emissions resulting from calculations via emission factors in specific and non-specific spend-based ratios is reported. It is recommended not to calculate more than 10% of the total assessment emissions via specific ratios and to use no non-specific ratio.
The use of non-specific spend-based ratios must be particularly well justified, and in the vast majority of cases excluded.
The organisation shall have **developed** specific emission factors for key categories.
The organisation shall build a robust documentation process that will improve the selection of emission factors for future Bilan Carbone® exercises. If carried out precisely, the data collection matrix may become an integral part of this documentation.
***
*Do you have a comprehension question?* [*Consult the FAQ*](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/appendices/faq)*. The method is living and therefore likely to evolve (clarifications, additions): find the* [*track of changes here*](https://www.bilancarbone-methode.com/methode-bilan-carbone-r-en/foreword/history-and-tracking-of-changes)*.*
