Home " How do I calculate my Bilan Carbone? " The role of emission factors in a Bilan Carbone® assessment

The role of emission factors in a Bilan Carbone®.

industry carbon footprint

Carrying out a greenhouse gas (GHG) emissions assessment, or Bilan Carbone®, is becoming a strategic challenge for companies in a context of climate change, ecological transition and energy transition for companies. France, for example, has adopted the goal of carbon neutrality by 2050, in its National Low-Carbon Strategy of 2022.

Carrying out a Bilan Carbone® enables an organization to quantify its carbon footprint, i.e. the quantity of greenhouse gases emitted over the course of a year, through a systematic assessment of its greenhouse gas emissions. Once these emissions have been quantified, the organization concerned can then identify its main sources of emissions, and implement a relevant and effective strategy for reducing its carbon footprint, with full knowledge of the facts. This strategy will, for example, reduce the company's impact on the climate and the environment. Some companies are eligible for subsidies.

A greenhouse gas emissions balance is not based on direct measurements, such as electricity consumption in kWh directly read off the meter. It is based on a calculation: the conversion of activity data (consumption in kWh, for example) into GHG emissions, using an emission factor (EF).
This article will focus on the role of EFs in a Bilan Carbone®.

1. The emission factor, a conversion coefficient.

1.1. Activity data

1.2 A coefficient.

1.3. A single-criteria LCA

1.4. "CO2 eq", a comparative unit for GHGs.

2. Choose an emission factor

2.1. Physical or monetary

2.2. Uncertainty

3. How do I find an emission factor?

3.1. The various existing databases.

3.1. Factors sourced directly from suppliers

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The emission factor, a conversion coefficient.

📊Activity data

Let's start by defining an essential concept for understanding FE: activity data.

This is data describing the activity of a company's emission source. For example, liters of diesel used for business travel, kWh of electricity consumed, m² of office space, number of screens in the company, number of t.km (tons per kilometer) covered by transporters... The unit depends on the nature of the item considered and the category (or scope, depending on the method used) of the balance sheet to which it belongs.

These activity data indicate the organization's use of the emissions item, how it uses it, or how many it owns, for example (depending on the unit considered). But it does not indicate the carbon footprint (greenhouse gas emissions) produced by this use. That's where the emission factor comes in.

✖️Un coefficient.

The emission factor is a coefficient that relates the activity data mentioned above to its actual greenhouse gas emissions. It gives the carbon footprint of these activity data.

It converts these data into CO2 equivalent (CO2 eq.) by the unit of activity data considered. For example, the EF of a printer is expressed in kg CO2e/unit. That of an inkjet printer is precisely 88 kg CO2e/unit, according to ADEME's Base Empreinte®. In a company's GHG balance sheet, this means that owning one inkjet printer emits 88 kg CO2 eq., owning 2 printers emits 88*2 = 176kg CO2 eq. and so on.

The EF for electricity consumption is expressed in kg eq.CO2/kWh, according to ADEME's Base Empreinte®. The unit changes because the nature of the item changes: we no longer speak of goods purchased and held, but of energy consumption. For example, the EF of the average electricity mix in France is 0.0520 kg CO2e/kWh.

It should be noted that EFs vary from one region of the world to another. Consuming electricity in France does not have the same carbon footprint as consuming electricity in Japan or the United States, depending on the country's energy mix, for example.

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🔬A single-criteria LCA

It is interesting and important to understand how an emission factor is determined. It comes down to a single-criteria Life Cycle Assessment (LCA).

An LCA assesses the overall environmental impact (on biodiversity, water, GHG emissions, etc.) of products or services provided by a company throughout their life cycle, from design to production, use and end-of-life. This is a multi-criteria analysis.

An emission factor is a single-criteria LCA, the criterion being greenhouse gas emissions, or its carbon footprint. It evaluates the GHG emissions of the product or service at each stage of its life cycle.


It is also interesting to note that a balance sheet is divided into several categories, or "scopes", which may differ according to the methods considered.

The GHG Protocol method defines 3 scopes:

  • Scope 1: the company's direct emissions.
  • Scope 2: the company's indirect emissions.
  • Scope 3: the company's uncontrolled indirect emissions.

Subsequent methods divide emission sources into 6 categories:

  • Direct emissions
  • Indirect emissions
    • Associated withenergy⚡
    • Associated with transport🚊
    • Associated with products purchased🛒
    • Associated with products sold💶
  • Other indirect emissions.

☁️"eq. CO2", a comparative unit for GHGs.

Let's take a look at "CO2 equivalents", used to express emission factors. This carbon accounting unit quantifies the flow of greenhouse gases (GHGs) generated by human activities. These GHGs include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), among others.

In order to compare the climate impact of each of these gases in a consistent way, it is necessary to convert these impacts into a common unit. The comparison criterion is their Global Warming Potential (GWP), which measures the impact of each gas on the climate in relation to CO2. Using the GWP of CO2 as a reference, the emissions of each GHG are converted into "CO2 equivalents", enabling a uniform assessment of their contribution to climate change.

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Choosing an emission factor

The role of the EF in a GHG emissions balance is essential. It is used to calculate the emissions that a company seeks to quantify by carrying out a balance sheet in the first place. Choosing the right EF is therefore crucial, since it determines the quality and reliability of the company's balance sheet calculation.

〽️Physiqueor monetary

One criterion to take into account is the nature of the emission factor: physical or monetary.

A physical emission factor represents the quantity of CO2 emitted by a physical unit consumed, such as kWh, liters, numbers, etc. It can therefore be used to account for physical flows. It can therefore be used to account for physical flows.

A monetary emission factor represents the quantity of CO2 emitted per euro spent on the item in question, and will be expressed in kg eq. CO2/k€ excluding VAT. This is a major methodological difference. While these factors make it possible to account for non-physical flows (such as the purchase of services), they are intrinsically less precise than physical factors, notably because they depend on price fluctuations. One example is the highly volatile energy markets: the emission factors concerned will therefore be highly sensitive to this volatility, and subject to regular change.

It is advisable to use them only for certain categories of the balance sheet (e.g. purchases of goods or services by companies), or when the physical data cannot be obtained.


Uncertainty refers to the possible difference between the value assigned to the quantified quantity and the actual value. It is expressed either as a fixed value (5%, 15%, 30%...), or as an interval (between 10 and 15% imprecision, for example) for a given confidence level. If the confidence level is 95%, then there is a 95% chance of finding the right value within the given interval.

EFs have an intrinsic uncertainty, which can be due to several factors:

  • Lack of data completeness: some measurements or data may not be available, because the process is not yet recognized or the measurement method does not yet exist. This leads to an incomplete conceptualization of the emission factor.
  • Lack of temporal representativeness: data and/or associated emissions calculations are dated. This may introduce a bias.
  • Complex models: some of the models used to measure GHG emissions and removals can be very complex. Their use can give rise to uncertainties for a variety of reasons. Two examples are :
    • These models are simplifications of real systems, and are therefore not exact.
    • Alternative formulas may lead to different estimates.
  • Lack of reliability: data may not be directly measured, or may simply not yet exist. Assumptions can then be used as substitutes, or data can be extrapolated.
  • Lack of technological representativeness: emissions linked to a certain process cannot be measured, and are therefore modeled by a similar process.
  • Measurement error

The determination of EF values is therefore relatively uncertain. Uncertainty in emission factors ranges from 5% to 80% (for monetary emission factors).

The choice of a PA also impacts the company's balance sheet, with its uncertainty. The overall uncertainty of a balance sheet is estimated from the uncertainty of the selected factors and the available business data. The more uncertain the factors chosen, the more uncertain the final balance sheet will be.

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How do I find an emission factor?

Now that we've established the role of an emission factor, let's look at where to find them.

📂The various existing databases.

EFs can be found in databases. Some are public, others are fee-based, while others are specific to GHG assessment tools. There are also databases for factors specific to certain sectors. Some examples are :


🤝Factors sourced directly from suppliers

To obtain the most accurate and relevant emission factor for corporate purchasing, the best way is to obtain the EF directly from the source: the supplier.

By drawing up a Product Carbon Footprint, or PCF, suppliers can assess the carbon weight of their products and provide their corporate customers with the most accurate EF possible.

And at GCI, it's free!


The right choice of EFs will enable us to produce a high-quality GHG balance sheet, with clearly identified sources of emissions, a well-measured carbon footprint, and relevant actions to reduce this footprint.

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