ADEME emission factors: using the Base Empreinte for your carbon footprint

Quick answer. An ADEME emission factor converts a piece of activity data (kilowatt-hours, litres of fuel, kilometres, euros of purchases) into kilograms of CO2 equivalent. The Base Empreinte is the official public database that gathers these factors. The method is a single multiplication: activity data multiplied by the emission factor equals emissions in tCO2e. The whole challenge is picking the right factor, with the right scope and the right unit.

A carbon footprint is not a mysterious exercise: it is a series of multiplications. For each item (energy, fuel, purchases, travel, freight, waste), you take a piece of activity data and multiply it by an emission factor. The difficulty is not the arithmetic, it is choosing the right emission factor and the quality of the input data. That is where ADEME's Base Empreinte and the company's accounting meet.

This guide explains how to use the Base Empreinte to link each piece of activity data to the right emission factor, how to choose between physical and monetary data, and why the accountant, who already holds the invoices and the entries, is ideally placed to make a carbon footprint reliable.

The Base Empreinte is ADEME's reference public database. It gathers the emission factors (formerly grouped in the Base Carbone) and the inventory data needed for carbon accounting and environmental labelling. In practice, it states how many kilograms of CO2 equivalent are emitted by a given activity unit: a kilowatt-hour of electricity, a litre of diesel, a kilometre travelled, a meal served, a tonne of paper.

Online consultation is free. The database is updated regularly, usually once a year, and each factor carries a value, a reference unit and a precise scope. Recording the version used is part of the discipline: two footprints calculated with different versions are not directly comparable.

The universal carbon footprint formula is simple:

Emissions (kg CO2e) = activity data multiplied by emission factor.

The activity data describes what the company actually consumed or bought. The emission factor translates that consumption into greenhouse gases. The result is expressed in kilograms then tonnes of CO2 equivalent (tCO2e), the common unit that aggregates all gases.

The orders of magnitude above are indicative and depend on the Base Empreinte version: the exact value must always be read in the database at the time of calculation. French electricity shows a particularly low factor, around 0.05 kg CO2e per kWh, because the mix is overwhelmingly nuclear and renewable. Conversely, fossil fuels concentrate most of an SME's direct emissions.

1. Define the scope and collect activity data. List the items (energy, fuel, purchases, travel, freight, waste) and gather the matching kWh, litres, kilometres and tonnes, largely from accounting and invoices.
2. Identify the category of each data point. Do you have physical data (10,000 kWh) or only an amount in euros? Physical data yields a more accurate factor.
3. Find the factor in the Base Empreinte. On base-empreinte.ademe.fr, locate the matching item and record its value, unit and identifier.
4. Check the scope and unit. Combustion only or combustion plus upstream? Unit in kWh, litre or kilogram? An error here distorts everything.
5. Multiply the data by the factor. Data multiplied by factor equals kg CO2e, divided by 1,000 for tonnes, then added up by scope 1, 2 and 3.
6. Document the source and version. Record the identifier, value, unit and database version, to compare years and justify the figures.

This step-by-step logic connects directly with the first carbon footprint method for SMEs, which sets out the split across scopes 1, 2 and 3.

The Base Empreinte offers two families of factors. Physical factors relate emissions to a concrete quantity: a litre, a kilowatt-hour, a kilogram. Monetary factors relate emissions to an amount spent: so many kg CO2e per euro of purchase in a product category.

The rule is simple: favour physical data whenever it is available, because it reflects real consumption. Monetary data is a useful fallback for diffuse purchases (supplies, services) that cannot be detailed item by item. It has the advantage of coming straight from the accounts, but it remains less precise: two suppliers at the same price do not necessarily have the same footprint.

In practice, a first footprint often combines both: physical data for energy and fuel, monetary ratios for part of the scope 3 purchases. The goal from one year to the next is to gradually replace monetary ratios with more reliable physical data.

The reflex we see most often is to chase perfect precision from the very first footprint. It is counterproductive. A complete footprint covering every item with a few monetary ratios beats a partial one built on a handful of physical factors. The value of a carbon footprint lies first in its ability to identify the dominant items, not in the third decimal of a factor.

The other point we stress: accounting data is the raw material of the carbon footprint. Energy invoices, fuel records, purchase accounts and travel expense reports already contain most of the activity data. That is why a carbon footprint is best built in connection with bookkeeping and review rather than in parallel, on an isolated file.

A service SME wants its first footprint. On energy, it records 10,000 kWh of electricity over 12 months: multiplied by a factor of around 0.05 kg CO2e per kWh, that gives about 0.5 tonne CO2e, a modest item thanks to the French mix. On travel, the fleet burns 1,000 litres of diesel: with a factor of around 3 kg CO2e per litre including upstream, that is nearly 3 tonnes CO2e, already six times more than electricity. On purchases, lacking physical data, the company applies monetary ratios to the booked amounts. The immediate conclusion: it is not the offices that weigh, but mobility and purchases. The action plan focuses where the tonnes are.

• Mixing up units. A factor expressed per kWh on a lower heating value basis does not apply to a higher heating value figure without correction; a factor per litre does not apply to kilograms.
• Forgetting the upstream. For fuels, the combustion-only factor underestimates emissions; the factor including upstream (extraction, refining, transport) is often required.
• Mixing versions. Comparing a footprint computed with an old version and another with a recent one distorts trend analysis.
• Going fully monetary. Monetary ratios are convenient but coarse: keep them for items you cannot detail physically.
• Not tracing your sources. Without recorded identifier and version, a footprint is neither reproducible nor auditable.