Vehicle Emissions

The carbon footprint from car usage can be calculated using different methods, providing the result in differing levels of accuracy. We propose three computations :

• From Fuel Consumption: Type of Fuel and, Consumption or Annual Mileage and actual MPG.
• From Registration Card: Type of Fuel, Mileage and original emission factor or consumption factor.
• From Vehicle Type: Annual Mileage and the gCO2e/km figure (explained below).

Although the first computation method is the most precise, it relies on a parameter that could be quite uncertain (depends on personal measure) or even unknown. Indeed, the exact MPG (or real fuel consumption) for the period of the annual mileage could be difficult to get with precision if not measured properly.

This is the best choice if you cannot guarantee the actual MPG/Consumption. This method is based on the constructor factor emission corrected by the vehicle age.

The last one is the least precise, but still allows you to get a fairly good CO2e emission estimation from only the vehicle type and your annual mileage.

Carbon Emission Factors

Sources:

Three datasets are currently available to compute emissions:

• ADEME (2022) - French Agency for Ecological Transition
• CCO2 (2022) - Aggregation of ADEME & CITEPA with some correction coefficients.
• CCO2 (2021) - Aggregation of ADEME & CITEPA with some correction coefficients.
• CITEPA (2022) - Technical Reference Center for Air Pollution and Climate Change (Non-Profit Association)
• CITEPA (2021) - Technical Reference Center for Air Pollution and Climate Change (Non-Profit Association)

Note

Why would ADEME emission factors are higher?

Those ones use an another computation methodology : taking into account both Combustion and Upstream (Extraction/Process, Transport, Refining, Distribution) emissions.

• You may find those numbers there: https://www.bilans-ges.ademe.fr/fr/basecarbone/.
• Those data are mainly calculated with the GWP at 100 years of the 5th IPCC report (the last). See the IPCC website: http://www.ipcc.ch/report/ar5/wg1/.

Fuel Consumption

The fuel emission factors are expressed in kgCO2e/litre (cf. datasets). Using this Emission Factor is straight and depends on a minimum of parameters.

Using real consumption

• Emission = Consumption * Factor
• [kgCO2e/year] = [L/year] * [kgCO2e/L]

Using Mileage & MPG

• Emission = MPG * (Mileage / 100) * Factor
• [kgCO2e/year] = [L/100Km] * [100Km/year] * [kgCO2e/L]

Registration Card

The vehicle carbon emission is computed here using the constructor emission factor or the original consumption factor. Both those values are trusted source as the measure is made on the exact reference of a vehicle and are available from the government data website (https://www.data.gouv.fr/fr/datasets/emissions-de-co2-et-de-polluants-des-vehicules-commercialises-en-france/). They are collected from UTAC (in charge of the homologation of vehicles before they are put on sale).

However, this value is evolving along the time as the vehicle get older and depends on different factors such as driving habits and maintains mechanics. We thus use an extra factor that takes into account aging (explained further).

Using emission factor

The constructor emission factor is expressed in gCO2e/km which can be found on the registration card of the vehicle - V.7 field (EU). Formula is as simple as:

• Emission = Mileage * Factor / 1000 * YearCorrection
• [kgCO2e/year] = [Km/year] * [kgCO2e/km] * Cste

Using consumption factor

Or it could either consumption factor expressed in L/100Km. We find back the formula of the first method using the fuel consumption factor coerced with the extra aging factor:

• Emission = MPG * (Mileage / 100) * FuelEmissionFactor * YearCorrection
• [kgCO2e/year] = [L/100Km] * [100Km/year] *[kgCO2e/L] * Cste

Note: On our side we use the "mix driving condition" measure for the ADEME data set.

Car Type - gCO2e/km figure

The unit is gCO2e/km and are statistic averages depending on the three following parameters:

• Vehicle Type: Light utility, Standard, Two Wheeler.
• Fuel Type: CNG, Diesel, Electric, LPG, Petrol.
• Year of manufacture: From 1990 To 2018.

So, the formula is kinda the same as the one used in "Registration Card". The change is on the emission factors that come from statistical source and already include vehicle aging.

• Emission = Mileage * Factor / 1000
• [kgCO2e/year] = [Km/year] * [kgCO2e/km]

The french factor emission constants - gCO2e/km figure - are coming from the "Citepa. Rapport Secten" (https://www.citepa.org/fr/secten/). "Citepa is a non-profit organisation and State operator for the French Environment Ministry, the Citepa meets reporting requirements for air pollutants and greenhouse gas emissions from France in different inventory formats, such as UNFCCC, EMEP, Kyoto Protocol and UNECE inventories."

National Average CO2 Emission

We use The National Institute of Statistics and Economic Studies (INSEE) - which collects, analyses and disseminates information on the French economy and society (https://www.insee.fr/fr/statistiques/5225246#tableau-figure1) to retrieve the population count:

• Population: 67,626,396

ADEME

Using the ADEME/CEREN source "Citepa Transports Secten edition 2021" - we compute the nation average co2 emission by taking the total private vehicle emission estimated from private vehicle divided by the number of person or vehicle.

CITEPA - CCO2

Here, the average is a simple ratio as well:

• totalEmission / #inhabitants
• totalEmission / #vehicles

The total emissions of passenger cars and two-wheelers, calculated in the SECTEN report of CITEPA, amount to 67.13 million tons of CO2 (80.6 the previous year).

This figure does not take into account all the emissions of the French road transport, i.e. 113.6 million tons of CO2 in 2020, in order to compare only the emissions of our private cars given by the carbon calculator, with the national average of our private cars.