With the emergence of the electric car, people started questioning the environmental impact, in particular the CO2 emissions. This article, based on scientific research, presents an analysis of the CO2 emissions of electric cars and how they compare to gasoline and diesel cars.
WTW, WTT & TTW
When CO2 emissions are discussed, often the following abbreviations are used: WTW, WTT and TTW. Figure 1 provides the meaning of each abbreviation.
CO2 emissions electricity, gasoline and diesel
CO2 emission factors are used to calculate the CO2 emissions for organisations and activities. An example of a CO2 emission factor is the Well-to-Wheel (WTW) emission of 2.800 grams of CO2 for every liter of E95 gasoline.
The Dutch website co2emissiefactoren.nl was founded by SKAO, Stimular, Connekt Milieu Centraal, the national government and various other experts. This website contains a large database of CO2 emission factors. Table 1 shows the relevant CO2 emission factors for cars. All numbers are from co2emissiefactoren.nl except for the electricity mix in the EU which is provided by Agora Energiewende.
CO2 emissions related to car usage
When the CO2 emissions of a car are calculated, usually only the direct emissions are being taken into account. The Worldwide harmonised Light vehicles Test Procedure (WLTP) only considers the direct emissions and therefore only the Tank-to-Wheel (TTW) emissions. Manufacturers provide only the TTW emissions as required by law. Therefor, the numbers provided by the manufacturers are too low. The indirect (WTT) emissions should be taken into account as well. For electric vehicles, charging losses are included in both the WLTP and EPA test procedures.
For the fuel economy, the data from the American Environmental Protection Agency (EPA) is used. The EPA fuel economy tests include the charging loss of charging electric cars. The EPA uses different drive cycles to simulate real life driving behaviour. The consumption per 100 km for several cars, including charge loss, are presented in table 2.
To calculate the CO2 emissions of the electric cars, the information in table 1 is used with the efficiency numbers in table 2. The result provides an overview of the CO2 emissions and a comparison of the fuel consumption of gasoline and diesel cars to match the emissions of electric cars. The difference is clear as the electric vehicles emit much less CO2 than comparable fossil fuel cars.
CO2 emissions including the production of the battery
However, what about the production of the car? Let’s keep it simple and assume that only the battery is different. In reality, the electric car (except for the battery) will require less materials to be manufactured (no internal combustion engine, fuel pump or gearbox to name a few), but for simplicity let’s assume only the battery is the differentiator.
According to a recent study, the production of batteries emit 106 kg of CO2 per kWh. Industry insiders even speak of 65 kg per kWh. Let’s take the 106 kg per kWh to be conservative.
Table 3 shows for several cars the battery capacity, the battery production CO2 emissions (based on 106 kg CO2 per kWh), the CO2 emissions related to driving one km, the break-even point where the CO2 emissions of the battery are compensated, and finally the total CO2 emissions after 300.000 km including the production of the battery. 300.000 km is a lot, but the warranty on the batteries is better than any warranty on components of fossil fuel cars and those can generally drive for 300.000 km without major repairs or replacements. Also, early electric cars show that they can drive (well) over 300.000 km without major repairs or replacements.
Table 3: Break-even point and total CO2 emissions after 300.000 km.
As EV’s should ideally be charged with renewable electricity, and many public chargers use renewable electricity (e.g. Fastned, 2019), the total CO2 emissions over 300.000 km gets even lower as shown in table 4.
Table 4: Total CO2 emissions on renewable electricity after 300.000 km.
When we look at the reduction of the CO2 emissions from the battery production as mentioned by industry insiders (65 kg CO2 per kWh) and combine this with driving on renewable electricity, the results get even more significant as shown in table 5.
Table 5: Total CO2 emissions on renewable electricity after 300.000 km and with industry insider numbers for battery production.
Based on the results, it is clear that battery electric cars cause up to 3,2 times less CO2 emissions over 300.000 km when using the average electricity mix in Europe. When using renewable electricity, electric cars cause up to 16 times less CO2 emissions over 300.000 km. When also including the probable CO2 intensity of 65 kg/kWh for battery production, an EV causes up to 26 times less CO2 emissions over 300.000 km.
These results do not even take into account lower maintenance for electric cars or even that electric cars do not have fossil fuel related parts such as an internal combustion engine, gear box or fuel pump. In other words, these results are conservative and real world results should be even more favourable to electric cars.
There are four developments that help further reduce the environmental impact of electric cars:
- Electric cars appear to drive well over 300.000 km (up to 800.000 km) without major repairs/replacements. A great example is the Tesla Model 3. The drive unit is designed, tested and validated to drive 1,6 milion km. The batteries are expected to last for 500.000 km (standard range battery) or 800.000 km (long range battery).
- The use of renewable electricity to produce the batteries (Tesla). As about 50% of battery emissions come from electricity used in the manufacturing process, using renewable electricity can lead to major emission reductions.
- The use of renewable energy to manufacture the cars (Audi, BMW, VW and Tesla).
- Recycling the batteries at end of life (Audi and Tesla). Recycling will significantly reduce the emissions of battery production since less mining is necessary.