The Environment and Energy Management Agency has just published a document on emissions of non-gaseous particles caused by the use of cars and light commercial vehicles. However, the document must be read carefully before deducing too hastily that electric models would not really do better than diesel models.
Following the release by Ademe of a state of knowledge on the abrasion particles of the brakes, tires and road, various media have concluded that electric cars would have as heavy an impact as thermal models on this. theme.
For example, this Phonandroid title: ” Electric cars emit as many particles as others, it has been shown “. Automobile magazine for its part deduces:” Despite the absence of combustion in the engine, the electric car would therefore be just as harmful if only these two types of fine particles were taken into account. “.
This is the result of an overly hasty interpretation of this phrase from the Ademe document: “ There is no significant difference in total particulate emissions between long-range electric vehicles and current new internal combustion vehicles that emit almost no more particles in the exhaust. “.
Ademe’s inconvenience passed in silence
Interestingly, the following sentence is passed almost systematically in silence: “ However, it should not be forgotten that thermal vehicles emit nitrogen oxides and volatile organic compounds that can contribute, depending on atmospheric conditions, to the formation of secondary particles, which is not the case with electric vehicles. “.
And there, we already have a first difference that, if Ademe could not take more into account for a random presence, is far from neutral in the final environmental impact of the two categories of vehicles.
In addition, for the same driver, driving an electric car will not be identical to that of an equivalent thermal model. Even with significant autonomy, driving is often more flexible, closer to eco-driving. This inevitably has the effect of reducing abrasion particles.
Everyone has noticed, however, that electric cars emit far fewer particles related to braking systems than thermal ones. But accuracy is also rarely proposed. This is the finesse of these powders. They are getting smaller and smaller and therefore more and more harmful, with long and sustained decelerations. This is due to the heating of the friction parts.
” At the beginning of the braking phase a breaking of fine particles is observed (around 1 to 2 μm) and then with the increase of the braking force and the increase of the temperature an important formation takes place of particles around 200 nm by evaporation and condensation of the carbon components of the brake pads “, explains Ademe.
However, with their regenerative systems, electric vehicles are less often in extreme phases. The agency also cites powerful braking as an example. ” arrival at a toll road ”, Which can be achieved in large part through the regeneration of electric cars.
Resuspension and tire size
The resuspension of particles in the passage of vehicles is not directly associated with the energy that drives the machines. However, Ademe indicates that due to the larger mass of electric models, the width of the tires would be greater. This would therefore increase the impact of electric vehicles on the dust mixture on the ground. However, this scenario is not systematic.
A Peugeot e-208, for example, is equipped with 195 or 205 mm wide flanges. This is also the case with gasoline and diesel engines. Same observation for the Renault Twingo marketed in 2022 on which we find widths of 165 (front) and 185 mm (rear) in electric and petrol versions. It should be noted that the electric Hyundai Kona is based on 215 mm tires, while many of its thermal versions are wider, at 235 mm.
What is real, however, is this drive from motorists to SUVs. Going, for example, from a versatile 208 (195 or 205 mm) to a 2008 Peugeot (215 mm) will have a systematic negative impact. The search for greater autonomy can obviously lead to an electric motorist abandoning an urban electric car for a motorized SUV in the same way. Very often, this translates into a wider tire fit.
Harm of abrasion particles
Inhaled en masse, the particles will surely be harmful, especially for people who already suffer from chronic respiratory problems. This includes pollen, domestic and agricultural dust, and emissions related to brakes, tires and road abrasion. So it’s not a matter of ignoring them, or even minimizing them.
On the other hand, it seems essential to be able to classify them by their danger, which will necessarily take into account their composition. On this point, precisely Ademe has expressed doubts, because the studies on the subject are still few: “ It is not certain that the actual concentrations of non-exhaust particles have significant effects, or that their nuisance is similar to that of other pollutants in the exhaust fumes of vehicles. “.
The agency reports fears of some toxicological studies pointing to the presence of metallic elements as an aggravating factor. Thus copper, barium, zinc and iron are found in the brake pads, but not, or very little, in the part of the tires in contact with the road. Which again would increase the balance of thermal vehicles compared to electric.
Means of struggle
However, to combat all these particles, whether or not they come from the exhaust pipes, there are several means. First, reduce the sources. For example, favoring walking, personal transport vehicles, public transport and car sharing.
And then there are those systems that allow you to capture emissions in a very localized way at the level of vehicles or in a less targeted way with devices installed on the edge of traffic lanes. Ademe gave the example of the suction collection of Mann and Hummel, which we have already mentioned. But also the TrapAparT particle trap, which will be placed along the main urban roads.
Producing less emissive tires and brake pads with less hazardous materials is now an idea that is spreading across Europe. The future Euro 7 standard will begin to take this into account.