what the controversial Adime report REALLY says

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Brake caliper from Tesla Model S

The Environment and Energy Management Agency has just published a paper on non-exhaust particulate emissions from the use of cars and light commercial vehicles. However, it is necessary to read the document carefully before we conclude very hastily that electric models would not really do better than diesels.

Wrong interpretation

Following the spread by Adime of a knowledge base on friction particles from brakes, tires and the road, various media outlets have concluded that electric cars would have as much of an impact as thermal models.

For example, this title from Phonandroid: Electric cars emit as many particles as any other, it has been proven Automobile Magazine concludes: 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 sentence by the Adime document: There is no significant difference in total particulate emissions between long-range electric vehicles and new internal combustion vehicles that emit almost no exhaust particles. “.

The negative side of Anteme passed silently

Surprisingly, the following sentence is almost systematically conveyed in silence: However, we must not forget 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. “.

Modified Citroën 2 CV van

And there, we already have a first difference, which, if it could not be taken more seriously by Adime due to its accidental presence, is far from being neutral on 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 driving an equivalent thermal model. Even with considerable autonomy, driving is often more flexible, closer to eco-driving. This inevitably results in reduced friction particles.

Brake particles

Everyone has noted, however, that electric cars emit far fewer particles associated with braking systems than thermal ones. But accuracy is rarely projected as well. This is the fineness of these powders. They get smaller and smaller, and therefore more and more harmful, with long-term and continuous slowdowns. This is due to the heating of the friction components.

Ademi - Friction particles

At the beginning of the braking phase, thin particles (about 1 to 2 μm) are split and then with increasing braking force and temperature, a significant particle formation of about 200 nm occurs with evaporation and condensation of the carbonaceous components of the pads. brakes “, Explains Andeme.

However, with their regenerative systems, EVs are less often in the extreme phases. The agency also cites as an example of strong braking ” arrival at motorway tolls ”, Which is exactly what can be achieved to a very large extent with the use of electric car regeneration.

Suspension and tire size

The resuscitation of the particles as the vehicles pass is not directly related to the energy pushed by the machines. However, Adime suggests that due to the larger mass of the electric models, the tire width would be greater. This will therefore increase the impact of electric vehicles on dust mixing on the ground. However, this scenario is not systematic.

A Peugeot e-208, for example, is equipped with flanges 195 or 205 mm wide. This is also the case with petrol and diesel engines. Same remark for the Renault Twingo released in 2022 in which we find 165 width (front) and 185 mm (rear) in electric and petrol versions. Note that the electric Hyundai Kona is based on 215 mm tires, while many of its thermal versions are equipped with wider tires, at 235 mm.

What is real, on the other hand, is this drive of SUVs. The transition from a flexible 208 (195 or 205 mm) to a Peugeot 2008 (215 mm) for example will indeed have a systematic negative impact. The search for greater autonomy can obviously decide an electrician to abandon an electric city car for a busy motor vehicle in the same way. This often results in a wider tire fit.

Harmfulness of friction particles

Inhaling massively, the particles are sure to be harmful, especially to people who already suffer from chronic respiratory problems. Thus pollen, household and agricultural dust and emissions related to brakes, tires and road friction. Therefore, it is not a matter of their ignorance, nor even of their minimization.

On the other hand, it seems necessary to be able to classify them on the basis of their risk, which will necessarily take into account their composition. On this point, Ademi has expressed doubts, because there are not many studies on the subject yet: ” it is not certain that actual concentrations of non-exhaust gases have a significant effect or that their annoyance is similar to that of other vehicle exhaust pollutants “.

The agency cites fears of some toxicological studies pointing to the presence of minerals as an aggravating factor. Thus, copper, barium, zinc and iron are found in the brake pads, but not, or very little, in the section of tires that come in contact with the road. Which in turn would increase the balance of thermal vehicles versus electric ones.

Means of struggle

However, there are many ways to combat all of these particles, whether they come from the exhaust pipes or not. First reduce the sources. For example, favoring walking, personal transport, public transport and group car use.

And then, there are those systems that make it possible to record emissions in a very localized way at the vehicle level or in a less targeted way with devices installed at the edge of the lanes. Adime cited as an example the Mann and Hummel suction collection, which we have already mentioned. But also the TrapAparT body trap, which will be placed along major urban roads.

Making tires with fewer emissions 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.


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