A study by Ademe takes stock of the emissions of non-exhaust particles from our cars. Here are the main lessons.
No, this is not a trial of the electric car… nor of the thermal car. The Environment and Energy Management Agency (Ademe) published in April a study on non-exhaust fine particulate emissions from our vehicle fleet. The public body thus intends to draw attention to the impact of brakes and tires in the production of these microscopic materialsconsidered as dangerous by the World Health Organization.
In this note, the public establishment estimates that the fine particles resulting from the friction of tires and brakes are now “preponderant and represent in France 59% of PM10 (particles with a diameter of less than 10 micrometers, editor’s note) and 45% of PM2.5 (less than 2.5 micrometers)”. Ademe attributes these results to the reduction in emissions from internal combustion vehicles linked to “the generalization of particulate filters”.
Electric vs thermal
Beyond that, there is the question of the virtues of so-called “zero emissions” vehicles in this area. As Ademe reminds us, electric motors do not directly emit PM10 or PM2.5, unlike their thermal counterparts. On the other hand, a driving electric car emits many fine particles because of its brakes or its tires.
Excluding the “engine” part, ” there is no significant difference in total particle emissions between self-driving electric vehicles and new current thermal vehicles which emit almost no more particles in the exhaust”. We will take this last statement with a grain of salt, due to the difference between homologation values and actual driving conditions. How many vehicles with clogged filters – and therefore inoperative – are currently driving in our cities and countryside? Let’s remember the example of a manufacturer whose pollution control systems only operated within certain temperature windows…
“If electric vehicles, thanks to the regenerative brakingemit less brake particles than their thermal equivalents, the trend is reversed for particles resulting from tire-road contact and resuspensiondue to their larger tire size, due to their greater mass,” write the authors. Weighted by their batteries, electric cars make their rubbers suffer more… which then emit more fine particles than on a conventional car.
“However, it should not be forgotten that thermal vehicles emit nitrogen oxides and volatile organic compounds which can contribute […] to the formation of secondary particles, which is not the case with electric vehicles,” the note continues.
Solutions ?
In order to limit emissions of fine particles, the standards should no doubt focus on tires and brakes. In addition, Ademe recommends several other measures… including the generalization of the electric car, which emits fewer particles when braking thanks to energy recovery. And at the same time, the public establishment advises lighter vehicles, very incompatible with XXL autonomy. The mass of vehicles could have a real weight in the discussions on automobile pollution in the years to come…
Photo: Hamdi Ben Lagha
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