Slide 1. Introduction.
The class develops the pollutant emissions from brakes that can be more harmful to health than the pollutant emissions from the diesel engine, and the possible solutions to minimize their impact.
Slide 2. Index.
- Pollutant emissions from brakes.
- Proposed solutions to reduce pollutant emissions.
- Implications for fleet management.
Slide 3. Pollutant emissions from brakes.
- Pollutant emissions from brakes.
There is a pollution problem associated with the use of vehicles that has no solution, whether they are combustion or fully electric vehicles: the toxic particles that are released during the braking process.
Brake pads and discs, or brake shoes and drums work on the basis of mutual destruction, i.e. they wear down and produce dust while generating enough friction to slow the car down. That black dust with sometimes coppery tones that dirty the rims is the result of the friction of the brake pads and brake discs. And its composition is not exactly healthy.
Friction destruction is a rather brutal process, based on converting the car's kinetic energy into heat. The heat generated during braking is directly related to the starting speed and weight of a car.
One of the consequences is the need for brakes, pads and discs to withstand enormous temperatures and brutal thermal shocks. Originally, brake friction materials contained asbestos and, surprisingly, asbestos-containing brake pads were allowed for a long time in the European Union - until 2003 in France and until 2009 in the United Kingdom, for example. And yet no new car after January 1, 1997 could leave the factory with asbestos-containing brake pads.
Today, most friction materials fall into two main categories: non-asbestos organic and metallic or semi-metallic. Organic brake pads are popular as original equipment because they are quiet, work well when cold and do not wear the brake disc very much, but the pads wear faster instead.
Non-asbestos organic materials are usually made of resins, fiberglass, Kevlar and even rubber, while semi-metallic and metallic materials contain copper, steel, iron and other metals. Metallic or semi-metallic pads are more aggressive to the discs, wear less and are a little noisier, but operate over wide temperature ranges. They are better able to withstand high temperatures and tend to be used in sportier or heavier cars, such as SUVs.
Component manufacturers have taken note and have developed pads with less harmful compositions, such as Federal Mogul, one of the world's largest automotive component manufacturers, which has developed pads in which the copper content has been reduced to approximately 0.5%, when 10 years ago copper could represent, in some cases, up to 20% of the pad.
Others have come up with more original solutions, such as the Tallano Technologies studio, which came up with a particle vacuum cleaner. Although it leaves the tires clean, what do we do with the particles? Not to mention what it means for the car manufacturer to integrate a new component. In the end, it didn't make it into production cars.
- Studies conducted.
While Europe is preparing to ban the sale of gasoline and diesel cars in 2035, although it is already considering opening its hand by allowing hybrid models, little focus has been placed on the pollution generated by the brakes of cars and vehicles. It has been done for the first time with the Euro 7 regulation, which will finally apply from 2030.
Now, a recent British study concludes that the dust generated by brake pads is more harmful to health than thermal engine exhaust gases, and that it accounts for up to 55% of non-exhaust emissions in terms of mass. Yes, that black substance that accumulates in the tires as the brake pads wear out, but that also stays in the atmosphere, straight to our lungs.
This analysis by the University of Southampton is not the first to point against the pollution generated by car and vehicle brakes. In 2019, a study by the also British Air Quality Expert Group pointed out that 60% of all fine particles emitted by road transport do not come from engines, but mainly from brakes, but also from tires or the road itself.
Europe had previously set its sights on pollution from brakes. In 2014, it commissioned a group of experts to analyze this pollution hotspot and they concluded that brakes emit between “16% and 55% of PM 10 particles” derived from road traffic. It has been pointed out that friction between brake pads and brake discs has come to be responsible for one fifth of the pollution caused by cars.
- More harmful to the lungs than the smoke from a 12-liter diesel engine.
The analysis is signed by several experts from various faculties of the University of Southampton, England, and focuses on particles derived from wear on brake pads enriched with copper. Their main conclusion is that they can alter alveolar cell homeostasis to a greater extent than exhaust particles from diesel engines. This promotes serious lung diseases such as fibrosis, cancer or adenocarcinoma.
Particulate matter generated by brakes is included among the fine suspended particles, such as PM2,5 or PM10. The amount of this pollutant resulting from brake pad dust is not negligible: according to data from the National Institute of Applied Sciences in Lyon, brake pads cause 20,000 tons of suspended dust per year, with 9,000 tons remaining in suspension in the atmosphere.
Copper in brake pads is carcinogenic. Wear particles in vehicle brakes are generated by friction between the brake pad and the disc. The materials of the brake pads play a key role in this, with metals such as iron, copper and zinc being common, as well as various abrasives, lubricants and reinforcing fibers.
- Pollutant emissions caused by copper.
The study focuses on copper, a transition metal that has replaced asbestos in organic NAO brake pads, the most widely used in the United States, for example. Asbestos, or asbestos, is a group of fibrous minerals whose use has been banned in more than a few countries because of its high likelihood of causing lung cancer.
The problem is that copper is also notably harmful to respiratory health. This is postulated by this analysis based on laboratory tests in which the generation of particles produced by copper-enriched brake pads was measured in comparison with those produced by low-metal or semi-metal brake pads or those caused by a diesel engine:
"We identified that brake wear particles from copper-enriched organic and non-asbestos ceramic brake pads induce the highest oxidative stress, inflammation and pseudohypoxic HIF activation, a pathway implicated in diseases associated with air pollution exposure, including cancer and pulmonary fibrosis, as well as disruption of metal metabolism and homeostasis compared to brake wear particles from low metal or semi-metal pads and, more importantly, diesel exhaust particles."
It should be noted that a 12.6-liter, six-cylinder, Euro 3-compliant diesel engine with six cylinders was used for the test bench analysis, and the fuel chosen was low-sulfur EN590 commercial diesel. It was kept at 1,200 rpm to “simulate typical highway conditions”.
Blocks of this type are found in high-tonnage trucks or heavy industrial vehicles, such as agricultural or construction vehicles. It is not exactly a clean diesel, compared to those fitted in today's diesel cars.
- Electric vehicle.
Electric cars do not help, another interesting reading of this study is that the volume of particulate matter emissions from car brakes is expected to increase in the coming years due to the proliferation of electric and plug-in cars.
What they argue by pointing out the greater weight of electric vehicles, which equip huge batteries: “they generate more of these non-exhaust emissions derived from friction”. While zero-emission vehicles use systems such as regenerative braking or engine braking, electric cars wear out brake pads or tires sooner because they are heavier.
The study does not intend to go against the electric car, but it does highlight that regulations should focus on curbing pollution caused by brakes by reducing the use of metals such as copper in their composition.
- Legislation to limit brake pollution.
The Euro 7 standard was the first in Europe to focus on reducing particulate matter from tire and brake wear. Europe seeks to limit emissions of PM2,5 and nanoparticles from all types of combustion engines, as well as brakes in conventional and electric vehicles.
Ultra-fine particles from brake pad abrasion will be covered for the first time by an EU regulation along with nitrogen oxides and sulfur oxides emitted by automobiles.
Based on the latest evidence, the need to limit emissions of PM2,5 and nanoparticles from all types of combustion engines and brakes in conventional and electric vehicles will be considered, along with the need to reduce pollutant emissions under a broader set of conditions of use and over the lifetime of vehicles, states the text published by the European Commission.
In the case of PM2,5, their size makes them 100% respirable as they travel deep into the lungs, penetrating the respiratory tract and settling in the pulmonary alveoli, and can even reach the bloodstream.
In addition, these smaller particles are composed of elements that are more toxic, such as heavy metals and organic compounds than those that generally make up the larger particles.
Among the effects of inhaling the heavy metals they release are bronchitis, cardiovascular ailments and reduced lung function, since their size makes them lighter and therefore they generally remain in the air longer.
A report by the European Environment Agency estimated that chronic exposure to particulate matter resulted in some 307,000 premature deaths in the European Union in 2019 alone.
In this regard, heavier combustion vehicles, such as SUVs and off-road vehicles, will be most affected by the rule. Also electric and hybrid vehicles that use brake discs, and also have a high weight due to their batteries, although there are the electric vehicles with drums on the rear axle.
This new standard was scheduled to come into force in 2026, but has finally been delayed to 2030 after pressure from manufacturers. Pressure derived essentially from meeting the average emissions of the ranges of their cars, which require a much higher mix of electric or electrified cars.
Slide 4. Proposed solutions to reduce pollutant emissions.
- Filter.
A possible affordable solution could be the one developed by Mann+Hummel, currently in the final phase. The German manufacturer has proposed to combat these pollutant emissions with a filter for braking systems. It is a kind of clamp that is placed downstream of the brake caliper in the direction of wheel rotation, and where the particles should be deposited as they are released.
Inside, the system is a hollow space with different waves of absorbent material where the particles should be trapped. At the end of its useful life, it is enough to remove it from the brake caliper support and replace it with another one. According to the brand, the system has already been tested in real conditions and the results have been satisfactory.
The best thing is that it is a scalable product, which can be easily sized to the size of the vehicle for which it is to be used. Thus, these filters can be used in cars, trucks, buses and trains.
- Box.
This is a box-trap for these emissions, in the style of catalytic converters, but for tires developed by the company The Tyre Collective.
It is based on a basic principle to provide a solution to this problem: static electricity to attract and capture the nanoparticles released by tires.
Thus, a kind of box-shaped filter is placed as close as possible to the area where the tire comes into contact with the surface, to take advantage of the air flow around it.
In this way, the box traps tire particles by means of electrostatic plates. As the car tire rolls, the discarded particles are “charged by friction on the road” and the box attracts them.
In order to incentivize the circular economy after collection, these fragments are separated using simple techniques. Particles smaller than 50 microns are small enough to be reused in new tires and other applications.
Slide 5. Implications for fleet management.
- Quantify brake emissions.
To achieve net zero emissions in an electric vehicle, the power has to be generated by renewable energy such as solar or wind.
But they have pollutant emissions from the braking system and tires.
It is necessary to quantify the pollutant emissions from the brakes of the vehicles in the fleet.
Although today there are no values of how much each car model pollutes due to brakes, in the future they will be limited and/or quantified.
When this information is available, priority should be given to the acquisition of vehicles that pollute less by braking.
- Approximate measurement of pollutant emissions.
An approximate measure is to weigh the brake pads, drums and discs before and after use and divide them by the kilometers driven to obtain the ratio grams/kilometers.
These values can be used as a reference, to better choose the brake pads, drums and discs, and to improve the braking style of the drivers.
- Acquisition of the vehicle.
Before acquiring the vehicle it would be advisable to know what type of brake pads, drums and discs the vehicle is equipped with in order to know how much they can pollute.
Priority should be given to components with low copper content and materials that are not harmful to health.
As a fleet, it is recommended to acquire the vehicles by large lots to have greater bargaining power and obtain more economical prices, you can also exercise this purchasing power to change the braking system for a less polluting one at the factory.
- Maintenance.
When it is necessary to change the brake pads, drums and discs, it is recommended to install those that pollute less, for this it is necessary to know what materials they are made of, or that the manufacturer advises us which one to use.
- Install brake dust collection devices.
At present, no vehicles are equipped with brake dust collection devices as standard, but in the future, vehicle manufacturers will install them as standard.
When these devices become available, vehicles with such devices should be purchased.
It is also possible to install these devices in a workshop once the vehicle has been purchased, such as the box developed by The Tyre Collective.
- Emerging technologies.
Brake dust collection is an emerging technology, and it is recommended that we keep abreast of potential technologies as they become available to see if they can be installed on our fleet vehicles.
Slide 6. Thank you for your time.
The class has developed the pollutant emissions from brakes that can be more harmful to health than the pollutant emissions from the diesel engine, and possible solutions to minimize their impact, see you soon.
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