Vehicle particulates do not just come from the emission system. Tyres also create fine particles that can affect the environment, cause air pollution and create health problems. Yet unlike emissions, there is no easy way to manage tyre particulates. Autovista24 editor Phil Curry and deputy editor Tom Geggus discuss the problem with particulates, the role of electric vehicles, and solutions the automotive industry is working on.
The issue of particulate matter is not solely the problem of emission systems. Any parts that create friction are susceptible to producing fine particles that can impact air-pollution levels or harm the environment. In this respect, tyres are a big part of the particulate problem and have been since the inception of the car over 100 years ago. For vehicle sustainability to continue, tyre wear must be a factor in automotive research.
However, unlike the emissions system, there is little that can be done to halt the creation of particulates. Instead, tyre suppliers and car manufacturers are doing their best to slow their creation, while drivers too have an important role to play.
According to German vehicle-testing agency ADAC, around 500,000 tonnes of particulates are created by tyres each year in Europe. These range from 10 microns in size to 2.5 microns – an atmospheric size.
The electric-vehicle problem
Carmakers are shifting their focus away from internal-combustion engine (ICE) cars to electric vehicles (EVs). One reason for this is the issue of air pollution, a matter that increased after the Dieselgate scandal. This saw a lot of attention around the subject of particulates, especially nitrogen oxide (NOx) pollution. The decline in the diesel market meant drivers moved towards petrol models, creating a problem with CO2 emissions that the car industry was trying hard to avoid.
But electric cars have their own part to play in tyre particulate matter creation. They are often heavier than standard ICE counterparts, and this places more pressure on the tyres. This, in turn, creates more friction with the road surface, and therefore more wear. Electric-vehicle sustainability is not, therefore, reliant on its zero-emission capabilities alone.
The UK’s environment secretary George Eustice recently highlighted to MPs that it is unknown how far switching from ICE to EVs will help. ‘There is scepticism,’ he said. ‘Some say that just wear and tear on the roads and the fact that these vehicles are heavier means that the gains may be less than some people hope, but it is slightly unknown at the moment.’
In answer to this, one of the country’s automotive organisations, the RAC, commissioned a report from battery electrochemist Dr Euan McTurk. He used real-world findings to explore the actual impact of electromobility on tyre and brake wear.
RAC EV spokesperson Simon Williams said: ‘George Eustice’s remarks about EVs not being as green as some may think were very unhelpful and could put some drivers off making the switch to zero-emission driving. There are far too many negative myths surrounding electric cars which need to be busted as soon as possible in order to speed up the electric revolution.’
One solution to the particulate problem is to filter them away from the environment. For emissions systems on petrol and diesel cars, this is done with a particulate filter fitted in line on the exhaust system. However, it would be difficult to fit a filter to a tyre, while the potential of a suction device behind the wheel is limited due to restricted space and constantly moving objects.
Therefore, fitting filters to areas where particulates can enter the environment, such as around the drainage system to prevent ingression into water supplies, is something that could help reduce the problem. This is the thinking of German carmaker Audi who, together with the Technical University of Berlin, is developing tyre-particulate filters to help protect the ecosystem.
The Urbanfilter can be combined individually depending on the road and traffic situation. They trap the particles as close as possible to the location of creation – before rainwater can rinse them into the sewers. Laboratory and field testing has shown the filters are effective, but can they work together to solve the issue of tyre particulates?