#plasticfree: Car tyres are the main microplastic pollutant [deu/eng]

Part 4: Tyre abrasion is in Germany responsible for one third of the total microplastic input into the environment.

The Mattern family pays careful attention to how much microplastic it generates. Ever since Lena, the mother, read in the newspaper that a lot of microplastic comes off when fleece jackets are washed, the Matterns don't buy new garments made from fleece anymore. The article also stated that microplastic particles can be found in shampoos, shower gels and other care products. This has led David, the father, to always look out for the "microplastic-free'' seal on products in the drugstore.

When coming home from school recently, the daughter Amira surprised her parents by asking: "Do you know what the biggest source of microplastics is? The abrasion of car tyres when driving on the road!" Her parents looked at her in disbelief. "Yes, that’s what we learned in chemistry today," Almira said. In the course of the same evening, Lena and David decide to do some research on the internet and find out it's true. That's right! Over the next few weeks, all family members tried to reduce their contact with microplastics. Amira now often rides her bike to school, while her little brother Max and his friends go to school with the “run bus”. Father David is quite happy that he is spared the stressful task of driving the children to school. Instead, he now enjoys walking the way to the tram stop. Last but not least, Lena bought herself an e-bike, with which she sometimes manages the 12 kilometres to the office even faster than she did in the past in the car.

1. The problem

According to a study by the Fraunhofer Institute UMSICHT, the abrasion of car tyres is by far the largest cause of microplastics. At a rate of around 100,000 tons per year, tyre abrasion is responsible for a third of the total microplastic input of Germany.

Yet, vehicle tyres have so far played almost no role in the discussion on the avoidance of plastics, even though large quantities of used tyres are produced every year and large quantities of microplastics are released into the environment through the tyre abrasion caused by driving.

Tyres consist to a large extent of natural and synthetic deformable plastics, the so-called elastomers. Other materials and substances such as steel, rayon synthetic fibres, polyamide plastics and industrial carbon black, as well as plasticisers and other chemicals are added to the mixture for tyre production.

Since 2003, used tyres may no longer be deposited in landfills in Germany. In 2016, Germany therefore recycled 577,000 tonnes of used tyres or incorporated it in cement production. Only five percent of used tyres were re-treaded; only the running surface needs to be fixed, thus avoiding the use of new elastomers. This re-treading is done much more frequently with truck tyres. One reason for this is that there are many more different tyres types for passenger cars, which face stiff competition from cheap imported tyres.

Despite the ban on landfill disposal, there are paths through which tyre material enters the environment. In addition to illegal disposal, tyre abrasion plays a significant role in its input into the environment. Although tyres are - at least partially - made from biogenic raw materials such as natural rubber and rayon, they are hardly or not at all biodegradable. Hence, the rubber of tyres stays in the environment for years. Due to the many acceleration and breaking processes and curves in cities, abrasion is particularly high there. It also particularly accumulates in places where it can easily get into the sewage system or, in case of heavy rainfall, directly into water bodies. Little is known today about the distribution routes and effects on individual organisms and entire ecosystems.

Mobility: Ten times more cars since 1960

In the last century, the emergence of cars has fundamentally changed the mobility behaviour of Germans. While numbers only rose slowly initially, the number of cars has increased by a tenfold since the 1960s to the present day. Cars have become a means of mass transportation. More than half of all journeys and three quarters of all passenger transport is now made by car. The distances travelled have also grown considerably. This has created a so-called lock-in effect: The car has made it possible to travel long distances in comfort, which in turn has had an impact on the living environment. Many places such as shopping facilities, workplaces, authorities or doctors are often difficult to reach by foot. At the same time, the road infrastructure has been expanded in order to cope with increasing traffic. This expansion has made car mobility even more attractive, which is why car traffic has continued to increase. The large number of passenger cars has also led to a reduction in public transport in suburban and rural areas. This, in turn, is fuelling the demand for cars even more. For many people today, it seems impossible to manage everyday life without their own car.

Attitude towards life: freedom & status

A further aspect also plays a big role in the matter: Due to omnipresent advertising, cars have become a symbol of freedom and mobility in the eyes of many people. It is more than just a means of transport: it is a status symbol. This is having an impact on the cars themselves and on their production: they are becoming bigger, heavier and faster. This becomes especially apparent through the use of off-road SUVs in cities. These SUVs are too big for urban traffic and do not fit into the existing infrastructure, making their use in cities very impractical. Additionally, the wide tires of SUVs, which in this case rather serve a decorative function, are the cause of much more microplastic pollution.

Freight transport

The demand for consumer goods has witnessed a clear increase over the past years; European integration and globalisation have led to a sharp rise in truck transport. Just-in-time delivery reduces the need for warehousing, but in turn requires fast and flexible transportation. For this, only small trucks can be used, as 500-ton trains would not have this flexibility. The more environmentally friendly transport on waterways and rail is mainly for bulk goods.

Tyre purchase

More vehicles = more tyres. Based on current requirements, a complete renunciation of tyres seems impossible. While passenger car tyres today are mainly built with the main concern being safety, truck tyres also focus on the highest possible mileage. The EU tyre label enables consumers to compare fuel consumption, noise emissions and wet grip when buying tyres. Information on the abrasion of microplastics, on the other hand, cannot yet be included in the purchase decision.

Driving style & tyre pressure

A wrong usage of tyres can also cause an increase in the normal microplastic abrasion, such as when the tyre does not have the right pressure or when winter tyres are used in summer. This is where drivers can watch out and minimize the amount of plastic entering the environment that they are responsible for. The same applies to the driving style, ideally including less braking and acceleration processes. Driving schools should therefore put more weight on the training of driving in an environmentally-friendly manner and on teaching the appropriate use of tyres.

All a matter of education!

Traffic education should begin with teaching children the advantages of cycling and walking starting in primary school. Instead of being taken to school in their parent taxi, children can become independent, reduce the burden on the environment and be more alert and concentrated at school. This also leaves children with the fun possibility of meeting school friends on the way. To this day, efforts are also put in organizing “run buses”, where primary school children get together in a larger group at certain meeting points and walk to school together.

2. Action-based solutions: Being mobile without a car

Whether it is in the world of work or of leisure, whether it is in shopping or on vacation: a complete renunciation of vehicle tyres seems difficult to imagine due to today's lifestyle incorporating boundless mobility. However, the transport sector is facing major changes due to necessary steps in climate protection. Nonetheless, more can be done. Plastic-based tyres, for example, could be better utilized by known methods to reduce the abrasion of microplastics.

Bikes in cities: increasing popularity

Particularly in cities, where cars are a particular nuisance due to their enormous land consumption when parking and driving, their air pollution, traffic jams and resulting noise, a positive development is becoming apparent: the car is no longer a status symbol for many young people. The desire to ride a bicycle is spreading and bicycle traffic is growing rapidly. Citizens' movements are pushing through referendums to make roads and paths safer for cyclists. Cycling cities such as Copenhagen have made cycling attractive through a convenient infrastructure.

Cities: Scooters, cars and bikes "to go"

The number of carsharing users and providers has been rising continuously for several years. Thousands of free-floating vehicles are available in large cities, which can be rented and then be dropped off and parked elsewhere. The importance of tyres, however, even increases for car-sharing vehicles, as they are driven much more than private cars. Here producers and consumers can do their part, in making sure the tyres used are conceived in a way to minimize abrasion and through drivers being advised of environmentally friendly driving with electronic support. Incentive systems, such as fare credits or lower fares, could reinforce this.

Bicycles are also being shared more and more flexibly, whilst electrically operated scooters that can be borrowed are becoming more popular. City dwellers who do not want to drive themselves can make use of ridesharing services in inner-city regions, a kind of shared taxi that makes virtual stops and takes passengers on board on demand.

Land: e-Bikes, carpools and public transport

In the countryside, buses run less frequently, distances are longer, making supermarkets, cinemas and theatres harder to reach. Shared cars can also be of help here: drivers and passengers can be connected via smartphones and thus share the car and costs. E-bikes are also starting to be increasingly used, also for longer distances. Commuters can also switch to two-wheelers more easily thanks to new cycle expressway routes. Elsewhere, people are attempting to make public transport more flexible to provide an alternative to private car use. The idea of an on-call bus or taxi was also introduced to prevent an almost empty bus from travelling a fixed route every hour. Instead, buses or shared taxis would run when they are needed and also make stops on demand also off the route.

Profit: No more inspection, tax and insurance costs

People who no longer drive their own car have another benefit: they do not have to worry about cleaning, servicing, maintenance, insurance or registering and deregistering their vehicles. And they do not lose mobility, but instead make use of a better type of mobility that is more suitable for the respective route.

Still, buses, car-sharing vehicles and bicycles require plastic-based tyres and generate tyre abrasion. All in all, the environmental impact and tyre consumption will nevertheless be much lower than when using privately-owned cars.

3. Technical solutions: Re-treading and digitalization

The potential of tyres has not come close to being exhausted yet.  As is already the case with many truck tyres today, the material of car tyres could be optimized with a focus on low abrasion and long durability.

Possible negative effects of new tyre components such as the toxicity of Nanosilica and the propagation paths of its abrasion, should be researched from the start and thus prevented. Cooperation between manufacturers could reduce the number of tyre types, so that re-treading car tyres becomes more common and popular as an alternative to producing new tyres. For dangerous situations, technical assistance systems are set up in vehicles. This helps to avoid the situation that slightly longer braking distances due to "cross-country tyres" are at the expense of safety.

Furthermore, technical developments will also help to reduce tyre consumption and abrasion. Digitalization allows for a communication channel between vehicles and infrastructure and thereby ensures that traffic flows with fewer brakes and accelerations. As a result, the speed limit can be reduced without increasing travel time. This positively affects abrasion and safety and counteracts traffic that could be generated through driving becoming more comfortable.

4. Regulatory solutions: Financial incentives and standardised test procedures

The developments listed above can be promoted by legal measures. The development of a standardised test procedure that determines tyre wear at different stages of a tyre's life would provide the basis for the further development of the EU tyre label. This could be used to define minimum requirements or limit values for abrasion. A market for particularly low-abrasion tyres could be stimulated by mandatory requirements in public procurement. If producer responsibility is extended, tyre manufacturers could also be made to contribute to the costs of street cleaning depending on the abrasion classes of their tyres.

The EU Tyre Label informs customers about rolling resistance, wet grip and external noise when buying tyres. Low rolling resistance has a positive effect on fuel consumption. On the label, the tyres are classified by the manufacturers in classes A to G according to an energy efficiency label. Wet braking performance is also classified in classes A to F, with class A tyres having a shorter braking distance than class F tyres. In addition, the label states the level of external noise and shows which limits are being observed by means of a loudspeaker symbol with three rings. Three rings mean that the tyre complies with the EU limit valid until 2016, two rings mean that it complies with the noise limit valid since 2016 or falls below it by up to 3 dB(A). One ring means that the tyre is particularly quiet and falls below the limit value valid since 2016 by more than 3 dB(A). Tyre abrasion is not yet part of the label.

5. End-of-Pipe: targeted street cleaning

Since the input of microplastics can be reduced but not prevented by the developments described above, complementary end-of-pipe measures can contribute to ensuring that the input of microplastic particles into ecosystems is reduced. End-of-pipe activities are additive environmental measures. These measures can only be implemented after the particles have already been formed. Since urban traffic causes a particularly high level of abrasion, streets that are particularly affected could be cleaned in order to prevent the entry of microplastic particles into the sewage system and waterways during heavy rainfall. Traffic data can provide information on hot spots to estimate particle emissions. This information can then help detect particularly relevant gullies where filter systems can be put in place.

Dr. Andreas Köhler, Moritz Mottschall and Martin Möller are senior researchers at Oeko-Institut in Freiburg and Berlin. As part of the donation-based project „Living without plastic – but how?“, they have been investigating the possibilities and effects of living without plastic. This includes an analysis of the reasons for using plastic, the experiences of consumers in avoiding plastic and alternative materials. The results of the project will be published in the Oeko-Institute blog under #plasticfree.

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