How much microplastic is generated during mountain biking?

Comparison of a new, unused tyre (left) with a front tyre (middle) and a rear tyre (right) after covering a distance of 1,500 km. 

For years, it has been known that tyre wear from motor vehicles is a major contributor to microplastic pollution. Approximately 11 grams of microplastic are released per 100 kilometres driven, accounting for about 57% of microplastic pollution from road traffic and roughly 35% of total microplastic pollution in Germany. In contrast, cycling is considered an environmentally friendly mode of transport and is also a popular recreational activity. Mountain biking, in particular, has been growing in popularity, with around 20% of the German population now participating in this sport – sometimes in pristine natural environments. However, no data has been available on the quantity and significance of tyre abrasion from mountain biking. To gain a broader understanding of the environmental impact of cycling, researchers at the Chair of Sport Ecology at the University of Bayreuth have now conducted the first study on the abrasion of mountain bike tyres. 

For the study, a team led by doctoral researcher Fabian Sommer equipped nine mountain bikers with brand-new tyres. The participants then followed their usual riding habits while tracking their routes via GPS. At predetermined intervals, the tyres were weighed in the lab to measure and document material loss due to abrasion. 

On average, the study found that tyre abrasion amounted to approximately 3.5 grams per 100 kilometres, equating to a per-capita abrasion rate of up to 88 grams per year. When scaled up to the total microplastic pollution in Germany, mountain bikes contribute to less than one percent. The researchers also observed that the abrasion rate was higher during the first 500 kilometres of riding with new tyres compared to after the 500-kilometre mark. According to the researchers, this could be due to the rounding of tyre edges and the relatively quick wear of excess material from the manufacturing process – the small hair-like structures found on new tyres. 

"Our study provides the first reliable data on the amount of tyre abrasion from mountain bikes under real-world conditions. The results show that while mountain bike tyres release microplastics directly into nature, the amount is significantly lower compared to motorised vehicles. This highlights another advantage of cycling as a sustainable mode of transport," says Sommer. 

As part of ongoing research, a follow-up study is now being conducted, focusing on tyres from road bikes, gravel bikes, and mountain bikes/e-mountain bikes. This study aims to provide additional insights into the dynamics and rates of tyre abrasion for these different types of bicycles. In addition, environmental samples will be analysed in collaboration with the laboratory of Prof. Dr. Christian Laforsch from the Collaborative Research Centre 1357 Microplastics at the University of Bayreuth to better understand the impact of microplastics on the environment.