The gripping world of tyre recycling

This week I attended the Materials Research Exchange 2024 in London, which provided an insight into the world of materials innovation, featuring an exhibition, investor showcase, and seminars on technology transfer from the UK’s world-class research base.

One subject that caught my attention was the environmental impact of tyres. Tyre abrasion is the mechanism by which tyres grip the road and so it is essential for their function. However, it means that rubber particles are constantly emitted from a tyre in motion and these particles persist in the environment like microplastics and leach chemicals into the waterways when it rains. There were a number of presentations on how this issue could be mitigated, including changes that can be made to the design of tyres that can increase their wear resistance without impacting wet grip and rolling resistance.

Another challenge with car tyres is how to recycle them. It is difficult to process scrap car tyres in a way that allows the components in the tyre “rubber” to be reused. During production, tyres are vulcanised, which is a process that links polymer chains with sulfur bridges.  Vulcanisation is an irreversible process, meaning it is not possible to break the bridges and recover the polymer chains: this prevents scrap tyres from being used to make new tyres. Several components of car tyres can be recovered, including the steel in the bead and the inorganic filler salts. Once these have been removed, the “rubber” part is often incinerated or taken to landfill. Students at Queen Mary University presented their research into alternative, reversible vulcanisation techniques that may allow the polymers to be recovered and used for making new tyres.

Finally, a topic that was of particular interest to me as a keen cyclist was the specific challenges of recycling bicycle tyres. I was completely unaware that bicycle tyres are not recycled in the same way as car tyres. I learned from a presentation by Velorim that the steel in bicycle tyres is different to that in car tyres, meaning that the machines that process scrap car tyres cannot be used with bicycle tyres. As a result, the whole of a bicycle tyre is usually sent to landfill or incinerated, with none of its components recycled. Velorim has developed a process specifically for bicycle tyres and is developing a network of recycling centres around the UK. They also announced the opening of a new recycling plant in the UK later this year. It was great to hear about a UK business tackling this important challenge.