Stopping the rubber meeting the road
Every time a car brakes, accelerates or changes direction, friction wears down the exterior of the tyres, sending tiny particles into the environment. Some remain suspended in the air while others get swept into local waterways, where they can adversely affect plant and animal life.
The world generates just over six million tonnes of tyre pollution every year, more than enough dust and particles to outweigh the Great Pyramid of Giza.
Now, a group of master’s students from Imperial College London and the Royal College of Art are asking what if the tyres picked up after themselves?
The Tyre Collective — a project by recent graduates Hugo Richardson, Siobhan Anderson, Deepak Mallya and Hanson Cheng — wants to capture this pollutant as it flies off the wheel as we drive. For the past year, they’ve been working on a device attached to the bottom of a car that uses electrostatic charges along with the airflow of the moving wheel to collect particles for reuse. The inspiration came from rubbing a balloon over a sweater and seeing the pieces “dancing around”, says Richardson, the group’s chief technical officer. “That led us to the assumption that particles are charged due to the friction.”
Using a bicycle wheel and sandpaper road test rig, they were able to collect 60% of all airborne tyre emissions as the wheel rubbed against the sandpaper.
After winning the 2020 UK James Dyson Award for innovation and reaching the finals of the international version, the collective caught the attention of the Tyre Industry Project, an initiative of the World Business Council for Sustainable Development, which aims to better understand the potential health and environmental impact of tyres. “We understand very well how difficult it is to try and capture and isolate these particles,” manager Gavin Whitmore told Christian Science Monitor. “We’re certainly interested to learn more, because it could be a very, very promising thing.”
Tyres are more complex than they look. The vulcanised rubber compound that makes up the outermost layer — the tread — often contains sulphur, zinc, carbon black, bisphenol A, and other chemicals. A lot of that gets swept off the roads by rain, along with motor oil, bits of cement, and other litter.
A three-year study by the San Francisco Estuary Institute (SFEI) found that stormwater carries roughly seven trillion microplastic pieces into San Francisco Bay annually — more than 300 times the discharge from the area’s wastewater treatment plant. Nearly half of those pieces appear to be tyre fragments.
“Seeing all these black rubbery particles was a surprise,” says Rebecca Sutton, a senior scientist at SFEI. “Tyres might be a big deal, but, honestly, no one had really looked at stormwater. It’s also probably just the tip of the iceberg, because most tyre particles are actually smaller than our sieve size.”
After synthetic textiles, tyres are the largest source of primary microplastic pollution in the ocean. But it’s difficult to figure out just how much material tyres are actually shedding. Tyre wear is heavily influenced by the road surface, the weight and type of vehicle, and the driver’s behaviour. In London, The Tyre Collective says a busy bus route can generate a grapefruit-size pile of tyre dust in a day. And that dust won’t just sit in water. The chemical mix leaking out from pieces of tyre tread is worrying.
A study conducted in western Washington state found tyre leachate had caused an elevation in coho salmon deaths in Puget Sound. Anna O’Brien, a postgraduate student at the University of Toronto, observed tyre leachate change the relationship between duckweed, a small plant that flourishes in still water, and the microbes that live on it. The problem is researchers don’t know exactly which chemicals are responsible for these reactions. “Just because something is more abundant doesn’t mean it’s what’s causing the effect,” says O’Brien. “Other things about the environment are changing, too. That might mean these effects we see aren’t constant. We might think we know what the effect of a chemical is only to have it change in the future.”
While tyre companies are researching less damaging materials, changing the chemical and physical makeup of the tyre also poses challenges, says Sarah Amick, vice president of environment, health, safety, and sustainability for the US Tyre Manufacturers’ Association. “Tyres are one of the most regulated products for safety in the United States,” she says. “Ensuring we can continue to meet those safety requirements, plus adding more renewable and recyclable materials to our tyres, is a challenge, but our members are working on that.”
For their part, The Tyre Collective did consider developing a biodegradable tyre, but quickly ran into several problems, including the realisation that most people probably don’t want a “degrading tyre” separating their moving cars from the road.
“We decided that a more practical solution would be looking at how we could collect this wear as it is right now,” says Siobhan Anderson, the collective’s chief scientific officer.
During lockdown, the team has been focusing on turning their vision into a fully-fledged startup. They say several manufacturers have expressed interest in their design, though no partnership has been formalised yet. When restrictions due to covid ease, they’ll be keen to get back to the lab and produce a set of first-generation prototypes to test with potential partners.
“We’ve been working hard to make it a true business offering,” says Richardson, “and not just a cool university project.”
ABOVE TOP A rendering of The Tyre Collective’s award-winning design shows how the device could be attached to the underside of a vehicle, where it would use electrostatics and airflow to capture up to 60% of tyre particles as the car is driven
ABOVE BOTTOM (left to right) Hugo Richardson, Siobhan Anderson, Deepak Mallya and Hanson Cheng from The Tyre Collective