Bridgestone takes sustainability faster, further with bio-monomers

INDIANAPOLIS—Sustainability is a step-by-step kind of thing. A start small and then scale it up mentality.

That's exactly how it works for Bridgestone Americas Inc. as it embarks on its journey to 100-percent sustainable materials tires by 2050. And just about every step of the way, the tire maker is testing its scientific mettle against some of automotive's most grueling conditions.

Sustainability, meet the Indianapolis 500.

All 241 mph of it.

"It is very important to use this phenomenal proving grounds that we have—which is motorsports, the Indianapolis Motor Speedway—to be able to show that we can do sustainability without sacrificing performance," Cara Krstolic, Bridgestone Americas' executive director of race tire engineering and production, said about Bridgestone's role as the NTT IndyCar Series' sole tire supplier.

This year, the Nashville-based tire maker took sustainability further—and faster—with another material science step forward at the Indianapolis 500. Built into the more than 5,000 Firestone Firehawk IndyCar racing tires used May 26 were two monomers—bio-styrene and butadiene—sourced from waste residue of palm oil processing.

Both were certified by the International Sustainability and Carbon Certification (ISCC) for supply chain transparency and traceability.

More importantly, though, those two monomers helped to diversify Bridgestone's sustainable materials options and insights. Because last year, the tire maker tested the use of another monomer, which was sourced from post-consumer plastics such as plastic shopping bags.

"The diversity (of material usage) is important because we are learning from what we are doing here in racing, and that makes its way into Bridgestone and Firestone passenger tires," Krstolic said. "So looking at all the different sources gives us options, and you are not single-sourced or you are (not) putting yourself in a situation where you are relying on just one thing.

"Our sustainability team is constantly looking at what materials are the best materials from an overall environmental impact. There is a lot of work that is done behind the scenes to understand what are the best types of materials, and how do we get the materials in and into the race tires without changing the performance of the tires?"

And believe Krstolic when she says drivers would notice any performance changes. Good or bad.

"Race drivers are very sensitive to any sort of little change in the tire, whether it is a material supplier or a slightly different weave of a fabric, they are very, very sensitive," Krstolic told Rubber News last year. "So we want to make sure when we introduce things, we keep the durability, the dependability, that predictability that comes with the Firestone Firehawk race tire."

Moreover, motorsports offer Bridgestone the opportunity to test those big ideas because the tires come in small batches.

And fewer tires made means less materials used. That's especially helpful for trialling ideas, but also if the more sustainable material isn't yet at scale.

Once the tires are built, it's all up to testing. And for that Bridgestone just lets IndyCar do its thing.

"You have speeds of up to 241 mph," Krstolic said of the Indy 500. "You have average lap speeds of 234 mph. You have lateral forces of over 3Gs sideways. And through all of this, the tire needs to be able to grip and maintain that small contact patch that you have on all four tires, but it needs to be able to hold the car to the track at those grueling conditions."

This year, IndyCar upped the sustainability ante, introducing the NTT IndyCar Series 2.2-liter twin-turbocharged V-6 engine with hybrid technology.

That forced Bridgestone engineers to design more sustainable tires for the more sustainable cars, which ultimately place different demands on their fitments.

"Our engineers not only had the challenge of designing for a difficult track like the Indianapolis Motor Speedway and taking into concern all of learnings we had from last year," Kristolic said, "but they also had to design a tire that would be good for a hybrid system, which is a lot heavier, has different weight distribution and a lot more power vs. the non-hybrid system."

So far, Bridgestone has tested several more-sustainable monomers on IndyCar tracks, but it's also taken one of its biggest investments to the streets with IndyCar.

Two years ago, Bridgestone built its Firestone Firehawk alternate race tires for NTT IndyCar street course races with 100 percent guayule natural rubber in the sidewalls, completely replacing hevea in that application. That was a critical step forward in understanding guayule's mettle.

"We see lots of braking and accelerating in street courses, and there is a lot of heat that goes into tires. The surface of the tires get hotter than the boiling point of water, so there is a lot of heat that goes into it. There is a lot of demands on that tire," Krstolic said.

And those 100-percent guayule sidewalls performed exactly as expected. It's why the tire maker still uses the alternative natural rubber in those same tires today, proving again why it's doubling down on guayule research and development and the scaling up of the raw material.

From her perspective, Krstolic gets to watch it all fall into place. She gets to be on the cutting edge of technology and design with the race tires, but she can also see Bridgestone's bigger picture and how sustainability could fit for the entire product portfolio.

"It's really phenomenal for us to be able to prove out something, and then I love seeing that transfer from our race tires into our passenger tires," Krstolic said. " … I think it just shows our commitment to making sure we are being good stewards of the environment."