Sustainability a selling point for airless tires

Imagine a tire.

A tire made completely of sustainably sourced, bio-based, renewable and recycled materials.

Now imagine that sustainable materials tire can be retreaded, not just a few times, but many times. And then imagine that the tire, at the end of its life, is 100-percent recyclable.

That is exactly how the world's three largest tire makers—Michelin, Bridgestone and Goodyear—are viewing the future of the tire industry. It's a philosophy shaping their approach to innovation.

And that shape is airless.

"When you have Air Free, and when you think about the tire that is able to last longer from a durability standpoint, you are thinking about the R's within sustainability with reduce, reuse, renew, recycle," Jon Kimpel, Bridgestone Americas vice president of extended mobility solutions, told Rubber News.

So far, each of the top three tire makers have been able to wrap those Rs into the innovative strides they have made in the nonpneumatic tire development space. And those successes and ideas are propelling them forward as they work to define the tire industry's more sustainable future.

One of the greatest ways that airless tires move the industry forward to its sustainability goals is by addressing the number of scrapped tires generated.

"Airless tires actually help in that case, because there are quite a few very good tires that, unfortunately, need to be scrapped because they did have an unexpected event or integrity issue and they were removed from service early," said Michael Rachita, senior program manager on Goodyear's nonpneumatic tires team. "You can eliminate a lot of scrap tires by having this airless architecture."

How many scrap tires?

Michelin's done the math.

According to a webpage dedicated to the French tire maker's airless tire development, 12 percent of scrapped tires are removed from service early because of cuts, punctures or other air-loss failures. Another 8 percent of tires were scrapped early because of issues related to improper air pressure.

In all, that's 20 percent of scrap tires that can be removed from the equation when addressed with nonpneumatic options. By Michelin's estimates, that 20 percent represents 200 million tires globally each year.

For the world's three largest tire makers, sustainability literally will be built into every aspect of the nonpneumatic tires they roll out. That means expanding their understanding of bio-based and recycled materials, while also exploring new, viable and more-renewable natural rubber options.

In the alternative natural rubber space, Bridgestone is working toward what it believes could be among its crowning achievements: the commercialization of guayule as a more sustainable alternative rubber source.

The tire maker already has invested more than $100 million in the development and cultivation of the desert shrub, and has seen some significant successes along the way. Among them was the recent unveiling of a pneumatic Firestone Firehawk race tire that featured 100-percent guayule-derived rubber in its sidewalls.

And you can bet, Kimpel said, that when Bridgestone brings its nonpneumatic tires to market, it's going to do the best it can to tap all of its materials insights.

"Bridgestone has this overall portfolio of sustainable materials, and it is definitely something (we are looking at) with guayule," Kimpel said. "…It is definitely something we can consider going into the Air Free and pulling together that bigger sustainability message and promise."

By nature, the quest for sustainability demands the right ingredients. And Michelin is making moves to ensure it has exactly what it needs.

Michelin's Vision concept tire embodies a nonpneumatic tire philosophy built on three key facets: connectivity, recharge-ability (retreading) and 100-percent sustainability. It's a feat the tire maker says it will achieve by 2050.

And it appears the company is making significant strides to that end, at least on the materials side. Through investments, acquisitions and partnerships, Michelin is bringing into its arsenal a number of materials and material science developments that could propel it significantly toward its "Vision."

"Once we grow in the high-tech materials, we open the group to new business territories like medical or like aerospace, for example," Alexis Garcin, Michelin North America Inc. chairman and CEO, told Rubber News last year. "And, at the same time, we have access to and we develop new high-tech materials that help us to bring to the market by 2050, a tire that will be made 100 percent of fully renewable and recyclable materials."

Michelin's partnerships, acquisitions and investments have been wide-ranging. In recent years, the global tire maker has:

• Taken full ownership of a sustainably sourced natural rubber project;
• Taken a majority stake in Enviro Systems A.B., which focuses on recycled scrap tire derivatives such as recycled carbon black;
• Acquired Lehigh Technologies, a maker of micronized rubber powders for applications including tires;
• Partnered with Carbios on the development of polyester tire fibers from polyethylene terephthalate (PET) plastic waste; and
• Partnered with Pyrowave to produce commercially yieldable synthetic rubber from styrene.

All of these moves—among others—are likely to position the tire maker to do exactly what Garcin said it would: harness technology across a range of industries to make a better-performing, more efficient, 100-percent sustainable material tire.

One the company envisions being nonpneumatic as well.

Like Michelin, Goodyear has a big vision for sustainability.

"Goodyear has, within our global technology organization, a bunch of 'bold goals,' as we call them, to help align and prioritize—set the targets," Rachita said.

One of those goals is to, by 2030, bring a 100-percent sustainable materials tire to the market that is also maintenance-free.

And Goodyear is making progress, having already unveiled a pneumatic tire that it says contains 90 percent sustainable materials. The achievement, the Akron-based tire maker said in January, resulted from the use of 13 key materials across nine different tire components. These included:

• Soybean oil;
• Rice husk ash silica;
• Bio-based polymers;
• Fabrics made from recycled plastic bottles;
• Renewable resins;
• Chemicals; and
• Three different sustainably derived carbon blacks.

Hitting that 100-percent sustainable and maintenance-free target will require pulling in all those innovations that have granted Goodyear's greatest material science successes. Naturally, Rachita said, that includes Goodyear's highly championed soybean oil technology, which has proven to effectively replace petrochemical-derived oils in the tire compounds while enhancing performance and safety.

"In fact, the compound we are using for the microdelivery (airless tires) has the soybean oil in it," Rachita said. "… And we are definitely looking at: How are we using recycled materials? How are we using bio-based materials? How are we taking advantage of our 70-percent sustainable material tire and using that?"

For airless tires, though, it's not just about the rubber compound. It's about the supporting structure of the tire that connects the tread to the rim. Because, yes, the tire makers are reimagining every part of the tire and its wheel.

"We have different ideas in that same space including, can you make a plastic or composite-based wheel system that is recyclable?" Rachita said.

Bridgestone also aims to bring a game-changing nonpneumatic tire to the market, one that will be sustainable all the way around. From its materials composition and tread compound all the way down to its reusability and recyclability.

In the end, Kimpel said, that involves retreading.

"What I find is really exciting with (Air Free tires) as well, is that we fully intend to have a big advantage of this to be retreading," Kimpel said. "So you are going to be reusing the tire as well. You are going to have the casing, and we are going to be retreading it, which is amazing in terms of the CO2 benefits associated with just retreading in general."

Both Goodyear and Michelin also are looking to retreading to help with sustainability of nonpneumatic tires. But not just retreading. It would be retreading again and again.

And again.

"One of the problems with the air tire is, obviously, you continue to age the carcass," Rachita said. "You can retread a few times, but then the carcass has just gotten to its useful age, and it's not holding the air pressure. … There is a really good opportunity that the carcass of the airless tire could last quite a few more retreads."

Bridgestone has been a vocal proponent of retreading in the truck/bus tire space, backing a recently proposed U.S. House Bill that would incentivize the use of retreads in the trucking industry. And the benefits derived from retreading pneumatic tires translate to nonpneumatic tires, Kimpel said.

According to Bridgestone, retreading of tires—nonpneumatic and pneumatic—has the potential to:

• Use 15 fewer gallons of oil and 90 fewer pounds of total material per tire;
• Save about 215 million gallons of oil per year in the U.S. and Canada;
• Reduce CO2 emissions by 24 percent;
• Cut water consumption by 19 percent;
• Reduce air pollution by 21 percent; and
• Remove about 1.4 billion pounds per year from the waste stream.

"We ballparked it as, for every truck tire you retread, you are saving at least 100 kg of CO2," Kimpel said. "… And 100 kg of CO2 takes the place of a brand-new, full casing that we would have to make. It is pretty significant."

Michelin would agree. Retreading is essential in the nonpneumatic tire space.

Not only does the tire maker believe that retreading is a key to the sustainability of airless tires, it imagines taking the technology even further through 3D printing.

Why? Think 3D-printed customizable retreads.

It's a concept that Michelin contends would be more sustainable than traditional retreading, should the capability be harnessed.

"Having a tire with a 3D-printed tread makes it possible to deposit just the right amount of rubber compound, thereby reducing the use of raw materials," Michelin said of its ultimate goals for retreading, something embodied by its Vision concept tire unveiled in 2017. "The tread can be 'recharged' using a 3D printer, which means that Vision can be adapted to motorists' changing needs, for maximum comfort, safety and sustainability."

And while it's important to note that Vision is a concept tire, the philosophies surrounding it—sustainable, connected, rechargeable (retreaded)—are guiding innovation for the company.

To date, the tire maker has touted its 3D printing capabilities as they relate to metal and the ways it supports advancements around tire development and molding. With Vision, though, Michelin hinted it would like to explore the possibility of 3D printing in the rubber space.

However Michelin achieves sustainability through retreading—3D printing or not—Garcin notes that it is only one piece—albeit an important one—of the broader, more sustainable vision for all of Michelin's tires.

"Clearly, the automotive industry is going through different revolutions," Garcin said at Motor Bella last year. "The first one is the electrical revolution, no doubt. The second one is a digital revolution and the third one is an environmental revolution. … One way that Michelin wants to contribute to better and cleaner mobility is by providing different tires that will be sustainable, connected and rechargeable."