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The concept of sustainability has impacted nearly every industry and tire manufacturing is no exception.

In fact, the majority of U.S. Tire Manufacturers Association (USTMA) members are pursuing technological advancements that improve sustainability (safety, economics and environmental impact) of today’s tires. As a result, these tires may feature different material composition and components than in the past. For example, some new tires contain RFID chips for connected mobility, Kevlar for strength, and bio-based and reclaimed recycled materials. Another potential game changer may be airless (or non-pneumatic) tires, for which prototypes have been developed, with a Michelin fitment on a GM vehicle announced for the 2024 model year.

“These materials may require recyclers to modify their recycling processes and update their equipment,” said John Sheerin, director, End-of-Life Tire Programs at USTMA.

Indeed, it’s important to note that several tire manufacturers are looking at ways to make tires partially or entirely from bio-based, renewable or biodegradable materials over the coming years.

Simultaneously, USTMA said some tire manufacturers are investing in their own recycling efforts, such as:

•Bridgestone’s at-scale use of recovered carbon black (rCB) in the tire market as part of its long-standing partnership with Delta-Energy Group, LLC. •Continental Tires’ agreement with Pyrum Innovations, a specialist in the pyrolysis of end-of-life tires. The aim of the collaboration is to further optimize and expand the recycling of end-of-life tires through pyrolysis. •Michelin’s first tire pyrolysis plant in collaboration with Enviro, a Swedish company that has developed a patented tire pyrolysis technology to recover carbon black, oil, steel and gas from end-of-life tires.

According to William Niaura, director of sustainable materials and circular economy at Bridgestone Americas Technology Center, from retreading to creating different production processes for carbon black using end-of-life tires and exploring waste biomass carbon sources as a substitute for petrochemicals, Bridgestone America has established a technical roadmap to achieve 100 percent renewable tires.

“To achieve these sustainability targets, we are working closely with the recycling industry to encourage the recovery and reuse of end-of-life tires,” Niaura said. Indeed, Sarah Amick, vice president EHS&S and senior counsel at USTMA, said tire manufacturers are working to further support scrap tire markets through their sustainability efforts in product development and manufacturing.

“The management of scrap tires has been a priority for USTMA members for almost three decades. USTMA works with stakeholders, including states, the U.S. EPA and the industry, to incentivize market development and advance federal and state regulations that foster sustainable scrap tire markets,” Amick said. According to USTMA’s 2019 Scrap Tire Management Report, approximately 76 percent of scrap tires currently go to scrap tire markets.

USTMA is working with states and the federal government, industry groups, recyclers, researchers and environmental groups to grow new and existing markets, which require:

•Investment in scrap tire solutions that advance the circular economy; •State grant programs to grow new and existing markets; •Federal investment in sustainable infrastructure that advances innovation while protecting health, safety and the environment; and •Additional research to assess lifecycle impacts.

“USTMA members support sustainable and circular markets for scrap tires, including markets that reduce CO2 emissions by reducing emissions compared to those associated with the manufacture and transport of virgin materials,” Amick said.

And here’s why: According to Sheerin, rubber modified asphalt made with scrap tires, in addition to offering durability and maintenance advantages, has been shown to contribute lifecycle CO2 emissions at least 32 percent lower than conventional pavement.

Also, pyrolysis of scrap tires to yield recycled carbon black – used to reinforce and manage heat in a tire – produces 81 percent less CO2 per ton compared to virgin carbon black.

“In 2019, 36.8 percent of recovered scrap tires were used as tire derived fuel (TDF) by cement kilns, pulp and paper mills, and other industrial users,” Sheerin said. The U.S. Environmental Protection Agency has recognized the biogenic or natural rubber fraction in TDF as carbon neutral, reducing the CO2 emissions profile of TDF and, therefore, the tire’s life cycle. In cement kilns, TDF has an added circularity benefit because the steel belts replace the ferrous oxide that would otherwise need to be added to the cement mix.

“While the challenges are complex, our mission is simple: 100 percent of scrap tires enter sustainable and circular markets,” Sheerin said.

Maureen Kline, vice president of public affairs & sustainability for Pirelli Tires North America, said that Pirelli Tires’ hope is for scrap tire material to be sustainably useful as a raw material for other products, so it will become more valuable.

“As a company and as an industry we are focusing R&D efforts on designing tires with less chemicals, doubling down on efforts to refine the quality of recycled material like recovered carbon black, for use in new tire production, and promoting stakeholder dialogue and research funding for market development,” Kline said. “As an industry we want to partner with states and the recycling value chain to evolve the recycling possibilities for tires. Everything is inter-connected. For example, lighter-weight electric vehicle tires will wear faster and produce more scrap material.”

Manufacturing more sustainable tires is top of mind for most tire companies as they recognize the challenges of fully recycling all components of today’s scrap tires.

“Globally, an estimated one billion tires reach the end of their useful life each year,” Niaura said. “Recycling end-of-life tires is a major challenge for the tire industry and its customers. Many of the technical challenges surrounding the use of recycled or recovered materials from end-of-life tires are well understood, but significant barriers remain in achieving material circularity at a scale that is necessary to realize a cleaner and more sustainable mobility ecosystem.”

USTMA is working with other stakeholders on multiple fronts to encourage the growth of circular, sustainable markets for scrap tires, including the use of ground tire rubber in rubber-modified asphalt (RMA).

“RMA has been used in the U.S. since the 1960s. To date, 31 states are either using, testing or planning projects using RMA but despite demonstrable performance and environmental benefits, extensive market adoption has yet to occur,” Sheerin said. “USTMA also has identified the use of scrap tire aggregate in roadside water infiltration galleries as a promising new market that repurposes scrap tires while protecting precious groundwater supplies.”

Niaura added that global adoption of sustainable practices is the biggest challenge facing the tire industry today. It will take partnerships across all aspects of the value chain to achieve material circularity.

“As we increase the recycled content of our tires with materials such as rice husk silica, recovered carbon black and recycled steel, another challenge will be the availability of materials at scale to support the industry at large,” Niaura said. “With the importance companies are placing on recycling end-of-life tires, recyclers must understand the needs of the rubber industry to establish a downstream market.”

For example, carbon black is a necessary reinforcing agent and filler in tires. According to Niaura, today, less than one percent of all carbon black used in new tire production globally is recovered. With that in mind, Bridgestone has made a minority investment in Delta Energy Group, a market leader in material recovery from end-of-life tires and a supplier of recovered carbon black to the company’s Americas business.

“Recovered carbon black (rCB) is a promising substitute for virgin carbon black (vCB) as it offers more sustainable performance with minimal tradeoffs,” Niaura said. “The process used by Delta-Energy Group to extract materials produces 81 percent less CO2 per ton as compared to traditional or vCB. Through this partnership, we were able to introduce the industry’s first at-scale use of rCB in the tire market in 2019.”

Kline added that, “Recycling companies are probably the best at keeping up with innovation, but as innovative solutions arise, all the stakeholders in the tire recycling system need to promote awareness of new solutions – for example, the excellent road properties of rubber modified asphalt, which need to be promoted to localities making paving decisions. This is why we favor scaling up the stakeholder approach to end-of-life tire market development: including all the players, educating on solutions and promoting research to fill data gaps.”

Published in the May  2022 Edition

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