Ground rubber applications growing | Nantong Rail Clip Group Co.,Ltd

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For years, tire derived rubber has been used to manufacture numerous recycled rubber products. By mechanically shredding tires and then magnetically separating the steel from bead and tread wires, high quality rubber granules are liberated for further use.

According to John Sheerin, director of U.S. Tire Manufacturers Association’s (USTMA) End-of-Life Tire Programs, ground rubber applications have been growing recently, including mats of all types, loose fill and poured in place playground surfaces, landscaping mulch and infrastructure applications like sign bases, car stops, and weights.

The USTMA Scrap Tire Management Report for 2021 illustrates that ground rubber uses have increased. More specifically, the report shows that the ground rubber market increased by 29 percent since 2019, making it the largest scrap tire market, consuming roughly 28 percent of all scrap tires in the following areas:

Since scrap tire management is primarily the responsibility of state governments, Sheerin said it is important for states to have robust scrap tire management programs that generate revenue streams to fund research that develops and assesses existing and emerging markets and addresses scrap tire abatement. “USTMA continues to work closely with states to encourage the adoption of effective elements of state scrap tire programs identified in the our 2021 report document,” he said.

Bjornulf Ostvik, chief executive officer of Ecogensus, said the recycled rubber market is dominated by the recycled tires market (tires are already a separated waste stream.) The general consensus is that the generation of scrap tires (some 300 million tires per year in the U.S.) is outpacing the demand for recycled rubber.

“This, of course, has reverberating effects on other recovered rubber waste,” Ostvik said. “Historically, waste-to-energy applications represented a significant pathway for scrap tires but demand has been declining. There is increased focus now on asphalt and general roadway applications (e.g., as an aggregate), as well as other conventional applications such as playgrounds, running tracks, landscapes, and small projects such as decks, ramps and patios.”

An ongoing evolution

Although rubber recycling has been readily embraced by various industries over the years, rubber recycling has become more consistent and high-quality materials are now expected.

As Sheerin explained, mechanical shredding is the industry standard, but cryogenic grinding is also used to produce finely ground material.

“We have seen a shift towards ground rubber applications and away from what was historically the largest market – tire derived fuel,” Sheerin said. “This is because solid fuel combustion has been declining, while new and better ground rubber markets have grown. The mulch market has grown significantly, and the rubber modified asphalt market is poised for growth as well.”

With the passing of the Bipartisan Infrastructure Law (BIL), USTMA has been focused on expanding opportunities to grow scrap tire markets that offer sustainable infrastructure solutions. USTMA continues to support the use of scrap tires in rubber modified asphalt (RMA) and tire derived aggregate in civil engineering projects. In USTMA’s recent 2023 legislative priorities letter, the USTMA explained that RMA increases pavement service life and reduces road maintenance activities, leading to significant cost savings compared to traditional asphalt. It reduces CO2 emissions by 32 percent, lowering energy consumption over the lifetime of pavement as compared to traditional asphalt. RMA also provides performance and safety benefits by increasing skid resistance, reducing road noise and reducing road spray in wet conditions.

Given RMA’s proven economic, environmental and performance benefits, USTMA urged Congress to:

• IdentifyRMAasapreferredpavement material for federal projects;

• Support funding for research to further study RMA use benefits, including supplementing preliminary findings of reductions in environmental impact when using RMA.

The USTMA letter also addressed the use of Tire Derived Aggregate (TDA), large shreds of scrap tires that can be used as cost-effective infill material for roadside embankments, retaining walls and stormwater infiltration galleries.

As the USTMA pointed out, TDA reduces costs compared to traditional mined minerals like gravel, since the lightweight recycled material costs less to transport. “It provides improved drainage in stormwater infiltration galleries due to its larger void space compared to gravel, potentially capturing greater water volume with a smaller gallery footprint,” the legislative letter stated. “Studies show TDA use in infiltration galleries can reduce metals loading in stormwater. TDA used under railroad tracks also has proven effective and cost-efficient in mitigating ground vibrations from rail lines, a significant benefit to neighboring communities. For these compelling benefits, USTMA urges Congress to fund research and demonstration projects using TDA in federal, state and local construction projects.”

“The industry is doing great things on the innovation front, from tire production to scrap tire processing, manufacturers and recyclers are thinking about the entire life cycle of the tire,” Ostvik said. “In my opinion, there’s a gap between the state of technical innovation and realization in the marketplace. In recent years we’ve continued to see increases in scrap tire generation, but reports of increases in tire landfilling due to reduced demand for recycled rubber in conventional recycling pathways (e.g. tire-derived fuel). So tire manufacturing itself, and scrap tire processing, have evolved and improved dramatically, but the next frontier is in applications.”

“Rubber recycling technology may benefit from the widespread adoption of advanced chemical recycling,” Sheerin said. “One example is pyrolysis, the high heat decomposition of tires in the absence of oxygen. Pyrolysis can be used to produce reclaimed carbon black and tire pyrolysis oil which can then be circulated back into new tires. Closing the production loop to place old tire material back into new tires has tremendous environmental benefits and will change the tire industry in the future.”

Michael Lobsinger, vice president of operations at Eco-Flex, said his company has created an industry chaining sound barrier wall made of recycled rubber. This can be used by municipalities in the place of concrete and has better sound baffling than the alternative. It has the potential to recycle all used tires in North America if adopted. Eco-Flex also makes access mats, commercial, automotive, and equestrian products.

“We are seeing different processes used such as devulcanization and pyrolysis,” Lobsinger said. “There are some companies testing methods of creating new tires, from the crumb of used tires. There is always innovation taking place, such as I mentioned with our sound barrier wall. Also, consumers and governments are now seeing the importance of using recycled products and environmentally friendly alternatives driven largely by the ESG movement.”

Eco-Flex is always testing and creating new products. Each year the company brings two to three new products onto the market.

“With some of the challenges with logistics and the supply chain that we saw during COVID, many companies are looking locally to manufacturers instead of sourcing cheaply made products from China, Lobsinger said. “This is giving companies. such as ours, a greater opportunity to grab the market share for recycled products.”

While the tire manufacturing and scrap tire processing industries continue to innovate and make efficiency gains, Ostvik said the big focus is going to be on applications R&D. “That’s the exciting new frontier in rubber recycling. Long term, it’ll be innovations in advanced materials science that will enable optimal scrap tires and recycled rubber use – areas such as new sustainable and cost-effective TPE (thermoplastic elastomers) compounds and rubber depolymerization,” Ostvik said. “In the nearer term, there are a number of companies focusing on new applications ranging from bicycle tires to roadway projects to higher grade carbon black. There is increased awareness of potential safety issues related to consumer uses, which also acts as a driver to discover new applications.”

by MAURA [email protected]

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Published in the July 2023 Edition of American Recycler News

An ongoing evolution