Rubber-modified asphalt a key growth area for tire recycling

Washington – Tire-derived fuel and rubber-modified asphalt are the key growth areas in tire recycling, according to John Sheerin, director, end-of-life tire programs, at the US Tire Manufacturers Association.

But the paths of TDF and rubberised asphalt to market dominance haven't exactly been straightforward, Sheerin said in an interview connected with the July 18 release of the USTMA's 2017 Scrap Tire Report, which records progress in scrap tire abatement and end-use up to that year.

"Added up, there's been a net decrease in TDF, but markets go up and down all the time," he said. "We're lucky to have multiple markets for TDF."

In fact, the very figures on scrap tire utilisation vary from year to year, thanks to the vagaries of scrap tire generation, according to Sheerin.

In 2017, for example, 81.4% of the scrap tires generated in the US reached end-use markets. This compares with 95% in 2013 and 87.9% in 2015.

But this decrease, Sheerin said, mostly is due to the constant increase in scrap tire generation. In 2017, it grew 4% to 4.19 million tonnes, according to the report.

TDF was the largest market for scrap tires in 2017, accounting for 43% of the total, the report said. Economic factors have created a drop in TDF demand, but also creates promise for the future in that market, Sheerin said.

TDF demand in the pulp and paper industry fell with decreasing demand from newspaper and magazine publishers, he said. In utilities, TDF must compete with low-cost natural gas.

On the other hand, the demand for TDF in cement kilns is growing steadily.

"Demand in the construction market has been very strong," Sheerin said. "The cement industry is using more TDF than ever before."

Similarly, changes in rubberised asphalt technology and within state highway departments are helping that material gain acceptance, according to Sheerin.

A provision of ISTEA required the states to use an ever-increasing amount of rubberised asphalt in their road projects as a condition of receiving federal funds.

However, a series of botched pilot projects turned highway officials against the material. The provision was repealed, and for years afterward most state highway departments were extremely reluctant to use rubberised asphalt.

Recently, though, the situation has changed substantially, according to Sheerin.

"Rubber-modified asphalt is different today," he said. "The technology has improved over the last 30-plus years, and there are multiple options—wet process, dry process, Arizona process."

As for state highway departments, the officials who turned against rubberised asphalt because of ISTEA have either retired or are retiring, according to Sheerin. The engineers taking their place see that rubberised asphalt is longer-lasting, more economical and less prone to failure than conventional paving materials, he said.

"The fresh new faces are seeing the changes in the technology, rather than saying, 'We tried that and it didn't work,' " Sheerin said.

Ground rubber was the second-largest market for scrap tires in 2017, at 25%, according to the report. Mats, garbage cans, flooring, landscaping and playground mulch remain the top end-uses in that area, along with rubberised asphalt, it said.

Playground mulch, along with athletic turf infill, has suffered in recent years because of environmental concerns, especially reports on NBC News in 2014 and 2015 that anecdotally connected crumb rubber on athletic fields with increased rates of cancer among young women athletes.

"The concerns that were around in 2015 have pretty much died down," he said.

Those concerns should become even more remote when the US Environmental Protection Agency and California's Office of Environmental Health Hazard Assessment complete their investigations of rubber athletic turf, according to Sheerin. Those studies should be completed in 2019, although they could be extended, he said.

The 2017 report shows that 37 states collect a fee on the sale of new tires to fund scrap tire abatement and market promotion for recycled rubber. Also according to the report:

Thirty states have stockpile clean-up programmes, 23 of which are active;

Thirty-eight states allow shredded tires in landfills, 24 states allow monofills, and 10 states allow whole tires in landfills;

Forty-four states have scrap tire storage and disposal regulations; and

Thirty-six states require financial assurance for scrap tire processors, 17 states require financial assurance for scrap tire haulers, and 36 states require haulers to have permits.

State scrap tire programs are "a bit of a mixed bag," according to Sheerin.

"Some states have very solid programs and are making good progress with markets and cleaning up stockpiles," he said. "Others are just diverting scrap tire funds for other purposes."

"New York has done a good job cleaning up its stockpiles," he said. "But its fee on new tire sales is the highest in the country—$2.50 per tire—and the funds aren't always used for scrap tire programs."

However, the basic message of the 2017 report is that only about 60 million stockpiled scrap tires remain in the US, according to Sheerin. That compares with more than 1 billion stockpiled tires that existed in 1991, the year the USTMA began its scrap tire program.

"Scrap tires have a higher use rate than almost any other commodity," he said. "Only automobile batteries have a higher use rate."

Michelin's plan to recycle 100% of its tires by 2048 and have 80% recycled content in its tires by the same year is very much the goal of the tire industry as a whole, according to Sheerin.

"Scrap tire recycling is an environmental success story," he said.