WASHINGTON — Tire-derived fuel (TDF) and rubber-modified asphalt are the key growth areas in tire recycling, according to John Sheerin, director, end-of-life tire programs at the U.S. Tire Manufacturers Association (USTMA).
But the paths of TDF and rubberized asphalt to market dominance haven't exactly been straightforward, Mr. Sheerin said in an interview connected with the 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 figures on scrap tire use vary from year to year, thanks to the vagaries of scrap tire generation, according to Mr. Sheerin.
In 2017, for example, 81.4 percent of the scrap tires generated in the U.S. reached end-use markets. This compares with 95 percent in 2013 and 87.9 percent in 2015.
But this decrease, Mr. Sheerin said, is due mostly to the constant increase in scrap tire generation. In 2017 it grew 4 percent, to 4.19 million tons, according to the report.
TDF was the largest market for scrap tires in 2017, accounting for 43 percent of the total, the report said. Economic factors have created a drop in TDF demand but also create promise for the future in that market, Mr. 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," Mr. Sheerin said. "The cement industry is using more TDF than ever before."
Similarly, changes in rubberized asphalt technology and within state highway departments are helping that material gain acceptance, according to Mr. Sheerin.
For decades, rubberized asphalt suffered a bad reputation because of the Intermodal Surface Transportation Efficiency Act (ISTEA) in the early 1990s.
A provision of ISTEA required states to use an ever-increasing amount of rubberized 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 The provision was repealed, and for years afterward most state highway departments were reluctant to use rubberized asphalt.
However, the situation has changed substantially, Mr. Sheerin said.
"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 rubberized asphalt because of ISTEA have either retired or are retiring, according to Mr. Sheerin. The engineers taking their place see that rubberized asphalt is longer-lasting, more economical and less prone to failure than conventional paving materials, he said.