This puts rubber modified asphalt (RMA), which uses ground rubber, squarely in the spotlight, a material that can be "stripped up and used again."
"It can circle back through the economy over and over again," Sheerin said.
But even as the ground rubber market grows, due in part to the Bipartisan Infrastructure Act passed earlier last year, the 15th biennial scrap tire report shows a 13-percent hike in scrap tire generation against a 6-percent increase in end markets.
And still there is optimism from the USTMA.
Only batteries and cardboard are recycled at a higher rate than scrap tires, which continue to find end uses at a higher rate than glass, plastic, aluminum, metal and paper, according to the USTMA.
"We see real opportunities for growth in the RMA sector, in part because of the provisions of the infrastructure and jobs act and in part because of the inflation reduction act—both of these pieces of legislation provide plenty of opportunities to work with the federal government to update specifications and open the markets to this material," Sheerin said.
As well, tire-derived aggregate (TDA) has gained considerable interest for use in civil engineering projects.
TDA, which is more coarsely cut from scrap tires than ground rubber (for RMA), is used as a cost-effective fill material in stormwater infiltration galleries, where it serves to clean stormwater.
"TDA can be used as a lightweight fill for retention or drainage systems," Sheerin said. "And (it can be used) as a filtration media in galleries, which can improve stormwater quality as it trickles through."
TDA has a larger void space, providing greater water volume capture when compared to gravel. This allows for flexibility in design of stormwater infiltration galleries without compromising stormwater capture capacity where space is limited, according to the USTMA.
TDA also can be used as weights along highway construction sites and as truck tire sidewalls, Sheerin said.
While ground rubber and TDF represented the majority of scrap tire dispositions from 2021 at about 56 percent combined, civil engineering accounted for about 6 percent, or about 276,000 tons of scrap tires, in 2021.