By Anna Barnes
Michigan may have a sustainable answer to the contentious issue of fixing its roads: asphalt made from recycled rubber tires.
A partnership among state regulators, Michigan Technological University and county road commissions has been looking for ways to reduce the piles of used tires around Michigan, said Kirsten Clemens, the scrap tire coordinator at the Department of Environment, Great Lakes and Energy. Run-off from these piles can contaminate water and are a breeding ground for mosquitoes that could carry harmful viruses
“We have a grant program that is not only for cleanup but is also for development of markets to reuse or recycle scrap tires,” Clemens said. “I think we started with rubber-modified asphalt in probably 1998, so we have been involved for quite some time.
There is a big potential for recycling scrap tires, she said. Her agency invested $2 million into scrap tire market development in 2023.
And there are a lot of tires to recycle. Michigan has about one scrap tire discarded per person each year, Clemens said.
“So in Michigan we’re at about 10 million scrap tires on an annual basis,” she said.
According to the state environment agency, road projects using rubber from scrap tires have been underway since 2005, but more recent partnerships with Michigan Tech helped move the projects in the right direction.
“They help with the design, getting the design correct for the location, and they’re also doing the scientific study of how the road is performing,” Clemens said.
Zhanping You, a Michigan Tech professor and member of the state’s Scrap Tire Advisory Committee, had also been looking to put scrap tires to use after noticing the piles on the Gulf Coast of Texas.
“What can I do to help those things?” You said he asked himself. “There are some ways we can deal with those tires. Basically, we started some lab research work.”
More than 100 road projects using recycled rubber have been completed with state assistance. Early projects used shredded tires, large in size and hard to use, Clemens said. More recent projects use micronized rubber powder, smaller and easier to work with, allowing the results to be more consistent.
“For all of the projects (using micronized rubber powder) we have been observing over the years, they are performing pretty well,” You said. They are “at least as good as the conventional roads we are building, but in a lot of cases they are better.”
Construction using this rubber-modified asphalt is more cost effective than conventional roads, if the roads last longer.
“Right now at current market [price], the rubber materials cost actually less than asphalt costs,” You said. “Even if your costs are the same, it’s still a really big gain for a rubber asphalt because you gain five years of life.”
Even if the rubber asphalt costs 5% to 10% more, the longer lifespan makes it a better investment, You said.
Earlier projects used rubber chip seal, epoxy resin, recycled aggregate of crushed glass and poly fiber crumb rubber. The rubber-modified asphalt now being tested seems to withstand Michigan’s weather longer.
Over 10 tire processors are creating an industry out of recycling the tires and making mulch, car parts, livestock arena footing and other products, Clemens said.
Muskegon applied for one of the grants for rubber roads. Joel Brookens, assistant city engineer of Muskegon, had to get approval from both state and federal highway agencies.
“If it had been a local, city-funded project, then it would have only required city commission approval,” Brookens said. “Getting federal highway approval can be challenging, especially for a local municipality that never deals with them.”
Once past these obstacles, Muskegon paved one lane on a five lane road for a half mile. The city may try the rubbery roads again after evaluating them, he said.
Rubber-modified asphalt use could spread to the rest of the country, Clemens said. Road work involving recycled tires is already happening in Illinois, California and Arizona.
Editors note: A name spelling was corrected in this story on Feb. 8, 2024.