By Amy Epps Martin and Edith Arambula
Ask just about anybody to name the most recycled material in America, and you’re likely to get some predictable responses: Aluminum cans. Plastic bottles. Glass bottles. Paper.
Each guess is logical. And each one is wrong.
That’s because 99% of reclaimed asphalt pavement is reintroduced in new or rebuilt roadways, making it the nation’s reuse champion. Rates for other materials pale in comparison: 60% for aluminum cans, 37% for plastic drink bottles, 31% for glass beverage bottles, and 56% for newsprint (all according to the U.S. Environmental Protection Agency).
The rapid growth we see in recycled pavements is dramatically outpacing consumer product recycling trends, which showed an increase of less than 1% in recent years, according to the EPA, due in part to a 3% drop in plastic bottle recycling in 2017. Reclaimed asphalt pavement use, on the other hand, is on the upswing, up 36% from only 10 years ago.
Of course, recyclers of asphalt pavement have an advantage over their consumer product counterparts. Construction industry players simply reclaim materials by scraping up old roadways. There’s no need to rely on the diligence of people who may or may not choose to participate in a community’s waste recycling program. Roadway recyclers seek out their product, while consumer product recyclers must wait for the product to come to them.
The surfaces we drive our cars and trucks upon every day consist mostly of aggregate (crushed rocks) to provide stability for heavy vehicle loads, and binder (asphalt made from petroleum) to serve as the glue that holds those rocks together. For most of our transportation history, we’ve relied upon virgin materials to build or rebuild streets and highways. But in recent years, there’s been a growing shift toward the use of reclaimed asphalt pavement.
It’s an idea that makes sense on three fronts: engineering, environmental and economic.
To justify their costly investment, roads need to last a long time, preferably a couple of decades or more. Our experience shows that roads containing recycled materials (which include roofing shingles that, like pavements, are made with asphalt and aggregates) can be just as durable and last just as long as those built with virgin materials.
Asphalt comes from petroleum, a finite resource. The same is true for aggregates; we can mine those materials from the earth for only so long. The more we can take advantage of available recycled pavements and shingles, the better job we can do as stewards of the only planet we have.
Building streets and highways is a costly endeavor, so even marginal savings per ton of material can add up quickly. The combined use of recycled pavements and shingles in road construction nationwide in 2017 produced savings of more than $2.2 billion, according to the National Asphalt Pavement Association.
About 76 million tons of ground-up pavement this year in the U.S. will displace the need for the same amount of virgin roadway materials. Pretty impressive, no question. But that’s still just a fraction of what’s possible.
State usage rates vary from about 10% to 35%, with the average calling for a mix involving 4 parts virgin material and 1 part recycled material. Double the amount of recycled materials in the mix, and you can double the associated cost savings, as well. That goal is within reach, but it has to be pursued carefully, since relying on too high a percentage of recycled materials can compromise the quality and life span of a roadway. There’s a need to hit a sweet spot where economics, engineering and environmental stars align.
When that ideal balance is achieved, we not only reduce our environmental impact, we save money. In Texas, those savings (combined for recycled asphalt and shingles) amounted to $98 million in 2017. To save even more, we’re limited only by our stockpiles and our ingenuity, both of which are abundant.
At the Texas A&M Transportation Institute, we’re conducting research that aims to drive reclaimed asphalt pavement use even higher, eventually doubling the current quantity without sacrificing quality.
You might never know whether the road you’re driving on is a recycled one. And if it’s built right, you wouldn’t be able to tell the difference.
Amy Epps Martin is a research engineer at the Texas A&M Transportation Institute.
Edith Arambula is an associate research engineer at the institute.
This article was originally published in the The Dallas Morning News, September 29, 2019.