This is a guest post. I concur with it. I can’t post the whole thing here because it is a little long. Please go to the website listed below and read the rest.
Green Roads Construction: Are Contractors Our Roadblock?
The buzz of innovative ideas on how to build cheaper, greener roads is all around us. These ideas range from using scrap construction materials and rubber tires to using recycled glass to reduce our reliance on asphalt. While these brainstorms are laudable, they’ve yet to prove themselves in a total life-cycle analysis.
The green construction practices that have a demonstrated track record can’t gain traction because of an archaic contractor bidding process. And herein lies the problem. A problem that we can no longer afford to ignore given the sheer cost and impact of our highway system.
“Our roads are everywhere. Anywhere you turn, you’re automatically on a road. We can’t get away from them. We step outside of our house and we’re on a road. If we go to a National Park, we take a road. People don’t realize this but [building roads] is one of the highest impact things we do.” – Shane Stathert, Think Green Roads
The need for lower impact roads is a pressing economic issue. Each year, we spend roughly 7 percent of our Gross Domestic Product (GDP) on transportation infrastructure. For fiscal year 2010, that amounted to nearly $1 trillion. A key input to these costs is the amount of asphalt we use. But the costs don’t end there.
A typical two-lane mile stretch of highway uses roughly 25,000 tons of crushed stone, which is what makes aggregate (the base layer for roads) one of the most mined materials in the world. Then there’s the CO2 emissions. The 32,300 lane miles of road the United States paves every year emits millions of tons of CO2. Here’s a conservative estimate.
Constructing a single-lane mile of road emits 1,200 tons of CO2. If we assume every mile of road built is single-laned (yeah right, not in America) then building our roads emits 38,760,000 tons of CO2 every year. That’s the same as the annual energy use of 6 million homes. Seriously, 6 million, stop and think about that for a second.
Needless to say, these exorbitant costs – both fiscal and environmental – left many in the industry wondering: how can we reduce expense and still maintain the quality of road construction? Thus, the green road construction movement was born.
Recycled Materials: A Reliable Aggregate Alternative?
With 94 percent of paved roads covered in asphalt, the first obvious target was determining how excessive use of asphalt could be reduced to minimize economic and environmental impacts. One idea that’s gaining a lot of attention in the green construction movement is the use of recycled materials for aggregate.
The logic is simple: pick a material with a good consistency that would normally sit in a landfill, grind it up and you’ve got an aggregate substitute or aggregate base. Popular fillers and aggregate replacements include rubber tires, roofing shingles and even glass.
Using recycled material for aggregate in this way not only saves money, but it also makes use of a material that would otherwise remain unused. A single lane mile of road constructed with rubber tires will use roughly 2,000 tires and save as much as $50,000. It also diverts rubber tires from landfills where they’d otherwise pile up and present a fire hazard or act as a breeding ground for disease-carrying mosquitoes.
But putting what would otherwise be considered trash into our roads raises a healthy amount of skepticism. What happens when the roads break apart? Is it safe for plastics, rubber and used construction material to be exposed to the elements? What if these wash into our water system?
There is a dearth of research on the environmental costs of using such recycled materials for aggregate or mixing them with asphalt. And using recycled rubber is one of the most promoted ways to green a road today. Both the Green Highway Partnership and National Asphalt Association tout recycled rubber as an environmentally safe and viable alternative.