A Norwegian startup is building carbon-negative roads.
Carbon Crusher combines recycled asphalt with plant-based glue to repair the blacktop instead of using traditional bitumen—a viscous form of petroleum that has a significant environmental impact and even continues to emit air pollution once in place on the road.
According to the company, the over 40-million miles of roads worldwide emit approximately 400 million tons of CO2 per year through both construction and maintenance. One study, published in 2019, reported that each kilometer of road produced around 65.8 kilograms of CO2 equivalent.
In addition to being more sustainable than traditional methods, Carbon Crusher says that its process is faster, more cost-effective, and even sequesters carbon once implemented. The company also believes that its road surfaces are more durable than others.
“We’re making roads that are part of the solution to the climate crisis, not part of the problem,” Carbon Crusher cofounder Haakon Brunell told Fast Company. “And it also happens to be a cheaper, more durable way of rehabilitating roads.”
Building carbon-negative roads out of… Old roads
When a road needs resurfacing, Carbon Crusher uses a heavy-duty machine to break up the existing, damaged top layer of the road. Once this material is sufficiently broken down, the company mixes through lignin, a class of complex organic polymers that make up the supporting tissue within plants. (It adds strength, stiffness, and waterproofing to the plant cell wall.)
Lignin, which is particularly important in trees’ wood and bark, is what enables these resurfaced roads to store carbon in the same way that plant life does. Furthermore, lignin is a common byproduct of paper production, and the Norwegian industry frequently burns it for energy.
So damaged roads get an extension to their useful life and virgin construction materials are avoided at the beginning stage. Then, high-impact bitumen is swapped for carbon-busting lignin, which would otherwise be burned and produce additional CO2 in the paper industry. It’s a neat, efficient, and sustainable example of the circular economy in action.
Carbon Crusher’s technology can also be used to repair concrete surfaces, providing they are not reinforced with steel. Overall, the construction industry accounts for approximately 38 percent of CO2 emissions. Repairing and reusing what already exists—from road surfaces to other materials to whole buildings—will likely be the only way to reduce the industry’s footprint sufficiently.
“The world doesn’t necessarily need new roads,” adds Brunell. “It needs better roads.”