A typical road is filled with oil: A thick, sticky form of crude oil called bitumen holds together rocks and sand in asphalt. But in Norway, a startup called Carbon Crusher is recycling old roads with a plant-based binder instead. The approach shrinks the carbon footprint of road repair projects so much that the roads actually become carbon negative.
The process starts with recycling. Instead of trucking in new materials when a damaged stretch of asphalt needs repair, the company uses a machine that grinds up the top layer of the existing road. The equipment can also be used with concrete, another high-carbon material, as long as the concrete isn’t reinforced with steel. Then, the company uses lignin—a material in plants that’s a major byproduct of the paper industry—to glue the crushed material together. Because trees capture carbon from the atmosphere as they grow, embedding this material in the road actually sequesters that carbon. (Right now, the paper industry in Norway often burns lignin for energy, releasing CO2 emissions.)
“We’re making roads that are part of the solution to the climate crisis, not part of the problem,” says cofounder Haakon Brunell. “And it also happens to be a cheaper, more durable way of rehabilitating roads.”
A year ago, Brunell and cofounder Kristoffer Roil were searching for a high-impact way to reduce emissions, and considered dozens of different types of climate tech. They realized that roads were a somewhat overlooked area. “There hasn’t been much innovation, to speak of, since the Roman age,” Brunell says. The company cites a stat that the 40 million-plus miles of roads on the planet today emit around 400 million tons of CO2 a year in construction and maintenance. Brunell and Roil then connected with a third founder, Hans Arne Flåto, who had been using the same basic technology they’re using now to repave roads; the tech has been tested over the last decade in Norway. Together, they decided to help scale it up.
The company’s proprietary equipment crushes asphalt and rocks finely, so it’s possible to work without needing new materials; others also use equipment to “mill” existing roads, but typically need to haul in more aggregate. Because trucks don’t have to bring in more material or haul out pieces of the former road, the process is faster. And the lignin can help roads last longer, the company says.
Like other places with harsh winters, Norway’s climate is hard on roads, with cracks and bumps and potholes common as the ground repeatedly freezes and thaws. The standard binder, bitumen, “gets very stiff when we get some frost,” says Flåto. “It cracks up, and then they have to fix it and put new asphalt on. And then you have the same problem next year.” Lignin is more flexible, so a road can adjust more easily to the changing ground without cracking.
The start-up, part of the current cohort at the tech accelerator Y Combinator, is now scaling up operations outside of Norway, beginning with other parts of Europe. It’s also working on software that can track changes in roads via satellites, so it can proactively find highways and streets that need repair, and exploring other ways to improve roads, including adding inductive charging for electric vehicles. The team is also improving its equipment to make the process more efficient; future versions may be autonomous and able to run on hydrogen fuel, to lower the carbon footprint even further. “Today we take out around a ton of C02 from the atmosphere for every 60 feet of road,” says Brunell. “We want to increase that.”
While building new roads can increase emissions by adding traffic, the company is focused on repairing the roads that already exist. “The world doesn’t necessarily need new roads,” he says. “It needs better roads.”