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.