Coming Soon: Plant-Based Roads

With all the attention focused on shifting from fossil fuels to renewables, there has been less emphasis on the hundreds of other products made from petroleum and finding substitutes for them. Some of the more common commodities are plastics, shoes, lubricants, paints, sports equipment, synthetic fibers for clothing, and building materials, including roofing.

One ubiquitous product is bitumen, a fossil-fuel-derived binder that holds asphalt aggregate together. A company in Norway is recycling old, damaged roads by using a plant-based binder instead of bitumen. Currently, it has applied this process only to repairing roads. Because Norway is far north, its roads suffer from repeated freeze-thaw cycles. The non-petroleum bioasphaltic binder it employs is lignin — a wood-based material essential to creating structure for trees and plants. The company utilizes a machine called the Carbon Crusher to grind up the top layer of damaged roads before applying the lignin to rebind the ground-up aggregate into a new, durable top layer. 

Approximately 18 billion tons of asphalt make up U.S. roads. All these roads need to be maintained. Asphalt is energy- and resource-intensive, contributing substantially to climate change. Lignin, one of the most abundant natural polymers, is an ideal substitute for crude oil bitumen. Because trees capture CO₂ as they grow, using lignin on roads sequesters carbon. This significantly shrinks the carbon impact, especially for road repair. When the road aggregate is recycled, as in Norway, the use of new material is avoided and their associated carbon emissions from production and transportation, often making the entire process carbon-negative.