Swedish road and infrastructure operator Svevia aims to replace part of the oil-based binder with nature’s own binder – lignin. The lignin containing asphalt is currently being tested out on Swedish roads. Source: Timberbiz
Svevia is carrying out road paving work on road 224 between the towns of Sandbrink and Gnesta on behalf of the Swedish Transport Administration and is using Lineo by Stora Enso. Of the total 15-kilometre stretch, Svevia has chosen to test Lineo on a couple of hundred meters, where lignin will replace bitumen. Lignin was chosen as it is a bio-based natural binder found in trees with the potential of reducing the negative climate impact of asphalt.
“Asphalt consists of stone and bitumen, which is a product made from crude oil. If we can find something that can replace bitumen as a binder in the asphalt mass, our negative climate impact could be reduced dramatically,” Mattias Andersson, asphalt product specialist at Svevia said.
Svevia reviewed the lifecycle of the process from raw material to the paved road. In their production, the asphalt plants have switched to bio-based oil and use renewable electricity instead of fossil-based resources. Simultaneously, switching to renewable electricity is also underway in the quarries.
The industry still has developments to make in fully replacing bitumen.
“In the Netherlands, lignin has been mixed into asphalt since 2015, and is used in production. But even there, they have only succeeded in replacing bitumen in a limited amount.”
Lignin is a complex plant-derived polymer found in the cell walls of almost all dry-land plants. It binds cellulose and hemicellulose together, giving wood its stiffness, strength and resistance to rotting. Mattias Andersson believes that these are the properties that make it interesting for asphalt production.
“All players in the road industry need to take responsibility in the transition to sustainable development. We are constantly trying to find solutions that allow us to reduce our negative climate impact. At Svevia’s laboratory, we have tested different variants of, among other things, lignin, and when we presented an alternative that we believed in, the Swedish Transport Administration did not hesitate to let us test it on a stretch,” he said.
Svevia’s first lignin-based asphalt experiment was carried out in September 2020, already providing promising results.
“The surface looks good and homogeneous, it will be exciting to see what happens to the asphalt during winter, after snow removal and thawing brought on by spring. I think it will withstand these stresses and that we have something really good on the track,” Mr Andersson said.
Stora Enso’s lignin has also been tested in other asphalt projects with good results.