Could infusing asphalt with pulp mill waste reduce carbon emissions and potholes? Thunder Bay gives it a try

A stretch of road at Thunder Bay's Solid Waste and Recycling Facility, paved with asphalt infused with pulp mill waste is holding up as well as roads paved with a standard, more carbon intense, product.

That's according to the latest inspection by a team at Lakehead University that works in partnership with Pioneer Construction and FP Innovations, the forest industry research and development non-profit that's testing the product.

The team has been monitoring asphalt in which five per cent of the bitumen is replaced with lignin, a polymer contained in trees that binds the tree together and gives it its brown colour. 

"Based on the literature review and practically seeing [it], lignin modified asphalt has more resistance to the cracking," said Aseer Masnoon, a graduate student at Lakehead who is studying lignin-modified asphalt. 

"Virgin asphalt always has potholes. The literature review suggests that lignin-modified asphalt would have comparatively less potholes compared to virgin asphalt."

There are currently no potholes on either the lignin-modified stretch of road or the adjacent stretch paved with regular asphalt.

Lignin is a waste product of the pulp and paper process.  And researchers around the world have been racing to find ways to use it to create green alternatives to fossil fuel products like chemicals, resins and plastics. 

Finding markets for the material could create new revenue streams for the pulp and paper industry in places like northwestern Ontario. 

The federal and provincial governments have both invested heavily in Thunder Bay as a site of lignin research, supporting the installation of two pilot biorefineries at the Thunder Bay pulp mill –  which extract lignin from mill waste – and funding advanced research facilities at Lakehead.

It's been two years since the lignin-modified asphalt road went in in Thunder Bay, and since then, FP Innovations has paved roads in Quebec and British Columbia with asphalts containing lignin concentrations of 10 and 20 per cent respectively, said Peter Holt-Hindle, the supervisor of the non-profit's Thunder Bay operation.

"We're kind of working in baby steps here to see up to what substitution level we can get to. But this is one of the initial tests we did to prove that the technology works in real-world conditions."

On a hot day in late June, Masnoon and fellow graduate student Omotunde Adeniran walked the approximately 100-metre stretch of road, inspecting long cracks in the pavement, assessing the depth of depressions and measuring areas marked by "alligator cracks," clusters of short cracks jutting out in multiple directions in a manner that resemble the flesh of an alligator. 

The students compare the findings to previous years' measurements to determine how quickly the asphalt is degrading.

Despite the product's positive performance so far, buyers are still wary, said Fred Hakala, the general manager of Pioneer Construction, a partner in testing the product.