Bio-Sourced Modified Asphalt Offers Emissions Reductions
Approved for funding in ERA’s Food, Farming, and Forestry Challenge in 2020, FPInnovations designed a project to accelerate the commercialization of a new lignin-based asphalt and demonstrate its feasibility under Canadian conditions. By its completion in 2023, the project’s six commercial demonstrations developed the lignin-based asphalt to reach commercial readiness.
Asphalt for roads is manufactured by binding aggregate with bitumen, a petroleum product. FPInnovations developed a modified asphalt formulation by substituting part of the bitumen use with lignin, a by-product of the pulp making process, sometimes known as natural wood glue. The process aims to reduce greenhouse gas (GHG) emissions by replacing some of the non-renewable, fossil-based bitumen with renewable, bio-sourced lignin from Canadian forests. To produce a lignin-based asphalt that is suitable for the Canadian paving industry all performance requirements of road owners and asphalt producers must be met. FPInnovations compared the constructability and performance of a lignin-asphalt pavement to that of unmodified pavements to quantify the cost and environmental advantages of the bio-product.
Lignin-Based Asphalt Field Validated and Commercially Ready, But Needs a Buyer
The project conducted field, lab, and accelerated pavement testing comparing conventional and lignin-modified asphalt test pavements. Field test locations included 140 meter, 215 meter, and 250 meter segments of road, respectively in Sturgeon County, Alberta, Thunder Bay, Ontario, and Quebec City, Quebec. Results confirmed that lignin-modified asphalt mixes can meet the technical performance requirements at substitution levels of up to 15 percent.
Six industrial-scale field demonstrations were completed across Canada, which showed the workability and performance of lignin-modified asphalt. The demonstrations validated the use of lignin-based asphalt under a range of paving applications such as different mixing methods, mix designs, and in batch or continuous asphalt plants. Monitoring these field demonstrations will last several years to assess performance under climatic variations; however, they have already proven lignin is a viable bio-based alternative to bitumen in road construction.
During the project, a life cycle assessment of lignin-modified asphalt has shown that the partial substitution of lignin has GHG reduction benefits from replacing bitumen and offers carbon sequestration benefits that can help the paving industry decarbonize, while still maintaining comparable performance to conventional bitumen-based asphalt.
What’s next?
The project’s commercial demonstration details have been widely communicated, and technical results of the project were published. During the project, communication with lignin, bitumen, and asphalt producers occurred to discuss the pathway to commercialization, including GHG reduction, packaging and storage considerations, methods for lignin addition into the asphalt making process, and evaluation of the necessary equipment upgrades. Future work on the LignoForceTM technology will focus on reducing production and operating costs.
An important change has occurred since the project begin that impacts future commercialization. The lignin for the project was sourced and processed at the Hinton Pulp Mill, which was purchased by Mondi in 2023. Mondi is currently in the process of investing in and upgrading the mill to streamline operations, making the future of lignin production, a tangential part of the business, uncertain. The ideal scenario for the technology would be for an to take over lignin production that is focused on the technology’s commercialization.
Furthermore, a specialized processing treatment facility will ultimately be required to scale up production of asphalt-ready lignin. This requires a business case with sufficient demand. To make this business case requires a large, sustainability-focused customer intent on implementing the technology, potentially as a green procurement initiative – but green procurement initiatives for road infrastructure are rare. This is a challenge for all technologies involving novel formations of structural materials like concrete and asphalt. Potential “customers” for a green procurement initiative like this could be in locations where the Lignoforce technology has already been piloted and de-risked. Going forward, the future of lignin-based asphalt is dependant on drive from the forest and asphalt industries for further commercialization and commercial availability of lignin. FPInnovations jointly developed a technology to produce high-quality lignin from black liquor. The LignoForce System can be used at kraft pulp mills and is available through NORAM Engineering.