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Using lignin for greener asphalt

08 December 2020, 09:54

NCC and RISE Research Institutes of Sweden have commenced collaboration to test the renewable raw material lignin as a binding agent in asphalt. The project is part of the efforts to reduce emissions of greenhouse gases and dependence on fossil products.

- By replacing fossil raw materials with renewables, we will reduce greenhouse gas emissions from road construction and maintenance, while also broadening the range of raw materials for our end product. In this project, we see potential to reduce carbon emissions by up to 20 percent for finished asphalt and we are now set to test and evaluate this, says Robert Lundström, R&D manager NCC Industry.

The project uses lignin extracted from black liquor, a residual product from the pulp industry. Lignin is a domestic raw material that is available in large quantities, thereby facilitating a large-scale and cost-effective environmental initiative.

- The black liquor is processed, and the lignin is extracted at our demonstration facility in Bäckhammar, in Värmland. The facility collaborates with Nordic Paper. They send us the black liquor and then the filtrate is returned to them after processing. We ensure that NCC receives lignin of the right quality for mixing into the asphalt, says Maria Ölmhult, project manager at RISE.

The project is expected to continue for more than six years and comprises full-scale trials using various types of mixing methods in various volumes in the asphalt. In 2021, the finished asphalt will be laid on five different stretches of road in Värmland to evaluate its durability and function.

Since roads are in place and used for long periods of time, it is particularly important that evaluations and calculations encompass the asphalt’s complete lifecycle. In addition to looking at the raw material’s inherent properties, major importance is attached to the environmental impact when the asphalt is being laid and maintained, and its recycling possibilities.

- To enable us to make rational decisions in the transition to more renewable raw materials, it is important to eliminate risks of sub-optimization, meaning that the whole becomes poorer as a result of replacing the parts. We need to ensure that lignin does not result in higher net carbon emissions due to, for example, a shorter useful life, increased consumption or reduced recycling possibilities, says Robert Lundström, NCC Industry.

The project involves a number of different players. NCC is leading the project and is responsible for the field trials and laying the asphalt on behalf of Karlstad and Kristinehamn municipalities. RISE is contributing its knowledge of lignin, and the production and upscaling capacity of lignin for asphalt. In this, Wageningen University contributes with important experiences from previous work in the Netherlands with lignin in asphalt. The asphalt is produced at Karlstad asphalt plant. Production development is being conducted at LignoCity in Bäckhammar and the project is supported by the Development Fund of the Swedish Construction Industry (SBUF) and the Swedish Transport Administration.

For additional information, please contact:

Maria Ölmhult, project leader, RISE

+46 76 876 70 05