The construction sector accounts for a quarter of CO₂ emissions, in Sweden and globally. Researchers from Chalmers University of Technology and the University of Gothenburg studied the construction of an 8km stretch of road in detail and calculated how much emissions can be reduced now and until 2045, looking at everything from materials choice, production technology, supply chains and transport.

The results indicate that it is technically possible to halve road construction CO₂ emissions with today's best available technologies and practices, to abate more than three-quarters of the emissions by 2030 and achieve close to net zero emissions by 2045. Realizing the current potential would rely on sufficient availability of sustainably produced second-generation biofuels, indicating a need to speed up the implementation of alternative abatement measures, including optimization of material use and mass handling requirements, increased recycling of steel, asphalt and aggregates and enhanced use of alternative binders in concrete. Policy measures and procurement strategies should be aligned to support these measures with a clear supply chain focus.

—Karlsson et al.

The 8km stretch of the Swedish highway 44 between Lidköping and Källby was finished in 2019. It was one of the Swedish Transport Agency’s first projects in which a complete climate calculation was made. All the materials and activities involved in its construction were calculated for their total climate impact: energy and materials used in the construction and what emissions these contribute to.

Estimated GHG emission, by category, from the construction of Road 44 in the benchmark case—i.e. before considering any measures to reduce emissions. Karlsson et al.

The climate calculation showed that the contractor was able to reduce emissions by 20% compared to the Swedish Transport Agency’s reference values. But the researchers also demonstrated that emissions could be halved with technology already available today—and completely eliminated by the year 2045. An open-access paper on the study is published in the journal Renewable and Sustainable Energy Reviews.

We identified several low hanging fruits, and if we address those first, it will become easier and cheaper to make bigger emission reductions in the future. We used the contractor Skanska’s climate calculation as an input for breaking down emissions by materials and activities and then analysed how much they could be reduced. What materials are used? How are they produced? What alternatives are available, and how might those alternatives develop until 2045?

—Ida Karlsson, PhD student at Chalmers, and participant in the Mistra Carbon Exit project

Summary graph of emissions reduction measures and potential to reduce CO₂ emissions at present and over time until 2045 in the Transformative scenario. Karlsson et al.

Ida Karlsson’s research is part of the project Mistra Carbon Exit, which focuses on transformative solutions. These require both time and large investments and include, for example, production of steel, cement, concrete and asphalt without carbon dioxide emissions, as well as fossil-free or electric vehicles. Solutions are being developed and implemented, but climate-saving technologies and choices exist already today. Ida Karlsson wants to highlight four of these:

• Transport optimization
• Recycling and reuse of excavation masses, asphalt and steel
• Material efficiency and design optimization
• Replacement of cement clinker as a binder in concrete

If you were to optimize the transportation of materials, excavation masses and waste, for example, large gains could be made. We could be better at transport logistics in Sweden. In addition to transporting materials and waste to and from a road construction site, many movements also take place within projects.

—Ida Karlsson

Resources

• Ida Karlsson, Johan Rootzén, Filip Johnsson (2020) “Reaching net-zero carbon emissions in construction supply chains – Analysis of a Swedish road construction project,” Renewable and Sustainable Energy Reviews, Volume 120, doi: 10.1016/j.rser.2019.109651