Climate and energy

In partnership with the Käppala Association, NCC is expanding the Käppala wastewater treatment plant on Lidingö in Stockholm. In addition to deploying various methods to minimize the overall need for concrete, NCC used a concrete mixture that includes slag, a waste product from steel production. By using concrete with less cement, the climate impact of the concrete in the project could be reduced by 28 percent versus conventional concrete. The use of slag in concrete has several benefits. When concrete with cement cures, it produces heat and must be cooled to prevent cracking. Concrete containing slag does not reach such high temperatures and therefore requires less cooling, at the same time as the risk of cracking is reduced. In addition, the concrete is stronger and better able to withstand the harsh environment of a wastewater treatment plant compared with conventional concrete. 

NCC’s asphalt laboratory southwest of Oslo has developed a new asphalt mixture that results in almost emissions-free asphalt, based on a lifecycle assessment. The first surface to be paved with the new asphalt was located in Kristiansand, in southern Norway. The 150-meter stretch of road is a pilot and a key milestone.  

The mixture replaces traditional fossil-based resin with wood oil derived from forest industry waste. Forests absorb carbon dioxide from the atmosphere, which is then stored in the wood material. When asphalt is laid, it binds carbon dioxide in the road surface.  

The tested asphalt uses 40 percent reclaimed asphalt pavement (RAP) and 60 percent new asphalt. The RAP contains some bitumen, which is included in climate calculations. The wood oil comes from pine trees and is a residual product from paper production. Average CO2e emissions per ton of asphalt produced is 44 kg (reference value, Norwegian Public Roads Administration, 2023). 90 tons of asphalt were used to pave the 150-meter-long stretch in Kristiansand, yielding a reduction of almost 7 tons of CO2e.