Stockholm Exergi, the utility company supplying district heat to the city of Stockholm, made the commitment to become climate positive by 2025. The goal is to reach “negative emissions”, primarily by deploying BECCS (bioenergy with carbon capture and storage) at the large biomass–fueled combined heat and power plant (CHP) at Värtan in central Stockholm. This plant is one of the world’s largest, and it uses woodchips from Sweden and the whole Baltic region to supply the city of Stockholm with heat and power. Today, more than 800.000 inhabitants of Stockholm and around 400 locations (public buildings like hospitals + data centres) are connected to the district heating network.
This large CHP was inaugurated in 2016, and has a total capacity of 380 MW, with a biomass fuel use of over 2 TWh. The fuel is primarily forest residues, tops and branches, collected from felling and thinning operations and then transported to Stockholm either by train or boat. If left in the forest, these residues would decompose within a few years and release large amounts of carbon dioxide. Instead, they are being used to substitute fossil fuels. Stockholm Exergi closed down its last coal boiler in April 2020. This unit had not been used during the preceding winter due to relatively warm winter weather and low heat demand. From now on, the only fossil fuel used by Stockholm Exergi is the fossil plastics from municipal waste at two other heat plants.
In December 2019 a pilot unit for carbon capture was opened at the Värtan plant. After successful results, Stockholm Exergi is ready to invest in a full-scale installation (BECCS Stockholm) that captures 800.000 tons of carbon dioxide annually – creating a very large carbon sink. This unit can be up and running by 2025. Capacity for storage of this CO2 in the North Sea can be in place by 2024, according to Stockholm Exergi. This will include cooperation between Swedish and Norwegian actors. The project is funded with EUR 180 million from the European Union under the EU Innovation Fund.
New legislation and a governmental support scheme will be necessary to implement BECCS technology at such a large scale. A governmental study on how to make this possible was published in January 2020, and the reactions to the proposals have been positive. If implemented at all major Swedish biobased CHP plants and large pulp mills, BECCS could mean storage of up to 30 million tonnes per year of biogenic CO2 from Swedish sources. This is more than half of the total greenhouse gas emissions in Sweden today. Large-scale deployment of BECCS will be needed to reach ambitious climate targets by mid-century. The total cost will be EUR 60 – 100/tonne CO2, according to the Swedish study.
Besides BECCS at the Värtan plant, Stockholm Exergi will also produce bio-char to improve soils in parks and gardens and thus create additional carbon sinks. The company is also investing in improved technology for plastic recycling from municipal waste. These measures will also contribute to making Stockholm the first global city to have negative emissions – something truly positive for the climate!