In the journey towards a carbon-negative energy production, Sweden’s first bioenergy carbon capture and storage pilot plant was commissioned in 2019. This project is a part of Stockholm’s target towards a positive carbon footprint by 2040.
As early as 2018, the IPCC climate panel concluded that reducing CO2 emissions was not enough to meet the Paris agreement objectives. What was also needed, it said, was to cut the concentration of greenhouse gases in the atmosphere through ‘negative emissions’ or ‘carbon sinks’.
One method to remove greenhouse gases from the atmosphere is BECCS, or bio-CCS, which stands for bioenergy carbon capture and storage. This involves carbon dioxide from the combustion of biofuels being separated, compressed into liquid form and then stored deep underground. A pioneering BECCS project started in 2019 at the Värtaverket bio-cogeneration plant in Stockholm. With the support of the Swedish Energy Agency, municipal energy company Stockholm Exergi has installed a test facility that aims to establish the technology for separating carbon dioxide from flue gases. Värtaverket is among the first in the world to test this technology in an operating environment.
The bio-cogeneration plant in Värtan uses biofuel to produce district heating and electricity. The combustion provides biogenic CO2 that will ‘return’ to plants through photosynthesis, creating a climate-neutral cycle. Sweden has well-established infrastructure for biomass, so the prerequisites for a successful implementation of BECCS are already in place.
Using efficient HPC technology
The technology that Stockholm Exergi has chosen for the project in Värtahamnen is Hot Potassium Carbonate (HPC), also known as carbon scrubbing. HPC involves mixing inorganic compound potassium carbonate with a gas mixture, with the resulting liquid absorbing carbon dioxide through chemical processes. It has been assessed as the technology that best meets the requirements for a plant such as Värtaverket. This is because of the high energy efficiency, space requirements, high availability, scalability, environmental sustainability and the relatively low risk associated with the technology.
Cutting 800,000 tonnes of CO2
Stockholm Exergi’s calculations show the potential to capture up to 800,000 tonnes of carbon dioxide a year at Värtaverket’s CHP plant. Including Greater Stockholm and businesses, the potential is two million tonnes a year, which is roughly equivalent to the CO2 emissions from all road traffic in Stockholm.
The pilot plant at Värtan will likely be the largest of its kind in the world and showcases the potential to create carbon sinks through bioenergy carbon capture and storage.