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Oxyfuel combustion of black liquor in Swedish recovery boilers

The pulp and paper industry can clearly contribute to achieving the Swedish adopted climate goals. The industry has great potential to capture biogenic carbon dioxide, which is a prerequisite for achieving negative emissions. Oxyfuel combustion is a technology that can lower the cost of BECCS while maintaining boiler performance at the mills.

To limit global warming to a maximum of 1.5 °C, measures in terms of negative emissions of carbon dioxide (CO2) are required. Negative emissions refer to the separation and permanent storage of CO2 of biogenic origin, shortened BECCS (bio-energy with carbon capture and storage). In Sweden, there are approximately seventy larger plants that each release over 100,000 tons of biogenic CO2 annually. Together, they contribute over 30 million tonnes of CO2 to the atmosphere, of which the largest emission sources are found in the paper and pulp industry. Sweden thus has particularly good conditions for creating negative net emissions of CO2 at these large point emission sources by implementing BECCS. Combustion of black liquor in the Swedish pulp and paper industry annually releases approx. 20 million tonnes of biogenic CO2 into the atmosphere. By implementing oxyfuel combustion in existing soda ash boilers, it would be possible to create negative net emissions of CO2 at these large point emission sources.

Oxyfuel combustion, which means that the combustion air is replaced with oxygen diluted with recirculated flue gases, results in a stream of easily accessible CO2. In recent years, oxyfuel combustion has gained a lot of interest due to the improved possibilities for simple and cheap CCS (Carbon Capture and Storage). An advantage of the technology is that it can be implemented in existing boilers. After conventional flue gas purification and condensation of water vapor, only a highly concentrated stream of CO2 remains, which can be compressed directly without further purification for further permanent storage. Oxyfuel combustion thus means that complicated, expensive, and energy-intensive CO2 capture steps can be completely avoided.

This project creates the conditions  to implement new industrial solutions within the pulp and paper industry, which in the long term can result in significant technological leaps towards drastically reduced Swedish emissions of greenhouse gases. The project's objective is to produce essential knowledge for future implementation. Since the melting chemistry in the soda boiler affects the entire mill's chemical recycling, the project involves increasing the understanding of important chemical engineering challenges and opportunities that need to be considered before conversion to oxyfuel combustion. Some of the project's concrete goals are to:

  • Carry out extensive experimental tests with black liquor under varying oxyfuel conditions
  • Develop a model that describes the complex chemistry in the soda boiler under different oxyfuel conditions
  • Estimate costs for future implementation of the oxyfuel concept at an existing Swedish soda boiler and calculate the potential for CO2 reduction from the same, assuming a maintained steam production
  • Make the sapience available through scientific publications



Project name

Oxyfuel combustion of black liquor



RISE role in project


Project start


4 years

Total budget

6 665 600 SEK


Smurfit Kappa




Project members

Supports the UN sustainability goals

12. Responsible consumption and production
13. Climate action