Carbon Direct conducts deep diligence for Microsoft’s offtake deal with Stockholm Exergi

Carbon Direct conducts deep diligence for Microsoft’s offtake deal with Stockholm Exergi

Carbon Direct conducts deep diligence for Microsoft’s offtake deal with Stockholm Exergi

Integrating carbon capture and storage with combined heat and power (CHP) in a groundbreaking bioenergy plant.

Focus Areas

  • Assessed energy efficiency with a life-cycle analysis (LCA) based on the heat and material balance of Stockholm Exergi’s BECCS project.

  • Analyzed financial additionality taking into consideration local government support, accounting for Sweden’s subsidies for bio-CCS facilities. 

  • Identified key risks and developed mitigation plans for a first-of-a-kind carbon dioxide removal project integrating power, district heating, and hot potassium carbonate capture technology.

In May of 2024, Microsoft signed a memorandum of understanding for up to 3.3 million tonnes of carbon dioxide removal with Stockholm Exergi, a Swedish energy utility developing a large bioenergy with carbon capture and storage (BECCS) project. The agreement represents the world’s largest permanent carbon dioxide removal deal to date and a milestone for climate change mitigation.

The Stockholm Exergi BECCS project involves adding carbon capture and storage (CCS) to an existing bioenergy facility that will yield 800,000 tonnes of permanent carbon dioxide removal per year. Stockholm Exergi plans to begin the construction of the CCS components in 2025, and begin delivering carbon dioxide removal credits to Microsoft in 2028.

"The agreement with Microsoft is a huge step forward for our BECCS project, Stockholm Exergi as a company, and the climate. It was made possible by collaboration with Carbon Direct and its deep technical diligence, bringing us one step closer to a final investment decision in Q4 2024."

Anders Egelrud
CEO, Stockholm Exergi

Image source:

Stockholm Exergi

Image source:

Stockholm Exergi

Carbon Direct Diligence

Microsoft selected Carbon Direct to conduct technical diligence to ensure that the project meets its strict quality requirements, outlined in the Criteria for High-Quality Carbon Dioxide Removal. This involved an in-depth analysis of the technical components of Stockholm Exergi’s BECCS process, including interviews with Exergi’s in-house project team and an additionality assessment taking into account local government support and Sweden’s subsidies for bio-CCS facilities. Carbon Direct’s scientific experts in industrial decarbonization then went beyond standard scientific diligence to include a risk assessment to determine economic feasibility and potential delivery risks. This process resulted in a near 100-page report with specific recommendations to mitigate risks and guide the advanced purchasing of the Stockholm Exergi BECCS project. 

“As an engineer, I am impressed by the technical sophistication and efficiency of the BECCS Stockholm design,” says A.J. Simon, Director of Industrial Decarbonization at Carbon Direct. “It is a first-of-a-kind project that demonstrates what is possible for both carbon management and energy utilization in a modern city with a net-zero goal.” 

Behind the Credit

How Stockholm Exergi removes carbon dioxide

Carbon dioxide removal with the biomass-fired Vartan KVV8 combined heat and power facility as a utility serving the city of Stockholm.


BECCS Stockholm is a first-of-a-kind carbon capture project separating carbon dioxide from combustion flue gas on a combined heat and power (CHP) plant. The captured CO2 is permanently stored in a geologic reservoir. Stockholm Exergi’s process builds on 40 years of using hot potassium carbonate to remove CO2 from gas. This technology also allows Stockholm Exergi to recover waste heat for district heating at very high efficiency as well as remove residual pollutants from combustion.

“Leveraging existing biomass power plants is a crucial first step to building the global carbon dioxide removal capacity that we need,” says Brian Marrs, Senior Director of Energy and Carbon Removal at Microsoft. “We are excited by the potential of Stockholm Exergi’s innovative and energy-efficient approach to carbon dioxide removal.” In addition to evaluating the industrial processes of the project, Carbon Direct worked with Microsoft and Stockholm Exergi to ensure the sustainable sourcing of biomass to power the facilities. For the facility in Sweden, this means using traceable residues from forests in northern Europe with strong regulatory oversight and environmental protections.

What’s next

Looking ahead, Stockholm Exergi will continue to build on the capabilities of biomass power plants in Sweden to expand carbon removal capacity in collaboration with Carbon Direct.

“Whether it’s engineered carbon dioxide removal or sustainable biomass sourcing, we know that we can go to Carbon Direct to answer any question on carbon dioxide removal,” says Brian Marrs, Senior Director of Energy and Carbon Removal at Microsoft. “They are the scientific experts that we trust to evaluate the highest-integrity carbon dioxide removal projects today.”

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