Kati Koponen is senior scientist at VTT Technical Research Centre of Finland. She’s among the authors of a report commissioned by the European Parliament's Committee on Industry, Research and Energy on the role of Direct Air Capture (DAC).

 

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What are the major carbon dioxide capture technologies currently in use worldwide – and what are their operating principles, key advantages and limitations?

 

Kati Koponen: Carbon dioxide (CO₂) capture technologies are chemical processes which allow capturing CO₂ from industrial sources or energy production. CO₂ can also be captured directly from the atmosphere.

 

The role of different carbon capture technologies for climate change mitigation varies: if fossil CO₂ is captured and stored permanently in geological formations, emission reductions can be achieved. If CO₂ is captured directly from the atmosphere or from bioenergy production and stored permanently, so-called permanent carbon dioxide removals, or negative emissions, can be created.

 

Permanent carbon dioxide removals are needed to supplement drastic emission reductions and natural carbon sinks in forests and soils, to achieve the Paris agreement’s targets for climate change mitigation.

 

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What is their level of technological maturity, and what are the key barriers to large-scale adoption?

 

Kati Koponen: The carbon capture and storage technologies have already been piloted, and in principle these technologies exist. However, it is uncertain whether they can be scaled up to industrial scale for removals of dozens or hundreds of megatons of CO₂ per year from the atmosphere.

 

The key limitation for bioenergy combined with carbon capture and storage (BECCS) is the availability of sustainable biomass resources. For example, use of biomass for bioenergy production should not simultaneously cause decreasing carbon sinks in forests or soils.

 

The key limitation for direct air capture and storage (DACCS) technologies is the significant energy consumption: as CO₂ in the atmosphere is in very low concentrations, significant amounts of energy is needed to capture it.

 

The technology also currently has very high costs. Furthermore, the capacity to store CO₂ permanently in geological formations is still very limited and should be rapidly scaled up.

 

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How do these technologies compare with natural carbon sinks – such as oceans, intact forests, and wetlands – in terms of their effectiveness at removing carbon from the atmosphere?

 

Kati Koponen: Both natural carbon sinks and engineered (or industrial) carbon removals will be needed to achieve the European and global targets for the climate change mitigation. The natural carbon sinks should be enhanced to increase the carbon uptake from the atmosphere. In addition, they should be continuously managed to prevent the release of the CO₂ back to the atmosphere e.g. through increased forest fires due to warming climate. Taking care of natural carbon sinks often enables also e.g. improved biodiversity, and soil quality.

 

The engineered carbon sinks through bioenergy combined with carbon capture and storage or direct air carbon capture and storage provide permanent carbon dioxide removals which are needed to compensate the remaining residual fossil emissions when aiming to durable net zero emissions.

 

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Once removed from the atmosphere, how is the captured carbon handled, and what long-term outcomes are envisioned for it?

 

Kati Koponen: To reach permanent carbon dioxide removals, the carbon captured needs to be stored permanently, e.g. in geological formations under the sea. Another option is to mineralise the CO₂ in rock, where it is permanently bound.

 

There is also the option to use the CO₂ captured for products, such as synthetic fuels or plastics. These products can have varying lifetimes, e.g. from zero year to decades, but they do not provide permanent carbon dioxide removals.

 

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What are the environmental impacts of these technologies, which are actually intended to help mitigate the climate crisis?

 

Kati Koponen: The key environmental impact for direct air capture technologies comes through the significant energy consumption. This can increase the demand for critical materials, needed for wind and solar power production. Some of the direct air capture technologies also demand water.

 

The environmental impacts of bioenergy combined with carbon capture and storage are mainly related to the utilisation of biomass. The biomass used for bioenergy can come from purposely grown bioenergy crops, or e.g. from forest industry or agricultural residues. The environmental impacts created, depend significantly on the biomass type used and can also vary depending on the location. The purposely grown bioenergy crops could require large land areas and irrigation. The direct use of forest biomass for bioenergy could decrease the carbon sinks in the forests.

 

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What are the main targets Europe has set for carbon dioxide removal, storage, and utilisation? How feasible are these targets, and to what extent are they likely to contribute to addressing the climate challenge?

 

Kati Koponen: The European Union has not yet set an official target for the carbon dioxide removals, but it is very likely that these technologies are needed to reach the net zero target set for year 2050 in the European Climate Law.

 

The European Commission has estimated in their modelling for the 2040 Climate Target Impact Assessment that -75 megaton (Mt) per year of engineered removals are needed by 2040, in addition to -310 Mt carbon sink in the land-use sector. However, currently there are no support schemes specifically for the carbon dioxide removal, but e.g. some EU Innovation Fund investment funds have been allocated to specific projects.

 

In addition, the Commission has established the so called CRCF framework for the voluntary certification of the carbon dioxide removals. During year 2026 the inclusion of BECCS and DACCS in the European Emission Trading System will be discussed.

 

Separate targets for permanent carbon dioxide removals together with dedicated support schemes or purchase programmes are likely needed to help to scale up the engineered carbon removals.

 

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