CCS

The technology involved in capturing and storage of CO₂ is often referred to as ‘CCS’, which stands for ‘Carbon Capture and Storage’.

Technology is available today to remove CO₂ from the flue gases of power stations, and research is being carried out to improve and develop new technology to separate the CO₂ from power stations more energy-efficiently. The technology involves the CO₂ being trapped at the power station and then compressed and transported in liquid form to a special subsoil storage facility. The compressed CO₂ will be transported in pipelines.

Storage
The subsoil storage of CO₂ must take place at locations with suitable geological conditions. In Denmark, this will typically be porous and permeable sandstone layers at depths of more than approximately 1,000 m. Storage at this depth means that the CO₂ will be in liquid form due to the higher pressure. The sandstone layers must form a structure where the injected CO₂ can be trapped in the porous layers. Above the sandstone layers, there must be a tight clay formation, which is impermeable to CO₂, so that the stored CO₂ cannot escape. Such optimal geological conditions for the storage of CO₂ exist in many parts of the Danish subsoil, both on land and offshore.

The layers and structures in the subsoil that can be used for CO₂ storage may also be used for other purposes, such as storing natural gas or geothermal heat. Consequently, prioritizing the use of the subsoil is necessary.

Injection to oil fields
Another possibility is to inject the CO₂ into the oil fields of the North Sea. This has the added benefit of enabling more oil to be produced from the fields, as the injection of CO₂ in an oil field can release more oil from the layers, oil that would not otherwise be recoverable. Some of the injected CO₂ will however be extracted together with the oil, and it is therefore necessary to separate this CO₂ from the oil and reinject it in the subsoil. This method is not yet being used in the oil fields of the North Sea, primarily because the method is considered to be very expensive, one reason being that it would require many new installations as well as modifications to existing installations in the North Sea.

Danish Subsoil Act
In April 2009, the EU adopted a Directive on the geological storage of carbon dioxide, the so-called CCS Directive. In the autumn of 2010, the DEA carried out a consultation process regarding a draft Bill to amend the Danish Subsoil Act, including proposed provisions to implement the provisions of the CCS Directive. In February 2011, the Minister for Climate and Energy presented a Bill in the Danish Parliament on an amendment of the Subsoil Act. The more technical aspects of the CCS Directive will be implemented into an executive order. The introduction of the Amendment Bill does not involve any decision on the use of CO₂ storage in Denmark. The Bill sets up a legal framework for the use of CO₂ storage in the event that it is decided to introduce this technology in Denmark. The proposed Bill was adopted by the Danish Parliament in May 2011, and an executive order was issued in July 2011 implementing the more technical aspects of the CCS Directive.