The capture and geological storage of CO2 is a process that consists of separating and recovering the CO2 from process gases or flue gases at large industrial installations, then transporting it and injecting it into a suitable underground formation for storage.

Of the three main steps involved in the process (i.e., capture, transport and storage), the first phase in which the CO2 is separated from the other constituents (mainly water vapor and nitrogen) of flue gases or other gas streams is by far the most costly, estimated by the IPCC  to amount to two-thirds of the overall cost.

Yet this step is crucial for at least two reasons:

• Combustion gases contain an average of 3 to 15% CO2, so removing the CO2 reduces the volume that must be transported, and therefore the associated costs;
• Only a limited number of formations meet the specifications for CO2 storage, so isolating the CO2 is a means of optimizing the available storage capacity.
  
  

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*IPCC: Intergovernmental Panel on Climate Change