Feature Report: Carbon Capture and Storage

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Carbon Transport and Storage

Once the carbon dioxide (CO2) has been captured (see Close-Up:" Carbon Capture"), it must be transported to a permanent storage site then injected below the Earth's surface. Proper precautions need to be taken to ensure that the CO2 remains buried for thousands of years.

Carbon Transport and Storage
An engineer supervises underground carbon storage in Ketzin, Germany. ©AFP PHOTO DDP - MICHAEL URBAN

Step 2: Transport the CO₂

Transporting co2See Carbon Dioxid is not technically complicated. It involves the same methods as for natural gas, which are generally well understood. There are two solutions:

It is important to bear in mind that transporting CO2 becomes unfeasible if the biggest emitters are located too far away from the storage sites.

Step 3: Store the CO₂

While some captured CO2 can be reused in the food and chemical industries, demand falls far short of what would be needed to effectively combat climate change. That is why it must be stored in suitable sites.

Three storage solutions currently interest experts:

The water found in deep aquifers is saline, making it unsuitable for drinking, agricultural or industrial use.

Indeed, it is currently thought that saline aquifers offer the greatest capacity, with the Intergovernmental Panel on Climate Change (IPCC)Body established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988... putting the figure at between 1,000 and 10,000 billion metric tons of CO2. Annual CO2 emissions from human activities, by comparison, amount to approximately 30 billion metric tons. To be useable, though, saline aquifers must be more than 800 meters below the Earth's surface and covered in layers of impermeable caprock strong enough to withstand the pressure of the gas for thousands of years. Consequently, the subsurface must undergo extensive testing.

It remains to be seen whether there is sufficient storage capacity of this kind in the regions of the world responsible for the most carbon emissions.

800 meters: the minimum depth below the earth's surface for storing CO₂