What is carbon dioxide (CO₂) capture and storage?
Carbon capture and storage (CCS) is a technique that could limit CO₂ emissions from human activities such as the burning of fossil fuels. CCS involves collecting, at its source, CO₂, which is produced by power generation and industrial activities, then storing it away for a long time (thousands of years) in underground geological formations.

What is the difference between storage and sequestration?
Sequestration is a general term used to conceptualize permanent separation of CO₂ from the environment. It may refer to sequestration achieved through forestry practices or to underground, geologic sequestration, for example. “Storage” as the “S” in CCS refers to geologic sequestration.

Why do we need CCS?
Fossil fuels will remain a major energy source for many years. As such, the pursuit of techniques and technologies to capture and store CO₂ could help, alongside other efforts, to stabilize and even reduce greenhouse gas emissions and fight climate change.

Where can CO₂ emissions be captured?
CO₂ could be captured from power plants or industrial facilities that emit large amounts of CO₂.

How is CO₂ captured?
There are a variety of systems and technologies available to capture CO₂, many of the technologies are currently being trialed in different parts of the world. Once captured, the CO₂ has to be purified and compressed for transportation and storage.

How is the captured CO₂ transported?
Some proposals for CCS have a provision to store the CO₂ directly under the source site. Where this is not the case, pipelines would mostly be used and indeed have been used for this purpose in the U.S. for many years. The CO₂ can also be compressed into a liquid form and transported in tankers.

How is the CO₂ stored?
Using many of the techniques already employed by the oil and gas industry, the compressed CO₂ can be injected into porous rock formations below the Earth’s surface. There are three main types of storage sites, oil and gas reservoirs, unminable coal beds and deep saline formations. The CO₂ can be trapped under a sealed rock layer, or in the pore spaces of rock.

How long can the CO₂ be stored for?
Proper site selection and use of technology will ensure that CO₂ can be stored indefinitely.