What Is Carbon Capture?

Carbon capture refers to technologies used to separate carbon dioxide  (CO2) from other gases such as nitrogen (N2) and oxygen (O2) in gas mixtures, and to concentrate it into an almost pure stream of carbon dioxide. Once CO2 is captured, it can be utilized in biological and industrial processes or stored permanently underground. These technologies are often referred to as Carbon Capture Utilization and Storage, also known as CCUS, in which the “CC” stands for carbon capture, “U” for utilization, and “S” for storage. The idea behind CCUS is to reduce CO2 released to the atmosphere to combat climate change.

There are two different types of carbon capture: point source capture and direct air capture (DAC). Point source capture collects carbon dioxide directly from its source, or from where the CO2 is emitted from, such as coal or natural gas power plants, cement plants, and steel plants. Direct air capture, like the name suggests, captures carbon dioxide directly from the atmosphere and is done after the carbon dioxide is already emitted.

After CO2 is captured, it must be transported, and then either used or stored, hence the “utilization” and “storage” parts of CCUS. CO2 can be transported in high-pressure gas form via pipelines or in low-temperature liquid form via ships, trains, and trucks. 

CO2 can be used in many biological and industrial processes. Our mother nature is performing this magic every day. For example, plants use CO2 to make hydrocarbons in the photosynthesis process and oysters use CO2 to build their shells. One major industrial usage of captured CO2 is enhanced oil recovery, or EOR, where CO2 is ejected into oil reservoirs to recover more oil. It can also be used in making chemicals, fuels, and other materials and products. CO2 can also be used to make beverages like sodas and sparkling water. 

In some usages, CO2 is released back to the atmosphere, like the moment you open a bottle of soda. It is better to store CO2 permanently, such as pumping into geological formations such as old, used-up oil and gas reservoirs. Inside geological formations, layers of impermeable rock and other barriers prevent stored CO2 from escaping, and it was estimated that carefully selected and controlled geological sites are likely to keep over 99% of stored CO2 over 1,000 years.

Carbon Capture Utilization and Storage, Source: Shutterstock