User:Clayoquot/CCUS Terminology

Terminology
The terms carbon capture and storage (CCS), carbon capture and utilization (CCU), and carbon capture, utilization, and storage (CCUS) are closely related. For these terms, "carbon capture" refers to a process in which carbon dioxide (CO2) is separated from the other components of industrial or power plant flue gas. Once a relatively pure stream of CO2 has been captured and compressed, it can be transported and put to use ("utilized") and/or sequestered ("stored").

Terminology in this area is often inconsistent and confusing. Some institutions use these terms more broadly or more narrowly than others.

The terms CCS, CCU, and CCUS often refer to the practice of capturing CO2 and using it for enhanced oil recovery, a process in which CO2 is injected into partially-depleted oil reservoirs in order to extract more oil and then is left underground. As of 2022, around 73% of the CO2 captured annually is used for EOR. EOR is both "utilization" and "storage", as the CO2 left underground is intended to be trapped indefinitely. Prior to 2013, this practice was primarily called CCS; since then the more valuable-sounding CCUS has gained popularity.

However, CCS or CCUS can also be used to refer to the process is of injecting CO2 into underground formations such as saline aquifers with the intention of having it be trapped indefinitely, without attempting to extract oil or gas. This process, called dedicated geological storage, is used for around 27% of the CO2 captured each year.

Around 1% of captured CO2 is used as a feedstock for making products such fertilizer, synthetic fuels, and plastics. These uses are referred to as CCU. In some cases, the product durably stores the carbon from the CO2 and thus is also considered to be a form of CCS or CCUS. In CCS, carbon storage must be long-term, therefore utilization of  CO2  to produce fertilizer, fuel, or chemicals is not CCS because these substances release CO2  when burned or consumed.