CCUS is the term for a group of technologies that remove carbon dioxide (CO2) from industrial and power plant emissions, transport it – most often by pipeline – and then securely store it.
Possible storage sites include depleted oil or gas fields, rocks containing unpotable saline water formations, or incidental storage in oilfields during enhanced oil recovery (EOR) operations.
Captured CO2 can also be used directly or as a feedstock in industrial or chemical processes, to produce valuable carbon-containing products. This can result in a portion of the CO2 being permanently stored – for example, in concrete that has been cured using CO2.
CO2 extraction and transportation uses well understood current technologies that have been used safely across the globe for many years. Storage sites are several kilometres underground and undergo stringent testing to ensure that they are geologically suitable. Combined with robust monitoring techniques and government regulation, these factors ensure that CCUS is safe.
In addition to careful and rigorous selection of sites, storage of CO2 in CCUS employs sophisticated techniques for monitoring the gas’s behaviour deep underground. On the surface, air and soil sampling can be used to detect potential CO2 leaks, while changes underground can be monitored by detecting sound (seismic), electromagnetic, gravity or density changes within the geological formations. Monitoring, reporting and verifying processes are used to ensure that the CO2 is safely and permanently stored.