CO2 capture and storage (CCS) involves collecting CO2 produced by using fossil fuels in power generation and industrial activities and then storing it away for a long time (thousands of years) in underground geological formations.
The major application for the CCS technology is in reducing CO2 emissions from power generation from fossil fuels, principally coal and gas. However, CCS can also be applied to industries that generate a lot of CO2 in manufacturing and chemical processes such as cement, iron and steel production, petrochemicals, oil and gas processing and others.
Once captured, the CO2 has to be purified and compressed for transportation and storage. The CO2 is then transported to a suitable geological formation where it is injected, with the aim of isolating it from the atmosphere for good. Sometimes it is possible to store the CO2 directly under the source site. Where this is not the case, pipelines will mostly be used. The CO2 can also be compressed into a liquid form and transported by ship or truck.
Using many of the techniques already employed by the oil and gas industry, the compressed CO2 can be injected into deep rock formations below the Earth’s surface. There are three main types of storage sites: oil and gas reservoirs, unmineable coal beds and deep saline formations. The CO2 can be trapped under a sealed rock layer, or in the pore spaces of rock (at least 800m deep in order for the correct pressure and temperature conditions to exist). The same natural trapping mechanisms have already kept huge volumes of oil, gas and CO2 underground for millions of years.