6.10 Carbon capture, utilisation and storage (CCUS)

This technology collects the CO₂ from fuel combustion in factories or power stations and either buries it deep underground (a process called sequestering) or uses it in other industrial processes.

There are many possible locations for sequestering the CO₂. One is in the many large, deep, saline aquifers (i.e. porous rock layers containing salty water) that lie beneath the Earth’s surface. It must be said that the large-scale deployment of this technology is still in its infancy.

One example is at the offshore Sleipner natural gas field, halfway between the UK and Norway and operated by the Norwegian company Equinor. The gas in the Sleipner field is ‘acid’, i.e. it has a high (natural) CO₂ content, which must be separated out in order to make the gas saleable. Sequestration is used rather than releasing it into the atmosphere in order to avoid payment of Norway’s national carbon emission tax. The CO₂ is buried in a saline aquifer, the Utsira formation, 800–1000 m beneath its North Sea production platform. Since 1996 the company has sequestered over 20 million tonnes of CO₂. Equinor has calculated that the Utsira formation alone might be used to store some 600 gigatonnes of CO₂, equivalent to more than 15 years of global anthropogenic CO₂ emissions.