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Carbon capture and storage
One of the most promising technologies for rapidly reducing global emissions has been identified as carbon capture and storage (CCS).
Is this a new idea?
Nature has been storing CO2 underground for millions of years. It’s often found with oil and gas. And for decades, Shell and other companies have injected CO2 into reservoirs to boost oil recovery. Some man-made CO2 is captured and used - for example, to put the fizz into soft drinks or to help tomatoes grow.
How is CO2 captured?
Industrial sites that burn fossil fuels such as power stations, steelworks and refineries are major emitters of CO2.
There are three ways to separate CO2 from the other gases:
- Using chemicals to absorb CO2 from chimney stack emissions.
- Or gasifying coal or biomass to produce “synthesis gas”, from which chemicals or special filters extract CO2.
- Or burning fossil fuels with pure oxygen produces a highly concentrated stream of CO2, which can be separated from impurities.
- Once the CO2 has been separated, it is then compressed and sent by pipeline or tanker to a long-term storage site.
Pipelines have carried CO2 for more than 40 years: over 5,000 kilometres of CO2 pipelines exist in the USA alone.
Where is CO2 stored?
Potential storage sites are carefully selected and monitored at every step. CO2 can be injected into depleted oil and gas reservoirs or saline formations, generally at depths of over a kilometre and where an impenetrable “cap” rock seals it in. Over time the CO2 will dissolve. Some CO2 will form minerals.