Carbon Capture, Utilisation and Storage

Carbon capture, utilisation and storage (CCUS) mitigates industrial emissions by capturing carbon dioxide before it reaches the atmosphere and then using it or storing it underground. It is particularly relevant to process emissions, which arise from chemical transformations during manufacturing rather than merely from burning fuel. Its climate benefit depends on how much carbon dioxide is permanently prevented from entering the atmosphere after accounting for emissions from the entire CCUS chain.

Why industrial process emissions need carbon capture

Some industrial emissions cannot be eliminated simply by switching to renewable electricity because carbon dioxide is generated by the production chemistry itself.

• In cement manufacture, calcination converts limestone, calcium carbonate, into calcium oxide and releases carbon dioxide.
• Using cleaner energy can reduce emissions from supplying heat and electricity, but it does not directly eliminate carbon dioxide released by limestone decomposition.
• Capturing carbon dioxide from industrial exhaust gases can therefore address residual emissions that remain after energy efficiency, cleaner fuels and material-efficiency measures.

How capture, utilisation and storage work

CCUS links separation of carbon dioxide at an industrial facility with transport to a place where it can be used or stored.

• Capture separates carbon dioxide from gas streams, for example through absorption using chemical solvents; the captured gas is then compressed for transport.
• Carbon dioxide can be transported through pipelines or by other suitable modes to utilisation or storage sites.
• Utilisation uses captured carbon dioxide as an input for products such as chemicals, fuels or carbonated construction materials.
• Geological storage injects carbon dioxide into suitable deep underground formations, including saline formations and depleted oil and gas reservoirs.
• Site selection, effective sealing formations and monitoring are necessary to contain stored carbon dioxide and detect possible leakage.

What determines the actual climate benefit

Capturing carbon dioxide is not equivalent to permanently avoiding an equal quantity of emissions. Life-cycle assessment must consider capture efficiency, energy requirements, transport, product use and the permanence of storage.

• Capture and compression require additional energy, so the emissions associated with supplying that energy reduce the net mitigation benefit.
• Utilisation in fuels generally delays release because the carbon dioxide returns to the atmosphere when the fuel is burned.
• Utilisation through mineralisation can retain carbon dioxide in stable carbonates, whereas other products may store it only temporarily.
• Capturing fossil-based industrial emissions prevents releases but does not, by itself, remove carbon dioxide already in the atmosphere.
• Costs, transport infrastructure and access to suitable storage constrain deployment, making CCUS a complement to broader industrial decarbonisation rather than a substitute for it.