What is CCS?

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By Marie Hubschwerlen, Spinergie 

The energy sector is increasingly turning to carbon capture and storage (CCS) as part of ongoing efforts to accelerate decarbonization. CCS uses depleted oil and gas reservoirs as well as deep saline aquifers to store captured carbon dioxide (CO₂) beneath the seabed. 

What is the CCS process?

The CCS process captures CO₂ from industrial facilities and power plants, then transports it to a site where it can be permanently stored so it does not enter the atmosphere. CCS is particularly relevant for hard-to-abate sectors such as cement, steel, refining, chemicals and some power generation. 

It is a three-stage process: capture, transport and storage.

The aim is to prevent high levels of CO₂ emissions by separating the gas before it is released, then moving it to a secure storage site.

Stage 1: Capture

Capture is the first step of CCS. The goal is to separate CO₂ from the gases produced when fuel is burned or during industrial processes, so it can be transported and stored instead of released into the atmosphere. 

CO₂ is mainly applied at large industrial facilities, because they produce concentrated emissions. After CO₂ is separated from other gases, it is compressed into a dense fluid for transport to storage sites.

Stage 2: Transport

Transport is the second step in the CCS chain, between capture and storage. Its role is to move the captured CO₂ from industrial sources to the storage site, which may be located onshore or offshore in storage sites that are located beneath the seabed.

The most common method is through pipelines. CO₂ flows through steel pipelines under high pressure, with pumping stations maintaining the pressure. Pipelines are generally the most cost-effective option for large continuous volumes and rely on technology already well established in the oil and gas industry. Transportation through pipelines can be performed onshore and/or ashore.

The second main transport option is shipping. The CO₂ is cooled and liquefied, stored in insulated tanks and transported by specialized CO₂ carriers to the coastal terminal. It is more flexible.

Shipping is becoming increasingly important for European CCS networks, especially for cross-border transport. Historically, only a handful of small CO₂ carriers served niche markets such as food-grade CO₂ transport, but dedicated CCS shipping capacity is now being developed at scale. 

The first new ships specifically designed for CCS transport are now under construction, as Northern Lights* has ordered several 7,500 m³ CO₂ carriers, with the Northern Pioneer delivered in 2024.

*Learn more about the Northern Lights project in the case study below. 

Stage 3: Offshore storage

With CCS, CO₂ is injected into the storage site, which may be located onshore or offshore, generally using oil and gas fields.There are three primary methods of offshore CCS storage: enhanced oil recovery (EOR), brownfield and greenfield.

EOR: EOR sees captured CO₂ injected into oil reservoirs to help extract additional oil from mature fields. Some of the injected CO₂ remains underground. According to the International Energy Agency (IEA), about 80 Mt of CO₂ per year are currently used globally for EOR. 

Brownfield: Brownfield storage usually refers to projects that use depleted oil and gas reservoirs and may reuse or adapt parts of the existing infrastructure, such as platforms, pipelines or wells, where technically and economically feasible. 

Greenfield: Greenfield storage refers to a new CO₂ storage development built with new wells, transport infrastructure, injection facilities and monitoring systems. A good example is Northern Lights in Norway, a joint venture between Equinor, Shell and TotalEnergies that stores CO₂ in the Aurora saline aquifer offshore. 

What’s next for the CCS sector?

The North Sea is emerging as the leading basin for offshore CCS, with Norway and the UK at the forefront thanks to their offshore experience, storage potential and proximity to industrial emitters. 

Norway benefits from decades of offshore oil and gas experience and has several CCS projects in development, including Smeaheia and Polaris. The UK is following closely with multiple offshore storage projects, including Acorn, Net Zero Teesside, HyNet and Viking CCS. 

Outside of the North Sea, there is a large-scale project—Eni and Snam’s Ravenna CCS hub—in the Italian Adriatic. Meanwhile, in Australia, Chevron’s Gorgon project, which started up in 2019, is the world’s largest CCS system with ongoing optimization works.

Conclusion

CCS is emerging as a key technology in the global effort to reduce greenhouse-gas emissions, particularly for industries where decarbonization is difficult. By capturing CO₂ at its source, transporting through dedicated infrastructure and storing it safely underground, CCS offers a practical way to prevent large volumes of CO₂ from entering the atmosphere. 

The offshore sector is playing a central role in this development, leveraging decades of oil and gas expertise to transform depleted reservoirs and saline aquifers into long-term storage sites. As infrastructure expands and costs decrease, CCS is expected to become an increasingly important component of the global energy transition.