Carbon capture and storage (CCS/CCUS): what it is and what it is for

Carbon capture and storage (CCS) is a set of technologies that capture CO2 from a source (an industrial flue or a power plant) or directly from the air, transport it and store it permanently in deep geological formations such as saline aquifers or depleted oil and gas fields.

When the use or valorisation of the captured CO2 is added to the process (for example in materials, synthetic fuels or chemicals), it is called CCUS (Carbon Capture, Utilisation and Storage). This is an important distinction: many of those uses only delay the re-emission of the CO2 and are not equivalent to permanent storage.

CCS/CCUS is proposed above all for emissions that are very hard to eliminate any other way, the so-called residual emissions of hard-to-abate sectors. It is not an alternative to reducing emissions, but a limited complement.

What CCS is and how it differs from CCUS

CCS aims to prevent CO2 from reaching the atmosphere by capturing it and storing it underground indefinitely. CCUS adds a third route alongside storage: putting the captured CO2 to use. Both share the capture stage but differ in the final destination of the gas.

The distinction is more than terminology. Well-managed geological storage retains CO2 for centuries, whereas many uses (for example incorporating it into a fuel that is later burned) return it to the atmosphere in a short time. That is why CCS/CCUS should not be confused with carbon removal or with emissions offsetting through carbon credits: capturing CO2 at a flue avoids a specific emission, which is different from taking historical CO2 out of the air or financing a reduction elsewhere.

How it works: the CCS chain

Carbon capture and storage is not a single technology but a chain of three links that must work in a coordinated way.

Geological storage uses porous formations at great depth sealed by layers of impermeable rock. These geological carbon sinks can retain CO2 stably for long periods, provided the site is selected, monitored and closed with the right safeguards. When the goal is definitive carbon storage, this is the route that offers the greatest permanence.

Capture technologies

Capture is the most technically demanding link and, by far, the most expensive in the chain. There are four main approaches.

Post-combustion capture with amines is the most mature option for retrofitting existing installations. Direct air capture, by contrast, does not depend on a specific flue, but is far more expensive because CO2 in the atmosphere is extraordinarily diluted.

The role in hard-to-abate sectors

The main argument for CCUS lies in hard-to-abate sectors, those that are difficult to decarbonise. In cement, iron and steel, and much of the chemical industry, a fraction of the CO2 does not come from burning fuel but is inherent to the process itself. The clearest case is the calcination of limestone to make cement: the chemical reaction releases CO2 even if the kiln ran on entirely clean energy.

In these processes, where electrifying or switching fuel does not eliminate all the emission, CCUS is one of the few routes available today for that fraction of the emissions. That is why it appears repeatedly in industrial roadmaps and in any heavy-industry decarbonisation strategy. Europe already has cement plants operating or building industrial-scale capture units, although they are still isolated cases.

It is worth framing it well: CCUS helps reduce the greenhouse gas emissions that are hardest to eliminate, but it does not replace efficiency, electrification or material change. It is one more piece within a broader plan, as covered in how to build and execute a decarbonisation plan.

The European Union framework

CCS/CCUS has gained prominence in EU climate policy, with two particularly relevant pieces of legislation.

The carbon removals certification framework (CRCF)

Regulation (EU) 2024/3012, of 27 November 2024, in force since 26 December 2024, establishes a Union certification framework for permanent carbon removals, carbon farming and carbon storage in products, known as the CRCF (Carbon Removal Certification Framework). It is a voluntary framework that sets quality criteria under the acronym QU.A.L.ITY: quantification, additionality, long-term storage and sustainability, with verification by independent certification bodies. Delegated Regulation (EU) 2026/285, of 3 February 2026, complements it by establishing the certification methodologies for permanent carbon removal activities.

The Net-Zero Industry Act (NZIA)

The Net-Zero Industry Act, Regulation (EU) 2024/1735, sets in its Article 20 the objective of reaching in the EU an annual CO2 injection capacity of at least 50 million tonnes by 2030. Its Article 23 also requires holders of oil and gas production authorisations to make an individual contribution to that target, calculated in proportion to their share of Union production between 2020 and 2023, in order to speed up the availability of sites.

These rules coexist with instruments such as the EU Emissions Trading System (EU ETS), which puts a price on each tonne emitted and improves the relative economics of capturing CO2 rather than releasing it.

Limits and criticisms

CCS/CCUS is useful, but it is not a silver bullet, and communicating it rigorously is essential to avoid inflated expectations. These are its main limits.

• High cost. This is the biggest challenge for CCUS. Capture is the largest cost component of the chain, especially in diluted sources such as power plants and cement.
• Energy consumption. Capturing and compressing CO2 requires additional energy, which weighs heavily on operating costs and erodes part of the climate benefit if that energy is not clean.
• Still limited deployment. Installed capacity worldwide remains modest compared with the volume of emissions that would need to be treated.
• Fossil lock-in risk. There is a danger of using CCS as an excuse not to reduce emissions and to prolong carbon-intensive infrastructure.
• The "U" does not always store. Using CO2 does not necessarily mean permanent storage; it is important to distinguish clearly which uses retain the carbon and which only delay its re-emission.

The actual pace of deployment calls for caution: high investment and operating costs have pushed many projects into delay or cancellation, and operating capacity lags far behind what decarbonisation scenarios assume. This is an important nuance: CCUS will be a necessary tool for certain emissions, but not the main lever of the transition.

The underlying conclusion is clear: CCS/CCUS complements but does not replace emission reductions. It makes sense above all for the residual emissions of hard-to-abate processes, within a decarbonisation pathway that prioritises cutting the carbon footprint at source. It is one piece of the path towards net zero emissions and climate neutrality, not a shortcut that allows emitting as before.

Frequently asked questions

What is the difference between CCS and CCUS?

CCS captures CO2 and stores it permanently underground. CCUS adds the use or valorisation of the captured CO2 (materials, fuels, chemicals). Many of those uses only delay re-emission, so they are not equivalent to permanent storage.

Does carbon capture replace reducing emissions?

No. CCS/CCUS is a limited complement, designed above all for the residual emissions of hard-to-abate sectors. The priority remains reducing emissions through efficiency, electrification and clean energy.

Which sectors is CCUS most useful for?

For hard-to-abate sectors such as cement, iron and steel, and chemicals, where part of the CO2 is inherent to the process (for example the calcination of limestone) and cannot be eliminated just by changing the energy source.

Is carbon capture expensive?

Yes, cost is its biggest challenge. Capture is the most expensive link in the chain, especially in diluted sources such as power plants or cement, and the energy the process consumes is a significant share of operating costs.

Before considering capture, what makes the difference is measuring and reducing: with Manglai you can calculate your carbon footprint by scope and build a reduction plan on traceable data.