About CCUS

Today, CCUS facilities around the world have the capacity to capture more than 40 MtCO₂ each year. Some of these facilities have been operating since the 1970s and 1980s, when natural gas processing plants in the Val Verde area of Texas began supplying CO₂ to local oil producers for enhanced oil recovery operations.

Since these early projects, CCUS deployment has expanded to more regions and more applications. The first large-scale CO₂ capture and injection project with dedicated CO₂ storage and monitoring was commissioned at the Sleipner offshore gas facility in Norway in 1996. The project has now stored more than 20 MtCO₂ in a deep saline formation located around 1 km under the North Sea.

Stronger investment incentives and climate targets are building new momentum behind CCUS. The pipeline of planned projects is growing. Many of these plans involve the development of industrial “hubs” which capture CO₂ from a range of facilities with shared CO₂ transport and storage infrastructure. Examples include the Alberta Carbon Trunk Line in Canada, which started operating in 2020, and the planned Longship project in Norway.

CO₂ capture is an integral part of several industrial processes and, accordingly, technologies to separate or capture CO₂ from flue gas streams have been commercially available for many decades. The most advanced and widely adopted capture technologies are chemical absorption and physical separation; other technologies include membranes and looping cycles such as chemical looping or calcium looping. The various technologies are described futher below.

The availability of infrastructure to transport CO₂ safely and reliably is essential for deployment of CCUS. The two main options for the large-scale transport of CO₂ are via pipeline and ship, although for short distances and small volumes CO₂ can also be transported by truck or rail, albeit at higher cost per tonne of CO₂.

Pipelines are the cheapest way of transporting CO₂ in large quantities onshore and, depending on the distance and volumes, offshore. Transport by pipeline has been practised for many years and is already deployed at large scale. There is an extensive onshore CO₂ pipeline network in North America, with a combined length of more than 8 000 km.

While CO₂ is currently shipped in small quantities for use in the food and beverage industry, large-scale transportation of CO₂ by ship has not yet been demonstrated but would have similarities to the shipping of liquefied petroleum gas (LPG) and liquefied natural gas (LNG). Norway’s Longship CCS project will be the first to transport large quantities of CO₂ to an offshore CO₂ storage site.

CO₂ transportation by ship offers greater flexibility than pipelines, particularly where there is more than one offshore storage facility available to accept CO₂. The flexibility of shipping can also facilitate the initial development of CO₂ capture hubs (regional clusters), which could later be connected or converted into a more permanent pipeline network as CO₂ volumes grow. In some instances, shipping can be a cost-effective transport option, especially for long-distance transport, which might be needed for countries with limited domestic storage resources. 

CO₂ can be used as an input to a range of products and services. The potential applications for CO₂ use include direct use, where the CO₂ is not chemically altered (non-conversion), and the transformation of CO₂ to a useful product through chemical and biological processes (conversion).

Today arund 230 Mt of CO₂ are used globally each year, primarily to produce fertilisers (around 125 Mt/year) and for enhanced oil recovery (around 70-80 Mt/year). Other commercial uses of CO₂ include food and beverage production, cooling, water treatment and greenhouses. New CO₂ use pathways include: fuels (using carbon in CO₂ to convert hydrogen into a synthetic hydrocarbon fuel); chemicals (using carbon in CO₂ as an alternative to fossil fuels in the production of some chemicals); and building materials (using CO₂ in the production of building materials to replace water in concrete or as a raw material in its constituents.) Further detail can be found in the IEA report “Putting CO₂ to Use”. 

Storing CO₂ involves the injection of captured CO₂ into a deep underground geological reservoir of porous rock overlaid by an impermeable layer of rocks, which seals the reservoir and prevents the upward migration or “leakage” of CO₂ to the atmosphere. There are several types of reservoir suitable for CO₂ storage, with deep saline formations and depleted oil and gas reservoirs having the largest capacity. Deep saline formations are layers of porous and permeable rocks saturated with salty water (brine), which are widespread in both onshore and offshore sedimentary basins. Depleted oil and gas reservoirs are porous rock formations that have trapped crude oil or gas for millions of years before being extracted and which can similarly trap injected CO₂.

When CO₂ is injected into a reservoir, it flows through it, filling the pore space. The gas is usually compressed first to increase its density and the reservoir typically must be at depths greater than 800 metres to retain the CO₂ in a dense liquid-like state. The CO₂ is permanently trapped in the reservoir through several mechanisms: structural trapping by the seal, solubility trapping where the CO₂ dissolves in the  brine water, residual trapping where the CO₂ remains trapped in pore spaces between rocks, and mineral trapping where the CO₂ reacts with the reservoir rocks to form carbonate minerals (mineralisation). The nature and the type of the trapping mechanisms for reliable and effective CO₂ storage, which vary within and across the life of a site depending on geological conditions, are well-understood thanks to decades of experience in injecting CO₂ for EOR and dedicated storage.

CO₂ storage in basalts (igneous rocks) that have high concentrations of reactive chemicals is also possible, but is in an early stage of development. The injected CO₂ reacts with the chemical components to form stable minerals, trapping the CO₂.

Global CO₂ storage resources are considered to be well in excess of likely future requirements. In many regions, however, significant further assessment work is required to convert theoretical storage capacity into “bankable” storage to support CCUS investment. 

CCUS technologies can provide a means of removing CO₂ from the atmosphere, i.e. “negative emissions”, to offset emissions from sectors where reaching zero emissions may not be economically or technically feasible. There are two principal approaches:

Bioenergy with carbon capture and storage, or BECCS, involves capturing and permanently storing CO₂ from processes where biomass (which extracts CO₂ from the atmosphere as it grows) is burned to generate energy. A power station fuelled with biomass and equipped with CCUS is a type of BECCS technology, as are facilities that process biomass into biofuels, if the resulting CO₂ is captured and stored.

Direct air capture (DAC) involves the capture of CO₂ directly from ambient air (as opposed to a point source). The CO₂ can be used, for example as a climate-neutral CO₂ feedstock in synthetic fuels, or it can be permanently stored for carbon removal.

These technology-based approaches for carbon removal can complement and supplement nature-based solutions, such as afforestation and reforestation.

In the IEA Sustainable Development Scenario, in which global CO₂ emissions from the energy sector fall to zero on a net basis by 2070, CCUS accounts for nearly 15% of the cumulative reduction in emissions compared with the Stated Policies Scenario. The contribution of CCUS grows over time and extends to almost all parts of the global energy system. 

CCUS technologies play four strategic roles in the transition to net zero

CCUS can be retrofitted to existing power and industrial plants that could otherwise emit 600 billion tonnes of CO₂ over the next five decades – almost 17 years’ worth of current annual emissions.

In the Sustainable Development Scenario an initial focus of CCUS is on retrofitting fossil fuel-based power and industrial plants. By 2030, more than half of the CO₂ captured is from retrofitted existing assets.

CCUS can support a rapid scaling up of low-carbon hydrogen production to meet current and future demand from new applications in transport, industry and buildings. CCUS is one of the two main ways to produce low-carbon hydrogen.

Global hydrogen use in the Sustainable Development Scenario increases sevenfold to 520 megatonnes (Mt) by 2070. The majority of the growth in low-carbon hydrogen production is from water electrolysis using clean electricity, supported by 3 300 gigawatts (GW) of electrolysers (from less than 0.2 GW today). The remaining 40% of low-carbon hydrogen comes from fossil-based production that is equipped with CCUS, particularly in regions with access to low-cost fossil fuels and CO₂ storage.

Heavy industries account for almost 20% of global CO₂ emissions today. CCUS is virtually the only technology solution for deep emissions reductions from cement production. It is also the most cost-effective approach in many regions to curb emissions in iron and steel and chemicals manufacturing. Captured CO₂ is a critical part of the supply chain for synthetic fuels from CO₂ and hydrogen – one of a limited number of low-carbon options for long-distance transport, particularly aviation.

In the IEA’s Sustainable Development Scenario, CCUS accounts for between one quarter and two-thirds of the cumulative emissions reductions in heavy industry (cement, steel and chemicals production). By 2070, nearly half of global energy demand for aviation is met by synthetic fuels, requiring the capture of around 830 Mt of CO₂ for use as feedstock.

For emissions that cannot be avoided or reduced directly, CCUS underpins an important technological approach for removing carbon and delivering a net-zero energy system.

When net-zero emissions is reached in the Sustainable Development Scenario, 2.9 gigatonnes (Gt) of emissions remain, notably in the transport and industry sectors. These lingering emissions are offset by capturing CO₂ from bioenergy and the air and storing it.