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The world has vast capacity to store CO2: Net zero means we’ll need it

Carbon capture, utilisation and storage (CCUS) will need to be a key pillar in successful clean energy transitions. It is the only group of technologies that contributes both to directly reducing emissions in critical economic sectors and to removing CO2 to balance emissions that cannot be avoided – a balance that is at the heart of net-zero emission goals.

CO2 storage is a crucial component of the CCUS value chain. While CO2 can be captured from a range of sources – including from fossil- and biomass-based power generation, industrial processes and directly from the air – permanently storing this CO2 is the essential enabler of large-scale emissions reductions. Technology-based approaches to removing carbon from the atmosphere, critically depend on CO2 storage for “negative emissions”.

In IEA analysis of net-zero pathways, the need for CO2 storage grows from around 40 Mt/year today to more than 5000 Mt/year by mid-century. Carbon management services – transporting and storing CO2 in large quantities – would become a global industry supporting emissions reductions across multiple parts of the energy system.  

CO2 can be stored in deep geological formations in a process that mimics how oil and gas have been trapped underground for millions of years. Captured CO2 is compressed and injected deep beneath the earth’s surface into a reservoir of porous rock located under an impermeable layer of rock (known as a cap-rock). This acts as a seal. The CO2 is prevented from migrating to the surface by the cap rock as well as other “trapping mechanisms” related to how the CO2 behaves in the subsurface. Several types of reservoir are suitable for CO2 storage, with deep saline formations and depleted oil and gas reservoirs having the largest capacity.

The first large-scale CO2 capture and injection project with dedicated CO2 storage and monitoring was commissioned at the Sleipner offshore gas field in Norway in 1996. The project has now stored more than 20 Mt of CO2 in a deep saline formation, equivalent to taking around 4.3 million passenger vehicles off the road for one year. A further project in Norway (Snøhvit) and projects in Canada (Quest), the United States (Illinois Industrial) and Australia (Gorgon) have increased storage capacity to around 8 Mt per year. Operators of oilfields use and incidentally store a further 34 Mt of CO2 through enhanced oil recovery.

Concerns that CO2 stored underground could leak has raised questions about the effectiveness of CCUS as a climate mitigation measure as well as potential safety risks. Decades of experience with large-scale CO2 storage have demonstrated that risks of leakage are small and can be managed effectively, but careful storage site selection and appraisal are critical, together with comprehensive CO2 monitoring systems.

High-level geological analysis suggest that the world has ample CO2 storage capacity. Using geospatial data on sedimentary thickness and other parameters, total global storage capacity has been estimated at between 8 000 Gt and 55 000 Gt. Even the lowest estimates far exceed the 220 Gt of CO2 that is stored over the period 2020‑2070 in the IEA Sustainable Development Scenario. The vast majority of the estimated capacity is onshore in deep saline formations and depleted oil and gas fields, but there is also significant offshore capacity, ranging from 2 000 Gt to 13 000 Gt.

Of course, not all potential storage capacity will be accessible or commercially viable. Factors such as land use constraints and public acceptance will determine where CO2 storage sites can be developed. Technical factors relating to the geology will also act as a constraint on ultimate capacity, for example the quality of the cap rock or the rate at which the CO2 can be injected. These and other factors must be carefully assessed as part of the site selection process.

The availability of storage differs considerably across regions, with the Russian Federation, North America and Africa holding the largest capacities. Substantial capacity is also thought to exist in Australia. Despite the stark regional variations in storage capacity, only a few countries might face a shortfall in domestic storage capacity over the period to 2070.