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. 

The IEA recently examined the opportunity for CO₂ storage in three key regions: 

• The United States is the leader in global CCUS deployment, home to more than 60% of current CCUS capacity and around 50% of capacity under development.
• Europe is progressing significant CCUS development in the North Sea and around CCUS hubs. In September 2020 the Norwegian government committed USD 1.8 billion to the Longship CCS project, which includes the “Northern Lights” CO₂ transport and storage hub, and the UK government has announced GBP 1 billion to establish CCUS in four industrial regions.
• And in the People’s Republic of China, which accounts for around one-third of global emissions today, the 2060 carbon neutrality target announced in September 2020 is already providing a major push for CCUS.

Detailed geospatial analysis shows that around 70% of power and industrial emissions in China, Europe and the United States are within 100 km of potential storage. For comparison, in the United States, CO₂ captured at existing facilities is transported an average of 180 km via pipeline today.

The proximity of storage to emission sources, where feasible clustered around CCUS hubs with shared infrastructure, will be a crucial factor in reducing costs, decreasing infrastructure development times and enabling a rapid rollout of CCUS. 

The cost of CO₂ storage can vary greatly on a case-by-case basis, depending on the rate of CO₂ injection and the characteristics of the storage reservoirs, as well as their location.

The cost of onshore storage in the United States shows a large spread. However, more than half of onshore storage capacity is estimated to be available below USD 10/t CO₂.

In some cases, storage costs can even be negative if the CO₂ storage is associated with enhanced oil recovery, generating increased revenue from oil sales. 

New opportunities to use CO₂ in the production of fuels, chemicals and building materials are emerging and could play an important role in meeting climate goals. These opportunities are another tool in the climate toolbox, but are not an alternative to large-scale geological storage in net-zero pathways.

In a scenario with limited availability of CO₂ storage, CO₂ use within the energy system increases, but delivers less than 13% of the emissions reductions that would otherwise be provided by CO₂ storage. This reflects the fact that in most applications the CO₂ is ultimately emitted, for example when the fuel is combusted. By extension there is limited potential for CO₂ use to support carbon removal. 

IEA analysis highlights that billions of tonnes of CO₂ will need to be stored in a net-zero pathway, but this is dependent on identifying and developing the world’s vast geological storage resources.

While notional CO₂ storage volumes are vast, not all of this capacity will prove to be technically and commercially feasible. Most regions need significant further site characterisation and exploration to identify, assess and develop CO₂ storage resources so that the capacity is available when it is needed. The process of characterising and assessing CO₂ storage can be lengthy – up to ten years depending on existing data – underscoring the need for early action from government and industry.

CO₂ storage development will also need to be supported by robust legal and regulatory frameworks and improved public awareness and acceptance. The IEA will continue to work closely with industry and governments to share global experience and best practices for CO₂ storage development, with a new report on developing CO₂ storage resources to be published in 2021.