Carbon Capture and Storage

Carbon Capture and Storage

How a promising technology for tackling climate change works — and why its deployment has been so slow

A. Carbon capture and storage, commonly abbreviated as CCS, is a cluster of technologies that capture carbon dioxide emissions from industrial or power generation processes, transport the captured CO₂ to a suitable location, and inject it into geological formations deep underground where it can be stored for geological timescales. The technology has been advocated by energy companies, some governments, and a number of climate scientists as an important component of any credible pathway to net-zero emissions — particularly for industries, such as cement and steel production, where CO₂ emissions arise from chemical processes that cannot easily be electrified or otherwise decarbonised. Critics argue that CCS has consistently failed to deliver on its promises and that continued investment in it diverts resources from genuinely transformative clean energy solutions.

B. The capture stage typically uses one of three approaches. Post-combustion capture applies chemical solvents — most commonly amine solutions — to flue gases after combustion, where they absorb CO₂ selectively and release it when heated, producing a concentrated stream ready for compression and transport. Pre-combustion capture converts fuel to hydrogen and CO₂ before combustion, removing the CO₂ before the fuel is burned. Oxyfuel combustion burns fuel in pure oxygen rather than air, producing a flue gas that is almost entirely CO₂ and water vapour, making separation straightforward. Each approach involves significant energy costs: post-combustion capture typically reduces the power output of a gas or coal plant by between 10 and 15 percent, a penalty that must be set against the reduction in emissions it achieves.

C. The most mature and commercially proven storage method involves injecting compressed CO₂ into porous geological formations — typically depleted oil and gas reservoirs or deep saline aquifers — at depths where the pressure and temperature conditions keep the CO₂ in a dense, supercritical state. The CO₂ is expected to remain stored over geological timescales through a combination of physical and chemical trapping mechanisms: initially confined beneath an impermeable cap rock, it gradually dissolves in formation water and eventually reacts with minerals to form stable solid carbonate compounds. The largest operational CCS projects — including the Sleipner facility in the Norwegian North Sea, operating since 1996, and the Quest project in Canada — have demonstrated that large-scale geological storage is technically feasible.

D. The deployment of CCS has been far slower than projections made in the 2000s and 2010s anticipated. Global CCS capacity in 2024 captures approximately 50 million tonnes of CO₂ per year — a small fraction of the two or three billion tonnes per year that the International Energy Agency estimates will be required by 2050 under net- zero scenarios. The barriers to faster deployment are primarily economic: the cost of capturing CO₂ from dilute sources such as power plant flue gas — typically between $50 and $150 per tonne — is too high for commercial operation without either a sufficiently high carbon price or direct government subsidy. Many CCS demonstration projects that attracted public funding in the 2010s were cancelled before construction began, and a number that did reach operation failed to achieve their design capture rates.

E. Direct air capture, which extracts CO₂ directly from the ambient atmosphere rather than from concentrated industrial sources, represents a more flexible but currently much more expensive variant of carbon capture. Because atmospheric CO₂ is present at only about 420 parts per million — far more dilute than the concentrations found in power plant flue gas — the energy required to separate it is substantially greater, and current costs typically exceed $400 per tonne of CO₂. Several small commercial direct air capture facilities are operating, primarily in Iceland and North America, and the technology is improving rapidly, but the scale of deployment required to make a material difference to atmospheric CO₂ concentrations — hundreds of millions of tonnes per year — would require enormous quantities of energy, land, and capital.

F. The future of CCS is closely tied to the evolution of carbon pricing and climate policy. In jurisdictions where carbon prices are high enough to make capture economically attractive — as has been the case in Norway since the early 1990s, where a carbon tax made the Sleipner project commercially viable — CCS has demonstrated sustained operation. The United States Inflation Reduction Act of 2022 substantially increased the tax credits available for geological CO₂ storage, triggering a significant increase in CCS project announcements. The degree to which these announced projects will actually be built and operated, and whether the technology can be deployed at the pace required by net-zero scenarios, remains one of the central uncertainties of climate policy.

G. The ethical and political dimensions of CCS are significant. Critics argue that continued investment in CCS — which is closely associated with the fossil fuel industry, since depleted oil and gas reservoirs provide the most commercially attractive storage locations — provides a justification for continued fossil fuel use that delays the transition to renewable energy. Supporters respond that CCS is essential for hard-to-abate sectors where no clean alternative currently exists, and that combining CCS with bioenergy — known as BECCS — could actually generate net negative emissions by removing carbon from the biosphere. The debate reflects a deeper disagreement about whether reducing emissions to near-zero requires radical systemic change or can be achieved by modifying the existing energy system with cleaner technologies.