What is carbon capture and storage, and does it work?
Capturing carbon dioxide and putting it underground permanently. The technology demonstrably works; the contested questions are cost, scale, and whether its availability delays cutting emissions in the first place.
The three distinct things the term covers:
Point-source capture, taking CO₂ from a concentrated flue gas at a cement works, steel plant or power station — typically 5–15% CO₂, and comparatively tractable chemistry.
Direct air capture, pulling CO₂ from ordinary air at roughly 0.04%. Physics makes this far harder and far more expensive, because you must process enormous volumes of air for each tonne.
Storage, injecting CO₂ into deep geological formations — depleted oil and gas fields or saline aquifers — beneath impermeable cap rock, typically over 800 metres down where pressure keeps it dense.
What is genuinely established. Injection has been running at industrial scale since the 1990s, notably at Sleipner in the North Sea. Monitoring shows CO₂ stays where it is put, and over time some dissolves and some mineralises into rock, becoming progressively more secure.
The real objections:
Cost, which remains high per tonne, particularly for direct air capture, and has repeatedly disappointed projections.
Energy penalty. Capture consumes a substantial share of a plant's output, so more fuel must be burnt for the same useful energy.
Capture rates in operation have frequently fallen short of design figures.
Enhanced oil recovery. A large share of captured CO₂ historically went into pushing more oil out of the ground, which undercuts the climate case.
Moral hazard, the strongest argument — promised future capture has been used to justify continued emissions, and deployment has consistently lagged the promises.
Where it is genuinely needed. Cement and steel emit CO₂ from chemistry, not just fuel, so there is no efficiency route to zero. Most credible pathways also require some removal to offset residual emissions.
The honest summary: a necessary tool for a limited set of hard problems, not a substitute for decarbonising everything that can be decarbonised directly.