The cost of removing carbon dioxide directly from the atmosphere could be double previous estimates. Researchers from the university ETH Zurich also warn that the technology should not be treated as a substitute for carbon reduction policies.

Carbon removal is considered a possible solution to the problem of limiting global warming to within 2°C above pre-industrial levels. It could be particularly useful for sectors such as aviation and agriculture, which are particularly hard to abate using current technologies.

The researchers compared the potential costs of three direct air capture (DAC) technologies already in use. These included the method used by ETH spinoff Climeworks, as well as carbon capture using aqueous solutions and calcium oxide.

They estimate that the cost of removing one tonne of CO2 from the air will fall to between $230 and $540 by 2050 – nearly twice as high as previous estimates. None of the technologies studied have clear cost advantages over the others, but all three...