Utility-scale CCS has so far proved too expensive. Southern Co's project at a Mississippi coal plant in Kemper has been a sorry saga, running $4bn over budget and two years late. It will capture just 65pc of the emissions.

the UK is better placed than almost any other country to take the lead on CCS since it has storage sites in the North Sea and a nexus of pipelines already in place. Yet the government abandoned Britain's £1bn prize for twin projects in Scotland and North Yorkshire in 2105, citing budget costs.

While the abrupt decision caused uproar at the time, it may prove fortuitous if cheaper technologies emerge. "The most elegant solution is to disassemble the carbon molecule itself. We are not there yet," said Lord Browne of Madingley, former BP chief and now a champion of green energy causes.

NetPower is building a remarkable pilot project on the Texas Gulf coast with Exelon and Toshiba based on the Allam Cycle. Designed by British inventor Rodney Allam, it relies on supercritical oxy-combustion that captures C02 as part of the process - along with others gases - at zero net cost.