The Guardian newspaper has carried an article on present efforts to spur negative carbon dioxide equivalent emissions around the world. Starting in the US, the article looks at the endeavours of the companies Carbon Engineering and Greyrock to pioneer industrial scale direct air capture, where carbon dioxide is sucked from the atmosphere and then mixed with hydrogen (produced from the electrolysis of water using renewable electricity) to produce a synthetic diesel for use in heavy transport. The process as a whole is known as “air to fuels”, and has been used at a small scale in the past, but the companies see commercial potential in employing the technologies at industrial scale, provided there is a price on carbon. They argue that the process is the “way of the future, because it needs 100 times less land and water than biofuels, and can be scaled up and sited anywhere.” Meanwhile, research at the UK Carbon Capture and Storage Research Centre at Sheffield University is focusing on developing fuels, solvents and operating conditions for carbon capture and storage in the particular context of biomass firing (as the UK is planning to phase out unabated coal firing). The director of the centre, Professor Jon Gibbins, told the Guardian “Direct air capture is no substitute for using conventional CCS. Cutting emissions from existing sources at the scale of millions of tonnes a year, to stop the CO2 getting into the air in the first place, is the first priority.” Others such as climate scientists Professor Kevin Anderson and Dr Glen Peters warn that counting on negative emissions technologies to help mitigate future climate change is a “high risk gamble”. In a recent article in Science magazine, they wrote “By the middle of the century, many of the models assume as much removal of CO2 from the atmosphere by negative emission technologies as is absorbed naturally today by all of the world’s oceans and plants combined.” The point is certainly a good one, yet their characterisation of negative emissions technologies as “Dr Strangelove” ones may be somewhat unfair.