Professional Engineering

A geo-engineering scheme in which thousands of machines are deployed to capture greenhouse gases from the atmosphere could succeed in cutting emissions where existing efforts have failed and should be urgently prioritised ahead of other ideas, the IMechE has said.

Dr Tim Fox, head of energy and climate change at the institution, said the organisation had ranked various geo-engineering schemes in terms of feasibility and environmental impact and that air capture of CO₂ by machines – such as the artificial “trees” proposed by US physicist Klaus Lackner – represented the most promising route forward. 

He told PE: “Currently from the institution’s point of view we see air capture as the best possible candidate for a geo-engineering approach, and that’s the one we would like to see significant funding for.”

Fox’s comments came in the wake of a paper on air capture produced by the IMechE that was circulated to officials at the Intergovernmental Panel on Climate Change’s recent meeting on geo-engineering in Lima, Peru. 

He said: “I think geo-engineering has been pretty much neglected by the IPCC as a possible approach to tackling climate change – they have been focused very much on adaptation and mitigation – but I think there’s clearly a growing recognition that some of the geo-engineering approaches are practical and technically feasible, particularly air capture.”

Air-capture schemes would suck CO₂ out of the atmosphere and sequester it in underground stores or recycle it for industrial processes. They are being developed by Lackner, Canadian climate scientist Professor David Keith, and Professor Aldo Steinfeld of science and technology university ETH Zurich. But a pilot plant has yet to be developed and the ideas have only been tested at laboratory level. Fox said: “It’s only through a pilot plant that the engineering can be proved.”

Air-capture machines have the advantage that they could be deployed anywhere, perhaps in areas with renewable energy to power them. They could account for emissions not amenable to mitigation, such as from aircraft, giving a net balance of “negative emissions”. The air-capture systems could also be used next to power stations where carbon capture and storage (CCS) technology is unsuitable. 

It is thought the machines could even help to establish a global price ceiling for carbon in the absence of a legally binding international agreement on cutting emissions, where polluters would have to pay for the carbon they emit, or invest in air capture. 

Fox said: “What that would do is encourage and accelerate the development of alternative ways of abating, whether that’s through CCS with coal, CCS with gas or cheaper wind turbines, solar and biofuels.” Developers of air-capture machines could be encouraged into the market and the price of carbon could drop with increased competition. 

Fox said: “The current problem is that the market is failing, and the reason the market is failing is that there is no legally binding international agreement on carbon emissions. So we’ve got to think radically.” For the idea to work, an international mandate would be required in which CO₂ was treated as a pollutant much in the manner of CFCs, Fox said.