The Institute of Mechanical Engineers has called for the UK to adopt a strategy of "geo-engineering" techniques to extract huge quantities of carbon dioxide from the atmosphere.
The headline ideas are these: CO2-capturing "artificial trees", growing of biofuel algae on rooftops, and the use of reflective building materials to send solar energy back out of the atmosphere before it can cause global warming.
The IMechE report is called Geo-Engineering – Giving us time to act? In the introduction, it states bluntly that plans to reduce carbon emissions aren't working fast enough. It says that this is because of three things. First, green technologies such as efficient solar power "are still a significant way from being ready". Second, there is a lack of technically qualified people in the UK to take plans forward - specifically, it seems there aren't enough nuclear power specialists to build new nuke stations. Thirdly "and maybe most significant, markets around the world are simply not interested. Green energy is expensive".
The IMechE authors suggest that the only way for humanity to gain some breathing space before a disastrous temperature increase is to consider geo-engineering, the use of engineering on a planetary scale to remove CO2 or heat from the atmosphere. They offer three techniques which they say are the most promising ones.
First up is "artificial trees", essentially building- or goalpost-sized structures through which the wind blows. As air passes through them, the "trees" extract CO2 from it for later sequestration.
According to the report:
A unit based on current technology, the size of a standard shipping container, would capture about one tonne of CO2 per day or 365 tonnes annually ... However, it is conceivable that with further research ... a single unit with a larger collector would be able to capture as much as ten times more [in which case] 100,000 units would be sufficient to capture the whole of the UK's current emissions from non-stationary and dispersed sources [eg, those which it wouldn't be practical to capture at the source].
Or in other words, existing technology would require a million "trees" covering at least 15,000 acres of accessible land (or sea) to do a meaningful job, at an estimated fabrication cost (for landbased jobs) of US$20bn - say £12bn. And the trees are only 20 per cent of the cost of this plan - getting the CO2 out of them uses a third or so of the energy generated by burning the fuel in the first place, and then it has to be transported to an old oil or gas field and stuffed into the ground. The IMechE authors suggest that the "trees" actually be planted offshore among windfarms in the North Sea, so having a ready source of clean power and lots of old fossil fields close to hand - but this would increase costs, just as placing windfarms offshore does.