Kate Mackenzie Slime: The friendly face of geo-engineering

The UK’s Institution of Mechanical Engineering says geo-engineering should be taken seriously as an interim step to reducing carbon emissions, rather than taking the  “plan B” role that the government seems to have assigned it.

But they’re not talking about shooting discs into the air to creating a solar shield, or sulfur-aerosol injections.

Fake trees, slime (okay, algae) piped around building exteriors and the now famous reflecting roofs could do the trick, the engineers say. 

One of the options they discuss is artificial trees, which would be thousands of times more effective at capturing CO2 than real trees. The trees are really a concept rather than a tested and mass-manufactured device, but the IME says about 100,000 of them would be enough to capture all the UK’s “non-stationary and dispersed” CO2 emissions, such as those from transport. At a cost of $20,000 per tree and a footprint of 12 metre shipping container per tree, this would require about 600 hectares… and $20bn. To look at it in a more positive light, however, Klaus Lackner, the scientist who designed these trees, told The Breakthrough Institute last year that he estimated they might be able to capture carbon dioxide at a cost of $30 a tonne – not out of the ballpark for market price estimates in another decade or two.

And the algae? Running it pipes around buildings is the IME’s suggestion (or photobioreactors, aka PBRs) would take care of both the large amounts of space required and the sun exposure for algae’s photosynthesis. As the algae grows, it harvests CO2; as it dies, the report says, it could be harvested for fuel before it begins to decay and release the CO2. They suggest a pyrolysis, which also create biochar – which both traps CO2 and acts as a fertiliser – as a byproduct.  The report cautions that the algae solution is “very much at a conceptual stage” and PBRs are too expensive to be commercially viable. But, they say, biofuel-based energy generation and biochar are well-understood, so they could scale up some day. And compared to space-based schemes, it could be a relatively cheap type of geo-engineering.

The report also suggests painting roofs as a way of reducing energy needs in cities, particularly in big cities where ‘urban heat islands’ raise the temperature by several degrees.  The paint, they say, wouldn’t even need to be a particular colour, and it could reduce energy needs by as much as 60 per cent; although the roofs would need to be kept very clean and regularly maintained.

So should geo-engineering be getting more of a look-in? Part of its problem is the term ranges from very proven and cost-effective measures that would require little more than some new regulations to somewhat alarming proposals that are far from proven as effective, let alone safe. But the IME argues that these three measures could fit into a 100-year abatement programme and help buy time, particularly up until 2050, while longer-term endeavours such as lower-emission transport systems, nuclear expansion and Europe-wide smart grids are introduced.

Related links:

Geo-engineering to get mainstream scientific support (FT Energy Source, 21/07/09)
Use slime to save planet, say engineers (FT, 27/08/09)