Geo-engineering has been all the rage recently, and yesterday the UK-based Institution of Mechanical Engineers weighed in with their recommendations for how best to engineer the environment.

The report was a mix of the very specific and very vague. On the specific side, the panel recommended three technologies, which they believed represent the cheapest, quickest form of geo-engineering:

*Reflective roofs on buildings in order to cool urban areas (although the panel noted that this, technically doesn’t count as geoengineering, since it doesn’t actually involve changing the climate).

*Putting algae tanks on the side of buildings. The idea is that this algae would soak up carbon and could then be charred and sequestered.

*Finally came the suggestion that grabbed most of the headlines—fake trees. The trees are basically just carbon dioxide filters that are thousands of times more efficient than the real thing. 100,000 such trees would be able to remove all carbon from transport related CO2 emissions in the UK.

But the engineers were much more vague about how much such proposals might cost, or what their overall influence on carbon dioxide levels could be. This report is more a “case study of what needs to be done,” it says. Follow-up work could be done with £10-20 million from a UK contribution to an international research programme. The report comes just days ahead of a second, more comprehensive study by the Royal Society.