Geoengineering too expensive at $200 billion

I was over on this Next Big Future thread where Geoengineering came up. That’s the idea that, since we’re failing to reduce Co2 emissions by moving to clean coal, we may as well try and count the cost of other measures of fixing the climate. The ideas range from injecting sulfur dust 20km up into the stratosphere to cut a tiny bit of the incoming sunlight and save the climate, through to spreading Olivine across 5% of the land surface of the earth to suck up and safely lock away the Co2. The main problem? The cost! Both of these schemes would cost in the order of several hundred billion dollars a year, which should logically go straight into REAL solutions for global warming, such as moving to clean energy in the first place!

Engineer Poet contributed these thoughts.

The PDF says 0.5%, but more significantly it also claims “the sustainable removal of all CO2 produced will cost several hundred billion Euros annually”.

This needs to be compared to the cost of other measures.  A nuclear powerplant at €2000/kW (Nth of a kind, assuming a rationalized regulatory system) operating at 90% capacity factor displaces about 1 ton CO2 per MWH or about 7.9 million tons per 1 GW plant per year, ~470 million tons over a 60-year lifespan.  Investing €200 billion per year in nuclear powerplants would produce 100 GW of new plants per year, which would cut emissions by about 790 million tons/yr each year.  Ten years into a construction program at this pace, the net CO2 emissions from coal combustion would be cut by about 7.9 billion tons per year, roughly 1/3 of the total human emissions of 26.4 GT/yr.

This rate of production would quickly saturate the European, US and Japanese electric markets and require installations in nations far afield.  It would require less money (you’d be done after 30 years), require moving far less material, and have many knock-on effects such as radically reduced air pollution and improved balances of trade in the OECD.

I can’t figure out how long such a tiny particle would stay airborne, or whether that in itself is a health risk if people inhaled it, etc.

The big problems for human health are supposedly “PM10” (10μm) and smaller.  100μm is a tenth of a millimeter, small but naked-eye visible, and I doubt they would stay airborne long in anything less than gale-force winds.

I like the idea of crushing olivine to around 1 mm particles (far less energy-intensive than 100μm) and adding it to beaches where sand is desired; in other words, something somebody would probably pay for anyway.  The surface layer would weather to carbonates and wave action would continuously grind it off, exposing un-reacted olivine.  You could even transport it by barge or sailing ship.

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One Response to Geoengineering too expensive at $200 billion

  1. grlcowan says:

    I can’t figure out how long such a tiny particle would stay airborne … I doubt they would stay airborne long in anything less than gale-force winds.

    You guessed right, I think. The rule I use is the one for rise rate of small bubbles or sink rate of small sinkers. It works regardless of whether the surrounding fluid is a gas or a liquid:

    v = (2/9) g r^2 delta-rho / mu

    where ‘g’ is gravitational field strength — 9.8 m/s^2 for Earth surface, a lot more if you’re centrifuging — and delta ‘rho’ is the density difference between the fluid and the sinker or riser and
    ‘mu’ is the fluid viscosity.

    Maybe that doesn’t help much. Cutting to the chase, then, I find 100-micron olivine particles sink about 1 m/s in air, so if you make a conveyor belt that ends up launching a powder stream vertically into the sky at jetliner speed, and the stream is of such a diameter that the air it’s rising through picks it apart and stops it 5 km above the launch point, it then takes an hour or two to get back down. So with a suitably chosen location and at times when the prevailing winds are in fact prevailing, you get a deposition streak a few tens of km long.

    There’s a tradeoff between farther, more uniform distribution and, as you say, the energy cost of getting the particle size down. But at 25 microns that energy cost still is not exorbitant, and at this size the sink rate is 1/16th of a m/s, so the deposition plume length, from 5 km up, is the distance the wind goes in a day.

    I like the idea of crushing olivine to around 1 mm particles (far less energy-intensive …

    OK, but remember, this is for repairing hundreds of billions of tonnes of past CO2-dumping. It will take a lot — an affordable lot, but a lot — of surface area.

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