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Post by eclipse on Dec 1, 2012 11:39:14 GMT 9.5
Hi all, This geoengineering proposal is amazing and has less of the side-effects of the 'Sulfur Shield' used to block incoming sunlight, which could shut down the Indian Monsoons, hurt the ozone layer, and potentially bleach the sky white. It also has less plastic sheeting spread around all the world's deserts than the 'desert shield'. Instead, it's just spreading some dust around each year. Lots of it. It's spreading olivine across 5% of the land surface of this planet! 1/20th of the land! AND it requires rain. tinyurl.com/bmxzaq6I like the fact that this would give jobs and money to developing countries: but my questions are many. FINANCIAL They've outlined the cost of grinding the olivine, but what about the whole picture: mining + grinding + transporting + spreading? How much extra Co2 would this operation emit? ENVIRONMENTAL 5% of the land in a RAINY area? Come on! That's just got to be bad news for farmers, or ecosystems, or prairies. A rainy area! That sounds like otherwise potentially arable land getting a mass of trucks driven over it once a year. The main questions around this would be economic and political: who's going to pay, what's it going to cost to spread this dust around 5% of the surface area of the earth, and what effects would this dust have on the local environment? That's the main concern: finding suitable terrains to mine and disperse the olivine. Not damaging any more rainforests or endangered species! But if a suitable terrain was found, I imagine an olivine operation working like a clock. The mine is in the middle, and a series of conveyor belts carries the olivine out to trucks dispersing the dust in the 12 o'clock position. After a month, when that wedge of the dial is full, they move to 1 o'clock. They continue around the clock for a year, in which time the original olivine at 12 o'clock is fully 'weathered' and has taken up the Co2, and it starts all over again. There must be a few areas on earth like this where we don't have to move the olivine gravel *too* far to spread it. If this can happen, then climate change may not hit those horrifying tipping points we're all worried about. We may need a worldwide carbon tax to pay for the thing, and then once that's done we could just let the economic forces of peak oil, coal, and gas gradually take over the replacing of all our energy systems. |
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Post by edireland on Dec 1, 2012 19:10:01 GMT 9.5
Spreading the olivine would be horrifically expensive both in carbon dioxide and monetary terms.
The reaction works in the sea so how about simply dumping the powdered olivine into the sea and using the sea's surface as a carbon dioxide collector?
Reduing the acidity of the ocean back to preindustrial levels would cause it to soak up more and more of the atmospheric carbon dioxide.
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Post by eclipse on Dec 1, 2012 19:48:26 GMT 9.5
I'm no chemist, but I thought the reaction might have needed air and sunlight to trigger it? I don't know... anyone?
Mg2SiO4 + 4 CO2 + 4 H2O —> 2 Mg2+ + 4 HCO3
- + H4SiO4
I can't imagine these guys would have forgotten dumping it in the ocean as an option. After all, they mention using beaches and tidal areas. Does it need to be near the surface of the sea to work?
As the PDF said:
"Flexibility
To remove more CO2, one can use a larger surface area, make the olivine layer
thicker, or use also beaches and the high energy tidal zones. When olivine reacts
with sea water, the added alkalinity counteracts the danger of acidification of the
oceans."
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Post by edireland on Dec 1, 2012 20:41:44 GMT 9.5
I'm no chemist, but I thought the reaction might have needed air and sunlight to trigger it? I don't know... anyone? Finally a reason to use my expensive Chemistry degree!  Mg2SiO4 + 4 CO2 + 4 H2O —> 2 Mg2+ + 4 HCO3 - + H4SiO4 I can't imagine these guys would have forgotten dumping it in the ocean as an option. After all, they mention using beaches and tidal areas. Does it need to be near the surface of the sea to work? Well silicates tend to slowly undergo hydrolysis into silica and a variety of hydroxides when exposed to water under certain reaction conditions. (Indeed, portland cement is chiefly Calcium Silicate which hydrolyses into silica and calcium hydroxide) The reaction is very slow but with the hundred micron powder proposed by this paper I am pretty sure you should get measurable rates of reaction. Magnesium Hydroxide is almost totally insoluble in normal conditions but since the particles are very fine it is likely enough will dissolve rapidly enough to cause an equilibrium between the hydroxide and various acidic species (chiefly carbonic acid). It all depends on whether or not the powder can be suspended in the water column for significant periods of time prior to dropping out. They seem to mention the possibility of scattering the material in shallow oceans in the paper. One major concern may be ensuring that the material remains in the oceanic surface layer long enough to absorb large amounts of carbon dioxide. An alternative to using fields in the tropics may be to build nuclear power plants in various areas with lagoons into which rejected cooling water is dumped before being allowed to return to the sea. That would allow warm wet conditions to prevail at almost any latitude. |
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Post by grlcowan on Dec 2, 2012 5:21:58 GMT 9.5
This assumes the pulverized olivine isn't lofted 5 km into the air and distributed by the wind. My calculations for this latter option suggest the energy cost of this is about one-eighth of the energy that was yielded in putting the CO2 up, if a coal plant put it up.
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Post by eclipse on Dec 2, 2012 6:44:14 GMT 9.5
I'm loving the brainstorming here Mr Cowan, but of course every suggestion raises 20 questions. For instance, every ton of Co2 that goes out needs a ton of olivine dust. Would distributing via air create a health risk if local farmers and populations inhaled it?According to WHO silica dust is a major health hazard. www.ncbi.nlm.nih.gov/pmc/articles/PMC2395565/pdf/bullwho00439-0050.pdfHow far would the dust float? Would the wind distribute it evenly? Would it blow one direction predominantly, and end up burying a whole wheat crop? How would we test that it was being distributed in a cost-effective manner? As Wired magazine says: www.wired.com/wiredscience/2010/11/olivine-geoengineering/ |
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Post by David B. Benson on Dec 2, 2012 15:20:02 GMT 9.5
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Post by grlcowan on Dec 4, 2012 1:55:18 GMT 9.5
That RealClimate link works better this way: www.realclimate.org/?comments_popup=532#comment-87160Here are Schuiling and O. Tickell -- Tickell is quite poisonously antinuclear, so it's nice to find something we can agree on -- going on about some of the issues eclipse raises: Olivine against climate change and ocean acidification. Because olivine is the main component of the Earth's mantle and the main long-term natural CO2 sink, its chemistry is familiar to plant life, and the agricultural consequences of strewing it are not one-sided. |
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Post by eclipse on Jan 7, 2013 7:27:53 GMT 9.5
I was chatting about Olivine with a friend on the weekend and he suggested Australia having just one railway carriage devoted to dispersing Olivine along the edges of the tracks. It would just spray it out. The railway tracks and few meters of land either side of the rail is not going to suffer from a little Olivine dust. We'll switch the spray off when coming into a station or any other sensitive or inconvenient site. The carriage just sweeps around all of Australia's lines, and has one of those adjustable rail-gauge doovers underneath. Australia could probably do with just one carriage targeting seasonably appropriate States at the right time of year. I wish we had a real trainspotter here that could be obsessed enough to run the math of the world's train tracks and calculate an approximate annual dispersal. I'd love to know what the annual output would be just from this method alone. It was a brilliant idea anyway: the tracks are already there, the trains are already going that way, and it would probably only take 1 or 2 carriages to cover Australia's rail. Each continent could have their own few carriages travelling around as seasonably appropriate.
Also, with the big Aussie mining companies making so much dough here, and building some of our biggest railway lines, maybe they should pay for it hey?
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Post by anonposter on Jan 7, 2013 12:06:00 GMT 9.5
According to Wikipedia there is 41 461 km of track in the three main gauges and if can spread the dust as a 10 m wide strip (assuming you drop it on the track and a bit more than 3 m to each side) then you get an area of ≈415 km 2 over all of Australia's railway lines. I don't think that even comes close to being enough. |
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Post by eclipse on Jan 7, 2013 12:20:19 GMT 9.5
So that's not going to cover Australia's Co2 emissions? Is it only a tiny fraction of Australia's emissions? I guess it's hard to measure how many km's of rail are in the world and work out how much is a viable dispersal method, but 415km2 is a good start when one considers that it's just an extra carriage on a train that is going that way anyway.
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Post by anonposter on Jan 7, 2013 16:16:56 GMT 9.5
Australia has a lot of track relative to our population so it's even less likely to be effective elsewhere. Wikipedia's List of countries by rail transport network size gives a slightly different value to their article on Rail transport in Australia but the two figures are close enough to be believable (wouldn't surprise me if the difference is just the lines that have trees growing in the middle of the track). Whilst it probably wouldn't be too expensive, it also wouldn't be too effective either (and runs the same risk renewable energy does, i.e. diverting attention from things that might actually work). |
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