The price is wrong III
I made a booboo MCMLDXII^(XXII)

I just redid a calculation which suggests that fertilizing the ocean is a cost effective way to fight global warming and that I have made at least one arithmetic booboo (in this post or the one where I said it wasn't).

Basic points are

1) in some areas of the Ocean carbon fixation is limited by the availability of phosphorus (I read it somewhere on the web. In any case lack of minerals is certainly key in crystal clear equatorial waters)

2) Some Carbon fixed in the Ocean goes away effectively forever as sediment.

3) tossing Phosphate into some Oceanic areas will cause some Carbon to go away effectively forever.

4) C02 emissions credits in the EU cost a ton (about 20 euro per ton)

5) phosphate fertilizer doesn't cost very very much (although the price seems to have quadrupled recently).

So let me try the math again. First one mistake in an old post of mine was to look at the Stoichiometry of phytoplankton (if you ever look at the stoichiometry of phytoplankton don't come complaining to me that I didn't warn you). I should look at the stoichiometry of oceanic sediment -- that is basically the ratio of Carbon to phosphorus in oceanic sediment.

I read in a pdf somewhere on the web just now that it is 106/1 in moles
so equal to 106*44/95 tons of CO2 per ton of phosphate.

20 euros is about $30.

Phosphate costs about $400/tonne (the spelling convinces me that this too is a metric ton)

So $ 1 of Phosphate would end up fixing -$30*106*44/(95*400) worth of CO2 which is more than $3.50 !!!

so why did I calculate otherwise before ? I'm afraid that the price of "phosphate" isn't the price of, you know, P04 or even H2P04 but rather the price of the fertilizer farmers call phosphate which is only partly phosphate. I get phosphate rock (definitely not as rich in Phosphorus as "phosphate" "contains about 18 per cent P" so the formula becomes

$1 -> -$30*106*44*0.18/(31*400) > 1.5 still works (and calling phosphate rock "phosphate" is way cheating against it working).

Now spreading the stuff in the Ocean would cost money (and it better disolve and not just sink to the bottom so I should be pre-disolved and carried in a tanker) but it looks to me like there is a killing to be made in Ocean fertilizing IF the EU can be convinced to subsidize something which will make fertilizer cost still more than it currently does (of course the oceans will be fertilized by flying pigs long before that happens).