Thursday, June 19, 2008

Deep sea CO2

There have been a few articles in The Guardian about sending CO2 to the deep ocean. It has certain advantages over pumping it underground, and the fate of such CO2 is more complicated than I realised:

First, in order to ensure that the injected CO2 has adequate time to mix throughout the deep sea, injection should be at depths greater than 3,500 metres - that is, the depth below which "liquid" CO2 becomes more dense than sea water.

Experiments conducted by Peter Brewer, of the Monterey Bay Aquarium Research Institute, not only confirm that this is the case but also demonstrate that the CO2 injected rapidly reacts with sea water to form a solid clathrate, which is more dense than both liquid CO2 and sea water. Hence, the injected CO2 would end up on the sea floor as a slush. This would gradually dissolve, releasing the CO2 to the surrounding sea water, where it would react with the dissolved carbonate and borate ions to become chemically bound in the form of bicarbonate ion. As the concentration of carbonate and borate ions is small, the neutralisation would take place gradually as the CO2-rich sea water mixed into the surroundings.

But how much can you fit in the Pacific Ocean?:
Broecker says 480bn tonnes of carbon dioxide could be safely dumped directly into the waters of the deep Pacific, equivalent to the carbon pollution from about 16 years of the world's current fossil fuel use.
Not that much, really. And some say that it would increase the acidity of the deep ocean, which as we all know, may not be a great idea.

Just go back to nuclear sounds a much better option.

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