Tom Goreau is certainly correct that the scale of any whole ocean mitigation through this approach would require a huge effort -- an effort that is similar in scale to that of the global energy system.
Nevertheless, it might make sense in a possibly futile attempt to protect some isolated reefs in an enclosed bays. As an upper bound of an enclosed bay, let's consider the Mediterranean Sea. Looking up some old numbers, it seems as if the flow rate from the Atlantic into the Mediterranean is around 1.75 x 10^6 m3 / s (Pickard & Emergy, 1990 -- secondary source). (Incidentally, this source claims that the residence time of water in the Mediterranean is about 70 years.) If we assume that the excess CO2 to be neutralized is at a concentration of 60 umol/kg, this yields about 110 kmol / s. If we assume we need to dissolve one CaCO3 molecule per CO2 molecule at 100 g / molCaCO3, or about 11 tons CaCO3 / s. Since there are about 3 x 10^7 s / yr, this is about 3 x 10^8 tons CaCO3 (this might be a factor of two greater later this century). I am not sure what it would cost, but let's guess that it would cost something between $30 and $100 per ton CaCO3. Then, this means that "protecting" the Mediterranean would cost 10 to 30 billion dollars per year. (Given the approximate nature of this calculation, you can read the dollars and euros.) If we guess that there are around 300 million people living in the Mediterranean basin (a wild guess), then this would cost something like $30 to $100 per "Mediterranean" person per year. These are obviously just ballpark numbers. It does suggest that manipulations even at the scale of the Mediterranean are huge costly enterprises but not physically impossible. I will leave it to the reader to decide whether such actions are politically plausible. Best, Ken ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA +1 650 704 7212 [email protected] http://dge.stanford.edu/labs/caldeiralab @kencaldeira On Wed, May 11, 2011 at 4:07 AM, Thomas Goreau <[email protected]> wrote: > Thanks for sending this interesting New Scientist article on Greg Rau's > ocean alkalinization idea, Ron, but please use this email address! > > I've got a lot of respect for Greg Rau, but I doubt this proposal can help > on the scale needed for the reasons explained below. > > The aquarium tank metaphor has its limitations. Aquarium coral growers add > "kalkwasser" (chalk water in German) to their tanks. This is either > limestone shells dissolved in dilute acid to make a calcium bicarbonate > solution as he proposes, or better yet calcium hydroxide. This replaces the > the calcium lost from closed system tanks due to growth of coral skeletons, > and also raises the pH. It works fine in small tanks, but you can't change > the chemistry of the whole oceans as easily, it's just much too large and > the alkalinity added at any point will be rapidly diluted and neutralized > because the ocean is a pH buffered system! > > We do something quite different with our solar, wind, wave, or ocean > current powered Birorock electrolytic method by raising the pH directly at > the surface of growing limestone that we precipitate out of seawater. This > does not happen naturally, but we overcome the kinetic barriers that prevent > it even though it is thermodynamically favorable. This lets us grow corals > and oysters at record rates, which are more resistant to high temperatures > and other environmental stresses, even in acidic waters, without having to > change the chemistry of the entire ocean. > > Best wishes, > Tom > > Thomas J. Goreau, PhD > President, Global Coral Reef Alliance > President, Biorock International Corp. > Coordinator, United Nations Commission on Sustainable Development > Partnership in New Technologies for Small Island Developing States > 37 Pleasant Street, Cambridge MA 02139 > 617-864-4226 > [email protected] > http://www.globalcoral.org > > No one can change the past, every one can change the future > > > > --- On *Tue, 10/5/11, Ron Larson <[email protected]>* wrote: > > > From: Ron Larson <[email protected]> > Subject: Fighting ocean acidification the fish tank way - environment - 10 > May 2011 - New Scientist > To: "Tom Goreau" > Date: Tuesday, 10 May, 2011, 12:04 > > > http://www.newscientist.com/article/dn20461-fighting-ocean-acidification-the-fish-tank-way.html > > > Tom - > > I have been in a good bit of recent contact with Rau. Can you endorse > the limestone approach? > > Ron > > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
