The basic point is that carbonate formation exacerbates ocean acidification.
You can write the formula for CaCO3 formation schematically as follows: CO2 + H2O + Ca2+ --> CaCO3 + 2 H+ More-or-less, you are taking the positive charge on the calcium ions and replacing them with protons, which brings down pH. More important than where the CO2 comes from is where the Ca2+ comes from. If it comes from dissolving silicate minerals instead of the ocean, then this can be made to work. Another way of looking at it is to say you need a weathering reaction to consume those protons _______________ Ken Caldeira Carnegie Institution for Science Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA +1 650 704 7212 [email protected] http://dge.stanford.edu/labs/caldeiralab @kencaldeira *Caldeira Lab is hiring postdoctoral researchers.* *http://dge.stanford.edu/labs/caldeiralab/Caldeira_employment.html* *Our YouTube videos* The Great Climate Experiment: How far can we push the planet?<http://www.youtube.com/watch?v=ce2OWROToAI> Special AGU lecture: Ocean Aciditication: Adaptive Challenge or Extinction Threat? <https://www.youtube.com/watch?v=Pfz2l29aX9c> More videos <http://www.youtube.com/user/CarnegieGlobEcology/videos> On Sun, Jan 6, 2013 at 6:17 AM, JohnDuke <[email protected]> wrote: > ** > But doesn't the question whether CaCO3 formation is a net source or sink > of atmospheric CO2 depend on where the bicarbonate comes from? > > If CO2(aq, recently from atm) + H20 --> H2CO3 --> HCO3- + H+ is the > source of the HCO3-, as at present in the Southern Ocean, then there is a > net sink of one carbon. As the equation below requires two bicarbonate > ions, 2C from atmosphere & 1C returns to atmosphere, there is a net sink of > one carbon. > > It seems a blanket statement that CaCO3 formation emits CO2 presumes an > infinite oceanic capacity to hold bicarbonate. Is that true? Doesn't > increasing bicarbonate eventually degrade the ocean's H+ buffering function? > > Some may consider ocean acidification to be a more existential threat than > greenhouse warming, in the unknown unknown category. > > > ----- Original Message ----- > > *From:* Ken Caldeira <[email protected]> > *To:* [email protected] > *Cc:* [email protected] ; [email protected] > *Sent:* Saturday, January 05, 2013 1:49 PM > *Subject:* Re: [geo] Geoengineering: rules needed for climate-altering > science - International institute for Strategic Studies > > Russell has his facts right but chemical implications wrong: > > The net reaction for the formation of CaCO3 shells can be written: > > Ca2+ + 2 HCO3- ===> CaCO3 + H2O + CO2 > > Thus the formation of carbonate minerals from sea water acts as a carbon > source to the atmosphere, not a sink. > > Greg Rau, among others, has proposed trying to run this reaction to the > left to sequester CO2. This is sometimes known as "Accelerated Carbonate > Weathering". > > http://crustal.usgs.gov/projects/CO2_sequestration/limestone.html > > > _______________ > Ken Caldeira > > Carnegie Institution for Science > Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > +1 650 704 7212 [email protected] > http://dge.stanford.edu/labs/caldeiralab @kencaldeira > > *Caldeira Lab is hiring postdoctoral researchers.* > *http://dge.stanford.edu/labs/caldeiralab/Caldeira_employment.html* > > *Our YouTube videos* > The Great Climate Experiment: How far can we push the > planet?<http://www.youtube.com/watch?v=ce2OWROToAI> > > Special AGU lecture: Ocean Aciditication: Adaptive Challenge or > Extinction Threat? <https://www.youtube.com/watch?v=Pfz2l29aX9c> > More videos <http://www.youtube.com/user/CarnegieGlobEcology/videos> > > > On Sat, Jan 5, 2013 at 10:12 AM, Russell Seitz <[email protected]>wrote: > >> Given the proximity of so many of ISIS proncipal to Chesapeake Bay, I am >> shocked they have not hit on the opportunity to combine the Beltway's lust >> to regulate with the best features of carbon capture and SRM. >> >> The key to this win-win-win strategem is the humble mollusc* Ostrea >> edulis.* >> * >> * >> A dozen oysters sequester a hundred grams or more of carbon in their >> shells, and were the daily consumption of a dozen made mandatory, their >> removal from the sea would make room for the sequestration of a hundred >> grams more. In addition, discarding the shells on land would at once take >> a bite out of sea level rise, and, as ouster shells are pearly white , tend >> to reduce the albedo footprint of those consuming them, especially if they >> toss them on their asphalt coated roofs, parking lots and driveways to >> reduce the energy toll and radiative forcing burden of the urban heat >> island effect . >> >> Confident that perfoming the dimensional analysis necessary to persuade >> themselves of the relative worth of this concept will encourage readers to >> do likewise to their own submissions I remain >> >> Your , etc. >> >> >>> -- >> You received this message because you are subscribed to the Google Groups >> "geoengineering" group. >> To view this discussion on the web visit >> https://groups.google.com/d/msg/geoengineering/-/_KEqoHead7IJ. >> >> 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. >> > > -- > 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. > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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