Agreed. It's a hybrid. The thermo looks good, but kinetic and mass-transfer limitations are severe.
-D ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Ken Caldeira Sent: December 11, 2009 2:16 AM To: David Keith Cc: Greg Rau; [email protected] Subject: Re: [geo] Air Capture (re-naming the thread) It's hard to see how the energy cost of the ocean alkalinity scheme can get much below the cost of CaCO3 calcination . What about using power plant flue gases to dissolve carbonates? That seems to be an ocean alkalinity scheme that has energy costs well below calcination. ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA [email protected] http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 On Fri, Dec 11, 2009 at 11:33 AM, David Keith <[email protected]> wrote: Greg, To me it's just the common definition; I did not intend to say anything about relative merits. The topic was air capture and that seem enough for one article. I think the geochemical approaches that involve adding alkalinity to the oceans are worth serious work that's why I wrote the article geochemical carbon management article. I have also pushed this idea onto agendas at various research planning meetings (e.g., the NAS advanced sequestration meeting), and we have considered adapting calcination technology we develop for air capture to the CaO or MgO scheme though we are not putting serious work into it. In my view there is no way to make a simple choice between them. There are significant technical and institutional and governance challenges with adding alkalinity to the ocean. On the other hand, restoring PH could be a direct local environmental benefit. It's hard to see how the energy cost of the ocean alkalinity scheme can get much below the cost of CaCO3 calcination and the electrochemical schemes are expensive. One might argue, then, that air capture has lower theoretical energy cost (10's of kJ/mol vs 100's) but no one knows how to make the low energy AC work at low cost. Bottom line: real development work is needed on both; they should be linked where appropriate; and finally, it's far too early to pick winners. I know about the APS work, but I will reserve comments until it's out. The real test will be in a few years when serious end-to-end engineering cost estimates are made public. Yours, D -- 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] <mailto:geoengineering%[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. 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.
