*I'm starting this as a new thread, because this conversation was getting embedded in another thread ...*
Almost every carbon dioxide removal method by definition directly captures CO2 from the atmosphere, and thus they may all be thought of as some form of direct capture of CO2 from the air. As a result, the acronym DAC (for Direct Air Capture) has in some case led to unclear communication as some people are using Direct Air Capture to refer only to centralized chemical-industrial facilities that remove CO2 form the atmosphere and others, apparently, have been using term to refer more broadly to nearly all carbon dioxide removal (CDR) approaches. It would be useful to have some clear and consistent terminology to avoid such confusion. Important dimensions to consider are: 1. Biological vs. chemical approaches (Are you using plants to do your capture for you or are you using some sort of chemical process) 2. Centralized vs. distributed approaches (Is the approach deployed in a centralized facility or does the capture from air occur across broad extents of land and/or ocean surface?) 3. Is the carbon stored as oxidized (molecular CO2, HCO3-, etc) or reuced (organic carbon, black carbon)? These three binary choices suggest eight categories with limitless possibilities of sub-categories. So, for example; -- Centralized industrialized direct air capture is investigating (1) chemical approaches that are (2) centralized and (3) store the carbon as molecular CO2 [oxidized]. -- Ocean fertilization is (1) biological approach that is (2) distributed and (3) ultimately stores the carbon as HCO3- [oxidized] carbon in the deep sea. -- Biochar is a (1) biological approach to capture that is (2) distributed and seeks to (3) store the carbon as reduced carbon. -- Liming the ocean is a (1) chemical approach that is (2) distributed over a wide area and (3) stores the carbon as oxidized carbon (HCO3-). -- Afforestation is a (1) biological approach that is (2) distributed over a wide area and (3) stores the carbon as reduced [organic] carbon. Which of these 8 basic categories are populated? Do we have clear an unambiguous terms to refer to each of the populated categories? I think not. There are no feasible centralized biological approaches because photosynthesis by its very nature involves large areas to capture enough sunlight to be quantitatively important. _______________ 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 *YouTube:* <http://www.youtube.com/watch?v=a9LaYCbYCxo>Climate change and the transition from coal to low-carbon electricity<http://www.youtube.com/watch?v=a9LaYCbYCxo> Crop yields in a geoengineered climate<http://www.youtube.com/watch?v=-0LCXNoIu-c> -- 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.
