Also, returning to Peter's original email: "We found that the rate limiting step [for primary production?] was not sunlight or evaporation, but rather the transport of carbon dioxide from the atmosphere into the ocean. This was, as I recall, 10 times slower than the potential rate of growth of the algae."
Granted, if marine phototrophs used only CO2 they might get carbon limited considering that molecular CO2 is only about 10-20 uM in seawater. Yet total dissolved inorganic carbon in seawater is some 100 times higher in concentration, 2mM, nearly all of which is bicarbonate and a major carbon substrate for marine microalgae (though perhaps not macroalgae). So nutrient and light limitation of the marine carbon pump will occur way before carbon limitation does, e.g. Iron fertilization. In any case if/when molecular dissolved CO2 is consumed from seawater, then pH, [CO3--], and [OH-] rise, and air to sea CO2 flux is (greatly) chemically enhanced because of these reactions: CO2 + OH- ---> HCO3- and CO2 + H2O + CO3-- ---> 2HCO3-, relative to pure passive diffusion and hydration of CO2: CO2 + H2O ---> H+ + HCO3- . No? -Greg From: Chris <[email protected]<mailto:[email protected]>> Reply-To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Date: Wednesday, January 16, 2013 4:03 AM To: geoengineering <[email protected]<mailto:[email protected]>> Cc: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: Re: [geo] Ocean based algal growth: rate of CO2 transfer Michael, While deep seawater in the ocean does indeed contain a great deal of nutrients, it also contains high levels of dissolved inorganic carbon derived from the degradation of sinking organic matter generated in surface waters. Thus, bringing deep seawater to the surface will lead to outgassing of CO2 to the atmosphere that would greatly reduce if not eliminate the climate benefits of the schemes as indicated in the papers below: Dutreuil, S., Bopp, L. and Tagliabue, A. (2009) Impact of enhanced vertical mixing on marine biogeochemistry: Lessons for geo-engineering and natural variability. Biogeosciences Vol. 6, 901-912. http://www.biogeosciences.net/6/901/2009/bg-6-901-2009.pdf Oschlies, A., Pahlow, M., Yool, A. and Matear, R. J. (2010) Climate engineering by artificial ocean upwelling - channelling the sorcerer's apprentice Geophysical Research Letters, 37, L04701. http://onlinelibrary.wiley.com/doi/10.1029/2009GL041961/abstract Yool, A., Shepherd, J. G., Bryden, H. L. and Oschlies, A. (2009), Low efficiency of nutrient translocation for enhancing oceanic uptake of carbon dioxide, Journal of Geophysical research - Oceans 114, C08009, http://onlinelibrary.wiley.com/doi/10.1029/2008JC004792/abstract Note also that bringing up deep seawater for other purposes such as Ocean Thermal Energy Conversion (OTEC) and Deep Water Source Cooling/Seawater Air Conditioning has the same problem Chris. On Tuesday, 15 January 2013 22:21:14 UTC, Michael Hayes wrote: Also Peter, The 'Perpetual Salt Fountain' is a great addition to any large scale algae operation. http://www.terrapub.co.jp/journals/JO/pdf/6003/60030563.pdf "Deep seawater in the ocean contains a great deal of nutrients. Stommel et al. have proposed the notion of a “perpetual salt fountain” (Stommel et al., 1956). They noted the possibility of a permanent upwelling of deep seawater with no additional external energy source. If we can cause deep seawater to upwell extensively, we can achieve an ocean farm. We have succeeded in measuring the upwelling velocity by an experiment in the Mariana Trench area using a special measurement system. A 0.3 m diameter, 280 m long soft pipe made of PVC sheet was used in the experiment. The measured data, a verification experiment, and numerical simulation results, gave an estimate of upwelling velocity of 212 m/day." I've realized that the basic configuration of the tube can be converted into a large through put 'trash' pump, with minor mods, and powered by wave energy conversion. Deployed on a large scale, this system would significantly increase the microbial loop rate of production and thus produce a carbon sink multiplier for any macro algae farm system (not to mention an increase in marine life at all levels). Deep water C4 plant farms (gyres are lest problematic for production placement) can be scaled up to 'geoengineering' relevance with possible self funding commercial activities. Littoral deployments are possible but the artificial up welling would need a corresponding artifical down welling to prevent dead zones down current from the up welling. Here is a link to a few thoughts Mark and I exchanged some time ago. https://groups.google.com/d/topic/geoengineering/wyLXSagkvsw/discussion "Mark Capron has proposed Ocean Afforestation within this forum going back to at least 09. And, much of that work is centered around diatom enhancement for general CCS and possible biomass harvesting for methane fuel production and more. C4 halophytes (1) could be an important enhancement to that initial ocean afforestation strategy." I'm glad to see this issue come back up in this group. IMHO, Ocean Afforestation is our best long term hope to stabilize the climate and adjust the ocean pH. Initial math indicated that up to 6% of the earth needed to be put into production to off set current CO2 emissions. Wide spread use of the Perpetual Salt Fountain System may reduce the needed area substantially . I hope this helped. Michael On Thursday, January 10, 2013 8:29:54 PM UTC-8, MarkCapron wrote: Peter, The calculations in "Negative carbon via Ocean Afforestation" are based on actual macroalgae growth rates with whatever CO2 transfer and nutrients are naturally available. Either may be limiting. Your experience would appear to confirm our seaweed forests can be havens of high pH for critters in need of pre-industrial pH for shell formation. Mark E. Capron, PE Oxnard, California www.PODenergy.org<http://www.PODenergy.org> -------- Original Message -------- Subject: [geo] Ocean based algal growth: rate of CO2 transfer From: Peter Flynn <[email protected]> Date: Wed, January 09, 2013 6:36 pm To: [email protected] I am joining this discussion late, so I hope I am not covering ground already discussed. Some years back a graduate student and I looked at a conceptual scheme to grow algae and sink them into the deep ocean, using increased salinity from evaporation as the “pump”. We found that the rate limiting step was not sunlight or evaporation, but rather the transport of carbon dioxide from the atmosphere into the ocean. This was, as I recall, 10 times slower than the potential rate of growth of the algae. We came to understand why agitation and CO2 addition are included in some commercial algal farms. Peter Flynn Peter Flynn, P. Eng., Ph. D. Emeritus Professor and Poole Chair in Management for Engineers Department of Mechanical Engineering University of Alberta [email protected] cell: 928 451 4455 -- 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 view this discussion on the web visit https://groups.google.com/d/msg/geoengineering/-/HQZJQCJdd7gJ. To post to this group, send email to [email protected]<mailto:[email protected]>. To unsubscribe from this group, send email to [email protected]<mailto:[email protected]>. 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