Ron, IPCC list gross land and ocean CO2 influxes of 122.6 and 92.2 GT C/yr, respectively: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch7s7-3.html That's a total gross influx from the atmosphere (gross capture) of (122.6+92.2) x 44/12 = 788 GT CO2/yr. Granted, an almost equal amount of CO2 fluxes out of those systems, but even with this huge leakage enough is retained to account for the removal of 55-60% of anthropogenic CO2 emissions. My point is that air capture is already a vital and free part of reducing anthropogenic CO2 and it's impacts (minus the ocean acidification part). So in the context of increasing net air capture, the obvious routes would be to figure out how to increase these gross influxes and/or decrease gross outfluxes. BECCS, CROPS, and biochar address the latter, OIF (and probably also biochar) addresses the former, while increased ocean alkalinity and mineral weathering could address both. I'm not saying theses are the only technologies but I am saying why bother with purely artificial and expensive air capture apparatus (that in the end produce risky molecular CO2), when all that is needed are relatively minor tweakings of existing global scale air capture/retention systems that safely store carbon in forms other than molecular CO2?
Another interesting angle I recently came across is the electrochemical extraction of CO2 (and ocean acidity) from seawater: http://pubs.rsc.org/en/content/articlepdf/2012/ee/c2ee03393c Assuming you could safely store or use the extracted CO2 (e.g., convert to ocean alkalinity via limestone scrubbing; DO NOT use for EOR), the net effect would be to alkalize and de-acidify seawater, beneficially stabilizing or elevating ocean pH, increasing air CO2 uptake, and stabilizing/increasing coral and shellfish growth, etc. The electricity cost here alone looks to be around $100/tonne CO2, but even with capex it is likely to be a heck of a lot cheaper than House et al's $1000/tonne CO2 captured figure, without expensive air contacting and calcining paraphernalia, and with a significantly smaller land footprint. Plus there may be cheaper/better ways to do seawater CO2 extraction (other than OIF). I'm just saying… -Greg From: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Date: Thursday, July 26, 2012 9:26 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Cc: andrew lockley <[email protected]<mailto:[email protected]>>, geoengineering <[email protected]<mailto:[email protected]>> Subject: Re: [geo] Air capture: Modification of the Mg/DOBDC MOF with Amines to Enhance CO2 Adsorption from Ultradilute Gases Greg and ccs: This is partly to support your concern about Direct Air Capture (DAC), since we are hearing only part of the O&M portion of costs. We need to hear more, but I believe the $100/ton CO2 number (likely equivalent to about $300/ton of charcoal) is encouragingly lower than what we have heard before - and we should be pleased to hear of cost reductions, even though this is still a large number. But I am mostly asking how you calculate the "...in gross some 700+ GT of air CO2 capture/yr naturally going on...". If I divide by 3.67 for molecular weight differences, you are talking about 190 Gt C/yr. I often see a number around 60 Gt C/yr for both land-based and ocean based photosynthetic removal (of course mostly balanced by an annual return of about the same amount). But this presumably leaves (190-2*60=) 70 Gt C for some two-way annual ocean process? I'd like to hear your thoughts on the realistic net (not gross) removals that society might be able to achieve in say 2050 and 2100. I personally am hoping for new massive forest tree-planting to get us from 60 Gt C/yr up to 70. Then perhaps 5 of this added annual 10 can be harvested, leaving 5 for new added global standing biomass stock. The new annual harvestable 5 can be added to another 5 from today's already dying 60 (5/60=8% = new added human appropriation of the existing 60 Gt C/yr). Of this new available 5+5 =10, about half could be assigned to carbon-negative Biochar and half to carbon-neutral biofuels/biopower (2.5 Gt C/yr each). This would mean than about 1/6 of the total of 15 is being used primarily as backup for other (PV wind) sources of thermal and electric energy. This leaves considerable need for other forms of energy storage. Having only 2.5 Gt C/yr for biofuels, will greatly drop today's liquid/transportation portion of the total global energy budget - but 25% of annual biomass supply is all we can spare if we are serious about carbon negativity. In the above, I am imagining a scenario where there are no fossil fuels and the non-biomass RE sources are contributing about 10 Gt C/yr of fossil-replacement value. In other words- a total global energy equivalent of about 15 Gt C/yr - about twice today's fossil input, but now fossil-fuel-free.. I recognize this is aggressive and probably impossible. But I am projecting at only about 7 % (=15/190) of your 190 Gt C/yr "naturally going on". If we can achieve this new added harvest of 10 GtC/yr at a rate of 10 tonnes per hectare-yr (same as 1 kg/sqm-yr), then we need about 1 Gha - or 10 percent of the available arable land (including some off-shore resource - as is included in the computations at the Global Footprint Network (GFN). What alternative scenario would you propose to best exploit your 190 Gt C/y - to get CO2 down to 350 ppm soon? Thanks for giving the opportunity to be more scenario-oriented on this list. Ron ________________________________ From: "Greg Rau" <[email protected]<mailto:[email protected]>> To: "andrew lockley" <[email protected]<mailto:[email protected]>>, "geoengineering" <[email protected]<mailto:[email protected]>> Sent: Thursday, July 26, 2012 3:17:59 PM Subject: RE: [geo] Air capture: Modification of the Mg/DOBDC MOF with Amines to Enhance CO2 Adsorption from Ultradilute Gases Thanks, Andrew, for the recent updates on DAC. I remain puzzled, however, by the continuing interest in artificial air CO2 capture when we've got in gross some 700+ GT of air CO2 capture/yr naturally going on, in net consuming 55-60% of our CO2 emissions. Contrary to one of the articles*, air capture is not a "concept", it's what is currently saving our bacon right now. Wouldn't it make a lot more sense (and save a lot of cents) figuring out how to enhance/exploit these natural CO2 absorption and conversion processes (e.g, BECCS, CROPS, ocean alkalization, enhance mineral weathering, etc.) rather than trying to reinvent the wheel from the ground up, competing on a cost basis with what nature already does for free? How about investing in improving on the global scale "engineering" that's already in place? Regards, Greg *http://pubs.acs.org/doi/abs/10.1021/ie300691c?prevSearch=air%2Bcapture&searchHistoryKey= ________________________________________ From: [email protected]<mailto:[email protected]> [[email protected]<mailto:[email protected]>] On Behalf Of Andrew Lockley [[email protected]<mailto:[email protected]>] Sent: Wednesday, July 25, 2012 11:59 AM To: geoengineering Subject: [geo] Air capture: Modification of the Mg/DOBDC MOF with Amines to Enhance CO2 Adsorption from Ultradilute Gases http://pubs.acs.org/doi/abs/10.1021/jz300328j Modification of the Mg/DOBDC MOF with Amines to Enhance CO 2 Adsorption from Ultradilute Gases Sunho Choi, Taku Watanabe, Tae-Hyun Bae, David S. Sholl, Christopher W. Jones J. Phys. Chem. Lett., 2012, 3 (9), pp 1136–1141 DOI: 10.1021/jz300328j The MOF Mg/DOBDC has one of the highest known CO 2 adsorption capacities at the low to moderate CO 2 partial pressures relevant for CO 2 capture from flue gas but is difficult to regenerate for use in cyclic operation. In this work, Mg/DOBDC is modified by functionalization of its open metal coordination sites with ethylene diamine (ED) to introduce pendent amines into the MOF micropores. DFT calculations and experimental nitrogen physisorption and thermogravimetric analysis suggest that 1 ED molecule is added to each unit cell, on average. This modification both increases the material’s CO 2 adsorption capacity at ultradilute CO 2 partial pressures and increases the regenerability of the material, allowing for cyclic adsorption–desorption cycles with identical adsorption capacities. This is one of the first MOF materials demonstrated to yield significant adsorption capacities from simulated ambient air (400 ppm CO 2 ), and its capacity is competitive with the best-known adsorbents based on amine–oxide composites. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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]>. 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]<mailto:[email protected]>. To unsubscribe from this group, send email to [email protected]<mailto:[email protected]>. 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