The reason why the biomass route is so much lower cost than mechanical air capture depends on the common practice of discounting cash flows.
If you plant trees (very low cost) then they do the CO2 capture job for a decade or so, depending on the rotation length. When they are mature you can use them for fuel, leaving fossil fuel in the ground (zero emissions) or in a BECCS set up (negative emissions and likely just as expensive as Air Capture, but at least you get some energy out of it) or in a biochar set up (lower cost than BECCS, but less energy and C stored, though with soil improvement benefits not usually accounted for in geoengineering circles). A propos having been ticked off for stating the blindingly obvious, I did not say the advanced economies should not aim to reduce emissions, obviously they should. But whatever OECD countries can achieve by energy efficiency and over-hyped ambient energy technologies is obviously going to be outweighed by industrialization in advanced developing countries that have large reserves of coal. The world does not end at the Mexican border. Peter ----- Original Message ----- From: David Keith To: geoengineering Sent: Tuesday, November 03, 2009 4:37 AM Subject: [geo] Re: An interesting question (Air Capture Papers) Air capture does take a fair amount of energy. You may be interested in my recent overview in Science (enclosed). See also http://www.ucalgary.ca/~keith/AirCapture.html, paper #116 which is a longer overview of the engineering design constraints on air capture systems. We do talk about nuclear and solar driven air capture systems. In the long run, I think if air capture makes sense it will be powered by non-fossil energy. Peter Read has asserted that biomass with capture is far cheaper than air capture. He may turn out to be right, but I can say that I've worked on both, and I published cost analyses on both that use the same (relatively conservative) methodologies for cost estimation. I don't think there is a clear-cut winner for large-scale implementation, particularly not when you consider the environmental impacts of biofuels. One paper that compares the two is Frank S. Zeman and David W. Keith (2008). Carbon Neutral Hydrocarbons. Philosophical Transactions of the Royal Society (A), 366: 3901-3918, see #103 on the link above. Yours, David ------------------------------------------------------------------------------ From: [email protected] [mailto:[email protected]] On Behalf Of Andrew Lockley Sent: November 1, 2009 3:30 AM To: geoengineering Subject: [geo] An interesting question If energy was free, what could we do with geoengineering? It may seem a daft question, but bearing in mind that fusion power is only 40 years away (and always will be) then it is worth considering. My understanding is that Lackner's 'fake plastic trees' are energy-hungry, and fusion could make them a lot more attractive. (Perhaps an alternative technology could be used to remove dissolved C02 from the sea.) However, there is a potentially serious problem with this. What if we emit such large volumes of secondary GHGs (eg methane) that we need to reduce CO2 below natural levels to control temperature? If we take CO2 too low, plants will not grow and we'll all starve. Wildfires would then act to balance CO2 levels. Previously, I've outlined my ideas for tackling methane to this list, but what if none of them worked? What would our options be? How practical would it be to 'overshoot' CO2? We wouldn't need to worry about stability anymore, as it would be so cheap to draw down the CO2 that we could just dump it in the deep ocean and pump down a bit more when it leaks. Leakage in an 'overshoot' world would possibly be an advantage - bringing up CO2 levels 'naturally' when the secondary GHGs had decomposed chemically or photochemically in the atmosphere. I just thought I'd ask for comments as to the kind of geoengineering our grandchildren will be able to engage in once they have the 'Mr Fusion' machines which power the cars in 'Back to the Future', but in a world where secondary GHGs are the primary problem. Comments please. I think it's worth a paper on this. A ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.423 / Virus Database: 270.14.45/2476 - Release Date: 11/02/09 07:51:00 --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
