Thanks Ken, I think you are absolutely right re the Pielke approach. I think we are possibly quite near the edge of some tipping point precipice [and of course quite possibly not, but inaction is not a rational response to uncertainty] What I estimate could be done by mid century with a huge effort, using 1Gha of land, could have been done much more easily using 600 MHa starting 15 years ago, when my book "Responding to Global Warming" was published. Pielke is just being silly.
We shouldn't be too despondent about the areal power density of bioenergy. In good conditions Eucalypts can do 1000Gj/Ha-yr and sugar cane 1300. Over a decade or so of technolgical improvement, and with irrigation, biomass can likely supply most of the world's fuel demands. Add a bit of zero emissions coal-and-biofuel co-fired generation, then maybe the fat can be pulled from the fire despite Einsteins view that "only two things are infinite, the universe and mankind's stupidity - and I not sure about the universe". What I am concerned about is that scientists should be careful what they say to the media, and clarify the assumptions behind their work, maybe reminding journalists that studies of how the natural earth system works do not preclude geo-engineering options to forestall unwanted outcomes Peter ----- Original Message ----- From: Ken Caldeira To: [email protected] Cc: [email protected] ; [email protected] ; Leonard Ornstein Sent: Sunday, May 17, 2009 8:26 AM Subject: [geo] Re: [clim] Fwd: White/Cool Roofs Memo to MEF (Major Economies Forum) In response to Peter's earlier comment: Our studies on the long lifetime of CO2 emissions considered only natural and not engineered CO2 removal mechanisms. As Peter points out, several engineered CO2 removal approaches have been proposed, with biomass co-firing of power plants combined with carbon capture and geologic disposal perhaps being the most plausibly cost effective approach. One could look at engineered CO2 removal as a negative emission, with positive consequences equal and opposite to the negative consequences of a CO2 emission -- so the positive consequences of CO2 removal are similarly long-lived. Nevertheless, I think we need to be wary of suggestions, such as those made by Roger Pielke Jr and others (eg http://sciencepolicy.colorado.edu/admin/publication_files/resource-2716-2009.03.pdf), that it is OK to pollute today because others can clean it up tomorrow. On the other hand, the idea that we would continue using petroleum products as transportation fuels (especially for aviation) and then negate those emissions with near-simultaneous air capture may be a plausible and cost effective path forward. That said, we should be aware that biomass options are all plagued by low areal power densities, and so require large land areas to be quantitatively important -- and large land areas often come with large transportation and processing costs (not to mention costs associated with competing uses of that land for food production, biodiversity, etc). Best, Ken PS. I am a little suspicious about biochar, because I am skeptical that the best thing to do with reduced carbon is bury it underground (especially while we still have a coal mining industry trying to remove reduced carbon from underground), but that is another discussion and I haven't really investigated biochar carefully yet. ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA [email protected]; [email protected] http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 On Sat, May 16, 2009 at 12:11 PM, Peter Read <[email protected]> wrote: Gregory Many thanks. I would like to know more about the CROPS program if you have a reference But a propos "when the trees die", they don't die under commercial forrestation but get cut down when growth slows and the rate of increase of value falls below the operator's cost of borrowing. When that happens, if there is co-produced fuel and timber, is that some fossil fuel gets left in the ground and some other timber elsewhere gets left standing (hopefully in natural biodiverse forest), an ongoing process for "chipping away at atmospheric CO2 yearly" that can also support both REDD and biodiversity objectives. In a 'normal' commercial plantation there are equal area stands of all ages of maturity from just planted to due to be felled next year. Annual growth shifts each stand one year towards maturity, so that the average age of stand is half the maturity age and there is a total standing stock of carbon equal to approximately half of the maximum possible if all the stands were left unfelled after growing to maturity and then left to die (which would yield a zero return on investment). While a new forest is growing towards the maturity of its first stand, and a new stand is planted each year so as to eventually result in a normal forest, the "chipping away" comes from annual average growth of the forest, which ceases when the first stand is felled since thereafter annual felling removes as much C as is captured by the annual growth of the rest of the forest. Increased "chipping away" results from routing the fuel fraction through one of the negative emissions systems, biochar or BECCS, which results in C being stored as nearly pure C in the soil or as CO2 deep underground, as well as in leaving fossil fuel underground. Decreased chipping away results if the trees left standing in natural forests die off. A forthcoming paper by Len Ornstein suggests (from memory - some time since I saw the draft) that about 1Gt of carbon annually could be kept from the atmosphere if an organised program existed for sequestering C that would otherwise be returned to atmosphere following natural treefall. Peter ----- Original Message ----- From: <[email protected]> To: <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Sunday, May 17, 2009 4:20 AM Subject: Re: [geo] Re: [clim] Fwd: White/Cool Roofs Memo to MEF (Major Economies Forum) Peter: I might point out that commercial reforrestation works hand in hand with deep ocean sequestration as well. Forest growth can hold CO2 for centuries, but when the trees die, much of their debris can be sequestered in deep water, a la the CROPS program. Chipping away at the CO2 yearly makes sense, and each seasonal year we neglect doing it, that CO2 will be with us a long time: Sequestration by installment. Gregory Benford . . . 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