To put Peter's numbers into SI units: 1000Gj/Ha-yr = 3.2 W / m2 1300Gj/Ha-yr = 4.1 W / m2
These numbers seem mighty optimistic (are they supposed to include losses from inputs, processing etc?). (Most estimates I see are an order of magnitude lower [cf. http://www.biofuel2g.com/Ponencias/wim_corre.pdf].) How to reconcile this difference? How much land is there with "good conditions" that would not be better allocated to other purposes [food, biodiversity, etc]? Even so, land requirements are substantial for a high energy lifestyle ... And efficiency improvements only help bring about a low energy lifestyle if they are coupled to (or brought about by) strong incentives to reduce energy use. ( Remember James Watt and his steam engine !! ) On Sat, May 16, 2009 at 2:11 PM, Peter Read <[email protected]> wrote: > 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 <[email protected]> > *To:* [email protected] > *Cc:* [email protected] ; [email protected] ; Leonard > Ornstein <[email protected]> > *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 >> . >> . >> . >> (snipped by PR) >> >> >> >> > > > > ------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.0.238 / Virus Database: 270.12.32/2118 - Release Date: 05/16/09 > 17:05:00 > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
