Ken - below is the requested check on your numbers Ken Caldeira wrote: > Total land area is around 1.5 x 10^14 m2 and grazing might cover 25% > of this (Asner et al, 2004), so there must be an error in your > calculation. *RWL: Ken is speaking here to Stephen Salter's grazing land estimate of 5E15 m2, which (I agree) seems to be a factor of 100 too large (because there are 100 ha in a sq km??) But there is absolutely no reason to limit our land area to present grazing land. In the near term, we will only be using crop land, and many think the best economics will be for idle land. I want to double the land area estimate to 50% * > > Please give me a calculation in units of watts per m2. What kind of > efficiencies are you assuming for using sunlight to produce reduced > carbon in soils? > > This will tell us how much land area you need to store the 5.5 to 9.5 > PgC / yr claimed by Lehmann et al. (2006). *RWL: Side note 1 Pg C/yr =1E15 C/yr = 1 E9 C/yr = 1 GT C/yr (one wedge - well known to Ken, but maybe helpful to some.)* > Reversing the calculation and taking the upper bound. > > Let's assume it takes about 470 kJ/mol to reduce CO2 to C (I am > assuming something like glucose). This works out (unless I have made > an error to about 1.2 * 10^13 W. *[RWL: I have seen several cites showing the number 470 kJ/mol to be per mol of CO2 (not C). I can get Ken's later numbers using a mol as 12 gm. I believe we should use 44 grams. One cite is http://chem.pdx.edu/~wamserc/CH399S97/Notes4.htm (half way down). I also found 116 kcal/mol for CO2 at http://www.greenfuelonline.com/contact_faq.html, which is the same given 4185 joules per kcal. This will make it easier for Prof. Lehmann by factor of 44/12 = 3.67. Ken's wattage need of 12 terra watts I would put as 2*3.67 lower - call it 2 TW, just a factor of 6 here to be conservative, not 7.3.]* > > Normal ecosystem efficiencies are typically around 0.5 %. If we assume > average sunlight at ground at 200 W/ m2, we get 1 W/m2 ecosystem rates > of producing reduced carbon. *RWL: I found quite a few references showing 2% and larger. 8% for sugar cane, 11% for algae. I also think that we can go up to at least 250, and maybe 300 W/m2 for areas closer to the equator. I am going to assume that this factor is three times larger, giving now an easier job for Prof. Lehmann by a factor of 18 - with the number here being closer to 3 W/m2. I think this reasonable for the equatorial developing country areas , where I see Biochar being most valuable (often 3 crops per year for instance)*
> > What fraction of total ecosystem net productivity will be converted to > biochar after taking into account processing costs etc? Let's say 10%. > So this is 0.1 W/m2. Therefore, we will need about 1.2 * 10^14 m2 or > the same order of magnitude as all of the land in the world. *RWL: 10% also is appreciably lower than I believe Prof. Lehmann would have assumed. My guess is that he used 50% - a number that I have personally obtained often in pyrolysis (the ratio is 25% if one is comparing to total weight of the Biomass (which we aren't), as typical biomass is about 50% carbon. Prof. Mike Antal at the University of Hawaii has a pressurized pyrolysis system closer to 65 or 70%. The HTC methodology of Dr. Markus Antonietti is at 95%. Of course if the emphasis is on biofuels (fast pyrolysis) then 10% is OK (maybe even high). There will be some of that for sure. But I still will argue for a 50% number here, because I'll bet Prof. Lehmann was thinking of more equivalent sequestration than just CO2. See http://www.biochar-international.org/biochar/carbon. This was a chart prepared by Dr. Jim Amonnette of PNL (and I assisted a little, so feel qualified to speak on it). There should be some accounting of the carbon-neutral value of the pyrolysis gases - and Prof. Lehmann might have meant that. But I will ignore that since we are talking here of sequestration and carbon negativity. But he almost certainly would have had in mind BECs - which might add another 30% (could be much larger if we get really serious). But there is no mention in this location of increased biomass (bacteria and fungus), nor of the added above ground biomass to be expected. There is also a very conservative assumption built in as to the avoidance of N2O and methane release. So I am going to assume that the 5.5 GT/yr total is only for the direct sequestration and the 9.5 GT/yr includes all the other possible effects. Thus to go with Ken's use of 9.5 GT/yr, I will add a factor of 9.5/5.5 = 1.7 easier. With these extra factors of 5 (=50%/10%) and 1.7, we are up to about a factor of 80 difference from Ken's numbers (again rounding down). The specific number replacing 0.1 W/m2 is 0.5 W/m2. So 1.2*10^14 m2 (same as 12 G ha), I would make as 80 times less - or .15 Gha - or (by (almost) coincidence) 1% of the global area. * > > You can argue with particular numbers, but it seems that it will take > a great leap of faith to be confident that we can feasibly get more > than 10% of this number. *RWL: So by my count, we need only 10% of your leap-of-faith area value. I should also add that we have said nothing about using manures or sea weed. Also quite possible that there may be value in placing char in the oceans to decrease the ocean's acidity (char can be made up to about pH = 12). [Not claimed to be valid for the whole vast ocean of course , but maybe helpful in some near-shore regions.] Also no statement about increasing the productivity of the land both through better soil science related to the Biochar - nor to improved genetics for energy crops. I also hasten to add that I don't think we will ever get this high (or need to). But the exercise here is only on land area - which I believe I have shown need not be a constraint. Ken - based on your referrring to Haberl etal, I have re-read it and note that a different approach is to use (future) numbers closer to 1000 g/m2-yr (10 tons C/ha-yr). Multiplying these last figures by 50% to get char, 50% land area, and your 1.5 E14 m2 land area ( = 15 E9 ha) gives 375 E14 g Char /yr = 37.5 E9 T Char/yr. This is about 4 times larger than Prof. Lehmann's numbers. This saying he was conservative by a factor of 4 (probably assumed [like you] half as much land area and half the soil productivity (he probably used the Haberl value of about 5 T C/ha-yr = 500 g/m2-yr). Why was there only a factor of 4 here and 80 in the "energy-related" computation? Answer - there were multiplicative factor of 3.67 on theoretical reduction energy need, about 3 for assumed photosynthesis efficiency and 2 in land area. Now yours or someone's turn to check my numbers. Ron * > > > > > On Sun, Sep 27, 2009 at 10:59 AM, Stephen Salter <[email protected] > <mailto:[email protected]>> wrote: > > Ken > > Slide 10 of the Lovell Ward PowerPoint says grazing land is 5 E15 > m2. I would expect that this will include a lot of what we might > think of as desert but this is because it has been badly grazed > and they show that they can get it back. > > In another presentation Tony Lovell showed a photograph of a slice > through the topsoil of some land that had been managed by his > technique. I recall a deep black layer of what looked very > carbonish. Tony, if I am correct, can you circulate that photograph? > > If we multiply that land area by a soil depth of 0.3 metres and my > guess of soil density of 1800 kg/m3 we get 27000 G tonne of earth. > Each 1% of additional carbon mass that gets embedded is 270 G tonne. > > Nature keeps the herds concentrated with lion power. We would have > to do it by fences and gate control. I am not sure where solar > power or food mass comes in. Lovell and Ward are not charring the > roots or doing any digging. They are just leaving roots where they > grew holding onto their carbon. The food is only a tiny fraction > of vegetable matter. > > > Stephen > > Emeritus Professor of Engineering Design > School of Engineering and Electronics > University of Edinburgh > Mayfield Road > Edinburgh EH9 3JL > Scotland > tel +44 131 650 5704 > fax +44 131 650 5702 > Mobile 07795 203 195 > [email protected] <mailto:[email protected]> > http://www.see.ed.ac.uk/~shs <http://www.see.ed.ac.uk/%7Eshs> > > > Ken Caldeira wrote: > > Steven, > > What is the total area of the world that is susceptible to > such processes? > > I think what the Royal Society report basically said is that > in order of magnitudes, if we think 10 GtC/yr is the order of > magnitude of the 100% solutions, biochar is not a 100% > solution but could potentially be a 10% solution. > > I repeat my basic logic: > > /Note that Haberl et al (2007) estimate that total global > total food harvest is about 1.7 GtC / yr and global wood > extraction is about 1 GtC / yr, so the 9.5 PgC / yr number > cited by Lehmann et al (2006) represents carbon flows that are > more than 5 times bigger than all the food harvesting in the > world and more than 9 times bigger than all wood extraction in > the world. These kinds of flows may be physically possible, > but I remain skeptical regarding the practical feasibility of > producing biochar at this scale. > > / Nothing in this conversation has induced me to change this > perspective. > > Best, > > Ken > > PS. Please not that I am not speaking for the Royal Society in > making these comments. > > ___________________________________________________ > Ken Caldeira > > Carnegie Institution Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > > [email protected] <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>>; > [email protected] <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>> > > http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > +1 650 704 7212; fax: +1 650 462 5968 > > > On Sun, Sep 27, 2009 at 4:36 AM, Stephen Salter > <[email protected] <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>>> wrote: > > Hi All > > I may be able to answer Ken's questions about the ultimate > potential for bio-char by pointing to some work by the Australians > Tony Lovell and Bruce Ward. > The number Ken needs for energy to make the root equivalent of > bio-char is very close to zero and depends on the energy you need > for ranch fencing. We need to build fences and control gates > between grazing grounds and so manage the way livestock are > allowed to move around ranches. We want it to be more like the > way wildebeest move around the Serengeti and Masai Mara. We want > them to eat all the grass from a small area in a short time and > then leave it alone for a long time rather than nibbling a > moderate fraction all the time. The amount of root matter below > ground is set by the amount above ground when the grass is at its > tallest and affect the rates at which it can recover. The > photograph below makes the point. > > > > > Below are a pair of photographs from the Lovell and Ward > presentation taken from adjacent ranches with the same soil type > on the same day. > > > > > > > > > They quote a UN FAO figure of 1500 GT capacity for soil > uptake. As the reflectivity of grass is higher than bare earth > and grass > roots transfer carbon to the soil it looks like a useful technique > for albedo increase as well as carbon removal. > For more, PLEASE go to > http://www.soilcarbon.com.au/case_studies/pdf/08TL_SCCPPP_En.pdf > Then contact > > Tony Lovell > Soil Carbon (Australia) Pty Ltd > PO Box 157, BOND UNIVERSITY QLD 4229 > Suite 102, 20 Lake Orr Drive, VARSITY LAKES QLD 4227 > Ph: +61 (0)7 5553 7900 Fax: +61 (0)7 5553 7999 Mob: +61 (0)418 > 730340 > Email: [email protected] > <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>> > > > It should be very cheap to test the idea on a small scale and grow > it progressively. But in the short term why not mosey down > Mexico way and take your own photographs of La Inmaculada and next > door ranch? > > Stephen > > Emeritus Professor of Engineering Design > School of Engineering and Electronics > University of Edinburgh > Mayfield Road > Edinburgh EH9 3JL > Scotland > tel +44 131 650 5704 > fax +44 131 650 5702 > Mobile 07795 203 195 > [email protected] <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>> > http://www.see.ed.ac.uk/~shs <http://www.see.ed.ac.uk/%7Eshs> > <http://www.see.ed.ac.uk/%7Eshs> > > > Ken Caldeira wrote: > > > How many watts per square meter of solar energy can be used to > reduce carbon that can be stored as biochar? How many > watts per > square meter is needed to process this organic matter? > > Do you really think it reasonable to think that 10% of global > primary productivity of land plants can be stored as biochar? > > Note that Haberl et al (2007) estimate that total global total > food harvest is about 1.7 GtC / yr and global wood > extraction is > about 1 GtC / yr, so the 9.5 PgC / yr number cited by > Lehmann et > al (2006) represents carbon flows that are more than 5 times > bigger than all the food harvesting in the world and more > than 9 > times bigger than all wood extraction in the world. These > kinds > of flows may be physically possible, but I remain skeptical > regarding the practical feasibility of producing biochar > at this > scales. > > Haberl, H., K.-H. Erb, F. Krausmann, V. Gaube, A. Bondeau, C. > Plutzar, S. Gingrich, W. Lucht, M. Fischer-Kowalski, 2007. > Quantifying and mapping the human appropriation of net primary > production in earth’s terrestrial ecosystems. Proceedings > of the > National Academy of Sciences of the USA 104, 12942-12947. > > ___________________________________________________ > Ken Caldeira > > Carnegie Institution Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > > [email protected] <mailto:[email protected]> > <mailto:[email protected] <mailto:[email protected]>>; > [email protected] <mailto:[email protected]> > <mailto:[email protected] > <mailto:[email protected]>> > > http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > +1 650 704 7212; fax: +1 650 462 5968 > > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > > > -- > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > > > > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.409 / Virus Database: 270.13.113/2398 - Release Date: 09/27/09 > 05:51:00 > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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