On Wed, Nov 20, 2013 at 6:33 PM, Ronal W. Larson <rongretlar...@comcast.net> wrote: > Keith etal > > Thanks for the added material. It seems we understand the differences well, > so I will keep this short. > > 1. Re my #2: You found 1 ppm CO2 as 5.20 Gt CO2. Multiplying by 12/44 > would give 1.42 Gt C, whereas I had 2.13 Gt C ( a number I have seen many > times - such as at > http://cdiac.ornl.gov/pns/convert.html > http://www.skepticalscience.com/print.php?n=908 )
Ah, fundamental misunderstanding on my part. ppm is by volume and not mass. So your number is right. > 2. Re #4: I think we can live with electricity prices appreciably higher > than 2 c/kWh. Coal has an environmental cost sometimes reported at 15 > c/kWh. Nuclear seems unlikely to ever get anywhere near (is on a negative > learning curve). I like your two cites, but think we can only get 2c with > energy efficiency (but good luck on proving you can do it with SPS) It's not so much whether or not we can live with high energy costs, it's a question of if we can live well in a vibrant economy. Of course, if energy goes high enough we can no longer ship food and then comes the great die off when a crop fails. > Biochar has a chance at good economics when used with CHP - where > smallness is a virtue. > > Other (re your final added material): I have followed the SPS concept > since the early 1970s, after hearing Dr. Peter Glaser of AD Little. I am > in no position to comment on it now, but certainly hope that you can achieve > the 2 c/kWh target. That would be wonderful. In a little googling today I > was reminded that the Japanese have made a major commitment -which must be > very satisfying to you. Post Fukushima the Japanese canceled their power satellite plans. snip > - There is at least one firm using electricity to make char - with > a microwave system. Possibly some (magnetron) parallels with SPS there? > In general, the fact that pyrolysis is exothermic could keep most biochar > coming from strictly thermal approaches. If it will burn, you can make char out of it. But depending on how wet it is, it can be hard. Where with really cheap external energy it doesn't much matter. Keith > Ron > > > On Nov 20, 2013, at 1:59 PM, Keith Henson <hkeithhen...@gmail.com> wrote: > > On Tue, Nov 19, 2013 at 9:22 PM, Ronal W. Larson > <rongretlar...@comcast.net> wrote: > > Keith cc list > > 1. Since this is a thread with a biochar theme, I thought we should > compare a hypothetical biochar scenario with your solar power satellite > (SPS) scenario. > > 2. Because char is lighter than oil (I assume relative density of 1/3), > I got 1200 km3 of char, assuming 400 Gt of carbon needing to be removed for > a 100 ppm drop in CO2. This assumes almost as much has to come out of the > ocean as the atmosphere. Was your assumption similar on ocean CO2 release? > > > No. From the notes here: http://www.theoildrum.com/node/5485 > > "The area of the earth is ~5.1 x 1014 square meters; air pressure is > ~100,000 N/m2. The force would be ~5.1 x 1019 and the mass > (force/acceleration of 9.8 m/sec2) is ~5.2 x 1018kg or 5.2 x 1015 t. > One ppm would be 5.2 x 109 t and 100 ppm would be ~520 billion > tonnes." I agree that if the CO2 came down 100 ppm, the oceans would > be giving up that much again. > > Call it a 1000 B tons of CO2. Carbon is 12/44 of CO2, or about 270 > billion tons of carbon. Amorphous carbon has a density around 2 tons > per cubic meter so the volume would be around135 B cubic meters, about > 1/t0th of your estimate but that's close enough for this kind of > thought experiment. > > 3. To achieve the 1200 km3 of char, and an assumed depth of a uniform char > layer of 2.5 cm (roughly an inch) requires spreading over about 20% (2.4 > Gha) of the global land area. Yours would be a thinner layer of course, but > an oil would have to be deep underground to avoid conversion back to CO2. > Also a despoil sequestration can provide no out-year benefits. > > > Right. Oil on the surface would be a bad idea of course. Oil has the > advantage that you can pump it where char has to be moved around as a > solid. On the other hand, you make char as close as you can to the > fields where you are going to bury it. > > 4. Assuming that about half of biomass carbon will go to char and half to > energy (at 30 GJ/tonne C), means that the 2.5 cm layer (400 Gt C) will also > provide a beneficial (carbon neutral) release of about 12,000 EJ. > > > That's tricky. Biomass is a relatively expensive kind of energy and > hard to scale up to an efficient size. Gail Tverberg makes a case > that for economic reasons energy need to be not only environmentally > friendly, but really cheap. > http://theenergycollective.com/gail-tverberg/266116/oil-prices-lead-hard-financial-limits > At a conference in Baltimore couple of weeks ago she put it as 1-2 > cent per kWh power or (same thing) synthetic oil at $30-50 per bbl. I > don't think biomass can do that on either cost or the needed quantity. > David MacKay has a lot to say about this in his book > http://withouthotair.com/ > > 5. You estimate about 300 TWyrs for the SPS scenario. I calculate (using > 5 kWh = 18 MJ [about the energy in 1 kg wood] and 3600 seconds in an hour) > about 1 TWyr = 30 EJ (we are globally using near 600 EJ/yr in 2013), so the > 12,000 EJ is about 400 TWyr to compare to your 300 TWyrs. The difference is > that the biochar scenario supplies 1/3 more (not requires that much more). > This is also handling the required ocean carbon - I am not sure of your > “ocean” assumption. You suggest a new 15 TW for 20 years; this is 8 TW > for 50 years. > > > We are essentially in agreement. > > From here on is an extension of the SPS scenario > > 6. If we accomplish the 400 Gt C transfer at about today’s fossil input > rate of 8Gt C/yr (about 1% removal rate), all with biochar only) this would > supply in a carbon neutral sense about 240 EJ/yr = about 40% of today’s > total supply. (The SPS scenario would also be carbon neutral.) But biochar > also supplies out-year carbon negative benefits from increased above and > below-ground living matter. This augmentation is not well known at all, but > assuming 2 Gt C per year of afforestation, and placed-char having this > assumed eventual out-year doubling potential, then 3 Gt C/yr of placed-char > would be sufficient to meet the 8 Gt C/yr goal (this assumes zero fossil and > land disturbance positive contributions). > > 7. Because of this projected doubling of char impact, we are down to > 3*30 = 90 EJ/yr of supplied energy - about 15% of today’s supply - which is > in addition to today’s approximately 10% through biomass of 60 GJ/yr. > Biomass contributions in the neighborhood of 25% appear in some projections > for 2050. > > 8. The above was to try to get an annual average biomass tonnage of > carbon, with each tonne of carbon in wood supplying 1/2 tonne of carbon in > biochar and 9 GJ. So 3 Gt C/yr of biochar sequestration requires 6 Gt of C > in wood-input (or about 12 Gt dry biomass or 24 Gt of wet biomass). This > amount of input wood provides a new 54 EJ to be added to today’s roughly 60 > - approaching a needed doubling in wood supply going to energy. > > 9. The total needed added supply is 2 (afforestation) + 2*3 (biochar) = 8 > Gt C, which is to be compared with today’s global NPP of about 60 Gt C/yr. > Today’s standing biomass is about 500 Gt C, so this would increase to > perhaps 650 by a combination of afforestation and biochar annual and short > rotation feedstock. Today’s roughly 1500 Gt C of below ground carbon would > similarly increase by 50 years * 2 Gt C/yr = 100 Gt C. Together, after 50 > years, these assumptions change from about 2000 Gt C up to 2250 Gt C. This > (1/4% per year) seems conservative, compared to the annual productivity > improvements seen for grain crops over the last 50 years. > > Disclaimer: These are only intended as rough numbers to correspond to the > SPS scenario. Obviously there should be a ramping period in both > scenarios. The most important difference is the sign on the energy > contribution. It would be interesting to compare costs; none are shown > here, but my guess is that the bio alternative would be considered cheaper > and nearer to commercial readiness. > > > It can certainly be started on a very small scale where the power > satellite project takes perhaps twice the cost of Three Gorges Dam or > half the upper estimate of cost for > https://en.wikipedia.org/wiki/Kashagan_Field > > On the other hand, the power satellite project looks to make 500% > profit in ten years and looks like it could grow to the point of > displacing the vast majority of fossil fuel with cheaper electric > power and synthetic hydrocarbons. > > Not, mind you, that I am opposed to biomass as a way to capture CO2. > Carbon neutral synthetic transport fuels can be made very nicely using > plants to capture the carbon and power satellites to supply extra > hydrogen for the Fisher/Tropsch process. Long term, ExxonMobile is > inclined in this direction. Nor am I opposed to char to improve soil. > Making char with cheap electric heat from power satelliets would be a > less complicated process. > > Keith > > > Ron > > > > On Nov 19, 2013, at 1:14 PM, Keith Henson <hkeithhen...@gmail.com> wrote: > > Some years ago I calculated how much energy it would take to convert > 100 ppm of CO2 into synthetic oil which could be stored in old oil > fields safely for millions of years. > > 100 ppm of CO2 would be 470 cubic km of the stuff. It's what humans > added to the atmosphere since ~1960. > > Had to define a new measure of energy, it would take about 300 TW > years (check it if you want to quote it). > > I was doing this in the context of space based solar power. If you > kept building power plants in space beyond replacing fossil fuels, to > another 15 TW, it would take 20 years to put 100 ppm back in the > ground. > > Much less energy if you take it out as CO2, but less of a blowout problem > > Keith Henson > > http://en.wikipedia.org/wiki/L5_Society > > > On Tue, Nov 19, 2013 at 5:45 AM, Ning Zeng <z...@atmos.umd.edu> wrote: > > Or simply CRS (Carbon Removal and Storage). A few years back when this group > came up with the names SRM and CDR, I argued for CRS, reasoning that any CO2 > removal method has to be accompanied by storage as a truly workable carbon > sequestration strategy. many cheers, -Ning > > > On Monday, November 18, 2013 5:59:10 PM UTC-5, kcaldeira wrote: > > > Folks, > > The question about whether biochar is a CDR technique and therefore > "geoengineering" raises some interesting issues. > > Carbon Dioxide Removal (CDR) techniques involves to processes that are in > principle separable: > > 1. Carbon dioxide removal from the atmosphere (or oceans) > 2. Storage of that carbon in a long-lived pool. > > Carbon can be removed from the atmosphere using biological strategies > (e.g., land plants, phytoplankton) or chemical strategies (e.g., direct air > capture, accelerated chemical weathering). > > Carbon so removed must then be stored in a long-lived reservoir. Carbon > can be stored in a reduced form (e.g., biochar, living forests) or in an > oxidized form (e.g., CO2 injected in geologic reservoirs, Fe-fertilized > biomass that has oxided into dissolved inorganic carbon in the deep ocean). > > Carbon stored in an oxidized form can be largely in the form of molecular > CO2 (perhaps dissolved) or can be part of another compound such as CaCO3 > (perhaps dissolved). > > What makes something CDR approach is a system property (i.e., air capture > that vents back to the atmosphere is not a CDR approach; geologic CO2 > storage without air capture is not a CDR approach; but put the two together > and you have a CDR approach). > > On this taxonomy, I would consider biochar as a way of storing reduced > carbon for long periods of time. Under this interpretation, biochar could be > part of a CDR system, but as a process in-and-of-itself, biochar is an > approach for carbon storage. Biochar does no carbon dioxide removal, so > cannot itseld be a CDR technique. > > Therefore, it may make sense to talk about biochar as a carbon dioxide > storage approach. As part of a system of biological carbon capture by land > plants and storage using biochar, biochar can be part of a CDR system, but > biochar itself is not a CDR system. > > Maybe we should be talking about CDRS (Carbon Dioxide Removal and Storage) > instead of CDR. We should then specifiy both the Carbon Dioxide Removal > (CDR) approach and the Storage (S) approach. > > Biochar is an S approach, not a CDR approach. > > Best, > > Ken > > _______________ > Ken Caldeira > > Carnegie Institution for Science > Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > +1 650 704 7212 kcal...@carnegiescience.edu > http://dge.stanford.edu/labs/caldeiralab > https://twitter.com/KenCaldeira > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/groups/opt_out. > > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email togeoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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