Ken and list: The only way I can see to respond is paragraph by paragraph. Apologies in advance, but there are some important topics below for biochar.
On Nov 18, 2013, at 3:59 PM, Ken Caldeira <[email protected]> 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: [RWL0: Change “to” to “two”?] > > 1. Carbon dioxide removal from the atmosphere (or oceans) > 2. Storage of that carbon in a long-lived pool. [RWL1: Agreed (maybe). But I see a problem with “1” mentioning CO2, and “2” mentioning C. I’d prefer that both mention C - or make it clear that from an atmospheric perspective they are interchangeable terms. Later in this dialog, I am claiming “ removal” and “storage” are two terms for the same atmospheric benefit that biochar provides.] > > 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). [RWL2: I am worried that “pyrolysis” is not mentioned also in the concluding clause. I would replace “or” with “and/or”?] > 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). [RWL3: There are also proposals to store raw, unmodified biomass in the deep oceans or on land in deep trenches, where living organisms and O2 levels are sparse. The word “store” might imply that the carbon can be taken out of storage. This is essentially impossible with biochar (and is considered an asset that it can’t).] > > 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). [RWL4: OK. Biochar analysts would add also a third option - as a highly recalcitrant “product” that is “mostly” (>80%) pure carbon.] > > 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). [RWL5: OK. I certainly think of biochar as a system (with system elements described below)] > > 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. [RWL6: a. Sentence 1: No one claims biochar is as sure a storage mechanism as BECCS; biochar is at best thought of as leaky storage - but (with the right (high temperature) char) quite slow leakage - and not a simply described leakage (not a simple exponential decay). b. Sentence 2: Opening clause - agreed. Second clause - maybe not understanding a nuance here. I am not sure what “in-and-of-itself” means. It sounds like biochar could sometimes be not part of a system - whereas I think it always is (the system parts not yet mentioned are photosynthesis and avoidance (via pyrolysis) of decomposition of cellulose, hemicellulose and lignin). Lastly, I can agree “biochar is an approach for carbon storage”. But this should not preclude a storage label as also having a removal label. c. Sentence 3: Perhaps the key sentence. I argue that “approved” (low H:C ratio) biochar does in fact “remove" carbon dioxide for a sufficiently long time that, at least during this “non-storage” period (can be 1000 years), the carbon is NOT in the atmosphere. The word “storage” would seem inappropriate - when no-one is claiming that the “removal” is at all permanent. Only that the temporary removal is long enough to be beneficial in a societal policy sense. We are discussing semantics here. Another part of the semantics is whether carbon removal (going back to RWL1) is essentially the same as carbon dioxide removal in every atmospheric sense. I think it is - in part since many of us talk about 800 Gt C in the atmosphere, not using the CO2 equivalent which is 44/12 = 3.67 times larger. > > 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. [RWL7: a. Sentence 1: I can agree if a storage (especially a leaky storage) can also count as a removal. Glad to see the word “may” here. b. Sentence 2: Clauses 1 and 2 - agree totally. biochar cannot be separated from “biological carbon capture” (would add water and ocean plants to “land plants") c. Sentence 2: Clause 3. We are back to earlier sentences. I think/hope we are agreed that the word biochar means more than the mostly carbon product produced by pyrolysis, and placed into soil. It certainly means a photosynthesis component. It certain means a pyrolysis component. One cannot have a “biochar” without those two system elements. So I can agree that it would be very wrong to think of biochar as only a small chunk of black material in the absence of its full system characteristics. Biochar analysts mostly think of biochar in soil improvement terms. A very few of us also see biocha as every bit as much a CDR system as is BECCS (which also involves photosynthesis, and numerous other costly system elements).] > > 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. [RWL8: a. Sentence 1: We could do this, but I think it not particularly helpful. The “S" introduces nothing that will help in any policy decision process I can imagine. b. Sentence 2: Same response. I see two labels for the same physical process. I agree that biochar is not storing CO2, but treating biochar differently from others that are called CDR (such as afforestation) doesn’t serve any practical purpose I can think of. In what policy-important way should biochar be treated differently from afforestation or BECCS? > > Biochar is an S approach, not a CDR approach. [RWL9: I guess we have to agree to disagree. I concur that biochar doesn’t fit as neatly into the usual CDR groupings as does BECCS - but I see much bigger comparison issues - such as no other approach that has received the CDR label has (large) out-year soil benefits - that can even be growing exponentially if added biomass is itself turned into char. And no other CDR approach is providing energy for free - you can’t have biochar without also receiving a “gift”of energy (fuels, thermal, electrical, CHP). Onee key sentence above (#7) is this: “….biochar can be part of a CDR system, but biochar itself is not a CDR system…” with which I agree. However, this key sentence does not get into the “storage ….. removal” topics, which is where I am not yet understanding your emphases. My 17 Nov. message responding to Greg Rau was on the (maybe?) totally different topic of biochar fitting under both the terms “Adaptability” and “Mitigation”. Since you (Ken) have done a lot on these interface and nomenclature issues, I wonder if any of the above relates to my wanting biochar to be included under both the words “Adaptation” and “Mitigation”? Again apologies to all for excessive length. It takes a while to figure out important new topics like these. Ron > > Best, > > Ken > > _______________ > Ken Caldeira > > Carnegie Institution for Science > Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > +1 650 704 7212 [email protected] > 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 [email protected]. 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