Duncan, Ning, list: I wholeheartedly support the idea of sequestering through forestry products. The analysis of them is straightforward. But the potential is obviously quite limited compared to the GtC/yr values in your (Duncan's) recent report. So this seems like a good opportunity to ask Duncan what the criteria should be for evaluating different NET (CDR) options. I hope others will answer the following methodology questions as well.
2. Dr. Zeng obviously feels that ground burial is better (being cheaper as a NET (Negative Emissions Technology) and more widely applicable) than the BECCS approach which I believe Duncan has favored in his report. Duncan's likely reasoning: BECCS uses the same (tree) resource both for carbon-neutral replacement of fossil fuels at electrical power plants and then captures almost as much in a carbon-negative placement of the resulting CO2 deep underground. Presumably Duncan (maybe most on this list) would say that the large gain in carbon neutrality (with monetary income to offset part of the sequestration costs) more than balances the small (?) loss in carbon negativity. But is there a more specific definition of "better" here? How would Dr. Zeng rebut the argument that we need biomass for its energy content? Does it include questions about the eventual success of CCS? 3. I think almost the same questions would be asked by those favoring ocean burial of biomass. I presume that ocean or pit burial are roughly equivalent - and the preference would be based on location (and resulting cost differences). But both have foregone the carbon-neutral energy contribution. Nevertheless, I can understand both the pit and ocean burial proponents' concerns, as they are focusing on NET (carbon negativity). I hope Duncan can first address this narrow issue of combining carbon-neutrality and carbon-negativity; in discussing and comparing NETs, should carbon-neutral benefits be part of the dialog and/or exactly how should they be balanced? 4. But along comes Biochar - and it further confuses the debate by saying that other criteria should also prevail besides the neutral (Energy) - and negative carbon issue above. Biochar is almost as good as BECCS on both carbon-negativty and carbon-neutrality (much of biomass energy value is in the hydrogen content which both capture, and BECCS has some energy losses in capture). But overall, Biochar proponents can agree that BECCS is superficially able to impact more CO2 than can Biochar. But I say superficially because Biochar out-year benefits seem to have a chance of overcoming the first-year advantages of both BECCS and burial. Many of those are spelled out by Duncan, but they do not seem to have made their way into the numerical computation on either carbon neutral or carbon negative sides of the ledger. 5. I will send more on this to Duncan (others please let me know if they want to see this), but I think it likely that most readers will know that anthropogenic Amazonian Terra Preta soils (not mentioned by Duncan) are today several times more productive than the poor parent soils from which they were constructed. Increased Ag production may be replaced in some already excellent soils by a halving of fertilizer needs. Nitrous Oxide, methane, and nutrient capture are other carbon-equivalent out-year continuing benefits that do not appear in Duncan's analyses - some with long term offsetting dollar income values. The question for Duncan, Dr. Zeng and others on this list are whether these out-year CO2-climate benefits of Biochar should be included ? Or should all NET computations have the same (one year) time regime. 6. Second, whether non-CO2-related, but clear economic benefits (like increased multi-year crop yield and increased multi-year farmer income) should somehow enter into the dialog. For many in the Biochar research arena this is their main focus; NETs (carbon-negativity) are a distant second in their thinking. Increased soil productivity might obviate the need for carbon credits entirely (as was the case for the Amazonian Indians centuries ago.) This is somewhat like saying that it is important for BECCS proponents that there is an income from (carbon-neutral) electricity sales, but in this final NET (carbon-negativity) question, I am going one step further - carbon-neutrality is not involved. 7. It is my impression that Duncan has not included these last two issues when calculating a Biochar price in the curves of his Figures 5 and 7. Surprisingly, Biochar also doesn't appear in the economics of Table 10 - maybe because of these analytical hurdles. I have other questions on the potential magnitude of the Biochar resource, which I think should be larger than the other biomass options, but that is a different topic I will raise separately with Duncan. 8. Despite my questioning here, I think Duncan has done a better job than anyone else of comparing the NET options. I am only trying to make clear the process, and the assumptions for his second edition. If carbon-neutral (energy), out-year, and non-CO2 topics are to be either included or excluded from NET analyses, I feel it should be made clear why. Thoughts? Ron ----- Original Message ----- From: "Ning Zeng" <[email protected]> To: "geoengineering" <[email protected]> Sent: Wednesday, September 28, 2011 7:21:48 AM Subject: [geo] Re: New report(s) on carbon dioxide removal Talking about wood products for carbon sequestration, I don't know if you have seen this report from the Wilderness Society, perhaps the most in-depth I've seen? -Ning http://wilderness.org/files/Wood-Products-and-Carbon-Storage.pdf On Sep 27, 7:55 am, Duncan McLaren <[email protected]> wrote: > Thanks for your feedback. It's great to see more detailed work > ongoing, and I look forward to reading your paper. Hopefully I will > get the chance to use it to update my report. > > I agree that sustainable forestry has a role in a package of NETs, but > whether WHS is the best option for some or all of the accumulated > carbon is an open question for me still. Comentators above have argued > for BECCS and biochar. Personally I have a soft spot for timber use in > construction (even if the store is relatively shortlived). > > I agree that there are environmental impacts from most if not all > NETs, and hadn't intended to imply that forestry-related approaches > were particularly bad, simply to highlight that current forestry > techniques are not always sustainable (or ethical for that matter), > and expanding conventional approaches to plantation forestry, for > example, could be counterproductive, even in carbon terms. > > Best wishes > Duncan > > On Sep 25, 4:37 pm, Ning Zeng <[email protected]> wrote: > > > > > > > > > Hello Duncan: > > > I enjoyed reading through your very nice analysis of NETs over the > > weekend. I agree with Oliver Tickell's comment that we need > > "knowledge, not conjecture". I have been researching on the "wood > > burial" idea which has even less research compared to many others. > > > We have a paper that is in review at Climatic Change, which brings > > more information on wood burial's (we now call it Wood Harvest and > > Storage or WHS) harvest potential, and more information is on the way > > on cost and storage and other practical considerations. The abstract > > of the paper is below. It is relevant to some key factors you > > discussed in your report, including: > > > 1. We use GtC, while you use GtCO2, so that the estimate of Zeng > > (2008) of 10 GtC potential is really 37 GtC/y. However, that is just a > > theoretical potential based on coarse wood production rate of all > > world's forests. In this new paper (Zeng et al. 2011), we consider > > many practical constraints including land use and conservation needs, > > and we arrive at a range of 1-3 GtC/y (4-10 GtCO2/y). > > > 2. This new paper also shows the area of forest needed in order to > > accomplish these sequestration goals. At our low value of 1GtC/y, it > > requires 800 Mha forest land with a (modest) harvest intensity of 1 tC/ > > ha/y, a much lower rate than typically assumed bioenergy crop harvest > > rate. The amount of biomass (2Gt dry biomass) involved is equivalent > > to the current worldwide forest harvest. So this is definitely not > > business-as-usual, but a leap for forestry. > > > 3. The cost estimate of Zeng (2008) of $14/tCO2 was based on cost of > > harvesting. If including storage (mostly in situ around harvest > > landing site to minimize transportation cost), it will probably double > > to $30/tCO2. Adding other unforseen cost, bearing in mind the > > observation that real-world implementation often tends to be more > > expensive, I'd wave my hand (before realistic demo project) to put > > the cost at about $50/tCO2. I think this is actually what you used in > > the cost/potential plot (Fig. 7). > > > 4. I thought it's a bit unfair to apply environmental impact to wood > > burial, while not to other methods. All these have major environmental > > issues to consider, but my feeling is that sustainable forestry, we > > actually know better how to do it right. > > > Best Regards! > > -Ning Zeng > > > Ecological carbon sequestration via wood harvest and storage: An > > assessment of its practical harvest potential > > > Ning Zeng, Anthony King, Ben Zaitchik, Stan Wullschleger, Jay Gregg, > > Shaoqiang Wang, Dan Kirk-Davidoff > > > A carbon sequestration strategy has recently been proposed in which a > > forest is sustainably managed to optimal carbon productivity, and a > > fraction of the wood is selectively harvested and stored to prevent > > decomposition. The forest serves as a ‘carbon scrubber’ or ‘carbon > > remover’ that provides continuous sequestration (negative emissions). > > The stored wood is a semi-permanent carbon sink, but also serves as a > > ‘biomass/bioenergy reserve’ that could be utilized in the future. > > Earlier estimates of the theoretical potential of wood harvest and > > storage (WHS) were 10 ± 5 GtC y-1. Starting from this physical limit, > > here we apply a number of practical constraints: (1) land not > > available due to agriculture; (2) forest set aside as protected areas, > > assuming 50% in the tropics and 20% in temperate and boreal forests; > > (3) forests difficult to access due to steep terrain; (4) wood use for > > other purposes such as timber and paper. This ‘top-down’ approach > > yields a WHS potential 2.8 GtC y-1. Alternatively, a ‘bottom-up’ > > approach, assuming more efficient wood use without increasing harvest, > > finds 0.1-0.5 GtC y-1 available for carbon sequestration. We suggest a > > range of 1-3 GtC y-1 carbon sequestration potential if major > > investment is made to expand managed forests and/or to increase > > management intensity. > > The implementation of such a scheme at our estimated lower value of 1 > > GtC y-1 would imply a doubling of the current world wood harvest rate. > > This can be achieved by harvesting wood at a modest harvesting > > intensity of 1.2 tC ha-1 y-1, over a forest area of 8 Mkm2 (800 Mha). > > To achieve the higher value of 3 GtC y-1, forests need to be managed > > this way on half of the world’s forested land, or on a smaller area > > but with higher harvest intensity. We compare the potential of WHS > > with a number of other carbon sequestration methods, and recommend WHS > > be considered part of the portfolio of climate mitigation options. > > > On Sep 21, 7:11 am, Duncan McLaren <[email protected]> wrote: > > > > Group members may find my assessment of negative emissions > > > technologies (NETs) of interest. > > > > The full report runs to about 100 pages, and can be found > > > athttps://sites.google.com/site/mclarenerc/research/negative-emissions-... > > > > > > > A summary version written for Friends of the Earth (England, Wales and > > > NI) will be published online later today. > > > > The assessment covers a wide range of NETs, but not SRM techniques. It > > > considers capacity, cost, side effects, constraints, technical > > > readiness, accountability and more for about 30 options. > > > > I'd be delighted to get feedback and comments. > > > > regards > > > Duncan -- 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. -- 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.
