Citations please = Stuart =
Stuart E. Strand 490 Ben Hall IDR Bldg. Box 355014, Univ. Washington Seattle, WA 98195 voice 206-543-5350, fax 206-685-9996 skype: stuartestrand http://faculty.washington.edu/sstrand/ From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Wednesday, October 12, 2011 8:06 PM To: [email protected]; geoengineering Subject: Re: [geo] Biochar Nature paper Greg and list: Thanks for bringing this two-year old (downloadable) Biochar paper from "Nature" below to the list's attention. I admire the work of Wolff, Amonette (corresponding author, responsible for the Excel work), etal. But I think they went overboard on being conservative. They say: " Wherever possible, conservative assumptions were used to provide a high degree of confidence that our results represent a conservative estimate of the avoided GHG emissions achievable in each scenario.". I know three of the five authors; one of them gave a (much less-documented) estimate that was an order-of-magnitude higher. Tim Lenton has repeated this higher number. I believe the most recent paper by Jim Hansen, which I think proposes 100 GtC of new standing forests, is assuming larger land use change than is assumed in this paper, or by those promoting BECCS. In my view, there is probably one Gha available for reforestation and the paper limits the agroforestry total to 170 Mha (all with latitude less than 25 degrees). They also assume only about 4 tC/ha-yr to be available (with about half going into char - about 30% of their total annual combined carbon neutral and carbon negative peak). I believe we will do appreciably better than this assumed 400 grams C/sqm-yr in the tropics (with about half of this parameter being available for sequestration). Resources that receive little/zero consideration in this paper include a. The ocean - having an NPP roughly equal to that of land. Mangroves have always been highly regarded for char making - and can be harvested sustainably. Artificial nutrient upwelling and macroalgae are not mentioned. b. Freshwater microalgae - which provides potential access to the Gha of deserts. c. Fire-prevention possibilities (possibly another 1 GtC/yr) d. Conversion of considerable pasture and idle land (there is only a minimum assumed conversion of farm land - as noted above for agroforestry. As noted above considerably higher values than 4 tC/ha-yr are in the literature.) e. Potential for improved bioenergy species productivity (little past emphasis by geneticists on energy crops). f. There is little on the ability to manage forests to increase (maybe double or triple?) annual productivity by keeping the canopy open, using multiple species and multiple levels in forests, and employing a lot of people for coppicing etc.. g. Little emphasis on emphasizing the advantages of more extensive reforestation of tropical areas - where annual productivity can triple that in temperate zones. (But we can do both, where temperate land is idle.) h. No assumed increase in soil productivity due to Biochar application (and the terra preta literature talks of double and triple soil productivity increase). i. HTC - hydrothermal conversion (of moist resources, such as MSW, feedlot effluent, etc) - where HTC proponents talk about a potential for half of future carbon sequestration via that route. j. The use of charcoal-making stoves for the half of the world now predominantly getting their energy (very inefficiently) from biomass. This can be expanded readily to larger scale operations presently having zero fossil fuels. k. The potential role of Biochar for supporting (intermittent) wind and solar - as biomass can provide needed energy storage. l. I believe they show soil organic carbon (SOC) decreasing - and most Biochar analysts assume an increase. m. Any sense of political urgency - as being pushed by the 350 ppm movement (including Dr. Hansen) n. No discussion of what can happen with new policies that might come out of different politics. None of the above dozen possible resource expansion areas requires cutting existing forests, nor use of peat regions. I am also looking into the details of the paper's comparisons with combustion, etc. I think this may also have been conservative. For instance if one has added annual productivity after applying char, credit should be given for that additional annual growth (even if cut annually) and standing biomass. I believe no such credit is given although it would be the main claim for a new forest. There are a few other similar Biochar papers striving to get at the details. It is on these details that we must now concentrate - and the Wolff-Amonette paper contains as much or more detail as any I have seen. To repeat, their arguments are well supported - albeit mostly using the most conservative number in a spectrum. I am only declaring that our CDR world is large enough to have both conservative and more optimistic views being discussed. I would love to have further conversation with anyone on this list re my concerns on this paper being overly conservative. Thanks again to Greg for bringing this excellent paper to the list's attention. Ron ________________________________ From: "Greg Rau" <[email protected]<mailto:[email protected]>> To: "geoengineering" <[email protected]<mailto:[email protected]>> Sent: Wednesday, October 12, 2011 1:40:22 PM Subject: [geo] Biochar Nature paper http://www.nature.com/ncomms/journal/v1/n5/full/ncomms1053.html?WT.ec_id=EXTERNAL&WT.mc_id=NC1108CE061 Production of biochar (the carbon (C)-rich solid formed by pyrolysis of biomass) and its storage in soils have been suggested as a means of abating climate change by sequestering carbon, while simultaneously providing energy and increasing crop yields. Substantial uncertainties exist, however, regarding the impact, capacity and sustainability of biochar at the global level. In this paper we estimate the maximum sustainable technical potential of biochar to mitigate climate change. Annual net emissions of carbon dioxide (CO2), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO2-C equivalent (CO2-Ce) per year (12% of current anthropogenic CO2-Ce emissions; 1 Pg=1 Gt), and total net emissions over the course of a century by 130 Pg CO2-Ce, without endangering food security, habitat or soil conservation. Biochar has a larger climate-change mitigation potential than combustion of the same sustainably procured biomass for bioenergy, except when fertile soils are amended while coal is the fuel being offset. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]<mailto:[email protected]>. To unsubscribe from this group, send email to [email protected]<mailto:[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]<mailto:[email protected]>. To unsubscribe from this group, send email to [email protected]<mailto:[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.
