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.
