Practical potential of carbon sequestration via wood harvest and storage (WHS) in Climatic Change

[Ning Zeng]

Carbon sequestration via wood harvest and storage: An assessment of its harvest potential

Zeng, N., A.W. King, B. Zaitchik, S.D. Wullschleger, J. Gregg, S. Wang, D. Kirk-Davidoff, 2012: Climatic Change. DOI: 10.1007/s10584-012-0624-0.

A carbon sequestration strategy has recently been proposed in which a forest is actively managed, 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). Earlier estimates of the theoretical potential of wood harvest and storage (WHS) based on coarse wood production rates 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 aWHS 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 GtCy−1 carbon sequestration potential if major effort is made to expand managed forests and/or to increase harvest 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 moderate 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 recommendWHS be considered part of the portfolio of climate mitigation and adaptation options that needs further research.

[rongre...@comcast.net]

Professor  Zeng:

    Thanks you for both writing the cited article and attaching it for us all.  Makes reading it much easier and quicker, given usual paywalls..

    I see merit in WHS, but (as someone concentrating on the biochar alternative) want to ask a few questions especially on the total woody biomass resource base which is the larger part of your paper - and which you max out at 3 GtC/yr.

    As you are certainly aware, biochar will only sequester about half of the carbon that you are calculating (with the other half potentially providing carbon neutral  advantages).  But it can provide several (compensaitng) advantages that WHS cannot - some of which are in your article.  I mean first year energy  (income) and out-year (investment) soil improvement advantages (arguably growing exponentially).  But obviously WHS has first year sequestration advantages.  You may have looked at some of the questions following that would help demonstrate larger overall CDR advantages - on which we seem to agree.

    a.  You have identified about 10 GtC/yr as the technical maximum portion of the global 60 which is harvest-able in the form of (presumably somewhat uniform) tree trunks.  That sounds reasonable.  However, for bioenergy and biochar, smaller diameters and crooked woody material are still quite usable.  Can you identify how much larger the technical pool might be for using the same woody resources for biochar or bioenergy (rather than WHS)?  Might a doubling of woody resource be possible or is that too much?

    b.  It is not obvious that you have assumed an increase in today's global 60 GtC/yr.  I read Jim Hansen as proposing perhaps an additional 5 GtC/yr (or more?) of photosynthesis capability.  Are you increasing today's 60 GtC/yr in this article's computations and do you think we can increase to 65 or 70 GtC/yr?

    c.   You seem to have excluded the concept of plantations (including multi-species energy plantations [for biodiversity reasons].   Coppicing of plants like miscanthus, switch grass or even sugar cane offer much higher annual yield than you are assuming. Also many bioenergy approaches are assuming the use of ag residues (maybe even ocean resources).  Could you have additional WHS potential in non-tree species and complete annual harvesting?  (leading to minimizing the problem of plateauing of standing biomass which you identify.)

    d.  Many biochar supporters believe that energy, soil improvement, water retention and food are as important as carbon sequestration.  Can you comment on how WHS addresses these other sustainability issues?

   There are other questions along these lines (any topic to increase the total biomass availability beyond 3 GtC/yr) that I hope you can also address - hoping that you get my drift.    Alternatively stated,  how much additional sequestration potential can be gained as the WHS resource base is expanded beyond (relatively long, large and straight?) wood trunks?

Again thanks for the paper and the considerable work behind it.   Ron

---

From: "Ning Zeng" <ze...@atmos.umd.edu>
To: geoengi...@googlegroups.com
Sent: Sunday, January 20, 2013 10:02:48 AM
Subject: [geo] Practical potential of carbon sequestration via wood harvest and storage (WHS) in Climatic Change

Carbon sequestration via wood harvest and storage: An assessment of its harvest potential

Zeng, N., A.W. King, B. Zaitchik, S.D. Wullschleger, J. Gregg, S. Wang, D. Kirk-Davidoff, 2012: Climatic Change. DOI: 10.1007/s10584-012-0624-0.

A carbon sequestration strategy has recently been proposed in which a forest is actively managed, 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). Earlier estimates of the theoretical potential of wood harvest and storage (WHS) based on coarse wood production rates 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 aWHS 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 GtCy−1 carbon sequestration potential if major effort is made to expand managed forests and/or to increase harvest 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 moderate 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 recommendWHS be considered part of the portfolio of climate mitigation and adaptation options that needs further research.

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