An Introduction to Wood Harvesting and Storage
Image Taken by Chris Stubbs
A big focus at CLP is utilizing the carbon capture potential of trees. After all, they are a naturally occurring method of direct air capture, taking carbon dioxide out of the atmosphere via photosynthesis and storing it in the tree’s wood. There’s limited cost (both in terms of money and other resources) to this entirely natural sequestration process. This compares particularly favorably to other currently available direct air capture sequestration methods, many of which bear price tags in the hundreds of dollars per tonne (Sanz-Perez et al, 2016). Additionally, many direct air capture methods have significant restrictions on placement or scope, such as requiring an active point source of CO2 (ie an actively emitting smokestack) to operate at any efficiency (Sanz-Perez et al, 2016). None of these restrictions are applicable to biological based sequestration methods.
However, there are restrictions on conventional biological sequestration techniques. Land suitable for forestry is a limited resource and a major goal of CCS is tied to limiting the impacts of climate change in a timely manner. This sparks the question, what is the most efficient use of land and time in biological based carbon capture? The answer may be a technique called Wood Harvesting and Sequestration (WHS), a mixed natural and engineering CCS technique. In the early stage of a tree’s life, it grows quickly and captures a large amount of CO2 (Zeng et al, 2008). WHS aims to take advantage of this rapid growth phase to maximize efficiency. Once a forest exits its initial burst of growth and carbon storage, the trees are harvested and buried in a facility called a Wood Vault. Finally, a new generation of trees is planted and the process is repeated (Zeng & Hausmann, 2021). The same principle can also apply to redirected waste wood. That waste wood would otherwise be left to decompose, emitting its stored carbon back to the atmosphere. A combination of managed plantations and waste wood collection and redirection can provide significant stock for WHS projects.
The key to this entire procedure is the construction of secure and lasting Wood Vaults. The basic concept is to keep the buried wood in an oxygen free environment and below the active soil layer. This should minimize decomposition, with our initial estimates (as well as archeological evidence) demonstrating a sequestration timeline of over a millenia (Zeng & Hausmann, 2022). A basic Wood Vault facility has a land footprint of 1 hectare and sequestors 100 kilo-tonnes of CO2. And these facilities can be easily replicated wherever wood can be sourced, easily scaling up to Giga-Tonnes of CO2 sequestered annually, a significant fraction of annual anthropogenic emissions (Zeng et al, 2013). All at a cost of about $35/tonne, substantially less than any other sequestration technology of similar quality and well within the cost limits for viability in most carbon credit markets and emission trading schemes (Zeng & Hausmann, 2022). A particularly concerned reader may still be worried about the land use implications of such a project: tens of thousands of hectares of lands converted into Wood Vaults annually can sound like a lot. However, once the Vault is fully sealed, topsoil placed back on top and local flora allowed to regrow, there is no reason the land can’t see productive use. Solar farming, agriculture, recreation, or even light construction can all occur on the Wood Vault’s surface. The only real cost to the land is a year out of commission. Well worth the price for such an effective carbon sequestration project. Combined with reductions in emissions and other CCS strategies, WHS can play a critical role in preventing the worst effects of global warming.
Works Cited
Sanz-Pérez, E. S.; Murdock, C. R.; Didas, S. A.; Jones, C. W. (August 25, 2016). "Direct Capture of CO
2 from Ambient Air". Chem. Rev. 116 (19): 11840–11876. doi:10.1021/acs.chemrev.6b00173. PMID 27560307 – via ACS Publications.
Zeng, N., Hausmann, H. (2022). “Wood vault: Remove atmospheric CO2 with trees and store wood as
biomass, bioenergy and carbon for the future.” Carbon Balance and Management. Reviewed, to be Published.
Zeng, N.; King, A.; Zaitchilk, B. Valentini. R.; Tomberlin, D. (2008) “Wood harvest and storage: Using active forest management to fill the carbon sequestration gap.” Carbon Balance and Management.
Zeng, N., et al., Carbon sequestration via wood harvest and storage: An assessment of its
harvest potential. Climatic Change, 2013. 118(2): p. 245-257.
