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Computing Carbon in Teak Trees

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Written by treebankingllc
Sunday, 08 March 2009 00:00

The Science Behind Carbon Sequestration in Teak Trees

One of the loudest arguments against using forestry to offset carbon is the claim that there is no real science to prove how much Carbon Dioxide trees actually absorb.

Part of the reason we've chosen teak trees as the foundation of our business is the fact that there has been so much research around them and the simple fact that they grow so fast.

In January 2005 Raymond Keogh of The International Teak Unit of Coillte Consult published a paper in response to the CDM's research into the possibility of using afforestation and reforestation projects for sequestering CO².

The purpose of his research and subsequent paper was to provide owners, investors and other interested stakeholders an overview of the likely amounts of carbon that teak trees would sequester under a variety of conditions.

The tables Mr. Keough created are presented in such a way that Carbon or CO² can be estimated for the stem (trunk) or the entire tree -above and below ground - through time. It is relatively easy, by using the tables, to estimate the potential production for a wide range of teak plantation sites.

At the time Mr. Keough published his paper his opinion was that it was unlikely that teak would be planted strictly for carbon sequestration. He also suggested "payments are likely to provide a valuable return to growers early in the rotation, thus improving Internal Rates of Return. Alternatively, for those who are compelled to buy C or CO² the possibility of a return on the timber investment is an attractive option worth considering."

It seems Mr. Keough 'planted the seed' for TreeBanking LLC. The following is a complete copy of his table with small changes in the text for ease of explanation.
 
 
DERIVATION OF TABLES AND MODELS

The tables are derived from Trinidad models after Miller (1969) - the most complete models for the region. Each class is segregated according to Height Classes. In the present tables, a regional site classification chart is also provided, which was derived by Keogh (1982). Miller’s classification was based on Mean Height and that of Keogh on Top Height (i.e. mean height of the 100 largest diameter trees per hectare).

I. Miller’s original volumes were compiled for under bark (UB) values. These were transformed to over bark (OB) values as follows:
 
1. UB diameter at breast height (DBH) was calculated using the formula: DBH (UB) = 0.947 DBH (OB) – 0.918
2. Cylindrical tree volumes for UB were calculated for a range of DBHs and total tree heights. Form Factors (FFs) for UB volume we calculated as: merchantable volume (to 8 cm top diameter)/cylindrical volume to total height using DBH UB as the diameter of the cylinder. Merchantable volume UB was calculated using formula:
Merch. Vol. UB = -0.0111 + 0.000025 ((DBH OB)2 * H) (Keogh, 1987[RK2]) (2)
3. The same FFs were used to calculate merchantable OB tree volume from OB cylindrical volumes (DBH OB and total tree height used as variables);
4. The relationship between merchantable volume OB per hectare and DBH OB was established as follows:
Merchantable vol. OB/ha = -0.1087 Ln (average DBH OB) + 1.5855 (3)
(R2 of formula (3) = 0.9093);
 
II. Stem CO² was calculated as follows:
Stem CO² = Merch. vol. OB * (0.59) * (0.5) * 3.664 (4)
Where:
0.59 is wood density (derived from Keogh, 1987[RK3]; mean of oven dry wt: green volume);
0.5 is Carbon content (derived from Kraenzel et al, 2003; tissue carbon concentration of main trunk[RK4]);
3.664 is ratio of CO² to C (derived from atomic weights of carbon {12.011}and oxygen {15.9994[k5]}).

III. Stem Carbon is calculated using formula (4) above without the CO² to C ratio.


IV. Tree C and CO² were calculated using a Biomass Expansion Factor (BEF) derived from Kraenzel et al, 2003[RK6] as follows: BEF = Proportion of total tree biomass (100)/trunk biomass (65.28) = 1.531863 (5)

V. No estimate is made for litter and undergrowth C and CO² but Kraenzel et al, 2003 estimated these to be in the order of 3% and 2% respectively compared to total tree.

VI. Top Height is calculated for any regional class using the following formula:
Log h = Log S. I. + b (1/x – 1/xk) (6)
Where h is the top height; x is age in growing seasons and xk is the key year

(25 in this particular case); b is equation slope (-2.0776); S. I. is Site Index (i.e. top height at the key age for any particular class); after Keogh, 1982.

VII. The original Trinidad tables were translated from hoppus feet to metric measure and appear in Keogh, 1987.
Last Updated ( Sunday, 05 April 2009 15:37 )