Planting trees to offset fossil fuel consumption

B. Geerts and E. Linacre

3/02


In December 1997 United Nations members agreed in Kyoto, Japan, to limit greenhouse gas emissions in order to stabilize the global climate and minimize the anticipated global warming. Industrial countries pledged to cut emissions to 1990 levels or less within about 5 years. The United States, which is responsible for about one quarter of the historic fossil fuel consumption, does not abide by the Kyoto treatment.

An economic assessment of the costs of planting trees to absorb the carbon dioxide in vehicle exhausts (1) shows that in Australia this would be an economically more viable way of curbing the increase of emissions than applying a carbon tax, for instance, assuming that the alternatives are mutually exclusive. It is reckoned conservatively that the carbon locked up in a stand of plantation trees is about 220 tonnes per hectare, and that the stand is harvested each 35 years and the area replanted. The harvested wood is not burned. According to this estimate, about seven new trees would absorb what is emitted by an average car in Australia. Details are given in another paper (2).

About 14% of the greenhouse-gas emissions (in terms of warming potential) consists of methane (CH4). Methane is rather long-lived (its atmospheric residence time is12 years), and of all major greenhouse gases its rate of increase has been largest. Part of the methane emissions originate as flatulence by farm animals (3). Methane is produced by bacteria in the intestine, in the course of breaking down cellulose. However, it is now possible to inject a vaccine into cattle to produce antibodies which kill the bacteria involved, without harm to the animals.

 

References

(1) Australian Bureau of Transport & Communication Economics 1996. Trees and greenhouse: costs of sequestering Australian transport emissions. Climate Change Newsletter 8 (2), 6-7.

(2) Ormerod, W.G., I.C. Webster, H. Audus and P.W.F. Riemer 1993. An overview of large-scale CO2 disposal options. Energy Conversion Management 34 (9-11), 833-40.

(3) Grose, S. 1998. A quick-fix solution to global warming. Canberra Times, 16th November, p9.