Greenspirit Strategies - The Forest and Carbon Fixing - Some Stunning Figures

The Forest and Carbon Fixing - Some Stunning Figures - January, 2004

By Dr. Patrick Moore, Chairman & Chief Scientist, Greenspirit Strategies Ltd.

I was trying to figure out how to explain the role of forests in sequestering carbon from the atmosphere.

So I thought, I wonder how many cubic meters worth of atmospheric carbon are stored in a cubic meter of wood.

Much to my surprise the calculation reveals that a cubic meter of wood contains about 250 kg of carbon while a cubic meter of air contains about 0.117 g carbon.

This means that a cubic meter of wood contains the same amount of carbon as 1.4 million cubic meters of air.

The calculation is a follows: Air is 360 ppm CO2 by volume, not mass, therefore, the mass concentration depends on the molecular weight of the compound.

For CO2 (MW = 44), 1 ppm (v/v) = 0.001800 g/m3 @ 25C & 1 atm. Thus, 360 ppm (v/v) = 360 X 0.0018 = 0.648 g/m3.

The amount of carbon (MW = 12) in this much CO2 = 12/44 X 0.648= 0.177 g/m3.

250,000(g carbon/m3 wood)/0.177 = 1,412,429 times as much carbon in a cubic meter of wood as in a cubic meter of air.

I am amazed that trees are not only capable of fixing carbon but also of concentrating it to such an incredible extent.

This means that a forest growing at 10 m3/ha/year is fixing an amount of carbon equivalent to a column of air 1400 m high over each ha EVERY YEAR!

Is this really true? Have I made an error in math? It appears not.

These facts can be used to communicate the power of trees to offset CO2 emissions.

My thinking goes like this: Wood contains about 250 kg carbon per cubic meter. Air contains about 0.177 g carbon per cubic meter (0.05% by weight)

Therefore 1 cubic meter of wood contains approximately the same amount of carbon as 1.4 million cubic meters of air.

A forest growing at the rate of 10 m3 wood per hectare per year is absorbing the carbon from 14 million m3 of air (a column of air 1400 meters high on one hectare).

The combination of photosynthesis and a trees ability to lay down wood (cellulose and lignin) acts as a powerful concentrator of carbon from the atmosphere into a fixed form.

There is no parallel human technology that is capable of performing this kind of carbon concentration.

In particular, the energy supply for wood production is renewable solar energy. One tonne of lumber used in construction results in the release of 30 kg carbon and the storage of 250 kg carbon.

One tonne of steel used in construction results in the release of 700 kg carbon and zero storage of carbon.

One tonne of concrete used in construction results in the release of 50 kg carbon and zero storage of carbon.

Burning one tonne of sustainably grown wood for energy production results in a net release of zero kg carbon (250 kg released and 250 kg absorbed).

Burning one tonne of coal for energy results in a net release of about 500 kg carbon. (Both wood and coal use do require energy for harvesting/mining, transport, etc.)

Therefore, one of the most effective ways to help reduce CO2 concentrations in the atmosphere is to increase the standing biomass of forests, increase the growth rate of forests, increase the geographic extent of forests, AND MOST IMPORTANT, increase the amount of wood used by people where it can be substituted for steel, cement, fossil fuel , and other non-renewable, energy intensive materials, which will result in dramatic reductions in CO2 emissions.

Greenspirit Strategies >> The Forest and Carbon Fixing - Some Stunning Figures - January, 2004