Wood as a climate stabilizer
What is carbon dioxide (CO2), where does it come from?
There is probably no way that anyone has not heard of CO2 yet. It is perhaps better known as greenhouse gas or climate pollution that we must get rid of somehow. But it is not a poison; in fact you could say it is something important.
Everybody understands that there would be no fauna – no animals nor humans – without oxygen (O2) in our atmosphere. Just as well there would be no flora – no plants nor trees – without carbon dioxide (CO2).
The only problem is that there is too much CO2 or not enough trees. Land clearing and the combustion of fossil fuels like coal, gas and oil increase the concentration of carbon dioxide in the atmosphere dramatically. And that causes global warming, in other words less heat is able to leave our planet than new heat is inserted.
Many substances absorb energy and thereby contribute to global warming. Water vapour has a huge impact but that is (almost) natural. 9-26 % of global warming is caused by carbon dioxide [Wikipedia] and that is developed by all kind of combustion processes.
Photosynthesis – how can wood reduce carbon dioxide emissions?
As part of photosynthesis trees sequester (absorb), during the growth, carbon dioxide (CO2) of the air and nutrients of the water and soil to build up the organic material wood.
The oxygen (O2) will be released back into the environment. The glucose, also known as dextrose, including high-energy carbon (C) however, is an important substance for trees and enables them to grow.
Carbon becomes part of the organic structure of the trees and will be bound to them for the entire lifespan and often also a long time thereafter.
How much carbon is stored in trees?
The forests – actually the trees – store a tremendous amount of carbon during the growth. You could say they filter the carbon dioxide from the air and store pure energy like a battery, thereby contributing significantly to climate protection.
As long as a tree grows, even if it is an old tree, it filters carbon dioxide (CO2) out of the atmosphere and releases oxygen (O2) into the air. The carbon (C) however, stays in the tree and forms a substantial part of the wood.
The only way to reverse that process and convert carbon into carbon dioxide again is by burning or rotting wood or timber. Thus, not only forests, but also buildings, timber decks, furniture or even wooden toys are valuable carbon depositors which help enormously to reduce the CO2 load of the atmosphere.
About 45% of the dry mass (not including the water) of a tree comes from carbon. In other words, a 100 kilogram log of a tree that has been completely dried contains about 45 kilograms of stored carbon [ESA21].
The atomic mass of carbon is 12. The atomic mass of oxygen is 16 [periodic table]. To build a CO2 molecule we need one atom C and two atoms O.
The atomic mass of CO2 is: (C)12 + (O2)2x16 = (CO2)44
That in turn means that each carbon atom, which is stored in tree biomass, reduces the carbon dioxide emission by (44/12=) 3.67 of its own mass.
A one kilogram log of wood offsets carbon dioxide emissions by 1.65 kilograms. 1kg (wood) x 0.45 (carbon content) x 3.67 (CO2 / C) = 1.65kg CO2 reduction. This result gives an idea of how important trees are to remove carbon dioxide from the atmosphere.
How much carbon dioxide is removed by Australian forests?
Trees in Australia's native forests hold about 6.56 billion tonnes of carbon in their biomass (trunks, branches, leaves and roots). Australia's forest soils are another important carbon sink, they contain about 5.51 billion tonnes of carbon. That together is equivalent to about 44 billion tonnes of carbon dioxide removed from the atmosphere, or 84 years worth of Australia's total 2005 net emissions from all sources.
In 2005 Australia’s forests, plantations and wood products sequestered a net amount of 56.5 million tonnes of carbon dioxide, thereby offsetting total greenhouse gas emissions by nearly 10% [Department of Agriculture, Fisheries and Forestry, Forest Australia].
56.5 million tonnes of carbon dioxide equals 31 million tonnes of carbon stored in trees and that equals 68.5 million tonnes of 100% dry wood (100% dry wood is in reality not possible).
If we assume a realistic 20% moisture content for dry timber and 50% of a tree actual lumber, then Australia’s forests produce about 40 million tonnes of lumber each year or about 1.3 tonnes of lumber each second.