CO2 emissions are the main cause of Climate Change
The term ‘greenhouse effect’ refers to the way infrared radiation from the Earth is trapped, heating up the atmosphere. The most important greenhouse gas is carbon dioxide (CO2), but others include steam (H2O), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF6).
At least 60% of climate change can be attributed to CO2 emissions resulting from human activities – mostly the burning of fossil fuels, which contributes 6 billion tonnes of carbon emissions annually.
Just to contain CO2 concentrations in the atmosphere to their current levels would require a reduction in global emissions of more than 40%. As 85% of the energy necessary to run our societies comes from fossil fuels, a reduction in emissions of this order would involve politically unacceptable cuts in our energy consumption.
There are two ways to reduce CO2 in the atmosphere
- By reducing emissions, or
- By removing CO2 and storing it: reducing ‘carbon sources’ and increasing ‘carbon sinks’
Reducing carbon sources
Embodied energy – The energy used to create the materials that make up a building is a significant portion of the total energy expended over the lifetime of the building, so it is worth paying attention to the materials specified, as well as to the energy-efficiency of the structure. There is no other commonly used building material that requires so little energy to produce as wood. Thanks to photosynthesis, trees are able to capture CO2 in the air and to combine it with the water they get from the soil to produce the organic and renewable material; wood.
This process of photosynthesis also produces oxygen; all the oxygen we breathe and on which all animal life relies, comes from the photosynthesis activity of plants and trees. So, from every molecule of CO2, photosynthesis produces two key components essential to life: one atom of carbon, around which all living materials are built, and one molecule of oxygen, on which all animal life relies.
Substitution for other materials
Not only is the production and processing of wood highly energy-efficient, giving wood products an ultra-low carbon footprint, but wood can often be used to substitute for materials like steel, aluminium, concrete or plastics, which require large amounts of energy to produce.
In most cases the energy necessary for processing and transporting wood is less than the feedstock energy stored by photosynthesis in the wood.
Every cubic metre of wood used as a substitute for other building materials reduces CO2 emissions to the atmosphere by an average of 1.1 t CO2. If this is added to the 0.9 t of CO2 stored in wood, each cubic metre of wood saves a total of 2 t CO2. Based on these figures, a 10% increase in the percentage of wooden houses in Europe would produce sufficient CO2 savings to account for about 25% of the reductions prescribed by the Kyoto Protocol.
Forests as a carbon sink
Thanks to photosynthesis, the trees in a forest can trap large amounts of CO2 and store it as wood. Some 0.9 t CO2 is trapped in every cubic metre of wood.
However long the CO2 remains stored in the wood, any increase in the global volume of ‘wood storage’ will reduce the CO2 in the atmosphere. So increasing the use of wood is one simple way of reducing climate change.
According to the International Panel on Climate Change (2007), « mitigating options by the forest sector include extending carbon retention in HWP, product substitution, and producing biomass for bioenergy. »
- Wood can reduce CO2 sources
- Wood can increase CO2 sinks