Carbon sink and climate

CO2 causing climate change

At least 60% of climate change can be attributed to CO2 emissions resulting from human activities - mostly due to CO2 from the burning of fossil fuels, but also from tropical deforestation. As a result, mean temperatures are expected to rise at a rate of 0.1 to 0.4°C per decade during the first half of this century.

55-70% of the additional greenhouse effect is caused by CO2. Growing by 0.5% a year, according to the most optimistic estimates, the concentration of CO2 in the atmosphere will double by 2100. Just to contain CO2 concentrations in the atmosphere to their current levels would require a reduction in global emissions of more than 40%.

Using wood for the environmental benefit

In China, 20 billion square meters of new habitable area will be constructed by 2020. Environmental issue and energy crisis are two critical problems China and the world are facing in the urbanization process. China's 12th Five-Year Plan put forward stringent targets for both reduction in CO2 (17% reduction by 2015) and increase in forest coverage (to 12.5 million hectare by 2015). Using wood absorbs and stores CO2, which is an effective way to reduce the greenhouse gas emissions in the atmosphere and tackle the climate change. Life Cycle Assessment demonstrates that wood-based solutions have low environmental impact and high quality of wood buildings with minimum consumption of resources.

There are two ways to reduce CO2 in the atmosphere: either by reducing emissions, or by removing CO2 and storing it - reducing "carbon sources" and increasing "carbon sinks". Wood has the unique ability to do both.

Reducing carbon sources

Embodied energy

The energy used to create the materials that make up a building is typically 22% 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 material, wood. This process of photosynthesis also produces oxygen we breathe and on which all animal life relies. In most cases the energy necessary for processing and transporting wood is less than the energy stored by photosynthesis in the wood. Other building materials such as concrete, steel, glass etc. require much more energy, water and human resources to produce and inevitably cause much more negative impact to the environment.

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, aluminum, concrete or plastics, which require large amounts of energy to produce.

5% of all CO2 emissions in the world come from cement production. If a cubic meter of concrete is replaced by timber, CO2 emissions are 13 times lower. The equivalent 0.9 tons of CO2 are stored in every cubic meter of the wood and during the manufacturing phase CO2 emissions are reduced by a further 1.1 tons per cubic meter. In a word, each cubic meter of wood saves a total of 2 tons of 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.

Substitution for fossil fuel energy

Generally wood is good for reuse and recycling. When it cannot be re-used or recycled, it can still produce energy through combustion. The energy produced is effectively stored solar energy.

As the amount of CO2 emitted from combustion is no more than the amount previously stored, burning wood is carbon neutral, a fact well understood by the European wood industry which derives up to 75% of the energy it uses to process wood from wood by-products.

Increasing carbon sinks

The carbon cycle

Each year mankind contributes 7 900 million tons of carbon to the atmosphere, of which the carbon sinks absorb 4,600 million tones, leading to an annual net increase of 3,300 million tones.

This imbalance is so acute that it will not be enough simply to reduce carbon sources, as required by the Kyoto Protocol, carbon sinks will also have to be increased, and one of the simplest ways to increase carbon sinks is to increase the use of wood.

Forests as a carbon sink

On average, trees absorb 1t of CO2 and release almost 727kg O2 for every cubic meter growth because of the photosynthesis. The total carbon stored in Europe's forests, excluding the Russian Federation, is estimated at 9 552 million tons of carbon, increasing annually by 115.83 million tons of carbon.

Managed forests are more efficient carbon sinks than forests which are left in a natural state. Younger trees in vigorous growth absorb more CO2 than mature trees which will eventually die and rot. Therefore, forests need to be harvested sustainably as a metabolic ecosystem.

Wood products as a carbon store

Wood products do not themselves capture CO2 from the atmosphere but play an important role enhancing the effectiveness of the forest sinks, both by extending the period that the CO2 captured by the forests is kept out of the atmosphere and by encouraging increased forest growth. With an estimated European wood product stock of some 60 million tons of carbon, the carbon storage effect of wood products has a significant role to play in reducing greenhouse gases.

The CO2 stored in wood continues to be kept out of the atmosphere throughout the initial life of a wood product and then beyond, through re-use and recycling (for instance as wood panels or reconstituted wood), to be finally returned to the atmosphere through incineration for energy, or decomposition.

The average life of wood products varies between 2 months for newspapers and 75 years for structural wood. The longer, the better for the environment, not least because it makes better use of forest resources, but also because it reduces the energy necessary for replacing the products concerned.

Increasing concentration of CO2 in the atmosphere
Increasing concentration of CO2
in the atmosphere
Comparions of three main materials on ecosystem damage and resource consumption
Comparions of three main construction materials on ecosystem damage and resource consumption
Global carbon balance
Global carbon balance
Photosynthesis
Photosynthesis
Photosynthesis effects of tree growth
Photosynthesis effects of tree growth

 
European Wood (in China)
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Sino-European Wood Center
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