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Environment

Forests, Timber and the Greenhouse Effect

The Current Challenge

The increase in carbon dioxide and other gases in the atmosphere has resulted in concern about the possible effects on the world’s climate. This increase of carbon dioxide has been associated with global warming or the Greenhouse Effect. Forests and forest products play a vital role in using and reducing Greenhouse gases which influence the Greenhouse Effect.

The Greenhouse Effect Explained

The Greenhouse Effect occurs naturally. A combination of gases in the Earth’s atmosphere are known as Greenhouse gases. These include carbon dioxide, methane, water vapour and nitrous oxide. These gases form a shield around the Earth.

Sunlight passes through the Earth’s atmosphere and is reflected back into space. Some of this reflected light will be trapped by the Greenhouse gases. This is the Greenhouse Effect, which is a natural process that maintains an average temperature of 16 degrees Celsius on Earth and ensures survival of plant and animal life.

If there were no Greenhouse gases in the Earth’s atmosphere, the environment would be similar to that of the moon which has no evidence of life.

Only about one per cent of the Earth’s atmosphere is made up of naturally occurring Greenhouse gases. If this fine balance of gases is altered there could be significant effects on Earth. These could include increases in the average temperature, changes in the world’s rainfall pattern, vegetation cover and rising sea levels from melting ice caps.

Greenhouse gas emissions have increased due to human activity since the Industrial Revolution started in the 1800s. These activities include burning fossil fuels, increased mining and clearing of forested land for agriculture and housing. Carbon dioxide is the main Greenhouse gas produced from these activities. Scientists believe carbon dioxide levels have increased by 25 per cent between 1900 and 1985.

Use of Carbon Dioxide in Forests

Plants carry out a process called photosynthesis. They take in carbon dioxide from the air through their leaves and use energy from the sun, to make food. As part of this process the carbon is then stored or “fixed” within the stems, leaves and branches of the plant and oxygen is released into the air. The carbon dioxide is only released again when the plant is burnt or decomposes.

Carbon Credits

Carbon credits, or Certifiable Tradeable Offsets (CTOs) are recognised reductions or absorption of carbon relative to the normal way of doing things. So, as NSW works to reduce Greenhouse gas emissions and expand the use of Greenhouse sinks such as planted forests, these actions can be registered as credits. The credits should be certified and recognised by a certificate that can be owned by the individual or company that has created the Greenhouse gas saving.

Over time, companies or individuals who create more certificates than they need can sell the extra certificates to others who need to reduce their Greenhouse gas emissions.

The Role of Planted Forests

New pine and eucalypt plantations in NSW are established on existing cleared land. The larger the area of plantations established and the faster they grow, the more carbon dioxide will be removed from the atmosphere, thus reducing imbalance in the Greenhouse Effect.

The advantages of using timber

Timber and other wood products store the carbon dioxide they absorbed when they were growing trees. The carbon stored in the timber will not be released even when a tree has been harvested and processed into timber products.


Plastics (derived from petrochemicals) and metals such as steel or aluminium actually produce Greenhouse gases during their manufacture. Even the process of extracting some raw materials from the ground such as bauxite for aluminium, results in Greenhouse gas emissions.

Comparison of energy usage in production of building materials (producing one tonne of each)

Building Material Kilowatt Hours
(electricity)
Equivalent usage of ash-free
coal
Timber 435 0.13 tonnes
Steel 3780 1.15 tonnes
Aluminium 20169 6.12 tonnes

 
The table above demonstrates it takes far less energy to produce timber than it does to produce steel or aluminium for use as building materials.

Energy is equivalent to electricity. The main source of electricity in NSW is coal. Coal is formed from dead plant matter after millions of years of heat and compression. Coal therefore contains large amounts of carbon which is released into the air when it is burnt to make electricity. So, the less electricity used, the less carbon dioxide is released into the atmosphere.

Amount of carbon dioxide released during manufacture of different materials

Material Amount of CO2 released during the
manufacture per kg of material
Aluminium 27.50 kg
Copper 8.5 kg
Glass 1.30 kg
Iron 1.75 kg
Lead Lead 2.50 kg
Plastic 3.40 - 11.00 kg
Rubber 4.80 kg
Steel 3.20 kg
Wood n/a *


* Timber contains stored carbon dioxide from the atmosphere. Although some carbon dioxide is released during the milling of timber, the net effect is that 8.3 kg of carbon dioxide is actually absorbed during both the growth and milling process of timber, no carbon dioxide is produced.

The average floor area of a newly constructed house in NSW is 180 m2. In a timber-framed brick veneer house of this size, around 21 m3 (or a large truck load) of timber is used. In a steel-framed house, only 6.7 m3 of timber is used.

An average 180m2 house

  Timber Frame Steel Frame
Frame only 13 m3 wood 5 tonnes steel
Total house 21 m3 wood 6.7 m3 wood
Total carbon stored 9.7 tonnes 3.1 tonnes (in wood only)
Total carbon released to
atmosphere in production
2.2 tonnes 6.0 tonnes
Balance of carbon 7.5 tonnes stored -2.9 tonnes stored

 
A steel-framed, brick veneer house on a concrete slab releases lots of carbon dioxide into the air, compared with a timber-framed, timber-clad house with a timber floor.

Summary

Forests and forest products have an important role in reducing Greenhouse gases. Young, actively growing regrowth forests and plantations take in large amounts of carbon dioxide from the air. Older and mature forests are an important storehouse of carbon. Timber products not only require far less energy to produce than alternatives such as steel and aluminium, but also act as a longterm storage for carbon.

Information provide by State of New South Wales, 2005

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