The role trees play in sequestering carbon is well recognised around the world, but the role of wood products as long-term carbon storers is not.

Many people think that once a tree is harvested it has lost most of its environmental credentials, but that is far from the case, according to NSW Department of Primary Industries (DPI) researcher, Fabiano Ximenes.

“People need to recognise that carbon stored in wood products – both in use and after disposal in landfill – adds a whole new dimension to the carbon debate,” he said.

Fabiano said recognition of the carbon stored in wood products would also highlight wood’s environmental credentials, increase revenues for forestry from emissions trading, and provide further incentive for sustainable forestry.

Growing trees absorb carbon dioxide from the atmosphere through photosynthesis and store the carbon. About half the dry weight of a tree or wood product is carbon, with one tonne of carbon representing 3.67 tonnes of carbon dioxide.

Fabiano said carbon stored in wood was released back to the atmosphere only when the wood or wood product decayed or was burnt.

He said wood products have important environmental advantages over alternative building materials in addition to storing carbon from the atmosphere:

• Wood is a renewable resource;
• Comparatively small amounts of energy are used in the manufacture of most wood products;
• Residues generated during the manufacture and processing of wood products can be used in several forms, including replacing fossil fuels to generate energy;
• About 50 per cent of the energy used in the processing of wood comes from renewable sources.

Fabiano said the use of wood products resulted in overall lower greenhouse gas emissions than most alternatives.

“Research has shown that by choosing wood products wherever possible in house construction, greenhouse gas emissions equivalent to up to 25 tonnes of carbon dioxide a house could be saved in Australia,” he said.

“Construction materials such as aluminium, cement and plastic products require large energy inputs, usually from fossil fuels, during manufacture. The manufacture of wood products typically requires less energy than competing materials.

“Also the use of sustainably  harvested wood to generate energy eliminates greenhouse gas emissions that would have resulted from the use of fossil fuels.”

Net carbon dioxide emissions from the generation of electricity using biomass are typically only 5 per cent to 10 per cent those from fossil-fuel-based electricity generation.

At the end of their service life, most wood products in Australia are disposed of in landfill. About 2 million tonnes of wood products and 2.5 million tonnes of paper products are placed in landfill in Australia each year.

Research conducted by Fabiano and fellow researchers has shown that a high proportion of the carbon in solid forest products consumed in Australia remained stored in the product (in service and in landfills) for a period of at least 100 years - much longer than previously thought.

“While various policies and schemes around the world acknowledge the role trees play in sequestering carbon, they do not recognise the role of wood products in storing the carbon for the long term.

“By removing carbon dioxide from the atmosphere in our forests, and by storing the sequestered carbon through the use of wood products, forestry is helping mitigate climate change.

“And if wood products were to be included in emission trading schemes they could do so much more,” he said.

Did you know?

• Each year about seven million cubic metres of sawn and panel products and four million tonnes of paper are consumed in Australia
• Forest products in service store 100 million tonnes of carbon – equivalent to 65% of Australia’s annual greenhouse gas emissions
• Forest products in landfill store 140 million tonnes of carbon – equivalent to more than 90% of Australia’s annual greenhouse gas emissions

This article appears in the Spring 2008 edition of Bush Telegraph Magazine.