Ask an Expert

Ask an Expert

The environment, sustainability & recycling

Like to know what wood to use building a pergola or framing a barn? How about the difference between tung oil and polyurethane as a floor finish? How to revive decking or deal with merbau stains? Or how to meet the building code or bushfire standards? Or ask about the environmental advantages of wood or forest certification?

Q. There seems to be a lot of conflicting evidence about different building materials. Why is wood better?

Wood has many advantages – it takes less energy to convert logs into timber than to produce any other common building material. And we can grow more wood to replace the timber we use. Other building products are derived from limited resources. Although some products may have large resources to draw upon – now – we can only ‘grow’ wood products, not steel or concrete.

Q. Can using more wood help climate change?

Some people think we should leave our forests untouched, to store carbon. However, trees only take carbon dioxide from the atmosphere while they are growing. The more rapidly they are growing, the faster they remove CO2 and store carbon.

Mature trees require little or no carbon dioxide while over-mature trees may actually give off carbon dioxide as they begin to decay.

When we use wood to build something, we are putting carbon into long-term storage, making way in the forest for a new, vigorously growing tree.

Q. Does wood really store carbon? How does it work

Growing trees absorb carbon dioxide from the atmosphere through photosynthesis and then store the carbon by converting it into wood. About half the dry weight of a tree, or wood product, is carbon.

It takes 3.67 tonnes of carbon dioxide (CO2) to produce one tonne of carbon, so if you know the weight of a piece of wood you can work out how much carbon it contains and how much carbon dioxide it has taken from the air. (For example, 2 kg of wood contains approximately 1 kg of carbon that took approximately 3.67 kg of CO2 to produce.)

Carbon stored in wood is only released back to the atmosphere when the wood or wood product decays or is burnt.

Q. Is there info on how much carbon is released in the manufacture of your average brick, or in the manufacture of the bricks required for an average 4 x 2 home ?

We don’t have data on the carbon released per brick, or per house, but the brick industry acknowledges that brick manufacture is an emission-intensive process. Data is available relating emissions to the dollar value of production, and Think Brick Australia states that between 1200 and 1500 tonnes of C02 are released per million dollars of revenue. You might be interested to read their response to the Government’s proposed carbon pollution reduction scheme. It can be found on their website at www.thinkbrick.com.au.

Q. Why is more not done to highlight the fact that non renewable resources require digging a hole in the ground, making the planet smaller ! Timber is renewable & sustainable

It might be hard to sustain an argument that digging out non-renewable resources makes the planet smaller! Essentially the material is just moved somewhere else, and the planet stays the same size. However, we take your point that growing timber does not deplete non-renewable resources. The “Naturally Renewable” section of our website explains this in more detail.

Q. I found the section building with wood extremely interesting especially the comparisons with different materials. Have you looked at comparing wood based fibre products such as paper and Viscose with petroleum based products such as plastics and fibres.

To date we have focussed on building materials, rather than packaging materials. However, packaging materials that are derived from renewable sources clearly have the same advantages as building materials. They are also far more environmentally friendly at the disposal end of their life cycle. This is now being recognised by government proposals to phase out plastic shopping bags in parts of Australia. On the other hand, we have to recognise that some plastics are produced from by products arising out of the refining process.

Q. Chile in South America produces 70% of the world’s pine . Is this mainly from plantation forests. Also when treating Pine timber with Stains and lacquers for furniture is this counter productive. Eg the stain and lac giving off chemicals into the ozone.

Natural forests of radiata pine have a very limited distribution. Only five stands remain. Three of these are on the Californian coast, and the other two are on islands off the coast of Mexico, so radiata pine from anywhere else, including Chile, must come from a plantation.

While stains and lacquers emit solvents (if they are solvent based), the product as a whole (wood + coating) is still relatively environmentally friendly compared with other materials. And ofcourse water-based stains and coatings are available if desired, which do not produce any solvent emissions.

By the way, Chile doesn’t produce 70% of the world’s pine. Chile has 1.3 million hectares of radiata pine plantations, out of an approximate world total of 3.7 million hectares, which represents 35%.

Q. I'm a forester with Great Southern Plantations Limited and have been impressed with this campaign. I think to express the CO2 -e would be better than quoting carbon stored may be a better option.

Thanks for your encouraging comments about our campaign. Our understanding of “CO₂ equivalent” (CO₂-e) is that it provides a comparison between CO₂ and other greenhouse gases in terms of their global warming potential. So the global warming potential of methane, for example, can be assessed in terms of an equivalent quantity of CO₂. Anyway, we chose to talk about “carbon storage” because the tree takes CO₂ and turns it into carbon (or carbohydrates), and it seemed simpler to talk about how much carbon was stored in this way. But we are always interested in other points of view.

Q. I am interested in knowing how purchasing timber products can possibly be of assistance to climate change? Could you please explain this concept to me.

The answer to your question is two-fold.

Firstly, wood requires less energy to produce than other common materials so when you choose a wooden table instead of a metal one you are choosing a product that had less impact on the environment in its production. That assumes that you were going to buy a table anyway, and wood was the better choice. You could, of course, choose not to buy a table at all!

Secondly, wood products store carbon. This is explained in more detail on our website if you click on the tab that says "Tackling Climate Change".

Q. You state that carbon is “locked up” & only released into the atmosphere again once the wood is burnt or decays. Is this true for wood that is converted to pulp for paper making?

Wood is largely made up of cellulose and hemicellulose, bound together with lignin. Cellulose and hemicellulose are carbohydrates, and that is where carbon is stored. When wood is broken down into pulp, essentially the process involves separating the fibres, either by chemically removing lignin, or by mechanical grinding. Since it is cellulose fibres that form the basis of paper, carbon remains stored until the paper is burnt or decays. Newsprint has a short life, but the major portion is recycled. Other types of paper may be recycled or sent to landfill. Interestingly, research shows that paper products can last much longer in landfill than previously thought, depending on the availability of moisture.

WoodSolutions

Did you know?

About 6% of Australia’s 147 million hectares of native forests are public forests potentially available for timber harvesting. Timber is harvested from about 1% of those public native forests each year.