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. I was wondering what the LCA of Timber is. From the forest till its recyling period?

You will find an interesting and informative report on the Forest & Wood Products Australia (FWPA) website at The report is titled Review of the Environmental Impact of Wood Compared with Alternative Products Used in the Production of Furniture. Although focused on furniture, the report also touches on wooden windows and the use of wood as a building material.

Q. How much carbon goes up in producing 1 tonne of steel and how much carbon is absorbed by 1 cubic metre of pine. This may help us in selling timber pergolas versus steel. Regards Clive

It's estimated by one environmental group that producing 1 tonne of steel releases about 1 tonne of CO2. By contrast, 1 cubic metre of pine has a dry weight of about 500 kg, half of which is carbon. The CO2 required to produce 250 kg of carbon is 917 kg, so 1 cubic metre of wood stores about the same amount of CO2 as production of 1 tonne of steel emits! To be fair we have to take into account the CO2 emitted in the production of 1 cubic metre of wood. The energy used in timber production varies from mill to mill, but one study puts CO2 emissions from processes such as kiln drying at around 100 kg per cubic metre of wood. So the net removal of CO2 from the atmosphere would then be 917 - 100 = 817 kg, which still puts wood well ahead.

Q. I am trying to obtain a (concise as possible) list of timbers for furniture making that are sustainable as well as those that are to be avoided from an environmental standpoint. Can you help?

We are more familiar with the regulatory controls on Australian-produced timbers than those of other parts of the world, and you can be assured that any timber produced in this country is subject to the most rigorous monitoring. For more information about Australia's forests, refer to Australia's State of the Forests Report. This report is produced every five years and the latest (2008) edition can be ordered in hard copy, or downloaded from the net, at Regarding imported timbers, species that are endangered are prohibited imports and not likely to be encountered in the marketplace. You can find more information about these species on the Convention on International Trade of Endangered Species (CITES) website at Regarding species that are not necessarily endangered, but still might be unsustainably managed, the best way to deal with this issue is to seek out products certified by a credible third-party organisation. Banning certain species is not constructive (unless they are endangered), since this catches up producers who are operating sustainably, as well as those who aren't. Exporting countries are mostly well aware of the need to manage their forests sustainably and it is more helpful to support their efforts than to discriminate against their timber. Some developing countries are still working towards the goal of sustainability. For more on the this issue, go to the International Tropical Timber website at The latest newsletter in their Tropical Forest Update series includes an editiorial on Sustainable Forest Industries.

Q. How can I calculate how much carbon is stored in a piece of furniture, or eg. a wood bowl? Does it change with types of wood?

The denser the wood, the more carbon is stored in a specific volume, so a stick of jarrah stores more carbon than the same size stick of balsa wood. This variation between different types of wood is taken into account by calculating carbon content according to the weight of the object. 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 your bowl 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.

Q. I am building a pergola, I like the timber look, the wife likes colour bond - which one is the better choice for the environment and also lasts longer?

Timber has two major environmental advantages over steel products - one is that timber requires relatively small quantities of energy to produce, and the other is that it stores carbon. Trees grow on solar energy and we don't have to dig up the countryside to extract it. Trees also take carbon dioxide out of the air while they grow, and use it to form the various carbon compounds that make up wood. You can find out more about this on our website by clicking on the tab at the top of the page that says "Environmental Benefits". Regarding how long the two products last, that depends on how the structure is built, where it is located and how it is maintained. Timber structures built from durable timbers, or preservative treated timbers, correctly designed and well maintained will last almost indefinitely, and so will steel structures if they are correctly designed and built. One advantage timber has over steel is that it performs much better in a marine environment, so if you are building near the sea, timber is certainly the better choice!

Q. Hello, I am having some furniture made and I would like to know what is the best choice enviromentally. Radiata pine from NZ or Malaysian kauri pine. Thanks Ellen

New Zealand radiata pine is planted and harvested like any other crop, although on a somewhat larger scale than other agricultural products. As far as we are aware there are no doubts about the environmental qualities of New Zealand radiata pine, much of which is independently certified by the Forest Stewardship Council (FSC). You can find out more about the certification of New Zealand pine on the internet. Malaysian kauri pine is more commonly known internationally as damar minyak (Agathis borneensis). This species has been recommended for listing in Appendix II of the Convention on International Trade in Endangered Species (CITES). If the recommendation is adopted, trade in damar minyak may be subject to greater regulation in future, but this does not necessarily mean it is a threatened species. While there are no restrictions on trade at present under CITES, you may wish to seek further information from your supplier about the source of the timber being offered, including details of any certification.

Q. My husband Richard and I are interested in planting trees for carbon credits and helping the enviroment instead of farming, on our property at Foster Victoria. We have 168 acres which we are agisting at the moment to a local farmer as we dont live there.

Planting trees is a practical way to help reduce carbon dioxide emissions. However, the economic viability of growing trees for timber production depends on rainfall, proximity to a sawmill, and a number of other factors. You will need to consider these factors carefully if you want to sell the logs at maturity, as opposed to just planting trees to help the environment. There are some useful booklets to help you get started, some of which you can download from the net. If you type “farm forestry” into your browser you will find the relevant links. Organisations such as Australian Forest Growers can also help. You can visit their website at Their booklet Getting Started in Farm Forestry sets out some of the basic issues. Once you complete your preliminary research, it might be worth engaging a consultant forester to advise you on the specifics.

Q. In reference to the Q on illegally harvested forests on 30th Sept 2008, your response does not give info about the industry in terms of how we minimize the risk. You should mention that state and private forests are certified.

Our answer refers to the illegal logging of forests outside Australia. It never occurred to us that anyone would think Australian forests were illegally logged, given the strict legislative framework under which they are managed. However, we take your point that the certification of Australian forests helps to reassure timber users that they are harvested sustainably.

Q. I'm doing a school project on energy efficiency in buildings. Can you tell me how much energy is used to make different building materials?

The figures for different materials can differ slightly, depending how the energy use is calculated.

Approximate energy requirements for creating a cubic metre of material are:

  • Timber – 750 MJ
  • Concrete - 4,800 MJ
  • Steel - 266,000 MJ
  • Aluminium - 1,100,000 MJ

So, in terms of energy requirements, timber uses much less than other building materials.

Q. I have some wood left over from a project – can I recycle it?

There are various ways to recycle wood, depending on the type and quantity. Most larger cities and towns in Australia have companies that specialise in recycled building materials. If you have sought-after types and sizes of timber, you might be able to sell your leftovers. Alternatively, you could donate the timber to a charity or sheltered workshop if it is suitable for making useful items. If your leftover material just consists of scraps, you can always use it for domestic fuel!


Did you know?

A government report showed there is no evidence proving that harvesting timber from native forests has reduced overall forest biodiversity or led to the extinction of any species of plant or animal.