Timber Building in Australia

Environmental Properties of Timber © FWPRDC

The range of building materials

Timber has a long and distinguished history as a building material - having been used for centuries for framing, lining, cladding, flooring and roofing in both domestic and industrial constructions, as well as for bridges, wharves, railway sleepers and so on.

In relatively recent times, a range of alternative materials (steel, aluminium, concrete etc) have been successfully introduced into the construction industry. New timber products (such as particleboard and glulam to name but two) have also been developed.

As a result, consumers now have a range of building materials from which to choose. In making their choice, they take into consideration a number of factors.

Selection criteria for building materials

In the past, the factors influencing the choice of building material were predominantly 'suitability', 'cost', 'availability' and 'appearance'.

However, these days, when it comes to selecting products, consumers are also often concerned about the impact which these products have on the environment. Their concerns relate to issues as varied as global warming, wildlife preservation and human health. Buyers want to know which of the possible products is the most environmentally friendly and often they will want to use that product in preference to those they see as 'less friendly'.

This trend is as apparent in the market for building materials as it is in other markets. Increasingly, consumers seek answers to the question: "How does timber perform environmentally - especially in comparison with its substitutes?'

This brochure provides information about the impact of timber and timber products on the environment. Wherever possible, these impacts or potential impacts are compared with those of substitutes for timber in the construction industry.

In providing this information, it is recognised that, if valid product comparisons are to be made, all environmental impacts occurring during the life of the products must be accounted for. It is the overall net benefit which should be considered.

The following section discusses the process of evaluating the total environmental impact of products by means of life-cycle assessment/analysis (LCA) techniques.

Life-Cycle Assessment/Analysis

Life-cycle assessment or analysis (LCA) means measuring the total impact of a product on the environment - from when the raw materials are extracted, through the product's life as a consumer item, to when it is disposed of or recycled.

Alternative terms for LCA include 'cradle-to-grave' analysis, ecobalance, product life-cycle analysis, and resource and environmental profile analysis.

LCAs build on earlier ways of comparing products. These compared the 'embodied energy' of a product - that is, the energy used to produce the materials, process them, transport them to where they are needed and construct and maintain the finished product. LCAs extend the concept of embodied energy by including the pollution associated with obtaining, using and disposing of products, and the extent to which resources are depleted or damaged in the product's manufacture, use and disposal.

There is no one LCA methodology (although the International Organisation for Standardisation is coordinating the development of global guidelines for LCAs) and LCA models vary in complexity. At the simplest are the systems such as the UK 'Ecolabelling' approach - an approach similar to the 'Energy Rating' system used for whitegoods in Australia. At the other end of the spectrum is the Canadian Wood Council's approach, which attempts to quantify and include factors such as manufacturing effluents and water demand in the assessment.

One LCA approach applicable to the Australian construction industry is the Building Material Ecological Sustainability Index (BES Index) which was developed at the University of New South Wales. This index enables products to be rated according to the following factors.

In the area of resource depletion -

the damage to the environment caused by the extraction of raw materials;
the extent of damage relative to the amount of material produced;
how much of the raw material exists;
how much of the product consists of recycled materials;
the environmental cost of maintaining the finished product; and
the extent to which the product can be recycled.

In the area of pollution -

the amounts of solid and liquid waste, greenhouse gases, toxins and particulates (dust) resulting from extraction, manufacture and production;
the environmental cost of fabrication and on-site waste and packaging;
the environmental impact during the building's life (such as that involved with heating, cooling and lighting); and
the environmental impact at the end of the life of the building (for example, the cost of disposal).

In the area of energy use -

the energy required to obtain raw materials, process them and produce the building material;
the energy used in transporting the material (at all stages); and
the energy used in construction and eventual demolition.

Life cycle assessments can help consumers compare the environmental and ecological credentials of substitute products and can help manufacturers identify where improvements in extraction, processing and disposal need to be made. However, they are not perfect tools. In using LCAs it is important to acknowledge that results:

are often based on incomplete data - especially in relation to Australian conditions;
inevitably involve some qualitative judgment (for example, is the potential impact on biodiversity caused by timber harvesting a more or less serious environmental impact then the effect of photochemical smog caused by steel-making and other industrial and transport activities?);
focus on environmental factors and, sometimes, do not address relevant technical, economic or social aspects of the product or process; and
depend on fundamental assumptions about the life of a product.

Notwithstanding these qualifications, LCAs can provide valuable insights into the nature of products.

The following section looks at the environmental impact of timber and substitute building materials during the stages of procurement, conversion, installation, maintenance, demolition and disposal.

The material is presented in line with what are seen as the 'big issues' fro consumers - the greenhouse effect, energy consumption, pollution, and sustainable development (including recycling).

By definition, LCA is a holistic approach. However, for ease of presentation and comprehension, in this document the various components of LCAs are treated separately. Nevertheless, it is emphasised that no one impact of a product at any stage of its life can be regarded as indicative of the product as a whole.

Timber and the environment

The greenhouse effect
The greenhouse effect - the periodic gradual warming of the earth's atmosphere - is a natural process. However, the effect is enhanced as human activity increases the input of particular gases into the atmosphere. The most significant gas in the enhanced greenhouse effect in terms of quantity is thought to be carbon dioxide.

There is an important link between trees and carbon dioxide. During their period of active growth, as part of the process of photosynthesis, trees absorb carbon dioxide from the air and 'sequester' (store or fix) it in woody tissue - thus reducing the greenhouse effect. Mature trees have little ability to further sequester carbon dioxide, although carbon storage does continue in the ecosystem in, for example, leaf litter on the forest floor.

People sometimes think that, because of the relationship between trees and carbon dioxide, the harvesting of timber contributes significantly to the accelerated greenhouse effect. However:

at the time when trees are harvested as saw logs, their capacity to absorb carbon dioxide is lower; thus, their ability to contribute to slowing the greenhouse effect is diminishing;
using saw logs for long-life products, such as buildings, ensures that the carbon dioxide remains 'fixed' for long periods; and
continually replacing felled trees with actively growing trees ensures that the sequestration of carbon dioxide continues.

Another related, but common, misconception is that, because products such as steel, aluminium and concrete do not release carbon dioxide to the atmosphere as they age, it is more environmentally-friendly to use them instead of timber. However, this overlooks the fact that the manufacture of these substitute products releases large amounts of carbon dioxide into the atmosphere. It is important to recognise, for example, that:

steel making, which requires energy and involves the burning of non-renewable fossil fuel, liberates about 2 tonnes of carbon dioxide for each tonne of steel produced;
a steel-framed house accounts for the release of 3.5 tonnes of carbon, but the equivalent house framed in timber can store 3.1 tonnes of carbon; and
timber stores up to 15 times the amount of carbon dioxide released during its manufacture, whereas steel and aluminium store negligible amounts.

The carbon dioxide released and stored by various building materials during their formation are summarised in Table 1.

Table 1: Carbon released and stored in the manufacture of building materials

Material	Carbon released (kg/t)	Carbon released (kg/m3)	Carbon stored (kg/m3)
Rough sawn timber	30	15	250
Steel	700	5320	0
Concrete	50	120	0
Aluminium	8700	22000	0

Source: Presented in Ferguson, I., La Fontaine, B., Vinden, P., Bren, L., Hateley, R. and Hermesec, B. 1996, 'Environmental Properties of Timber", Research Paper commissioned by the Forest & Wood Products Research & Development Corporation.

Overall, while trees are continually replanted and the timber used in long-life applications (such as buildings), timber is much less of a contributor to the enhanced greenhouse effect than are its substitutes in the construction industry.

Energy use
Consumers are increasingly aware of the need to conserve scarce resources and are keen to buy products and practices which are energy-efficient to operate. But efficient operation is only one aspect of a product. In any LCA study, total embodied energy is one of the key factors.

Embodied energy is:

the energy required to obtain raw materials, process them and produce the building material;
the energy used in transporting the material (at all stages); and
the energy used in construction.

This section looks at the energy embodied in the manufacture, transport, construction and maintenance of the product and the sum of these. Because climate, design and siting vary significantly for individual buildings, no data are presented for energy used in the operation of buildings.

Energy use in manufacture
The majority of energy consumed in association with building materials is used during the processes of manufacture. As can be seen in Table 2, the manufacture of rough sawn timber uses vastly less fossil fuel energy per unit volume than does that of steel, concrete or aluminium.

Table 2: Fossil fuel energy used in the manufacture of building materials

Material	Fossil fuel energy (MJ/kg)	Fossil fuel energy (MJ/m3)
Rough sawn timber	1.5	750
Steel	35	266000
Concrete	2	4800
Aluminium	435	1100000

Source: Presented in Ferguson, I., La Fontaine, B., Vinden, P., Bren, L., Hateley, R. and Hermesec, B. 1996, 'Environmental Properties of Timber", Research Paper commissioned by the Forest & Wood Products Research & Development Corporation.

Energy use in transport
In some cases, the transport of raw and processed materials consumes a significant amount of energy. The exact amount depends on the weight of the material, where the materials are extracted, processed and used, and the type of transport used. Because these factors vary on a case-by-case basis no exact data can be given here.

However, when transport costs are considered in LCA, the use of domestically-grown timber could be shown to be more environmentally-friendly than the use of imported timber - although even this depends on the distances over which the material is transported and the type of transport used. Some general data are available. It is known, for example, that road transport can be about six times more energy-intensive than rail transport and 15 times more energy-intensive than sea transport.

Energy use in construction and maintenance
Table 3 presents data for the construction and operation of houses built with different materials. It shows estimates of energy embodied in the walls of a house of standard size in terms of the initial energy required for the construction, and the total energy after allowing for subsequent maintenance over a 40 year life.

Again, the correlation between high timber use and low embodied energy is apparent.

Table 3: Energy embodied in construction and maintaining buildings with different wall materials

Type of Construction	Energy per unit area of assembly (MJ/m2)	Energy used to complete construction (MJ)	Energy used in maintenance over 40 years (MJ)
Timber frame, timber clad, painted	188	31020	24750
Timber frame, brick veneer, unpainted	561	92565	0
Double brick, unpainted	860	141900	0
Autoclaved Aerated Concrete, painted	464	76560	24750
Steel frame, fibre cement clad, painted	460	75900	24750

a steel beam requires more than 10 times the production energy of the equivalent timber beam;
brick cladding for houses uses significantly more energy than wood cladding;
aluminium window frames use over 50 times the energy equivalent wooden frames;
on a weight-for-weight basis, the manufacture of sawn timber involves approximately 10-30% of the energy needed to manufacture steel and less than 6% of the energy needed to manufacture aluminium; and
much of the energy used for drying kilns is waste material from the harvesting process. In comparison, most of the energy used in the extraction and processing of substitute materials is non-renewable fossil fuels.

Pollution
This section compares the by-products involved in the manufacture of various building products.

In terms of specific gas emissions, the manufacture of timber products is associated with lower emissions of carbon dioxide, carbon monoxide, sulphur dioxide and volatile organic compounds than is the manufacture of steel. While timber produces more weight of solid wastes, the wastes it does produce can be reused as, for example, particleboard, fibreboard, mulch or fuel.

In relation to the waste products and emissions of various building materials, the following summary points are relevant.

Timber and timber products

Forests act mainly as net sinks for sulphur dioxide and nitrogen oxides and for particulate matter. Continually replacing felled trees in plantations of actively growing trees ensures that this absorption continues.
Timber wastes can be (and usually are) recycled as, for example, particleboard, fibreboard, mulch or fuel for drying kilns.
Current processes reduce the extent of 'bleeding' of creosote (used in preserving timber) to a minimum, and poles and piles treated with creosote are invariably used in situations in which they pose little hazard.Copper chrome arsenic (CCA) preservatives are used to slow the decay of timber in situations ranging from insect attack to exposure to marine conditions. States and Territories have legislation limiting contaminant levels.
Light organic solvent preservative treatments have recently been improved to overcome excessive solvent and 'bleeding'. Solvent emission is rigorously controlled in Australia.

Iron and steel

In the manufacture of iron and steel, there are emissions to air of carbon monoxide, sulphur dioxide, and nitrogen oxides (totalling 40 kg/t of steel), and to water of heavy metals and oils.
Large quantities of solid waste (mainly slag) are created during manufacture, in addition to smaller quantities of hazardous waste, which may require disposal to landfill.
About 150,000 litres of contaminated water (containing hydrocarbons and other organic compounds, sulphides, phenolics, ammonia, metals, cyanide, oil and grease) are produced for each tonne of steel.

Aluminium

The most notorious by-products of aluminium production are caustic mud and red sand. Over 15 million tonnes (dry base) are generated each year in Australia and over 200 million tonnes are presently stockpiled.
Aluminium smelting is the source of fully fluorinated compounds (FFCs) which are much more powerful greenhouse gases then carbon dioxide because of their extremely long lives. Controls over these compounds are improving.

Cement and concrete

The manufacture of cement can involve the emission of up to 240g of sulphur dioxide and of up to 6kg of nitrogen oxides per tonne of cement.
Water consumption and liquid effluents are a significant aspect of concrete production and usage. Between 1500 and 3000 litres of alkaline effluents (pH8) may be generated fro each cubic metre of concrete.

The estimated dollar value of the environmental costs incurred in the production of comparable wood and steel walls is shown in table 4. The environmental externality cost imposed by timber is less than 30% of that imposed by steel.

Table 4: Environmental externality costs

Pollutant	Cost ($/kg)	Wood wall (4)	Steel wall (4)
Electricity		1.46	4.67
CO₂	0.15	47.00	145.65
SO₂	1.80	0.66	6.65
NO_X	4.47	4.52	7.04
Particulates	2.62	0.49	1.55
Effluents	0.05	0.61	24.80
Total		54.74	190.57

Source: Presented in Lawson, W.R., 1996, 'Timber in Building Construction: Ecological Implications', Research Paper commissioned by the Timber Development Association (NSW) Limited and the Forest & Wood Products Research & Development Corporation.

Overall it can be stated that, in terms of waste products and emissions, timber out-performs steel and aluminium and compares very favourably with cement and concrete.

Sustainable development
Resource depletion
Using any material decreases the supply of that material available - at least in the short term, and in some cases forever.

Trees are, of course, a renewable resource; whereas substitute building materials are generally non-renewable.

Steel is manufactured from the non-renewable resources iron ore, alloy metal ores, coal and limestone, and, although the supply of those resources at current rate of usage is guaranteed for many hundreds of years, the same may not be true for some of the minerals (chromium, nickel, cobalt, vanadium) needed to form the alloys which give steel its special properties.

Ecologically Sustainable Development (ESD)
The term ESD has become widely used. It refers to designing development so that ecosystems (the interactions of flora, fauna, soil, water and air) can be sustained, to the benefit of current and future societies. It is in this area that timber has the potential to be more environmentally expensive than substitute building materials. However, industry codes of practice and legislation are increasingly ameliorating this impact.

For many years Australia has been a world leader in applying legislation, regulations, policies, regional and site planning, and codes of practices to aspects of forest management. As a result, much of the forest and plantation management carried out in Australia is being carried out in a manner approaching ecological sustainability.

Most of the mandatory requirements have been developed by State Governments which have the primary responsibility for the health of forests. All States of Australia with native forest and plantation responsibilities have in force, or are in the process of implementing, Codes of Forest (Management) Practice.

More recently, the Commonwealth has been active in this field - with overarching policies that are also aimed at achieving sustainable forest management, including the creation of a national conservation reserve system. These reserves, appropriately managed, will help meet the nation's biodiversity and endangered species obligations.

Of course, alternative building materials are not 'ESD-neutral'. The extraction and preprocessing of ores disturbs wilderness, wildlife habitats and ecosystems, and involves solid and liquid waste disposal, noise and dust, subsidence, accelerated release of ground methane and site contamination due to fuel spillage.

Wildlife and biodiversity
Biodiversity - the existence of diverse ecosystems, species and genes - is important because human life depends on these resources and their interaction for all its food, many of its medicines and industrial products and much of its cultural values. Forests are an essential component of ecosystems and, therefore, harvesting of forests has an inevitable impact on biodiversity.

Mining operations also involve disturbance to the environment and to ecosystems. The obvious ones (such as scarred landscapes) occur across smaller areas than do those of timber harvesting, but the less visual impacts (such as the impact on specific species) may be significant.

In considering the impact of timber on biodiversity, the following points should be remembered:

The Resource Assessment Commission found 'no evidence to suggest the risks of extinction resulting from logging present an immediate threat to the ecological processes on which forest systems depend'. Nevertheless, the Commission adopted precautionary approaches in framing recommendations for the protection and management of vulnerable species and ecosystems. These are now being implemented through the joint Commonwealth/State regional Forest Agreements. Worldwide, Australia is seen to be in a leading position in relation to the protection of biodiversity.
The Resource Assessment Commission also stated that 'The principal threats to endangered forest and woodland species are agricultural expansion and grazing. Timber harvesting has the potential to directly affect about 5% of all endangered species and vulnerable plant species, an additional 30% of these species may be indirectly affected'.
Codes of Forest Practice are required steps in the Regional Forest Agreements being developed between the Commonwealth and the States.
Wilderness recreation is to be zoned under Regional Forest Agreements now in train, and most wilderness areas are already protected and within the prospective conservation reserve scheme.

Soil
Forestry operations impact on soils in a number of ways. Removal of vegetation in the form of snigging tracks exposes soil to increased erosion, and the movement of machinery may result in displacement and compaction of soil.

However, while forestry has the potential to influence soils, the impact is not always negative. Two examples of positive influences are provided below.

Where plantations are established on previously cleared agricultural land (as is very often the case), the impact may be beneficial in that soil condition can be improved through the application of fertilisers. Furthermore, aeration of soils by tree roots, and addition of organic matter by way of leaf litter, may improve the overall conditions of the soil. Soil erosion can actually be reduced by tree roots and leaf litter and by way of the sheltering effect of the plantation.

Plantations have been successful in ameliorating soil salinity caused by raised water tables.

Water
The use of forests for timber production has distinct but often complex interactions with waterways. Forestry tracks can be a major source of sediment input into streams in small catchments - although good design and use of roads will minimise this effect. Fertilisers, weedicides and pesticides can leach into waterways - but only to a small extent compared with pastures and short-life crops. Pesticides are little used in native forests and used only in the establishment phases of plantations. Permanent removal of trees can lead to rises in water tables - bet replanting can mitigate this.

Where plantations are established on previously cleared agricultural land, the impact may be beneficial in that:

trees can slow the rate of erosion and the movement of eroded soil into the waterways;
the deep-rooted trees, rather than shallow-rooted crops, can act to lower water tables; and
trees can shade aquatic ecosystems from excessive heat and light which contribute to agal blooms.

Recycling
Life-cycle assessment of products includes examination of the environmental impact of the product at the end of its life. How a product is recycled or disposed of id therefore relevant to any assessment of any product.

In considering the issue of recycling, the following points should be taken into account:

almost all the timber waste produced at the manufacturing stage is reused as fuel fro drying kilns, or as wood products such as particleboard, fibreboard, chips or mulch;
research into the safe disposal of treated timber is currently underway; and
while metals such as steel and aluminium may be recycled, the recycling processes themselves consume energy, release carbon dioxide and liberate wastes.

Such is the increasing demand for recycled hardwood in Australia that it is estimated that demand will outstrip supply in ten years.

Summary of comparative costs on an LCA basis

Using the Building Material Ecological Sustainability (BES) Index, table 5 rates the environmental impact of a range of building material, timber has a generally less harmful effect on the environment than do its substitutes.

Table 5: Comparisons of some common building materials (BES Index)

Element	Resource depletion	Inherent pollution	Embodied energy*
Autoclaved Aerated Concrete block	16.8	7.8	3.5
Autoclaved Aerated Concrete panel	16.8	6.2	5.4
Cement render	19.5	9.2	2.0
Cement mortar	15.5	55.9	2.0
Clay brick	13.4	4.2	2.0
Clay tile	13.4	4.2	2.0
Concrete - in situ	15.6	6.9	2.0
Copper sheet	30.2	28.9	100.0
PVC u/g pipe	14.0	17.3	79.0
PVC floor tiles	16.0	22.1	79.0
Plasterboard	13.5	9.3	4.5
Basic Oxygen Steel, coated sheet	18.2	19.2	38.0
Basic Oxygen Steel, stud	18.2	19.5	38.0
Electric Arc Furnace steel, reinforcing rod	8.3	9.5	19.0
Timber, softwood stud	9.2	5.7	3.5
Timber Particleboard (softwood)	9.2	7.1	8.0
Timber, hardboard (hardwood)	13.3	5.4	24.0
Timber, imported Western Red Cedar frame	13.6	6.8	4.5
Timber hardwood engineered product	11.2	4.1	11.0

Assembly		Resource depletion	Inherent pollution	Embodied energy
Ground floors	Timber on clay brick piers and fottings	12.0	4.9	2.7
	Autoclaved Aerated Concrete panels on Autoclaved Aerated Concrete block walls and concrete footings	50.0	21.0	9.5
	Concrete raft slab	58.0	26.0	8.4
Upper floors	Timber	3.7	2.6	1.9
	150mm Autoclaved Aerated Concrete	22.0	8.5	5.4
	150mm concrete slab	57.0	26.0	8.8
External walls	Timber frame, timber weatherboards, plasterboard lining	4.1	2.6	1.5
	Timber frame, brick veneer, plasterboard	34.0	12.0	5.5
	Double (cavity) brick	63.0	20.0	9.2
Internal walls	Autoclaved Aerated Concrete bock with render	16.0	6.3	4.8
	Clay brick with render	36.0	13.0	13.0
	Timber studs with plasterboard	3.6	2.4	1.3
	Steel studs with plasterboard	2.8	2.2	1.9
	Reinforced concrete, no render	37.0	17.0	5.3
Roofs	Corrugated iron on timber framing	5.2	4.0	5.0
	Clay tiles on timber framing	13.0	5.6	3.4

Further information

For further information on the environmental characteristics of timber and wood products, contact:

Kathryn Adams
Executive Director
Forest & Wood Products Research & Development Corporation
PO Box 157
Bond University
Queensland 4229
Ph 07 5578 7900
Fax 07 5578 7911
Email fwprdc@onthenet.com.au

Acknowledgments
Information in this brochure has been derived solely from the following reports of the FWPRDC. Further details can be obtained from the reports, which can be purchased form FWPRDC.

Ferguson, I., La Fontaine, B., Vinden, P., Bren, L., Hateley, R. and Hermesec, B. 1996, 'Environmental Properties of Timber', Research Paper commissioned by the FWPRDC.

Lawson, W.R. 1996, 'Timber in Building Construction: Ecological Implications', Research Paper commissioned by the Timber Development Association (NSW) Limited and the FWPRDC.

Todd, J.J. and Higham, R.K. 1996, 'Life-Cycle Assessment for Forestry and Wood Products' Research Paper commissioned by the FWPRDC and the Tasmanian Forest Research Council Inc.

Text: Wendy Tubman & Associates, Townsville.

The research and development activities on which this publication is based were partly funded by the Forest & Wood Products Research & Development Corporation (FWPRDC). The information contained in this publication does not necessarily represent FWPRDC policy. No person should act on the basis of the contents of this publication, whether as to matters of fact or opinion or other content, without first obtaining specific, independant professional advice which confirms the information contained in it.

©Forest & Wood Products Research & Development Corporation

Material in this publication may only be reproduced with the written permission of the Corporation.