Timber & Wood Products: Overview
Still an important environmental issue
Timber & wood products are potentially among the most sustainable products designers can specify.They can also be among the most environmentally destructive.
The challenge to those designing with and specifying timber and wood products is to determine whether products fall into the former or latter category. Many imported wood products come with environmental claims that are difficult to verify, and there remains a diversity of opinion over the ecological and social sustainability of management practices in Forests globally. and overseas. Forests and plantations remain a touchstone for a broad range of industrial, social and political interests.
An assessment of the environmental characteristics of timber and wood products from a specifier’s perspective must consider:
- The procurement of the raw material including forest management practices;
- The amount of energy used to extract and process timber into finished building components
- The impacts of timber throughout its use-phase including impacts on energy efficiency and air quality
- The fate of the product, its recyclability, reusability and biodegradability
- The social sustainability of the supply chain and actions within it.
Environmental Overview
Resources
Vast quantities of smaller section timber are not recycled as a result of our love affair with larger sections, ensuring that smaller sizes have little or no value. In addition demand for larger section timbers and decreasing public-land supply ensures a ready market for trees to be cut on private land that may or may not have appropriate management controls in place.
Using small sizes of timber up front maximizes choice in species, performance and finish while optimising the design to utilise smaller-dimensioned timber from forests and plantations. Specifying larger solid section sizes increasingly limits species choice, blows-out lead times, and increases costs as these sizes are less readily available and typically sourced only from older trees and forests. Larger solid sections (e.g. for boards over 140mm wide, beams over 300 deep) are not generally a characteristic of regrowth forests or plantations.
The selection of visual grade is a key decision that is entirely in the hands of the specifier. The selection of ‘clear’ grades greatly increases the likelihood of waste or lower value wood utilisation, and greatly decreases the potential for the use of regrowth and plantation timbers as these timbers typically have higher levels of ‘feature’.
Habitat & Land
The devastation by logging of ecosystems and associated cultures from the Amazon to Canada’s great Cedar forests is well known. Forest destruction continues to escalate, with increasing ramifications as more is removed. It is estimated that 80% of the worlds historic forests cover has been removed already, with an estimated 40% of the remaining ‘frontier’ or unlogged high-biodiversity forests likely to be destroyed or degraded in the next 10-20 years {Environment News Service, 2002}. This is of critical importance with the global replacement of forests by plantations, and the fundamental ecological differences between old-growth (primary/ frontier) forests, ‘managed’ forests, and plantations.
The desire for independent assessment of sustainability claims, domestically and internationally, and the perception that consumers will differentiate on the basis of environmental assurance, has driven the development of certification schemes and a variety of management initiatives {Drielsma, 2002 #688}. Refer ‘Standards and Benchmarks’ below.
These include the Pan European Forest Certification (PEFC) scheme and Forest Stewardship Council standard (FSC), quite widespread. Both standards claim to ensure high levels of environmental stewardship, and will provide ‘Chain of Custody’, a paper trail linking finished timber to the extraction source to allow verification of claims and build consume confidence that timbers are not from high conservation-value areas. However FSC is the scheme preferred by organisations like, WWF, Greenpeace, the World Green Building Council and the majority of its member countries including the US Green Building Council in their LEED Green Building Rating system and Ecospecifier because they are 3rd party schemes that are externally audited and provide key ecological benefits compared to industry self-assessed schemes such as PEFC and its member schemes in different countries e.g. SFI (Canada), AFS (Australia), MTCC (Malaysia).
Energy & Greenhouse
For buildings, operational energy generally outweighs the energy embodied in the sourcing of raw materials and manufacture within building structures in the range of between 10 - 5:1 {Pears, 2003;Treloar, 1999}.
However embodied energy is nonetheless significant, equivalent to potentially 8 years of commercial office operational energy, especially in highly efficient buildings. The embodied energy of timber and wood products is generally low, and timber is at a further advantage where its insulative properties are of value.
Of more importance is the fact that from a greenhouse point of view, timber is a carbon sink i.e. when you use timber in buildings over long term periods, we are effectively locking up the embodied carbon dioxide (a potent greenhouse gas) for that period. Wood products effectively bring with them 'negative carbon emissions'.
Embodied energy should also be considered in the context of end of life; timber has (in a worst case) the opportunity to release energy through combustion. The potential for this can be reduced or removed by the use of preservatives that include toxic heavy metals or chlorinated compounds.
