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What is Life Cycle Assessment?
Life Cycle Assessment (LCA) analyses the environmental impacts of a product, process or service system through the stages of extraction and processing of raw materials, manufacture, delivery, use and waste management.
LCA results can be used as part of an environmental management system or for providing information for eco-labelling or environmental rating schemes.
The International Standard directly applicable to Life Cycle Assessment is ISO 14040. A standard LCA is defined as being formed through a four-step process:
- Goal & Scope Definition: Determining what the aims are and whether these can be delivered in the given scope.
- Inventory Analysis (LCI): Modelling the flow of the life cycle and collecting any underlying data that is required.
- Life Cycle Impact Assessment (LCIA): characterising the impacts and evaluating against the defined impact categories (such as Global Warming Potential).
- Interpretation: Analysing the information and determining whether the aims of the study can or have been met.
(Source: Ministry of Economic Development)
How Does Wood Fare Under Life Cycle Assessment?
In New Zealand an LCA conducted by Scion – Scion’s Exemplar House, shows that a wood predominant house is the lowest environmental impact option.
International Life Cycle Assessment Studies including a Canadian and an American study also find that wood has the lowest environmental impact compared to concrete and steel.
The Canadian study – Energy and the Environment in Residential Construction, compared wood, concrete and steel designs for a house with the following results:
both the steel and concrete designs:
- embody and consume 12% and 20% more energy;
- emit 15% and 29% more greenhouse gases;
- release 10% and 12% more air pollution;
- discharge 3 and 2.25 times more water pollution;
- use 7% and 50% more resources from a weighted resource use perspective; and
- produce 6% and 16% more solid wastes, respectively.
An American study conducted by CORRIM used typical building designs to construct hypothetical homes, then compare the environmental benefits of wood-framed versus steel-framed houses in a cold climate (Minneapolis, MN) and wood versus concrete in a warm, humid climate (Atlanta, GA). The study found that:
- The global warming potential of the steel-frame home was 26% higher than the wood-frame home.
- The global warming potential for the concrete-frame home was 31% higher than for the wood-frame home.
- Using wood products instead of steel or concrete can further reduce greenhouse gas emissions from fossil fuels because more than half the energy used by wood mills comes from biomass – bark, sawdust and other residuals – a renewable source of energy (the use of wood residues for fuel is also common practice in New Zealand).
