You Won't Save the Planet by Using More Wood But You'll Lower Net CO2 Emissions

The forestry and wood products industry is well-ready to challenge exaggerated or unsubstantiated claims about the environmental credentials of non-wood building products (like steel, concrete and aluminium) – and so it should! We call this "green-wash". The reason that folk in the industry are so passionate about this is that there really is a story to tell, AND wood from sustainably-managed forests is arguably the most environmentally "friendly" building material by a long shot. Beyond the scientifically proven improvement in soil and water quality, biodiversity and recreation [compared to most other land uses], forest products have excellent weight to strength, thermal, acoustic and (yes) fire resistance qualities, as well as low embedded energy. But there's more; it is the low carbon footprint (read low net CO2 emissions) of wood products that we hope will capture the hearts and minds of consumers. And to make an impact on wood products demand, this also involves capturing the attention, logic and policy settings of architects, specifiers and the politicians/public sector. See NZWood >.

Bryce Heard, CEO of Lockwood, eloquently and passionately conveyed the low carbon footprint of wood products as a building material at the PF Olsen Forest Industries Expo Conference in Rotorua in September this year. Bryce presented two exhibits, shown and interpreted below.

Apart from raw logs (e.g. log houses) sawn timber (lumber) has one of the lowest carbon footprints of all the wood products; negative in fact. Despite the energy needed to harvest, convert and dry the product, sawn timber is still a nett absorber of CO2 based on it being made largely of cellulose/carbohydrates. Contrast this to the high level of net CO2carbon emissions from alternative non-wood materials, much of which comes from the smelting process (steel and aluminium).

This feature of wood products has a profound impact on the carbon life cycle profile of houses/households. The life cycle method of analysis includes the net CO2 emissions of not only the construction of the house, but also the running of the household (e.g. lighting, heating and maintenance). In the exhibit below, you can see the significantly lower net CO2 emissions from a house constructed of wooden products vs. one constructed from typical non-wood products. Ignoring the impact of the eco house option, the normal wooden house net CO2 emissions are more than a third less than the normal non-wooden house emissions over the 100 year period presented. In this analysis, this is due entirely to the difference in the starting point (the net CO2 emissions from the household running are the same between the two house types) which comes down to the lower net CO2 emissions from the wooden products. The comparison is even more dramatic when looking at the energy efficient eco house where total net CO2 emissions of the wooden house are half that of the non-wooden house over the 100 year life cycle.