Wooden building products in comparative LCA

Abstract

We revised the results of approx. 20 years of international research on the environmental impact of the life cycle of wood products used in the building sector compared to functionally equivalent products from other materials. Original studies either technical reports or scientific papers in English or German were considered. This literature was obtained via an extensive literature review (February 2006), via a consultation of compilations of life cycle assessments (LCA) of wood products (e.g. elaborated during the COST action E9) and from secondary literature. The resulting list of literature is considered to be quite complete and therefore covers the most relevant original comparative LCA studies of wood products in the building sector in Europe, Northern America and Australia. The documentation of the studies differs considerably in terms of completeness (life cycle stages included, assessment methods), transparency (description of methodological assumptions, characteristics of the products, available data, etc.) and scientific rigor (e.g. related to the functional equivalency). All encountered original studies are cited and their scope and transparency is shortly described. For the environmental ranking of wood products compared to functionally equivalent products, only quantitative, transparently described studies with no obvious methodological flaws were included, preferably covering the whole life cycle and conducted according to the ISO series of standards 14’040ff. For the assessment, the contribution of each product to an impact category was compared to the mean of all functionally equivalent products included in a study. Among the most important results are: fossil fuel consumption, potential contributions to the greenhouse effect and quantities of solid waste tend to be minor for wood products compared to competing products; impregnated wood products tend to be more critical than comparative products with respect to toxicological effects and/or photosmog depending on the type of preservative; incineration of wood products can cause higher impacts of acidification and eutrophication than other products, whereas thermal energy can be recovered; although composed wood products such as particle board or fibreboard make use of a larger share of wood of a tree compared to products out of solid wood, there is a high consumption of fossil energy associated with the production of fibres and particles/chips as well as with the production of glues, resins, etc. In LCAs of whole buildings, the materials used outside the areas of applicability of wood dominate the environmental profile of the building; current methods used for the impact assessment do not allow to consider (also favourable) impacts of forests, such as land occupation, impacts on biodiversity, purification of air, etc. Wood products that have been installed and are used in an appropriate way tend to have a favourable environmental profile compared to functionally equivalent products from other materials. For the dispersion and application of these conclusions, it is necessary to adapt LCA to a form, which can be used on a regular basis for the decision making of different actors in the construction sector. LCA methodology in general (the series of standards ISO 14’040ff) and for the environmental assessment of wood products in particular have been developed and consolidated considerably in Europe and Northern America during the last decade; the more and more representative and reliable LCI data for wood products and competing products has become available. For the future use of the environmental value of wood products within sustainable development, the general perception of the beneficiary use of wood products has to be increased at various stages of decision-making.