Embodied through-life carbon dioxide equivalent assessment for timber products

Abstract

This study illustrates the relative importance of embodied energy to buildings and summarises the broad merits of various material types. It then focuses on timber, being the most abundant bio-renewable material used. An audit is carried out on carbon flows from forest to end of life for timber products, initially based on the assumption that the timber will be disposed of to landfill at the end of life, and then considering alternative scenarios. The author challenges a common view that, when landfilled, nearly all the embodied carbon dioxide will be eventually released by rotting and that carbon dioxide sequestration should therefore be excluded. Two opposing arguments are given. Firstly, when landfilled, only a relatively small percentage of the embodied carbon will be released by rotting. Secondly, it is very probable that in the future most waste wood, rather than being landfilled, will be used as fuel, when it will displace some fossil fuel that would otherwise have been used. The study includes a sensitivity analysis of carbon dioxide equivalent emissions per final kilogramme of product and provides a summary of six scenarios, covering manufacturing complexity, various end-of-life scenarios and, most importantly, the provenance of the timber and the effect of sustainable forest management. A further sensitivity study is carried out for all scenarios on different levels of economic allocation and fossil fuel displacement.