Abstract
Wood remains one of our most important carbon neutral structural materials, but many wood species are susceptible to biodegradation. Preservative treatment can minimize degradation, but some species are exceptionally resistant to preservative penetration. An excellent example is shining gum, Eucalyptus nitens, which is globally planted and especially abundant in Tasmania. This species has low decay resistance and is exceedingly difficult to effectively treat using conventional processes. One alternative approach is to modify the treatment media using supercritical carbon dioxide (SC-CO). A previous study showed that shining gum could be effectively treated using a mixture of fungicides in SC-CO. However, the ability to deliver biocides into the wood may not necessarily translate into biological performance. The impregnated materials were subjected to laboratory decay tests using an aggressive brown rot fungi and above ground field tests in Queensland and Tasmania, Australia. Laboratory tests were inconsistent, owing to the wide variations in preservative retention. Field trials are nearly three years old and beginning to show results.