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2 Introduction Drying timber to produce material for high quality applications is an expensive and time- consuming operation. It is often referred to as the ‘bottleneck’ of the production process. The drying process consumes approximately 70% of the energy required to convert green logs into dried, value added products. Additionally, estimates suggest that up to 10% degrade occurs in dried wood due to the drying process because of checking, collapse, distortion, and moisture variation. Over the years the timber industry worldwide, in conjunction with researchers, engineers and manufacturers, have strived to dry quality timber as quickly and cheaply as possible to maximise profitability. Therefore, the timber industry pursues any technologies that can improve the quality and reduce timber drying times and costs. Conventional kiln drying with controlled heating, humidity and air-flow under atmospheric pressure conditions is the primary method for drying timber in Australia (Nolan et al., 2003). In recent years, with emerging technological advancements in construction, computer control and less expensive materials, vacuum drying of hardwood timber has been proven (particularly in Europe and USA) in many applications to be a more economical alternative to drying using conventional methods, with similar or better quality outcomes (Savard et al., 2004). For this reason, Queensland Government’s Department of Employment, Economic Development and Innovation (DEEDI) - Agri-Science Queensland expanded its seasoning research and development capacity through the purchase of a 2 m3 research vacuum kiln to investigate the viability of vacuum drying technology for drying Australian hardwood species. Initial kiln trials drying native forest Corymbia citriodora (spotted gum) and young plantation Eucalyptus cloeziana (Gympie messmate) have proven that these species can be vacuum dried approximately 60% faster than conventional drying, within acceptable grade quality limits (Redman, 2007). The results obtained from these preliminary vacuum drying trials generated much interest from the Australian hardwood timber industry. In response, Forest and Wood Products Australia (FWPA) in conjunction with various industry partners and DEEDI invested in this project to establish the viability of vacuum drying technology for drying four high commercial volume Australian hardwood species in terms of drying quality, time and cost. The first part of this work involved a series of applied drying trials and an applied economic model application to establish vacuum drying viability in terms of dried quality, time and cost. The industry partners involved in this part of the research were: • Dale and Meyers (QLD) • Burnett Sawmilling (QLD) • Boral Timber (NSW) • J. Notaras and Sons (NSW) • Hurford Hardwood (NSW) • ITC Timber (TAS) • Gunns (TAS) • Gunns (W A) • Brunner-Hildebrand (Germany) We recognised that a better knowledge of the material and associated drying behaviour was required to optimise the vacuum drying process in the future. Therefore, we chose to development a hardwood vacuum drying model. This required collaboration with a number of renowned experts in the field. The modelling collaborators and their areas of expertise were: 1PDF Image | Evaluation of super-heated steam vacuum drying
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