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Torrefaction is a mild pyrolysis process (usually up to 300 degrees C) that changes the chemical and physical properties of biomass. This process is a possible pre-treatment prior to further processes (transport, grinding, combustion, gasification, etc) to generate energy or biofuels. In this study, three eucalyptus wood species and bark were subjected to different torrefaction conditions to determine the alterations in their structural and energy properties. The most severe treatment (280 degrees C, 5h) causes mass losses of more than 35%, with severe damage to anatomical structure, and an increase of about 27% in the specific energy content. Bark is more sensitive to heat than wood. Energy yields are always higher than mass yields, thereby demonstrating the benefits of torrefaction in concentrating biomass energy. The overall mass loss is proposed as a relevant parameter to synthesize the effect of torrefaction conditions (temperature and duration). Accordingly, all results are summarised by analytical expressions able to predict the energy properties as a function of the overall mass loss. These expressions are intended to be used in any optimization procedure, from production in the field to the final use.

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Wood-water relationship of untreated and heat-treated wood was studied. Specimens of Eucalyptus grandis, E. saligna, and E. citriodora were submitted to five conditions of heat treatment: 1808C and 2208C with air; 2208C, 2508C, and 2808C with N 2 . The wood-water relationships were accurately studied in a special device, in which the moisture content (MC) of the sample was measured with a highly sensitive electronic microbalance placed in a climatic chamber. The dimensions of the sample were collected continuously without contact by means of two high-speed laser scan micrometers. Sorption curves and shrinkage-MC relationships were observed. To study the effects of heat treatment, the following parameters were also determined: fiber saturation point (FPS), wood anisotropy (T/R ratio), shrinkage slope, reduction in hygroscopicity, and anti-shrink efficiency (ASE). The physical properties were significantly affected only at 2208C and above. At heat temperature levels higher than 2208C, the reduction in hygroscopicity and ASE are higher than 40% and continue to be reduced with increasing temperature level. This work also demonstrates that heat treatment does not change the slope of the curves ''shrinkage vs. MC'', proving that heat treatment affects the domain of alterations in wood properties, but not the behavior within this domain.