The thermal-treatment is an established chemical-free process to modify wood, improving the durability and physical properties of wood through its service life. During the hydro-thermolysis several reactions from wood components occur, releasing volatile and non-volatile compounds from wood to the chamber. Once the process is accomplished, solid residues agglomerate below the wood load and gaseous products are released and collected as condensed water from the gas stream. In order to identify and characterize the industrial residues generated during the industrial thermal-treatment of Pinus radiata, solid and liquid samples were analyzed. The results indicated thermal and chemical differences among the evaluated waste materials. In case of the solid sample, a superior thermal stability (above 300 °C) was displayed, mostly formed by sugars and lignin derived compounds, with unremarkable antioxidant capacity. In contrast, the liquid sample started to degrade at lower temperatures (around 200 °C) and predominantly was composed by a large amount of phenolic and volatile compounds. Moreover, this liquid fraction exhibited a positive scavenging activity against DPPH free radical (about 54%). Furthermore, the principal products detected by chromatographic analysis in both residues were sugar derivatives such as furfural (up to 30%), phenolic derivatives as guaiacol (~2%), Guaiacyl acetone (~5%), coniferyl aldehydes (12.5%), along with fatty and resin acids (~ 9%) in the solid sample.

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