During the timber-drying process, volatile organic compounds, mainly comprising various terpenes, are released from wood with moisture into the atmosphere. Terpenes are known as essential oils and are utilized in aromatic products like perfume, cosmetics, and sanitary products. In this study, the recovery of terpenes from the exhaust steam from a timber-drying kiln was investigated using an easily developed (economical) system. Two cooling devices for exhaust steam that incorporating plate fins were prepared and attached to the wood-drying kilns of a sawmill operating at medium (60°C) and high (120°C) temperatures. During the test period, the kilns used only Japanese cedar, while the amount of recovered essential oil was monthly assessed for three years and the terpene content was analyzed using gas chromatography/mass spectrometry. Approximately 40% delta-cadinene was identified as the main terpene from both kilns, whereas the component profiles of the other terpenes were almost similar. The three-year average recoveries of the essential oil were 16. 4 and 106. 6 mL/m3-wood for medium and high temperature kilns, respectively. The temperature measurement of exhaust steam that passed cooling device suggested the cooling capacity of the developed device needs improvement to increase the oil recovery when used in a high temperature kiln. In contrast, the exhaust steam was sufficiently cooled in the medium temperature drying kiln; however, the recovered amount of essential oil was low, implying that the volatilization of terpenes in this case is low and prevents the collection of a large amount of essential oil. Furthermore, the fin plate of the prepared cooling devices was corroded by acid (wood vinegar) during the test period. Therefore, for their commercialization, the existing drawbacks should be addressed, e. g., improvement in the cooling efficiency and corrosion resistance.

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Durability tests for the heartwood of three species (Sugi (Cryptomeria japonica D. Don), Hinoki (Chamaecyparis obtusa Endl.) and Hinokiasunaro (Thujopsis dolabrata Sieb. et Zucc. var. hondae Makino) were conducted in accordance with the modified JIS Z 2101: 2009, and for the Sugi sapwood treated with BAAC, AZN, CUAZ or AAC in accordance with the modified JIS K 1571: 2010. Two strains of fungi fixed in JIS and ten strains isolated from decayed woods or fruit bodies were used in the tests.
Fomitopsis palustris as a designated fungus of JIS showed the highest mass loss against the heartwood of Sugi, whereas some isolated strains resulted in a little greater mass losses than the JIS strain against the heartwood of Hinoki in a decay period of 60 days. Mass losses of the heartwoods caused by most of strains decreased in order of Sugi, Hinoki, Hinokiasunaro. And mass losses of treated wood exposed in bottles for 12 weeks were less than 3% to all strains.

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