The longer a particular wood fibre is used, the longer those carbon atoms will stay out of the atmosphere. One very important reason for extending the lifetime of timber products is to maintain the binding of carbon that they represent. This is achieved, in part, by ensuring the preservation of timber elements as long as possible through effective protection against damp and other forces of decay. In addition, their recycling should be optimized.
The re-use of logs - in parts or as a whole - has traditionally been ubiquitous in most of Scandinavia. Both log construction and timber frame construction are building techniques where the components can be easily dismantled and re-erected without any waste. The Japanese have developed a whole series of techniques for timber joints without glue, the most well-known being the so-called 'timber locks'. Most structures in the twentieth century have been based upon less flexible principles; gluing and nailing have been the dominant methods of jointing.
Pure wood waste can be ground and recycled as raw material for various building boards, such as particle boards and oriented strand boards. It can also be energy recycled to good effect. However, glues, surface treatments and impregnating agents often turn these products into hazardous waste. Energy recovery then demands combustion in special ovens with high quality flue gas cleaning. Chemical impregnation requires combustion in very high temperature furnaces, such as at cement factories.
By using the available forms of re-use and recycling, it is estimated that the useful service life of pine could be extended from about 75 years to more than 350 years (Fraanje, 1997). In central Europe and the USA, comprehensive timber recycling is now developing. Old timber has the advantage that, since it is 'dead', it does not twist, and therefore provides high quality material for floors, for example. In Belgium and France, old quality timber costs about 25 to 50% of the price of new timber, while in Holland old timber costs up to 75% of the price of new.
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