Wood is an environmentally friendly and renewable material, but the susceptibility of Finnish wood species to biodegradation limits the use of wood in several applications. A plethora of methods have been developed to improve the durability of wood, but in recent years, new environmental regulations and increasing environmental awareness have increased the need to develop new, more environmentally friendly methods. One potential solution to this need is the use of wood’s own extractives. Several wood species contain extractives that have been found to limit, or even completely prevent, the growth of wood degrading and other fungi. Most successful extracts typically originate from naturally durable tropical hardwoods, but even Scots pine, the most common wood species in Finland, may have potential as a wood preservative agent: Scots pine contains a range of phenolic extractives and terpenes, both of which have been found to possess antifungal activity.
Virtually all Scots pine tissues contain some extractives, but their concentration has been found to be particularly high in knots, heartwood, and bark. In addition to their high extractives content, knots and bark are ideal sources of extractives, because these tissues have no valuable industrial applications. Bark is currently burned for energy, and knots, being an anatomical feature that lowers the quality of sawn timber and interferes with pulping processes, are rejected where possible. Due to their promising extractives content and lack of industrial applications, Scots pine bark and knots are worth studying as a source of chemicals for wood preservation. However, the use of extractives in wood impregnation is not without problems. The extractives preservative is known to be leachable, and screening tests on agar have indicated that the extractives are also degradable by fungi. Some potential solutions have been developed to combat these issues, but much work remains if the problems of leaching and degradation are to be fixed.
Research on the potential of Scots pine extractives as a wood preservative has recently begun in our laboratory. We are currently working to determine the activity of these extractives against wood rotting fungi, and if they prove successful, the research will be continued to obtain a deeper understanding of the protective function provided by the extractives, and also to attempt to eliminate the problems of leaching and degradation. Our poster presentation describes the potential and also the challenges of wood extractives-based preservatives.
Keywords: Scots pine, preservative, durability, extractives
Authors
Belt T.
Department of Forest Products Technology, Aalto University School of Chemical technology, Aalto
Rautkari L.
Department of Forest Products Technology, Aalto University School of Chemical technology, Aalto
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