A number of effective wood preservatives against decomposition and fungal attack have been banned in many countries due to their negative impact on human health as well as environmental problems in the disposal of impregnated wood. However, wood in its natural state is degraded by microorganisms in a relatively short time and the lifespan of wood products is then shorter than would be desirable. Therefore, one of the current efforts of scientists is to find suitable natural products for wood protection capable of fully replacing banned preparations containing heavy metals. Dr. Pánek from the Department of Wooden Products and Structures at FLD, together with colleagues from the Technical University of Zvolen, focused on the use of essential oils to protect wood and wooden products.
In recent years, several studies have been published pointing to the possibility of using biological methods of wood protection using plant extracts or very resistant woody plants, or the use of propolis or chilli extracts. An interesting method of wood protection is the use of essential oils. Essential oils have been used since time immemorial for the treatment of all sorts of ailments, in the fight against bacteria, fungi, insects, etc. Due to their insecticidal, antibacterial and inhibitory effects in connection with fungal attack, their use is offered to protect wood and thus prolong its life. The main advantage of essential oils is their renewable and low or no health hazards. The disadvantages can be considered the high volatility of essential oils and the variable concentration of the contained active substances.
The aim of the research was to determine the effectiveness, stability and minimum effective concentration of 10 essential oils in the protection of beech wood against wood-destroying fungi, Coniophora puteana and Trametes versicolor and against the growth of Aspergillus niger and Penicillium brevicomact. An additional goal of the research was also the analysis of colour and colour stability after impregnation of wood with essential oils.
Oils containing carvacrol and thymol, such as oregano and thyme, have been shown to be most effective in combating fungal attack. Essential oils containing methyl salicylate and eugenol (birch, cloves) were also effective, cloves mainly against brown rot caused by Coniophora. Of all the oils tested, cis-isoasarol trimethyl ether had the highest activity against white rot. In contrast, sage, lavender and tea tree oil, which do not contain these active ingredients, had little or no effectiveness. Additional analysis of wood colour after application of essential oils showed that stained wood significantly changes colour depending on the original colour of the essential oil, however, the newly acquired colours are very stable even when exposed to sun and water, so the negative effects of colour are minimal.
These results indicate the potential of essential oils to stop or at least slow down the growth of mold and wood-destroying fungi. The use of the biocidal effect of non-hazardous essential oils is expected mainly in interiors, for example against Coniophora and dangerous Serpula lacrymas, where the use of other health-hazardous preparations is inappropriate. Therefore, we may have the opportunity to choose furniture according to the scent in the future. Would you prefer a table with the scent of thyme or rather with a calamus?
Ing. Miloš Pánek, Ph.D.
The author studied Wood Engineering at the Technical University in Zvolen, where he also completed his doctoral studies on the topic of Improving the impregnability of wood. Since 2014, he has been an employee of the Faculty of Forestry and Wood Sciences at the CULS in Prague, where he is an assistant professor at the Department of Wooden Products and Structures. His research focuses mainly on the field of wood protection and its surface treatment with coatings.
Prepared by: Jitka Krykorková