Efficacy of Caffeine Treatment for Wood Protection-Influence of Wood and Fungi Species

In the future, we can expect increased requirements to the health and ecological integrity of biocides used for the protection of wood against bio-attacks, and it is therefore necessary to search for and thoroughly test new active substances. Caffeine has been shown to have biocidal efficacy against wood-destroying fungi, moulds and insects. The aim of the research was to determine whether the effectiveness of caffeine, as a fungicide of natural origin, is affected by a different type of treated wood. Norway spruce mature wood (Picea abies), Scots pine sapwood (Pinus sylvestris), and European beech wood (Fagus sylvatica) were tested in this work. The samples were treated using long-term dipping technology or coating (according to EN 152:2012) and then tested against selected wood-destroying brown rot fungi according to the standard EN 839:2015, wood-staining fungi according to EN 152:2012, and against mould growth according to EN 15457:2015. The penetration of caffeine solution into wood depth was also evaluated using liquid extraction chromatography, as well as the effect of the treatment used on selected physical and mechanical properties of wood. The test results showed that the type of wood used and the specific type of wood-degrading agent had a significant effect on the effectiveness of caffeine protection. The most resistant wood was the treated spruce, whereas the most susceptible to deterioration was the treated white pine and beech wood. The results of the work showed that caffeine treatment is effective against wood-destroying fungi at a concentration of 2%, and at 1% in some of the tested cases. It can be used as an ecologically acceptable short-term protection alternative against wood-staining fungi in lumber warehouses and is also partially effective against moulds. It also does not have negative effects on changes in the physical and mechanical properties of the tested wood species.