Caffeine – Perspective natural biocide for wood protection against decaying fungi and termites

Abstract

The aim of this study was to test caffeine – harmless to health and eco-friendly natural compound – as a potentially effective fungicide and insecticide for wood protection. Caffeine treatment of wood, using simple and cheap long-term dipping technology, was tested against the brown-rot fungus Rhodonia placenta and termite Reticulitermes flavipes. Fungi and insects can cause severe loss of functionality of wooden structures. The current search for of nature-friendly products is understandable in the context of the changing world environment. The experiment with caffeine-treated refractory Norway spruce (Picea abies) wood lasted for 16 weeks against the rot attack according to EN 113, and for 6 weeks against the termite attack according to EN 118. Mass losses of caffeine treated wood samples without ageing, caused by R. placenta and R. flavipes were small, only 1.4% or 0.5%, respectively. Results clearly suggested that caffeine is an alternative to commercial biocides, e.g., to the reference in wood well fixable Bochemit QB, containing boric acid and alkylbenzyldimethylammonium chloride. Caffeine was sensitive for leaching out from wood by water even in the presence of an additional hydrophobic protective layer. Based on the achieved results it is possible to recommend caffeine treatment as an environmentally friendly alternative for wood protection, but only in the interior or outdoor under roof area against termite attack and also against brown-rot fungi. Treatment with caffeine had no negative impact on the compression strength and colour of the spruce wood, while it improved surface wetting important for potentially follow-up coating or adhesive applications.