The anti-decay properties of birch bark extracts

Abstract

Birch bark has been used for centuries because of its water repellent and endurable characteristics. On top of this birch trees are widespread in the Nordic countries and birch bark is a side product of the wood industry giving it the potential to be used as a sustainable product in the wood preservatives industry. As part of the KOIVUA project at the LAB University of Applied Sciences, this research investigated the fungal resistance from birch bark extracts, such as betulin and pyrolysis distillates. In the experimental set-up spruce samples were treated with birch bark extracts and inoculated with two fungi, Serpula lacrymans and Fomitopsis pinicola. The used birch bark extracts were two pyrolysis distillates and a solution of betulin mixed with octadecyltrichlorosilane (OTS) and isopropyl alcohol (IPA). Results were measured by visual analysis throughout the experimental period and a pre- and post-test dry weight comparison of the treated spruce samples. After a 6-month incubation period a strong fungal growth was found on the betulin solution treated spruce samples inoculated with the Fomitopsis pinicola and a minor growth on the samples inoculated with the Serpula lacrymans. The two different pyrolysis distillates and a commercial reference product showed no growth at all for either fungus.