The aim of this thesis was to test the possibility of using the residues and side-streams from Finnish wood and coffee industries as active ingredients in wood preservative formulations, as well as to compare their acute ecotoxicity. Pyrolysis distillates of bark from Norway spruce (Picea abies (L.) H. Karst.), silver birch (Betula pendula Roth) and European aspen (Populus tremula L.), the organic acids identified in these distillates, spent coffee extract, coffee silverskin extract, caffeine and the commercial Colatan GT10 tannin-rich extract were tested. Celcure C4 industrial copper preservative (for above ground use) and pine oil were used as industrial references. Antifungal tests against wood-decaying fungi and wood decay—mini block—tests were performed in vitro, and leaching tests of the potential preservatives from wood were performed. An acute ecotoxicity test with Aliivibrio fischeri photoluminescent bacteria was performed in order to compare the ecotoxicity of the potential bio-based preservatives with that of the industrial reference.
All potential bio-based preservatives showed some activity against the fungi in the antifungal tests. The minimum inhibitory concentration of the extracts from coffee industry residues needed to inhibit completely all the wood-decaying fungi was over 1%. The pyrolysis distillates were able to inhibit most fungi at concentrations close to 1%. The organic acids and caffeine were able to inhibit wood-decaying fungi in the malt agar media at concentrations below 1%, showing that these constituents play a significant role in the antifungal activity of the tested distillates and extracts. However, when the potential bio-based preservatives and their constituents were tested in the wood decay tests, none of them performed efficiently as wood preservatives.
The acute ecotoxicity test showed that most of the potential bio-based preservatives had low ecotoxicity, but one of the distillates exhibited IC20 of 0.02 mg/L and IC50 of 0.2 mg/L, a much higher ecotoxicity than Celcure C4, which had IC20 and IC50 values of 12 mg/L and 19 mg/L respectively. This shows that we must test the ecotoxicity of all potential antifungals before proposing them as possible wood preservatives, to ensure that new solutions are not as harmful to the environment as the present ones. It can be concluded that some of the constituents of the potential bio-based preservatives act as antifungals against wood-decaying fungi and could be included in wood preservative formulations, but their performance alone is insufficient to function as wood preservatives.