Fungicidal Activity of Bio-oils as Wood Preservatives

Forestry-related industries produce increasing amounts of sawdust, chips and shavings. This waste poses environmental and public health concerns, as it is highly flammable, and fine dust can cause severe allergic reactions under certain conditions. However, it can be a valuable resource that supports resource efficiency and reduces carbon emissions. One approach to reducing its volume and adding value is to use it as feedstock for pyrolysis.
Pyrolysis is a thermochemical decomposition process carried out in the absence of oxygen, in which solid biomass is converted into solid, gaseous and liquid fractions. The latter, known as bio-oil, is a complex mixture of compounds including hydroxyaldehydes, hydroxyketones, carboxylic acids, and phenolic substances, which are generated during the thermal degradation of the main structural polymers of wood (cellulose, hemicellulose, and lignin). The composition and yield of bio-oil depend on the operating conditions under which pyrolysis is carried out, in which time is a main factor.
This study evaluates and compares the fungicidal activity of bio-oils produced by slow and fast pyrolysis against two white-rot fungi (Trametes versicolor and Pleurotus ostreatus), two brown-rot fungi (Gloeophyllum sepiarium and Laetiporus sulphureus) and a wood-staining fungi (Aspergillus niger and Penicillium sp.). Cultures were supplemented with increasing concentrations of the bio-oils, and mycelial growth was evaluated by measuring the diameter of the colony. The minimum inhibitory concentration (MIC), i.e. the lowest concentration leading to total growth inhibition, of each bio-oil against each fungal species was determined.
The results demonstrate the potential of pyrolysis-derived bio-oils as environmentally sustainable wood preservatives, and provide a foundation for the development of protective formulations with bio oils for both surface and deep wood treatments