Environmental concerns about tropical deforestation have emphasised the need to source wood from sustainably managed forests. At the same time, competition from alternative materials has amplified the demand for high-quality wood-based products that meet contemporary expectations. To date, most preservative treatments have involved impregnating wood with biocides, often derived from petrochemicals. However, many of these products have been banned or restricted in recent years in Europe, North America and other region due to their toxicity to humans and environment, as well as their fossil-based origins. This has led to an urgent need for new, non-toxic, non-biocidal, and sustainable wood treatments. To address these concerns, wood modification technologies have been extensively studied. Techniques such as thermal modification, acetylation and furfurylation have already been implemented in industrial applications. Tannin, a naturally occurring polyphenol found in plants, is the most abundant and widely available in the world and has potential as a wood preservative agent. This biomolecule can be extracted using only water or with the addition of solvents such as acetone, ethanol, methanol, sodium hydroxide and deep eutectic solvents. Tannins have been extensively studied and explored in various applications, including wood preservation. However, due to the low reactivity of wood and the high-water solubility of tannins, the use of cross-linker, additives, or other reactive chemical products has been necessary to develop efficient and non-leachable preservative formulations. The potential of condensed tannin as a non-toxic and renewable raw material for modifying wood, in combination with furfuryl alcohol (FA), has already been demonstrated in previous studies. However, these studies used tannins and/or FA only in low concentrations, and none considered the use of hydrolysable tannins. This study focuses on the use of large amounts of tannins extracted from chestnut (Castanea sativa) and Acacia (Acacia mearnssi) wood species, using them as a copolymer with FA. The aims to replace as much FA as possible while maintaining performance and comparing this method to conventional furfurylation impregnation process, in term of termite resistance. EN 113 size beech wood samples were vacuum impregnated with solutions containing hydrolysable tannins, FA and an acid catalyst. The impregnated wood blocks were oven-cured, and dried. Water leaching was performed after which Weight Percent Loss and Final Weight Percent Gain was calculated. A modified EN 117 termite test was carried out. The results obtained from the non-choice test demonstrated that replacing 25% of the furfuryl alcohol with hydrolysable or condensed tannin yielded equivalent or superior termite resistance, achieving termite resistance class D (Durable). However, mass loss analysis indicated that up to 50% of the mass of furfuryl alcohol could be replaced with tannin without compromising termite resistance. These results confirmed that the tannin-based preservatives could be considered as non-termite biocidal treatments. Therefore, it can be concluded that it is possible to replace up to 50% of the mass of furfuryl alcohol with tannin, further reducing its environmental impact.

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