Phenol-formaldehyde (PF) resin treatment has long been recognized as one of the most effective and widely used wood preservation methods, offering exceptional durability, dimensional stability, and resistance against biological degradation. However, traditional PF synthesis relies heavily on petroleum-derived phenol, raising concerns about environmental impact and resource sustainability. To date, there has been no comprehensive study that successfully utilizes biomass-derived precursors to synthesize low molecular weight PF resins, which could significantly reduce the dependence on phenol without compromising performance. In our work, we propose a novel design aiming to replace a portion of phenol with liquefied biomass, thus improving the environmental profile of PF resins. Three biomass sources were selected – Japanese cedar (Cryptomeria japonica), Formosa acacia (Acacia confusa), and a mixed sawdust blend representing common industrial wood waste. To systematically evaluate the effects of critical process variables on the liquefaction outcome, we employed response surface methodology (RSM) with a three-factor, three-level experimental design. Our results show higher catalyst levels tend to accelerate depolymerization but also promote undesirable side reactions, resulting in broader molecular distributions. Conversely, lower catalyst concentrations (particularly at 0.5%) favour the formation of more uniform, low molecular weight compounds suitable for resin synthesis. The optimal conditions identified through RSM analysis are 0.5% catalyst concentration, a reaction temperature of 120°C, and a reaction duration of 60 minutes. This study provides a foundation for developing more sustainable wood preservatives and sets the stage for future exploration into biomass valorisation within the wood protection industry.

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