This article presents the key results and scientific findings from two national postdoctoral research projects supported by the Ministry of Education, Science and Sport of the Republic of Slovenia (MIZŠ) and the Slovenian Research and Innovation Agency (ARIS). We analyzed the biorefinery potential of low-value Scots pine (Pinus sylvestris L.) and black locust (Robinia pseudoacacia L.) wood for the extraction of natural bioactive compounds. Knotwood and heartwood were used as biomass for extracting polyphenolic compounds, which were subsequently applied in bio-based wood preservatives. The results showed that hydrophilic extractives from Scots pine knotwood and black locust heartwood inhibit fungal decay and demonstrate strong potential as biocidal components and antioxidants in natural wood protection formulations. Further research on the antioxidant and antifungal properties of wood and bark extractives is ongoing.

Silver fir bark (Abies alba Mill.) is an underutilized renewable resource containing valuable extractives and polyphenols of industrial importance. This study compared the influence of two storage methods on the extraction of total hydrophilic extractives content (TEC) and total polyphenols content (TPC) from silver fir bark samples. Bark samples were collected from two storage types: bark left on stem sections and stored under cover (B-D), and mechanically removed industrial bark stored outdoors (B-IS), over a 12-month period with monthly sampling and extraction, followed by measurements of TEC and TPC using gravimetric and spectrophotometric methods. B-D samples showed no statistically significant decrease in TEC or TPC during one year of storage, while B-IS samples exhibited substantial losses, with TEC decreasing by more than half (50.82%) and TPC by 65.68%, most rapidly within the first 3 months when precipitation-driven leaching and degradation processes were obviously most pronounced. These results demonstrate that bark removed before storage is much more susceptible to degradation and leaching of the hydrophilic extractives than bark retained on logs, confirming that mechanical disintegration and exposure to weathering accelerate the loss of valuable extractives and polyphenols. A strong TEC–TPC correlation (r = 0.67–0.81, p < 0.0001) provides a practical methodological approach for rapid biomass quality screening. Overall, the findings offer quantitative guidance for optimizing debarking timing and storage practices to preserve extractive yield and enhance the efficiency of bark-based biorefinery processes.