Valorization of Recovered Mine Timber as a Secondary Feedstock for Medium-Density Fiberboard Manufacturing.

The recovery of timber residues from abandoned underground coal mines presents a unique opportunity to expand the raw material base for wood-based composites, aligning with the principles of cascade utilization. Large amounts of structural wood, embedded for decades under anaerobic and humid mining conditions, remain remarkably well-preserved and can be valorized as a secondary feedstock. The aim of this work was to investigate and evaluate the feasibility of incorporating recovered mining timber into the production of medium-density fiberboards (MDFs). Six types of laboratory panels were produced, containing different ratios of recovered and virgin pine fibers (0-100%), bonded with melamine-urea-formaldehyde resin and hot-pressed at 180 °C. Comprehensive testing of physical and mechanical properties demonstrated that panels with up to 40% recovered fibers fully complied with European standards for general-purpose boards, while up to 60% substitution was acceptable with respect to internal bond strength. At higher substitution levels, however, dimensional stability and strength were significantly reduced. These findings highlight the potential of mine timber recovery as a viable raw material pathway for MDF manufacturing, extending the service life of wood resources and reducing pressure on primary forests. The study emphasizes the role of recovered biomass in advancing circular bioeconomy objectives and resource efficiency in the wood-based panel sector.