Developing sustainable insulation materials: degradation and stabilization of mycelium-based bio-composites from recycled mattress waste

The growing demand for sustainable building materials has spurred interest in bio-based composites due to lower environmental impact and higher thermal performance. This study presents the fabrication and characterization of mycelium-based insulation materials derived from recycled mattress waste, using Penicillium chrysogenum cultivated under submerged fermentation conditions. The incorporation of shredded polyurethane foam into the fungal growth matrix resulted in cohesive bio-composites with exceptional thermal stability and insulation performance. Comprehensive physicochemical analyses, including scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), thermogravimetric analysis (TGA–DTG), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), revealed that fungal degradation of the polyurethane matrix facilitated the formation of calcium carbonate (CaCO₃) in the calcite phase. This biomineralization, driven by CO₂ released from enzymatic hydrolysis of urethane bonds, significantly enhanced the thermal resilience of the composite. The most thermally stable formulation, based on coarse shredded mattress waste (OS), retained 92.85% of its weight at 997°C and 90% at 1000°C, far exceeding benchmark insulation materials such as glass wool. With a measured thermal conductivity of 0.048 W/m·K, the mycelium–mattress composite matches or surpasses common sustainable insulators while offering the added benefit of valorising post-consumer waste. These findings highlight the potential of fungal bioprocessing and biomineralization in producing high-performance, fire-resistant, and environmentally sustainable insulation materials for circular economy applications.