Mycelium-based composites: A review of a sustainable alternative for thermal insulation

The modern physical product economy's main material production model mainly relies on extracting limited natural resources, often with little regard for end-of-life disposal or environmental impact. This review evaluates the thermal conductivity of mycelium-based composites (MBCs), a highly sustainable alternative produced through a biologically driven process in which fungal mycelia bind lignocellulosic agricultural wastes, such as hemp, flax, straw, and softwood, into lightweight, cohesive composites. Mycelium is introduced into fibrous substrates and grows into a dense three-dimensional network, after which the material is thermally inactivated to ensure stability and halt biological activity. The review compares composites made from three fiber types (hemp, flax, and straw) grown with the white-rot fungus Trametes versicolor. Their thermal conductivity is assessed against conventional insulation materials, including glass wool, rock wool, and extruded polystyrene. Findings show that MBCs containing flax, hemp, and straw generally outperform these conventional materials, particularly in water absorption and thermal conductivity. The mycelium-hemp composite achieves the lowest thermal conductivity at 0.0404 W/(m·K) with a density of 99 kg/m³. The study also reveals that fiber size and physical processing exert a stronger influence on mechanical behavior than chemical composition. This review highlights the potential of mycelium-based materials as environmentally friendly, low-impact alternatives for thermal insulation applications.