Using an Invasive Plant for Mycelium-Based Thermal Insulation Composites

Mycelium-based composites (MBCs)—biomaterials made from fungal-inoculated substrates—are promising candidates to replace conventional materials for thermal insulation. However, many MBCs are made from hemp, a plant material that is quite difficult to source in many countries for regulation reasons, and mobilizes agricultural field at the expense of food and feed crops. Meanwhile, many of our natural and urban ecosystems are subject to invasion by plants that are just burnt or even left on place, while they may be very good substrate for MBCs. This study investigated the comparative physical and thermal properties MBCs derived from two distinct lignocellulosic feedstocks: hemp shives (a traditional material) and biomass from the highly invasive species Reynoutria japonica. Polyisocyanurate (PIR) was included as a synthetic benchmark. The MBCs produced from R. japonica demonstrated as low thermal conductivity as hemp MBCs, but also as the PIR standard. However, they exhibited suboptimal physical characteristics: higher bulk density (166 vs 128 kg/m3 for hemp) and significantly greater water absorption (7.5% vs 3.5%volume uptake after 2 minutes). This suggest that they are a less viable alternative to hemp-based MBCs for heat insulation applications.