# Using an Invasive Plant (Japanese Knotweed) for Mycelium-Based Thermal Insulation Composites

## TL;DR

Researchers made thermal insulation composites using invasive Japanese Knotweed, finding they work as well as hemp but absorb more water.

## Contribution

Using invasive Japanese Knotweed as a substrate for mycelium-based composites offers a sustainable alternative to hemp.

## Key findings

- Mycelium composites from Japanese Knotweed matched hemp and PIR in thermal insulation.
- Japanese Knotweed composites had higher density and water absorption than hemp composites.
- Using invasive species avoids land-use conflicts and regulatory issues linked to hemp.

## Abstract

What are the main findings?
Mycomaterials were successfully made using Reynoutria japonica as a substrate.Their thermal insulation potential matched ones made from hemp or even PIR.However, they had higher density and double the water absorption compared to hemp.

Mycomaterials were successfully made using Reynoutria japonica as a substrate.

Their thermal insulation potential matched ones made from hemp or even PIR.

However, they had higher density and double the water absorption compared to hemp.

What are the implications of the main findings?
Using invasive biomass reduces land-use competition and regulatory issues linked to hemp.Using R. japonica turns an ecological threat into a value-added sustainable resource.High hydrophilicity suggests that R. japonica MBCs are best for moisture-controlled environments.

Using invasive biomass reduces land-use competition and regulatory issues linked to hemp.

Using R. japonica turns an ecological threat into a value-added sustainable resource.

High hydrophilicity suggests that R. japonica MBCs are best for moisture-controlled environments.

Mycelium-based composites (MBCs)—biomaterials made from fungal-inoculated substrates—are promising candidates to replace conventional rigid thermal insulation panels. 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 fields 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 in place, while they may be very good substrate for MBCs. This study investigated the comparative physical and thermal properties of 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 a thermal conductivity as the hemp MBCs in our internally developed method, but also as the PIR standard. However, they exhibited suboptimal physical characteristics: higher bulk density (166 vs. 128 kg/m3 for hemp) and significantly higher water absorption (7.5% vs. 3.5% volume uptake after 2 min). This suggest that they are a less viable alternative to hemp-based MBCs for heat insulation applications.