Comparing substrates for mycelium-based composite insulation materials with thermal and environmental assessment

Area of Science:

• Materials Science
• Environmental Science
• Biotechnology

Background:

• The construction industry seeks sustainable alternatives to traditional insulation materials with high embodied carbon.
• Mycelium-based composites (MBCs), grown on lignocellulosic feedstocks, present a promising bio-based insulation solution.
• Substrate selection critically influences the thermal and environmental performance of MBCs.

Purpose of the Study:

• To evaluate the thermal performance and environmental impacts of MBCs using different substrates.
• To emphasize the importance of a functional unit (FU) accounting for thermal performance in Life Cycle Assessment (LCA).
• To determine the dominant factors influencing the Global Warming Potential (GWP) of MBC insulation.

Main Methods:

• Production of MBCs using Lentinus tigrinus mycelium on five substrates: ash-wood chips, bark, beech-wood sawdust, hemp shiv, and wheat straw.
• Measurement of thermal conductivity (λ) using ASTM C518.
• Calculation of a mass-based functional unit (FU) for insulation (R-value of 1 m·K/W).
• Cradle-to-gate LCA (EN 15804) to compare environmental impacts per FU.
• Analysis of transport distance, waste designation, and carbon sequestration uncertainty.

Main Results:

• Straw-based MBCs exhibited the lowest thermal conductivity (λ = 0.031 W/m·K), while ash-wood chips had the highest (λ = 0.048 W/m·K).
• Ash-wood chip MBCs showed the lowest total GWP (-9.77 kg CO2 eq) per FU, whereas straw-based MBCs had the highest (4.04 kg CO2 eq).
• Carbon sequestration emerged as the dominant factor influencing GWP, overriding thermal conductivity and substrate sourcing strategies.

Conclusions:

• Low thermal conductivity MBCs can be produced from diverse substrates.
• Substrate selection for MBC insulation must balance thermal properties with environmental performance, prioritizing carbon sequestration.
• The study highlights the need for comprehensive environmental trade-offs in optimizing bio-based insulation materials.