A Study of the Potential for Developing Sound Absorbing and Heat Insulating Material from Mushroom Mycelium in a Hot and Humid Climate

Importance of the work: Mycelium has demonstrated potential as a high-performance alternative to conventional insulation materials.However, it remains an emerging technology.This research focused on developing mycelium-based materials under minimal environmental controls outside the laboratory.Objectives: This research aims to explore the potential of developing sound-absorbing and heat-insulating materials from suitable mushroom mycelium species grown on agricultural waste, under minimum environmental controls, in Thailand's hot and humid climate.Materials and Methods: Grey oyster mushroom [Pleurotus ostreatus (Jacq.exFr) Kummer] mycelium was cultivated in a box using different substrate mixing ratios of raw rice husks and rubberwood sawdust, under temperature and humidity controls ranging from 30C to 37C and 50% to 70%, respectively.The optimal substrate mixing ratio was then used to cultivate prototype materials for property testing in a laboratory. Results:The experimental results indicate that the optimal substrate composition for mycelium growth is a mixing ratio by weight of 2.5:0.1:0.5 (rubberwood sawdust:grey oyster mushroom mycelium:water).The square-shaped prototypes (size 10.50 10.50 cm, thickness 2.50 cm) exhibited an average density of 279.634.28g/cm, while the round-shaped prototypes (13.00 cm, thickness 2.00 cm) exhibited an average density of 329.689.58g/cm.The developed prototypes comply with ASTM C423 standards (NRC > 0.40) and TIS 2303-2549 standards (thermal conductivity 0.066 W/mK).They displayed effective sound absorption performance within the frequency range of 1,000-5,000 Hz, with rough surfaces achieving a higher noise reduction coefficient (NRC = 0.430.03)compared to smooth surfaces (NRC = 0.410.022).The average thermal conductivity (k-value) was recorded as 0.0650.001W/mK.Additionally, the prototypes demonstrated fire-retardant properties, enhancing their safety profile for construction and insulation applications.