From edible mushrooms to sustainable materials: Sound absorption of mycelium-based composites cultivated on spent mushroom substrates

The cultivation of edible mushrooms generates significant waste in the form of spent mushroom substrates (SMS), which are known to have the most significant environmental and waste issues in the mushroom industry. To address this issue, we transform the SMS into mycelium-based composites (MBC) as an effective acoustic biomaterial to potentially replace conventional acoustic panels. To demonstrate the acoustic effectiveness of the MBCs, acoustic absorption coefficients are measured for mushroom samples in various production stages utilized in actual mushroom cultivation practices: before fruiting, the first fruiting cycle, and the second fruiting cycle. We also compare the acoustic absorption of two substrates: straw (S) and straw with cotton (SC), alongside comparing with rectangular- and circular-shaped bags. Our results indicate that the acoustic biomaterial reaches absorption coefficients close to 1 at frequency ranges around 1000 Hz, achieving almost complete acoustic absorption. Altogether, most samples exhibit strong absorption in the higher frequencies of 2000 – 6000 Hz, with most coefficients exceeding 0.5, validating MBCs cultivated on SMS as an acoustic biomaterial. By repurposing SMS into MBCs as an effective acoustic biomaterial, these composites can serve as a sustainable alternative to conventional acoustic panels. Not only that, we also tackle the waste problem of SMSs and pecuniarily contribute to the mushroom industry, achieving significant environmental, economic, and practical benefits in one solution.