M. El Hajam*, W. Sun, I. Hafez, C. Howell, M. Tajvidi
University of Maine,
United States
Keywords: bio-foam, cellulose nanofibrils, mycelium, thermal insulation, acoustic properties
Summary:
The growing focus on sustainability and circular bioeconomy principles has significantly influenced consumer preferences in many sectors, namely in the construction industry. Traditional wall insulation materials, often synthetic or petroleum-based, pose environmental concerns due to their non-renewable origins and unfavorable life cycle effects. Consequently, the trend has shifted toward renewable, biodegradable, energy efficient and low-density biocomposites for use in thermal insulation. Mycelium-bound composites (MBCs) are among the most promising alternative to conventional insulator petroleum-based materials. However, manufacturing MBCs with highest thermal and sound insulation properties, as well as sufficient mechanical strength, remains a significant challenge. Molding process is the common traditional MBCs fabrication method, but it limits the design flexibility and some applications. To address this limitation, this study proposes a novel approach, involving the mycelium growth inside low-density lignocellulosic foam scaffolds. This method offers a viable solution, enabling design flexibility and enhanced structural properties. This work focuses on the development of hybrid low-density foams using lignocellulosic fibers, cellulose nanofibrils (CNFs), and mycelium (Trametes versicolor) as sustainable wall insulation composites. Foam forming method enabled by a surfactant was used to prepare the lightweight foam scaffolds, using softwood and hardwood fibers, with CNFs as a binder. The neat lignocellulosic foam scaffolds and the as-grown lignocellulosic/mycelium composites were characterized using different physico-chemical methods (thermal conductivity, sound absorption, water resistance, compressive strength, and morphological properties). Over a short period of two weeks, mycelium growth resulted in cost-effective, sustainable lightweight composites with excellent insulation properties. These composites showed thermal and acoustic performance to be comparable with or even better than expanded polystyrene, a commonly used, though unsustainable, insulator. This study has brought into focus the huge potential that lignocellulosic/mycelium composites have for being an environmentally friendly and resource-efficient alternative in construction insulation. Combining renewable raw materials with low-energy fabrication processes, this innovative approach will contribute to broader sustainability goals while meeting key performance requirements for modern building materials. Future work may be directed at further improving the material properties and studying its scalability for industrial applications.