Bio-Composite Progress (Part A): Advances in Mycelium-Based Composites as Sustainable Alternatives to Plastic and...

The increasing environmental burden of petroleum-based plastic and foam packaging has accelerated the search for sustainable bio-based alternatives. This study developed mycelium-based cushioning packaging (MBCP) using Lentinus sajor-caju cultivated on four abundant biomass residues (corn husk, rice straw, sawdust, and sugarcane leaves) and comprehensively evaluated their physical, mechanical, microstructural, biodegradation, phytotoxicity, and cushioning performances. Substrate selection significantly influenced composite properties. Sawdust-based MBCP exhibited the highest density (314.79 kg/m³), superior compressive strength (0.91 MPa), and the lowest water absorption and volumetric swelling, indicating excellent structural stability under humid conditions. In contrast, corn husk- and sugarcane leaf-based composites developed superiorly porous structures that enhanced impact energy dissipation, with corn husk demonstrating better cushioning performance in free-fall drop tests, outperforming conventional air bubble wrap and expanded polyethylene foam in preventing secondary damage to glass bottles. Scanning electron microscopy confirmed that variations in biomass composition affected mycelial formation, pore distribution, and network density, directly influencing mechanical behavior and impact resistance. Soil burial experiments revealed progressive biodegradation, with corn husk- and sugarcane leaf-based MBCP achieving over 60% degradation within 90 days, while phytotoxicity assays revealed no inhibitory effects on seed germination and even promoted early seedling growth in several vegetable species, supporting safe environmental disposal and potential secondary use as biodegradable planters. Collectively, these findings demonstrate that biomass residues can be strategically selected to improve the functional performance of MBCP by offering a compromise between biodegradability, mechanical durability, and cushioning efficiency. The developed MBCP represents a promising renewable alternative to conventional petroleum-derived plastic and foam packaging, supporting circular bioeconomy strategies through waste valorization and environmentally responsible packaging solutions.