Utilization of Ganoderma lucidum Spent Mushroom Substrate (SMS) and Coir Fiber (CF) into Heat-Insulating Cellulose-based Aerogel
Spent mushroom substrates (SMS) are abundant by-products in agriculture generated by commercial mushroom industries after the harvesting period of mushrooms. If not utilized, a huge amount of SMS is difficult to handle and is discarded through disposal and burning methods, which negatively affect the environment. Coir fiber (CF) is abundantly available in tropical countries and is one of the toughest natural fibers and a rich source of cellulose. The cellulose content from both Ganoderma lucidum SMS and CF was combined for the first time to produce thermal-insulating cellulose-based aerogels via an environmentally friendly and cost-effective freeze-drying process. The effect of the ratio of G. lucidum SMS and CF on the density, porosity, hydrophobicity, and thermal properties of aerogel composites was comprehensively investigated. The as-fabricated aerogel showed an exceedingly low density of 0.096–0.116 g cm^−3 with a high porosity of more than 92%. Due to the porous structure inside, the cellulose-based aerogels exhibit outstanding heat insulation with an extraordinarily low thermal conductivity of 0.039–0.0559 W m^−1 K^−1, which are comparable to commercial insulation materials such as mineral wool, foam glass, polystyrene, and glass wool. The water contact angles were measured on both the surface and cross-section of the cellulose-based aerogels, ranging from 92^o to 115^o, which demonstrated their hydrophobic nature. The research results increase the possibility of applying the developed cellulose-based aerogel from agricultural biomass to practical heat insulation applications.