From Wood and Hemp Biomass Wastes to Sustainable Nanocellulose Foams

•Hemp and birch wood waste were transformed into nanofibrillated cellulose foams•Hemp and wood foams can be applied as insulation material•Structure, mechanical and physical properties of foams were analyzed Transition to the circular economy requires the implementation of recycling and reuse routes for waste products. This research addresses one of the leading emerging areas, i.e., the development of sustainable materials and natural waste processing, namely wood and hemp byproducts. The cellulosic nanomaterials derived from these under-utilized waste residues and byproducts also serve as promising natural precursors for advanced applications, e.g., biomedical, pollution filtering, and thermal insulation. The wood and hemp fibrils were prepared by microfluidic processing of 0.2 – 1.0 wt% cellulose water suspensions. After freeze-drying, the resulting foam materials were characterized with a bulk density of 2 – 36 mg/cc. Key characteristics of the obtained hemp and wood nanocellulose (NC) foams were examined by the mechanical response, porosity, BET analysis, thermal conductivity, thermal degradation, chemical composition, and morphology. Hemp NC foams showed higher performance characteristics that coincide with almost twice the length of the fibrils, 1.5 times higher cellulose content, and a more homogeneous mesh-like structure compared to wood NC foams. In addition, the thermal performance of obtained NC foams was in the range of 34 – 44 mW/m·K, which makes their application comparable to commonly used insulation materials.