Biopolymers offer unique opportunities for developing sustainable materials and circular processing strategies, but their complex molecular interactions often challenge conventional processing routes. Our work investigates the rheology, phase behavior, and processability of natural polymers such as cellulose, starch, proteins, and polysaccharides in aqueous and non-aqueous environments, including ionic liquids and deep eutectic solvents. A major goal is to understand how processing conditions influence structure formation and performance, enabling the development of sustainable materials for industrial and biomedical applications.