Recyclable Extrudable Biopolymer Composites from Alginate and Lignocellulosic Biomass Waste

This paper reports the formulation of novel thermoprocessable alginate biopolymer composites filled with algae biomass or biomass waste side streams from the food industry. Plasticized alginates have classically been prepared by solvent casting from an aqueous solution. In the formulation that we report, substantially lower amounts of water are used to plasticize the alginate and make it temporarily thermoprocessable, while a permanent plasticizer (glycerol) is employed to control the final properties of the biopolymer composites after processing. Different bio-based wastes from food production were exploited as fillers (seagrass, apple pomace, and lignocellulosic side stream from different steps of the brewery process). The materials, the matrix, and its composites are processed by extrusion. Extrusion with a low water content results in a stiff material with Young′s modulus of 4 GPa and a tensile strength of 103 MPa, surpassing some of the currently used thermoprocessable bio-based and petroleum-based plastics. The addition of lignocellulosic biomass fillers brought a reduction of 28% in shrinkage and 7% in density, without significantly compromising the high stiffness of the alginate matrix. Further emphasizing the sustainable potentials, the developed materials showed to be recyclable up to 4 times without affecting the mechanical properties when the temporary plasticizer was reintroduced in the formulation.