Mechanical and Physical Properties of Biodegradable Foams Made from Sorghum Fiber and Rice Straw for Food Packaging Applications

Abstract

This study investigates the potential of agricultural by-products, rich in lignocellulosic materials, as sustainable food packaging materials to mitigate the environmental issues associated with nonbiodegradable plastics and styrofoam. Starch-based biodegradable food trays were developed using agricultural by-products, including sorghum stalk, rice straw, and kraft pulp through thermopressing method. By combining varying proportions of polyvinyl alcohol (PVA) and a sorghum-rice straw fiber mixture, biodegradable foam products with notable strength, water resistance, and cost-effectiveness for large-scale production were produced, exhibiting densities between 0.7 and 0.8 gr/m³. Notably, a 5% PVA composition in the sorghum fiber biodegradable foam displayed favourable mechanical properties and water resistance, with a tensile strength of 5 MPa and a contact angle of 73.79°, coupled with an appealing physical appearance. However, increasing PVA concentration beyond this level had negligible effects, indicates the optimal limit of PVA. Additionally, the distinct roles of rice straw powder as a matrix and sorghum fiber as reinforcement within the biodegradable foam were identified. Biodegradation tests revealed natural decomposition starting from the seventh day, with over 95% growth of Aspergillus Niger fungus, suggesting that these biodegradable foam products hold promise for mass production in the packaging industry, presenting a sustainable alternative to conventional plastic packaging.