Experimental Characterization of a Starch-Based Bioplastic Reinforced with Coffee Processing Residues

Abstract

Coffee-industrial residues have gained attention as reinforcement materials in biodegradable polymers due to their availability and environmental compatibility. In coffee-producing regions, large quantities of pulp and husk are generated during wet processing, representing a potential raw material for bioplastic production. This study evaluates a starch-based bioplastic reinforced with coffee residues through experimental variation of mixture composition. Twenty-five samples were prepared using coffee pulp and husk, glycerin, cornstarch, sodium alginate, and water, maintaining a total mass of 50 g per treatment. The material was characterized through density, tensile resistance, opacity, and biodegradability tests under natural environmental exposure. The best formulation reached a resistance of 2072 Pa (≈4 lb), density values comparable to conventional plastic, and more than 50% degradation after 19 days. Results indicate that increasing fiber content improves rigidity but reduces flexibility, while higher glycerin content increases flexibility and accelerates degradation. Although the material does not yet match the mechanical strength of conventional plastics, its behavior is consistent with low-load biodegradable applications such as disposable packaging. The study demonstrates the technical feasibility of valorizing coffee processing residues as reinforcement in biodegradable polymer matrices.