Enhancement of spent coffee grounds as biofiller in biodegradable polymer composite for sustainable packaging

This study explores the utilization of Spent Coffee Grounds (SCG), a residual product of the coffee industry, as a microfiller reinforcement in Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) biopolymer composites at varying concentrations (1%, 3%, 5%, and 7%). Melt compounding via a twin-screw extruder and subsequent compression molding were employed in the fabrication process. The SCG microfiller, with particle diameters ranging from 1.11 to 1.28 μm, exhibited a significant negative charge (zeta potential: −20 mV). Hydrophobicity increased up to 5% filler concentration, as indicated by higher water contact angles, but diminished at highest concentration likelihood of agglomeration of the spent coffee grounds within the biopolymer matrix. The addition of SCG enhanced overall mechanical properties, particularly at a 5% filler concentration. Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM) confirmed the successful incorporation of SCG microfiller, improving structural characteristics. Schematic drawings illustrated the interphase bonding of microfiller and matrix. However, properties diminished at the highest filler content (7%) due to coffee grounds' agglomeration. Despite this, SCG incorporation enhanced functional properties, making the biopolymer composite a promising material for sustainable packaging and various applications. Highlights: Enhancement of properties of spent coffee grounds in PHBV biocomposites. Characterization of Biocomposites for multifunctional properties. Fracture and 2D analysis of the tensile fractured surface of biocomposites. A promising material for sustainable and biodegradable packaging.