Comparative study of lignin from patchouli waste fibers and spent coffee grounds as biofillers in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based biodegradable packaging materials

Increasing interest in eco-friendly materials has driven innovation in biodegradable polymer composites for sustainable packaging. This study investigates the effects of two biofillers—soda-pulped lignin from patchouli fiber waste and spent coffee grounds (SCG) from Gayo Arabica—on PHBV-based composites. Biofillers were processed into microparticles and incorporated at 2 %, 4 %, 6 %, and 8 % (w/w) using a twin-screw extruder, followed by compression molding. Functional, thermal, mechanical, water barrier, and biodegradation properties were evaluated. At 4 % loading, lignin-filled composites exhibited higher tensile strength (37 MPa) and thermal stability (273 °C onset degradation), while SCG-filled composites improved elongation at break (2.42 %) and biodegradability (28 % mass loss in four months). Lignin-filled composites suited rigid applications, while SCG-filled ones were ideal for flexible, disposable packaging. Higher filler loadings led to agglomeration, affecting performance. This study highlights bioresource-efficient solutions for sustainable packaging.