This study advances the valorization of spent coffee grounds (SCG) by extracting lignin and oils to develop novel poly(lactic acid) (PLA) composite materials for high-potential use in UV-blocking packaging applications. SCG separated the oil by a dissolving process with hexane, and lignin was sedimented by an acidification process using sulfuric acid. Thus, the morphology and crystallinity of lignin were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the functional groups of lignin and oil were investigated by Fourier transform-infrared (FT-IR) spectroscopy. It was found that the powder forms with an amorphous region. The oil extracted illustrated the functional groups of fatty acids. The oil was blended into the PLA matrix at 1, 3, 5, and 7 phr, and lignin composites were prepared at 1, 3, and 5 phr. The morphological, mechanical, thermal, and optical properties of the blends and composites were analyzed using SEM, universal testing machine (UTM), differential scanning calorimeter (DSC), and UV-Vis spectrophotometer. The optimum formulation at 1 phr of lignin and 5 phr of oil blends exhibited the best mechanical properties and strong UV-Vis absorption. Furthermore, PLA blends and composites incorporating these optimized ratios demonstrated high toughness and excellent UV-blocking performance. This work presents a promising bio-circular-green economy (BCG) model strategy by converting coffee waste into value-added materials for high-performance biodegradable polymer improvement and environmentally friendly packaging applications.
