The present work investigated the biodegradable polymer composite through the injection molding method. The matrix material of polylactic acid (PLA) and reinforcement particulates of novel Saccharum spontaneum (SS) were incorporated into the polymer matrix in the range of 5 % to 25 %. In addition to this study, Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform infrared spectroscopy (FTIR), and X-ray diffraction analysis (XRD) were used to examine the structural and morphological analyses of a green polymer composite. Mechanical characteristics such as tensile strength, compressive strength, flexural strength, and shore D hardness have been studied. The soil degradation test and water absorption study were conducted as per the standards. The results showed that compared to pure PLA composite, the 25 wt. % SS-filled PLA composites showed better mechanical properties of tensile, flexural, compressive, and Shore D hardness at 87.41 MPa, 86.20 MPa, 86.4 MPa, and 91.4 SHN, respectively. Thus, the developed novel composite has a potential impact on low-speed applications. The excellent biodegradation property was confirmed with the help of a soil degradation test and water absorption study.