Aromatic spent, a low-value industrial byproduct generated during the processing of essential oils, is typically discarded or utilized in low-end applications such as mulch, animal fodder, incense sticks, soaps, mosquito repellents, cosmetics, and as raw material in paper and particle board manufacturing. However, this biomass is an excellent source of cellulose—a component that remains largely underutilized. In this study, an effort was made to extract cellulose from lemongrass spent for the development of biodegradable films, offering a sustainable alternative to petrochemical-based packaging materials, which are known to harm the environment. The process began with a series of unit operations, including the size reduction, cleaning, drying, grinding, and sieving of the spent material. Chemical treatments involving alkaline and acid solutions, followed by bleaching, were employed to remove lignin and hemicellulose, thereby isolating purified cellulose. This purified cellulose was then subjected to acid hydrolysis to obtain cellulose nanocrystals (CNCs). The CNCs were incorporated into a film-forming solution consisting of chitosan and glycerol in optimized proportions. The mixture was homogenized and solvent-cast onto a 300×300 mm² polypropylene sheet. Upon drying at ambient conditions, transparent films of 42 microns were obtained. To evaluate the biodegradability of the developed CNC–chitosan–glycerol films, soil burial tests were conducted. Results showed approximately 70% degradation within 15 days, demonstrating their eco-friendly nature. The nano-scale dimensions of the cellulose nanocrystals were confirmed using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Additionally, SEM analysis of the films was performed to check for any agglomeration of CNCs within the polymeric matrix. This study highlights the potential of aromatic spent as a sustainable resource for developing biodegradable packaging materials, contributing to environmental conservation and waste valorization.