This study investigates the synthesis and characterization of cellulose microfibril-reinforced polyvinyl alcohol (PVA) biodegradable composites. The research focuses on using cellulose microfibrils (CMFs) synthesized via different hydrolysis reactions as reinforcing agents in PVA at varying concentrations. The study explores the morphology, thermal properties, and chemical behavior of the cellulose particles. CMFs produced using citric acid exhibited the highest yield and aspect ratio. Particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles showing the highest thermal degradation temperature. PVA films reinforced with CMFs underwent comprehensive analyses, including FTIR, thermal degradation temperature (T_d), DSC, and tensile strength tests. The thermal behavior of the cast films changed with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures and a rise in crystallinity. The incorporation of cellulose particles significantly improved mechanical properties. Films containing CMF showed higher Young's modulus, with the 5% CMF sample derived from citric acid exhibiting the most significant increase in modulus. The study also compared CMFs from wood and hemp, analyzing their morphology, chemical, and thermal properties. The results indicate that CMFs from organic acids, particularly citric acid, offer better thermal stability and mechanical performance compared to those from sulfuric acid. The study highlights the potential of cellulose microfibrils as effective reinforcing agents in PVA composites, offering improved mechanical properties and thermal stability. The findings suggest that these composites could be suitable for applications such as food packaging, dissolving medical applications, and other disposable plastic items. Further research is needed to optimize the manufacturing process of hemp cellulose nanocrystals before considering downstream applications.This study investigates the synthesis and characterization of cellulose microfibril-reinforced polyvinyl alcohol (PVA) biodegradable composites. The research focuses on using cellulose microfibrils (CMFs) synthesized via different hydrolysis reactions as reinforcing agents in PVA at varying concentrations. The study explores the morphology, thermal properties, and chemical behavior of the cellulose particles. CMFs produced using citric acid exhibited the highest yield and aspect ratio. Particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles showing the highest thermal degradation temperature. PVA films reinforced with CMFs underwent comprehensive analyses, including FTIR, thermal degradation temperature (T_d), DSC, and tensile strength tests. The thermal behavior of the cast films changed with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures and a rise in crystallinity. The incorporation of cellulose particles significantly improved mechanical properties. Films containing CMF showed higher Young's modulus, with the 5% CMF sample derived from citric acid exhibiting the most significant increase in modulus. The study also compared CMFs from wood and hemp, analyzing their morphology, chemical, and thermal properties. The results indicate that CMFs from organic acids, particularly citric acid, offer better thermal stability and mechanical performance compared to those from sulfuric acid. The study highlights the potential of cellulose microfibrils as effective reinforcing agents in PVA composites, offering improved mechanical properties and thermal stability. The findings suggest that these composites could be suitable for applications such as food packaging, dissolving medical applications, and other disposable plastic items. Further research is needed to optimize the manufacturing process of hemp cellulose nanocrystals before considering downstream applications.