Green Production of Biodiesel from High Acid Value Oil via Glycerol Esterification and Transesterification Catalyzed by Nano Hydrated Eggshell-Derived CaO

Biodiesel is a widely recognized and favored liquid biofuel, primarily attributed to its biodegradability and non-toxicity. However, the development of biodiesel is hindered by its high production costs. Here, we developed a method that combines glycerol esterification and transesterification reaction catalyzed using nano-hydrated CaO for the green production of biodiesel from high acid value oil. Waste eggshell was chosen as the calcium source to examine the effect of hydration temperature and duration. The catalysts were optimized using a synthesis process involving under calcination for 3 h at 875 degrees C, followed by hydration at 60 degrees C for 6 h and subsequent dehydration at 725 degrees C. The catalyst loading, alcohol-to-oil mass ratio, reaction temperature, and duration were optimized to 2.5 wt%, 35%, 60 degrees C, and 2 h, respectively. Under the optimized conditions, the yield of fatty acid methyl ester reached 94.44%. The catalyst was successfully reused eight cycles while maintaining a yield of fatty acid methyl ester at 80.52%. In addition, a comprehensive overview was summarized to compare the catalyst preparation methods, reaction conditions, biodiesel yield, and reusability in the production of biodiesel using eggshell-derived CaO.