Sustainable biodiesel production with ZnO catalysts: A carbon footprint and fuel property analysis

The increasing global energy demand and environmental concerns have intensified interest in renewable fuels, with biodiesel emerging as a viable alternative to fossil fuels. This study investigates the impact of zinc oxide (ZnO) catalysts on biodiesel production from waste cooking oil, focusing on both fuel properties and environmental sustainability. The effects of ZnO concentration (2.5%, 5%, and 10%), methanol-to-oil ratio (6:1, 8:1, and 10:1), and reaction time (60, 80, and 100 min) were systematically analyzed. The biodiesel samples were evaluated for fatty acid methyl ester composition, cetane number, oxidative stability, viscosity, and freezing point using gas chromatography-mass spectrometry and fuel property assessments. Additionally, a carbon footprint analysis was conducted to assess the environmental impact of biodiesel production, incorporating electricity consumption, methanol usage, ZnO application, transportation emissions, and feedstock preprocessing. The findings indicate that longer reaction times and higher methanol-to-oil ratios increase carbon emissions, while optimizing reaction time and catalyst concentration can enhance both fuel quality and environmental performance. The study highlights the potential of ZnO as an effective heterogeneous catalyst and provides actionable strategies to improve biodiesel sustainability, including reaction parameter optimization, feedstock collection efficiency, and alternative catalyst exploration. These insights contribute to the development of eco-friendly biofuel production methods and the broader transition toward renewable energy solutions.