Fueling sustainability: Comparative GC-MS and property profiling of <i>Botryococcus braunii</i> biodiesel, n-butanol, and diesel

Fossil fuel dependency is a driver of climate change and energy insecurity. In this study, the potential of Botryococcus braunii (B. braunii) green microalgae from Bhalswa Lake in Delhi as a viable source for sustainable biodiesel has been evaluated. Cultivated on CHU-13 medium, it produced 53.7 wt. % lipids by n-hexane Soxhlet extraction. Biodiesel that conformed to American Society for Testing and Materials standards was produced using sodium hydroxide in the transesterification. Through gas chromatography-mass spectrometry, three most common esterifiable fatty acids were identified—hexadecanoic, tridecanoic, and octadecanoic—which are responsible for better combustion. Compared with diesel, B. braunii biodiesel possessed higher calorific value, cetane number, flash point, and lubricity and could provide more potential energy output, easier ignition, safer treatment and better wear resistance. The sulfur emission can be reduced by greater than 99% and oxidative stability is improved. Although n-butanol had better activity at extreme cold, the biodiesel was stable at 0 °C for over 3 h. Microscopy showed dense hydrocarbon-rich colonies. B. braunii biodiesel proved carbon-neutral, renewable, and environmentally better, making it a cleaner alternative to diesel and n-butanol in engine applications. Botryococcus braunii biodiesel shows the 15.7% higher cetane number, a 2.3% higher calorific value, and approximate 63% higher auto-ignition temperature compared to the conventional diesel, indicating the improved ignition quality, the energy output, and the fuel safety. Compared to n-butanol, it exhibits the significantly better combustion characteristics with over 145% higher cetane number and approximate 14.4% higher calorific value, ensuring the enhanced engine performance and the stability.