Hydrogen-assisted nannochloropsis sp. microalgae biodiesel to operate cleaner diesel engines

The need to find sustainable energy sources has taken the center stage in the light of the growing energy global requirements. The renewable energy sources have also taken much interest in biofuels, as they promise to add renewable and environmentally benign sources of energy. The feedstock used in biodiesel is usually a wide range of inexpensive feedstock. In the current research, a new synthesis method using a feedstock with a green microalga, namely, Nannochloropsis sp. is defined. According to the authors, bio-diesel blends based on this microalgal source would help in producing less toxic fuels, increase the functionality, and at the same time, minimize emissions. The present paper examines production of biodiesel using Nannochloropsis sp. a microalga with high calorific value thus qualifying as a feedstock. After one hour of ultrasonication at 500 Hz frequency, the recovery of bio-oil was around 720 mL. Afterwards, the resulting bio-oil was undergone to a single-pot transesterification with sodium hydroxide as the catalyst in methanol to extract the bio-oil with an extraction efficiency of 92%. Nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry, and Fourier-transform infrared spectroscopy were used to determine physicochemical properties of the resultant biodiesel ensuring it was suitable as a fuel. The combustion stability of the resulting B20 + 7.5H₂ blend was better than that of the diesel fuel, with peak in-cylinder pressure of 47 bar and a net heat release rate of 20.51 J/°CA compared to 46.5 bar and 19.98 J/°CA for diesel. The emission analysis showed that B20 resulted in a decrease in smoke (from 62 to 44.8%) and an increase in CO (from 0.012 to 0.3%) and hydrogen supplementation (2.5-7.5 L m^-1) further improved combustion. Notably, B20 + 7.5H₂ reduced CO₂ (from 9.3 to 8.5%), while NOx remained within 1763-1694 ppm. These results demonstrate that hydrogen-enriched algae biodiesel blends can improve engine efficiency and reduce harmful emissions, providing a viable, cleaner alternative for diesel engines.