Unlocking renewable potential: Biodiesel production from Nannorrhops ritchieana L. seed oil using phytosynthesized zinc oxide nano-catalyst

The use of high-value biomass resources for the green and renewable synthesis of biodiesel is an effective strategy for reducing greenhouse gas emissions and providing a sustainable alternative to depleting fossil fuels. In the present study, Nannorrhops ritchieana, a highly promising seed oil feedstock with 25 % oil content, was evaluated for biodiesel production using zinc oxide nanoparticles (ZnONPs) synthesized with aqueous leaf extract of Alternanthera pungens. The highest biodiesel yield of 95 % was achieved under optimum reaction conditions: a methanol to oil molar ratio of 7: 1, catalyst loading of 0.18 wt%, a reaction temperature of 80 °C, and a reaction time of 180 min. Analysis of the synthesized ZnONPs revealed its pure, thermally stable and nanoscale nature, with an average particle size of 22 nm. Gas chromatography mass spectroscopy (GC-MS) analysis identified distinct peaks of methyl esters, with 9-Octadecenoic acid, (Z)-methyl ester having the highest concentration. The fuel properties of the biodiesel— density (0.912 kg/m³), viscosity (6.45 mm²/s), flash point (93 °C), cloud (-7 °C), and pour point (-10 °C)— aligned with international fuel standards.