Valorization of waste seed oil from Cupressus macrocarpa L. for biodiesel production via green-synthesized iron oxide nanoparticles: A sustainable approach toward decarbonization

Abstract

The urgent need to combat climate change and reduce reliance on fossil fuels has accelerated the global transition toward renewable energy. Consequently, waste-to-biofuel conversion offers a promising pathway to both sustainable energy production and circular resource use. This study investigates the potential of a novel feedstock, Cupressus macrocarpa L., with a high nonedible seed oil content of 26% (w/w), for biodiesel production. Iron oxide nanoparticles (Fe2O3 NPs), synthesized using an aqueous leaf extract of Salvia moocroftiana L., were employed as a cost-effective and recyclable catalyst for the transesterification process. Under optimal conditions—methanol to oil molar ratio of 9:1, catalyst loading of 0.7 wt%, temperature of 60 °C, and a reaction time of 120 min—the process achieved a 93% conversion to fatty acid methyl esters (FAME). The Fe2O3 NPs catalyst, with an average particle size of 30 nm, effectively catalyzed the reaction and demonstrated reusability over 5 cycles. Analytical techniques, including Fourier transform infrared spectroscopy and nuclear magnetic resonance, confirmed FAME production, while gas chromatography-mass spectrometric analysis identified 9-octadecenoic acid methyl ester as the primary biodiesel component. The final product met international fuel standards and achieved an ultra-low sulfur concentration of 0.0009%, highlighting its environmental and economic viability.

Keywords

• Biodiesel
• Cupressus macrocarpa
• Decarbonization
• Iron oxide nanocatalyst