Alkali-catalyzed transesterification of coconut and sunflower oils for biodiesel production

Introduction: Biodiesel represents a promising renewable energy source because it is biodegradable, environmentally friendly, and can reduce dependence on fossil fuels. Coconut and sunflower oils, with their relatively high oil content and availability, are potential renewable feedstocks for biodiesel production. Materials and methods: Coconut and sunflower oils were converted into biodiesel through alkali-catalyzed transesterification using NaOH as the catalyst and methanol as the transesterifying agent at an oil-to-methanol volume ratio of 5:1. The reaction was conducted at 60 °C and atmospheric pressure for 60 min. The produced biodiesel was purified by water washing and drying, followed by evaluation of density, kinematic viscosity, and calorific value. Results: Distinct biodiesel- and glycerol-rich phases were observed after transesterification, providing qualitative evidence of product formation and phase separation. Coconut biodiesel exhibited a density of 723 kg/m 3 , kinematic viscosity of 5.59 mm 2 /s, and calorific value of 34.58 MJ/kg, whereas sunflower biodiesel showed 812 kg/m 3 , 3.61 mm 2 /s, and 39.32 MJ/kg, respectively. Both biodiesels showed kinematic viscosities within the American Society for Testing and Materials (ASTM) D6751-02 range of 1.9–6.0 mm 2 /s. Sunflower biodiesel exhibited fuel properties closer to conventional diesel. Conclusions: Coconut and sunflower oils are potential renewable feedstocks for biodiesel production. Sunflower biodiesel showed comparatively more favorable physicochemical properties and better fuel quality. These findings provide useful information for developing alternative renewable fuels and reducing fossil diesel use.