Watermelon (Citrullus vulgaris) seed oil as a potential feedstock for biodiesel production in Nigeria

Biodiesel fuel was successfully synthesized from Nigerian Watermelon (Citrullus vulgaris) seed oil through direct base-catalysed transesterification process using Methanol and sodium hydroxide as alcohol and catalyst, respectively. The solvent extraction method was used to extract the watermelon oil from the seed in order to determine its physic-chemical properties for relevant uses. Physical properties of the watermelon seed oil, its biodiesel and biodiesel blends were measured using the American Society for Testing and Materials (ASTM) methods for biodiesel and diesel fuels. Also, the effect of temperature and catalyst concentration on the biodiesel yield was studied. The properties of the produced watermelon oil and its biodiesel fuel were compared with that of vegetable oils from other feedstock and their respective biodiesel fuels. The result showed that the calorific value of the produced watermelon biodiesel is 40.10 MJ/Kg while that of the watermelon seed oil is 38.24 MJ/Kg. The cetane number, kinematic viscosity at 40 °C and pour point of the produced oil are 39.38, 8.50 mm2/s and 15 °C while that of the produced biodiesel are 53.165, 5.82mm2/s and 3 °C for Watermelon biodiesel, respectively. The maximum biodiesel yield (93.68%) was recorded at 55 °C with catalyst concentration of 1.0% of sodium hydroxide (NaOH) by weight. In comparison to biodiesel produced from other feedstock, the lower heating value and cetane number of watermelon seed oil methyl ester (40.10 MJ/kg and 53.165) were higher than that of palm kernel biodiesel (39.30 MJ/kg and 52.30), castor biodiesel (30.50 MJ/kg and 50), sandbox seed biodiesel (37.00 MJ/kg and 50), dika nut biodiesel (39.00 MJ/kg and 52) and kapok fibre biodiesel (40.064 MJ/kg), while that of physic nut biodiesel were higher. The obtained properties of watermelon seed oil and its biodiesel conformed to the ASTM standards for biodiesel and diesel fuels. The results further showed that watermelon seed oil is a potential feedstock for biodiesel production and the biodiesel produced can serve as an alternative fuel for diesel engines.