Optimization and characterization of bio-oil produced from Ricinus communis seeds via ultrasonic-assisted solvent extraction through response surface methodology

As the world confronts a surging price of fuel along with various environmental issues, researchers around the globe are scrambling to identify and develop potential biofuel feedstocks that fall outside the “food or fuel dilemma”. This justifies the need for non-edible oilseeds that can be used as sustainable feedstock for biofuel production. In this study, non-edible Ricinus communis seeds were utilized in the production of bio-based fuel to support the crusade for the use of renewable energy. Extraction of bio-oil from R. communis seeds was done through ultrasonic-assisted solvent extraction. The effects of n-hexane to biomass (HB) ratio, extraction time, and resonance amplitude on bio-oil yield were investigated. Optimization of bio-oil yield was done through central composite design of the response surface methodology. The optimum bio-oil yield was found to be 42% at optimum conditions of 10:1 HB ratio, 25 min extraction time and 50 μm resonance amplitude. Characterization of the extracted bio-oil revealed a density of 0.9 g mL−1, kinematic viscosity of 18.6 cSt at 40 °C, and higher heating value of 29.5 MJ kg−1. The Fourier Transform Infrared Radiation spectroscopy analysis of the bio-oil revealed that it contained ester functional groups. Gas chromatography analysis showed that the major fatty acids present in the bio-oil are palmitic (2.2%), stearic (2.4%), oleic (6.7%), linoleic (8.8%) and ricinoleic (77.1%). The R. communis bio-oil is enriched with unsaturated fatty acids while there is a relatively low content of saturated fatty acid accounting 87.8% and 11.3% of the total fatty acids composition, respectively. As confirmed by this study, the results indicate the potential of R. communis bio-oil as a source for biodiesel production. Keywords: Ricinus communis, Bio-oil, Optimization, Ultrasonic-assisted solvent extraction, Response surface methodology