Optimized bio-oil yield from Swietenia macrophylla seeds via ultrasonic cavitation through response surface methodology

Non-edible bio-oil is now produced to substitute crude oil in the production of clean biodiesel. In this study, the optimization of bio-oil yield from Swietenia macrophylla seeds through ultrasonic-assisted solvent extraction (UASE) was investigated. Central composite design of response surface methodology (RSM) was employed to analyze the effects of sonication time (5–25 min) and the hexane-to-biomass ratio (3:1–7:1 mL g⁻¹) to bio-oil yield. The result showed that hexane-to-biomass ratio of 6:1 mL g⁻¹, and sonication time of 10 min was the optimal conditions to attain optimum bio-oil yield of 46.7 ± 0.1 wt%. The bio-oil yield increased when the sonication times were increased, while the hexane-to-biomass ratio was found to have an erratic effect. UASE, compared to conventional method, produced higher bio-oil yield which utilized much lesser solvent at shorter extraction time of 10 min instead of 8 h. Also, UASE produced S. macrophylla bio-oil with much higher energy content than those derived from other recovery methods. GCMS and FTIR analyses results, at optimum conditions, demonstrated the presence of fatty acids and esters in the bio-oil suggesting a high potential for biodiesel production. These include oleic acid (30.0%), linoleic acid (29.2%), stearic acid (13.4%), palmitic acid (13.2%), linolenic acid (11.9%), ϒ-linolenic acid (1.5%) and small traces of some fatty acids. At optimum conditions, the bio-oil produced was found to have 0.95 g mL⁻¹ density, 45.2 cSt kinematic viscosity at 40 °C, 39.95 MJ kg⁻¹ high heating value and 0.55% ash content. The study verified the aid of ultrasonic cavitation in solvent extraction, and the use of RSM is innovative and advanced in perfecting bio-oil production. Typical transesterification of bio-oil was done where 65.8 ± 0.2 wt% biodiesel (fatty acid methyl ester) was produced. The production of biodiesel from bio-oil has scientifically proven which elevate to the limelight the high potential of S. macrophylla seeds for biodiesel production.