Biofuel production from locally sourced roselle (Hibiscus Sabdariffa L.) seed oil using transesterification process

Abstract

As a solution to the decreasing stocks of fossil fuels and the environmental unfriendliness arising from its combustion, alternative fuels from natural sources are emerging. Biofuel has drawn considerable attention as a substitute fuel for diesel engines among these various potential resources as it is renewable, non-toxic, eco-friendly etc. This research assessed the production of biofuel from crude roselle oil. Using solvent extraction technique, oil was obtained from roselle seed and the properties evaluated. For this purpose, N-hexane and pet-ether solutions were used. The extracted oil was transesterified. The transesterification reaction was performed at a 6:1 methanol / oil molar ratio, with a catalyst of 1 percent (w / w) CaO / ZnO. The crude roselle oil obtained for use in the production of biofuels was clear, viscous and yellowish in colour, and the oil yield was 13.56 %. The result of the transesterification reaction was a transparent yellowish colour liquid (biofuel) and the percentage yield was 52.77 %. The flash point of 206 ^oC, pour point of -3 ^oC, cloud point of 4^oC, cetane number of 5, fire point of 210 ^oC, specific gravity of 0.895 obtained at 29 ^oC, kinematic viscosity of 4.56 mm2/s, Iodine Value of 0.39 gI₂/100g, saponification value of 0.16 MgKOH/g, acid value of 0.42 MgKOH/g and density of 0.874 g/cm³ were all within the ASTM D6751 specification for biodiesel fuel. Roselle oil methyl ester was found to have good fuel quality and has potential to fuel a diesel powered engine.