Production and Physico-Chemical Characterisation of Kusum Oil Methyl Ester as an Alternative Fuel in Diesel Engine

The growing awareness regarding long-term availability of mineral diesel and its environmental consequences, the fluctuating nature of international crude oil prices, the vulnerability of energy security towards oil-based geopolitics, etc., have mandated the search for alternative fuel sources for diesel engines. In this context, biodiesel derived from a variety of feedstocks, like vegetable oils and animal fat, by transesterification has been considered as a promising solution to the crippling energy- and environment-related crises slowly engulfing India. Most of the vegetable oils used for biodiesel production in the developed countries are edible in nature. However, in India, edible oil-based biodiesel is a distant dream due to the lack of self-sufficiency of the country in edible oil production. Therefore, nonedible vegetable oil-producing plants growing in barren lands are a good source of biodiesel in the Indian scenario. Hence, there is an urgent need to explore the potential non-edible oil sources for biodiesel production that can supplement the Government of India's biofuel policy and may help to realise the vision of 20% biodiesel blending by 2017. The present research work deals with the production of biodiesel and a comprehensive physico-chemical characterisation of a relatively underutilised non-edible vegetable oil species known as Kusum oil (Schleichera oleosa), which has a near omnipresence throughout the subcontinent with special penetration in the remote and tribal locations. In the present study, kusum oil methyl ester (KOME) was produced using a two-stage esterification cum transesterification process on account of the high free fatty acid (FFA) contents of the oil. In the esterification stage, 0.85% by mass of catalyst (p-Toluenesulfonic acid), at 60°C temperature with constant agitation at 450 rpm led to less than 2% FFA in 45 min. Similarly, the transesterification stage led to 97.2% ester yield using 1.4% by mass of catalyst (potassium hydroxide), at 65°C temperature in 100 min under constant agitation at 450 rpm. Various physico-chemical properties of KOME, like density, viscosity, heating value, etc., were measured and found to be satisfactorily compliant with the corresponding ASTM/EN standards. The fatty acid profile suggested that KOME possessed 40% unsaturated fatty acids and around 53% saturated fatty acids. The results of oxidation stability indicated no substantial peroxide formations for 6 h in the biodiesel rancimat, thus conforming to the EN standard. The cold flow plugging point of KOME was -1°C, as compared with -9°C indicated by the neat diesel. In the light of the above study, it may be concluded that kusum oil is a promising feedstock for biodiesel production and efforts need to be made to exploit the same for commercial-scale usage.