Utilization of mixed oils for biodiesel preparation: a review
Sandeep Kumar, Mukesh Singhal, Mahendra Pal Sharma
Abstract
Demand for liquid fossil fuels like diesel and gasoline is rapidly increasing owing to the ever-growing world population, apart from their associated environmental consequences and their availability is getting limited day by day. The biofuels like bioethanol and biodiesel can be used to solve these problems with additional advantages and a cleaner environment. Several oils/fats are used to produce biodiesel as a substitute of petrodiesel, but due to their unavailability in bulk quantity and poor quality, biodiesel production still is a challenge. To overcome this challenge, the concept of mixed oils can be employed, which helps to cut the reliance on any individual oil. There is a lack of reviews that discuss the existing research for biodiesel properties produced from mixed oil. Hence, this review paper explores the effect of the fatty acid composition on physicochemical properties (constituent oils and resultant biodiesel), when two or more oils are blended for biodiesel production. The aim here is to define the selection criteria for choosing the mixed oils (two or more) to yield mixed oil biodiesel having much-improved biodiesel properties. The current study’s finding reveals an improvement in the oxidation stability of mixed oil biodiesel up to ~26 times in few cases. However, the oil properties viz. kinematic viscosity and free fatty acid were reduced by an average of 9 and 22 times, respectively. The review also found that mixing oils to produce biodiesel increases the utility of waste and low-grade oil, modifies the fatty acid composition, and reduces the overall biodiesel production cost and time. The mixing may also enhance many physicochemical properties like kinematic viscosity, acid value, cold flow properties, oxidation stability, etc. Hence mixing of oils for biodiesel production promotes the possibility of large-scale biodiesel production with improved quality and may fulfill the large-scale industrial and transport demand. Future research may be focused on further usage of waste or low-grade oil as constituent oil for biodiesel production via this method and explore different tools and techniques to optimize the oil ratio in mixed oil for better quality biodiesel.