Optimised transesterification of used frying oils: production and characterisation of biodiesel

Abstract

ABSTRACT To compete with the growing energy demands, it is necessary to explore some new alternative sources of energy. Presently, biodiesel is being acknowledged for its environmentally friendly and renewable nature. In order to avoid fuel versus fuel problem, biodiesel can be made by using low-cost feedstocks such as non-conventional seed oils (Jatropha, Karanja and Castor), discarded and repeated fried/used frying oils. This work is targeted towards production of biodiesel from used frying oils collected from local frying outlets. Alkali-catalysed transesterification reaction was applied to make biodiesel through optimisation of different reaction variables with glycerine as the byproduct. Optimised conditions/reaction variables such as catalyst type and concentration, methanol/oil molar ratio, reaction temperature and agitation intensity yielded good quality and high percentage yield of biodiesel. The optimum parameters for biodiesel production were observed as 9:1 molar ratio of methanol/used frying oil, 1.5% KOH by wt. of oil, 60°C reaction temperature and 600 rpm agitation intensity. GC-MS and FTIR analysis of the produced used frying oil methyl esters (UFOMEs) confirmed the complete conversion of oil into biodiesel. The biodiesel fuel properties like density, flash point, kinematic viscosity, cloud point, pour point were determined and found comparable with American (ASTM D6751) and European (EN 14214) standard methods. From the results, it can be concluded that low cost of used frying oil as raw material was observed to be the most important aspect for economic viability of biodiesel production using such feedstocks.