In this study the production of biodiesel from three mixtures of vegetable oil and used
cooking oil by alkali-catalyzed transesterification was investigated. Three kinds of vegetable
oils, including jatropha, roselle and coconut oilswere tested. The effect of used cooking oil
content in oil feedstock (used cooking oil/vegetable oil ratios of 0.03-0.2 v/v) on methyl
ester formation was investigated and optimized. The methyl ester content from each reaction
condition was determined by gas chromatography (GC). The optimum used cooking
oil/vegetable oil ratio was 0.03 v/v for all three kinds of oil feedstock. At this ratio, the
methyl ester content of three kinds of biodiesel were higher than the minimum limit set for
Thai biodiesel (B100) specification. The measured properties of three biodiesel products
were within the limit prescribed by Thai standards, except for the lower viscosity of
biodiesel produced from coconut-used cooking oil mixture. However, it was very close to
that of Thai petroleum diesel.
Keywords: transport fuels, transesterification, methyl ester content, used cooking
oil/vegetable oil ratio, Thailand