BIODIESEL PRODUCTION FROM WASTE FRYING OIL BY THE CHEMICAL CATALYSTS

D. K. Kim* and J. S. Lee

Biomass Research Center, Korea Institute of Energy Research

71-2, Jang-dong, Yuseong-gu, Daejon, 305-343, Korea

Phone: 82-42-860-3552; Fax: 82-42-860-3739; E-mail: dkkim@kier.re.kr

As the concerns over the environmental pollution and the shortcomings of fossil fuels are

increasing, renewable energies are emerged as promising alternatives. Biodiesel, as a renewable

fuel, has many merits. Compared to diesel, biodiesel has a more favorable combustion emission

profile, such as low emissions of CO, PM10, Smoke and HC. CO2 emitted by combustion of

biodiesel can be recycled by photosynthesis, thereby minimizing the global warming effect.

Although biodiesel has many merits, it has a major problem for the commercialization. The cost

of virgin vegetable oil biodiesel is about 2 times higher than that of mineral diesel. In addition to

that, vegetable oils are now imported in Korea and take about 70% of total production cost of

biodiesel. Therefore, cheaper feedstock is required to produce cheaper biodiesel. About 100,000

tons of waste frying oil is collected in Korea every year. Some of them are used as feedstuff and

raw materials for the chemical industry. But most of waste fats are discarded illegally and lead

to environmental pollution. If the waste fats are recycled as biodiesel feedstock, the cost of

biodiesel will be decreased and the environmental pollution also will be minimized.

Waste frying oil collected from food industry contains about 1-6% of free fatty acids. The

free fatty acid should be pretreated by acid catalyst to get higher biodiesel yields. Amberlyst 15

was identified to be the most suitable for the pretreatment based on the activity and durability.

When waste frying oil containing 6% of free fatty acids was pretreated by Amberlyst 15, more

than 90% of the free fatty acid was converted to fatty acid methyl esters(biodiesel). the

pretreated waste frying oil exhibits similar transesterification pattern with that of virgin

vegetable oil. It indicates that the inhibition effect on the base catalyst by free fatty acid is

negligible when the waste frying oil is pretreated properly.

In this presentation, the optimization of the pretreatment condition in a batch reactor,

continuous pretreatment using a packed bed reactor, transesterification of the pretreated waste

frying oils to biodiesel in a tubular type continuous reactor, and an evaluation of the waste

frying oil biodiesel as a motor fuel would be presented.