How to convert leftover cooking oil into biodiesel and run your car

Bengaluru: Do not throw away leftover cooking oil. You can convert it into biodiesel in a microwave and use that to run your car.

Turning cooking oil into auto fuel in an economical way is now possible with a new processing technique demonstrated by a team of scientists from Israel's Bar-Ilan University.

Biodiesel that comes from natural oils and fats can potentially wean cars and trucks away from gasoline and diesel made from fossil fuels. It is a renewable, biodegradable, nontoxic fuel. It also emits fewer hydrocarbons and carbon dioxide than conventional transportation fuels and could be a solution to the problem of environmental pollution faced by cities like New Delhi.

A variety of feedstock containing fatty acids, such as vegetable oils or animal fats, has been evaluated for the production of biodiesel. But the high price of vegetable oil ruled out its use for making biodiesel.

Waste cooking oil is, therefore, the preferred source because it is an environmental waste generated in tonnes worldwide. There have been efforts since 2006 to use non-edible or waste cooking oils as feedstock for biodiesel production, but till now, the processes have remained complicated and expensive.

Now, Aharon Gedanken and colleagues at the university's chemistry department claim to have evolved a method that is simpler and affordable. Using a microwave oven and catalyst-coated beads, they have devised a novel way to convert waste cooking oil into biodiesel, according to their report published in the latest issue of American Chemical Society journal Energy & Fuels.

The researchers developed silica (silicon dioxide) beads coated with a catalyst, strontium oxide nanoparticles, and added them to waste cooking oil they obtained from a restaurant near their university. Thereafter, they zapped the mixture with a modified microwave oven to spur the chemical reaction called "transesterification".

According to the report, nearly 100 percent of the waste oil was converted to biodiesel in just 10 seconds. The researchers could also easily recover the beads and reuse them at least 10 times with similar results.

The biodiesel obtained from waste oil can be used "without requiring major modifications in the physical structure of the engine in transportation vehicles," the report said.

According to the report, the strontium oxide coated silica beads used as catalysts exhibited "excellent performance, accelerating the transesterification reaction from hours to seconds when using microwave irradiation".

"Thus, fast and efficient biodiesel production based on the solid catalyst, together with continuous microwave irradiation, could be an important process for waste cooking oil transformation," the scientists said, adding that their current report is the first step towards constructing a semi-industrial pilot plant for making biodiesel from waste oil.