SAN DIEGO -- There's a new lesson being taught at San Diego High School -- how to take a fast-food snack and turn it into an alternative fuel source.

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Images: Teens Turn Snack Into Alternative Fuel | Watch Video

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A group of juniors and sophomores have been hard at work, trying to find ways to reduce the nation's need for oil. The real-life lesson is being taught by science and technology teacher, John Karanopoulos. Their goal is the production of biodiesel.

"From something that is a waste product, we can make something that is an energy product," he said.

But it's not a simple task, the students explained. First they begin by "filtering the used cooking oil, so we can get the impurities," said Woody Elwell, a junior.

Then, junior Joseph Humes said, "we turn on the reaction pump for at least an hour."

They then add a chemical and watch for reactions that tells them how many fatty acids are in the oil that they're using. It's a painstaking process that could change the way we fill up our tanks.

"It's great knowing that you're kind of a part of small steps towards making the environment better," Flores said.

The class gets oil to use from restaurants around town and Johnson & Johnson, which is a business partner at the school.