Not from buses and cars, but from ethanol made out of corn.

Scientists said turning forests into fields to grow fuel creates way more carbon dioxide than it saves, but with shrinking oil reserves and rising gas prices the search for a cleaner, greener fuel for transportation is critical.

However, the biofuel most likely to replace petroleum comes from the most unlikely place.

In the laboratory of Dr. Roger Ruan over at the University of Minnesota, he is helping discover the fuel of the future.

The green stuff in his lab isn't just any old pond scum -- its hundreds of species of algae -- the next cleaner, greener alternative to petroleum.

"Dr. Ruan everybody knows what algae looks like. So if somebody just picked up a bunch of algae out of their pond, or out of the front of the lake. How does that turn into oil?" WCCO-TV's Don Shelby asks.

"Oh right now, the common way is simply by dry it and then press oil out and then use solvent to extract the oil out," said Dr. Roger Ruan, from the University of Minnesota.

What's extracted from the algae is basically the same kind of oil that comes from soy beans which is used to make biodiesel fuel.

Ruan is experimenting with different ways to grow the algae too.

He has created a closed system so the water doesn't evaporate in the summer or freeze in the winter.

Another benefit, unlike most conventional fuels, is that algae is non-toxic.

"Some countries use it as food," Ruan said.

Other places simply use it at a spa treatment. And the algae grows so fast, some species can be harvested daily.

"But here's the big question though, Dr. Ruan. How much oil can you get from an acre, let's say, of algae?" asks Shelby.

"Soy beans for example we can get about 50 gallons per acre per year, but these algae can potentially get 5,000 gallons per acre per year or more," said Ruan.

That's 100 times more biodiesel from algae.

The Department of Energy estimates that we could replace all the petroleum used in the U.S. in one year by ultimately getting oil from just 15,000 square miles of algae. That's about one-sixth the size of Minnesota.

It's no wonder Dr. Ruan is looking beyond the lab for the right stuff to grow algae for fuel.