Doctor Emmett Brown introduced the concept in the movie "Back to the Future." To power his suped-up DeLorean, he put trash inside, and his invention turned it into a time-warping turbo prop.

Today, Chris Goodwin is doing it for real.

In his Capitol Hill automotive shop, he's developed a system that takes old vegetable oil used by restaurants, filters it, and converts it to fuel.

"I just redesigned the entire system from the ground up," Goodwin told KOMO News.

The veggie fuel, made from used oils that some just throw away, works in any diesel engine. But the engine does require some modifications. You see, the entire system has to be heated, because if it stayed cool, it would have the consistency of margarine.

"Above 160 degrees fahrenheit, it shares all of the same properties of diesel fuel," Goodwin says.

To use it requires a $2,500 engine conversion, which Goodwin manufactures and calls the "Frybrid." But after the initial investment, the fuel is free.

"Restaurants pay to dispose of it," Goodwin says.

"I talked to Chris about him using my oils, and he said I was using partially hydrogenated oil," says Alex Rosenast, owner of The Garage on Broadway.

Goodwin convinced him to switch to more healthy, 100 percent vegetable oil. Rosenast did, and his waste oils are taken away for free.

"This (veggie fuel) pollutes far less than even biodiesel, because it is straight vegetable oil," Goodwin insists.

And biodiesel still costs about $2.80 a gallon. Veggie fuel? Order it for free next time you pull up to the drive-up window.

For more information:

www.frybrid.com