Reply #51: Usually. Making bio-diesel from used deep-fryer grease, that's an exception.

[Kitty Herder]

I had friends who took advantage of the grease from the restaurant they worked at to provide free fuel for their truck. They were using waste that would otherwise have been thrown away, so they weren't taking food from any one's mouth.

Making ethanol from corn, on the other hand, is a huge mistake that is hurting people in South America.