[chittychittybangbang]

"Soy biodiesel and palm-oil biodiesel are generally better than petrodiesel on greenhouse gas emissions," Johnson told LiveScience. "It is mainly a function of crop yield and fertilizer amount."

The results do not agree with other studies. "The overwhelming evidence is that most biofuels offer a greenhouse gas savings," said Greg Archer, director of the Low Carbon Vehicle Partnership, a UK group that promotes eco-friendly cars and fuels. The amount of savings depends on how the biofuel is produced. Smart practices—such as limiting fertilizer amount, heating with biomass instead of coal and generating electricity from waste heat—can make practically any biofuel less polluting than petroleum, Archer said.

This is the main issue I see, new studies always contradict last year's studies. And how efficiently you grow the fuel is a big issue as well.