"Cambridge, England - A new study by Nobel Prize-winning chemist Paul Crutzen suggests that growing and burning biofuel crops may actually raise greenhouse gas emissions, rather than lower them.
The study says that growing some of the most commonly-used biofuel crops release around twice the amount of the potent greenhouse gas nitrous oxide than previously thought. The amount of nitrous oxide - N2O, also known as "laughing gas" - could wipe out any benefits from not using fossil fuels, and probably contribute to global warming."
Biofuels may be carbon neutral but they are not NxOx neutral.
The problem is not just fertilizer for crops. But when you burn any fuel it produces NxOx emissions as well. These too are considered green house gas emissions. Also NxOx's are very bad for the ozone layer.