The big business these days is biofuel, which includes products like ethanol. Ethanol is made from products like corn or soybeans and is a big industry in the agrictultural midwestern states. Ethanol does burn ‘clean’ when it is used as a source of fuel but people tend to forget that it takes energy to produce these ‘clean’ fuels. That energy is going to come from oil, which is going to cause pollution. Not to mention that the byproducts of these processes can be pollutants themselves. This article in the NY Times today describes the seedier side of this ‘clean’ fuel business.
I just want to add that I don’t pretend to be an expert in this field so feel free to post your own information in the comments section.