There are 1,865 biofuels companies out there, and sometimes it seems that there are at least 1,865 different ways of turning every manner of biological material into fuel for a car, truck, train or plane. A big part of the reason, of course, is that petroleum is, basically, old biological gunk. Changing new biological stuff into old biological stuff is relatively easy to do in a lab, at least. The problem is finding a way of doing this alchemy on the scale of millions of gallons a year at a cost that comes somewhere near the price of gasoline without leveling the world's forests, sucking the world's fresh water supply dry or starving the world's humans.The race is starting to shape up. The contest: Take some type of agricultural waste, easy-to-grow non-food crop or just sunshine; add water and carbon dioxide and turn it into some type of fuel, like ethanol, butanol, gasoline, diesel or jet fuel.The entrants: enzymes, algae, yeast, bacteria and plain old chemistry. The winners will be the methods that use the least amount of energy to produce a fuel that stores the most amount of energy, at the best cost.
http://www.forbes.com/2009/04/28/biofuels-ethanol-virent-technology-breakthroughs-biofuels.html