Confused with hype and controversies on bio-fuel, read this article by Graig Rubens in earth2tech.
First-generation biofuels rely on food crops as their feedstock. Corn, soy, palm and sugarcane all have readily accessible sugars, starches and oils. So brewing them into biofeuls simply involves either fermenting the sugars or chopping up the fatty oils through transesterfication. Second-generation biofuels use lignocellulosic biomass as feedstock, among them dedicated biofuel crops like switchgrass and agricultural residue such as corn stalks. Rather than improving the fuel-making process, third-generation biofuels seek to improve the feedstock. Designing oilier crops, for example, could greatly boost yield.Fourth-generation technology combines genetically optimized feedstocks, which are designed to capture large amounts of carbon, with genomically synthesized microbes, which are made to efficiently make fuels.