Traditionally, to make ethanol, butanol or other biofuels, producers have used corn, beets or other plant matter that is high in starches or simple sugars. However, since those crops are also significant staple foods, biofuels are competing with people for those crops.
However, other forms of biomass - such as switchgrass or inedible corn stalks - can also be used to make biofuels. But these other crops pose their own problem: their energy potential is locked away inside the plant's lignin - the woody, protective material that provides each plant's structural support.
Breaking down that lignin to reach the plant's component carbohydrates is an essential first step toward making biofuels.