Compared with petroleum, biomass raw materials are inexpensive. Much of the raw materials are now considered waste -- stems and stalks left over after plants are harvested. But the processing costs for turning plant materials into ethanol, biodiesel and other biochemicals traditionally have been much higher than the costs for turning crude oil into gasoline and diesel fuel. This has been a longstanding roadblock for widespread acceptance of biofuels. When gasoline was cheap and plentiful, not many people wanted to pay more for ethanol, despite its many environmental benefits.