Corn based bioethanol refineries have been popping up all over the United States over the past couple of years. This in turn has led to a spike in corn prices as more corn is being diverted from food and animal feed to fuel production which has led to criticism of the promotion of ethanol as a fuel. Even the Deputy Secretary of Energy Clay Sell has acknowledged that corn will not remain a factor in fuel production in the future. As progress is made in processing cellulosic biomass like wood chips, grasses and corn stalks. Sell feels that cellulosic ethanol and bio-butanol will take over from current corn-based ethanol over the next 5-10 years as enzyme and bacteria based processing methods move into commercial applications. Currently those fuels are more expensive than existing processes, but they have the potential for much higher yields and the costs will likely drop by a factor of ten as new processes come on stream.