A process operator pours ethanol into a bottle at the GreenField Ethanol plant in Chatham, Ontario, in this April 10, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)