The Bush administration has been pushing ethanol as a renewable, homegrown alternative to gasoline. Now, the auto industry is abuzz with the promise of its flexible-fuel vehicles (FFVs), which are designed to run on either gasoline or the blend of 85 percent ethanol and 15 percent gasoline called E85. GM’s advertising says, “Energy independence? The answer may be growing in our own backyard,” and has coined the slogan “Live green, go yellow,” referring to the corn from which most U.S. ethanol is made. DaimlerChrysler, Ford, and GM have said that they plan to double production of FFVs and other biofuel...