Scientists for decades have raised questions about ethanol's viability as a fuel source for three reasons:
(1) They argue that it is unethical to produce fuel from a food crop, especially if it drives up food prices. Most of the ethanol in the United States is made from corn.
(2) Ethanol contains less energy than gasoline, and it takes a lot of energy to produce.
(3) A variety of conflicting studies have shown that producing ethanol may—or may not—increase emissions of carbon-dioxide, a gas linked to global warming.