Corn ethanol processing plant. Corn ethanol plant with grain cars carrying corn to the plant (bottom left) and fuel cars carrying ethanol away from the plant (bottom right), Shenandoah, Iowa, USA. Corn ethanol is a biofuel that is primarily used in the United States as an alternative to gasoline and petroleum. It is produced from corn through industrial fermentation, processing and distillation. The processing plant shown is operated by Green Plains Renewable Energy.