Ethanol source can refer to two different sources: CORN and MAIZE. CORN, also known as Zea mays, is a cereal grain that is widely grown as a food crop and used for ethanol production. MAIZE, also known as Zea mays var. indentata, is a variety of CORN that is used for ethanol production. Both CORN and MAIZE are used to produce ethanol, which is a type of alcohol that is used as a fuel and in the production of other chemicals.