Humans have been harvesting the small, dry seeds known as grain for thousands of years. The two main categories of grains are cereals, such as wheat, rye, and corn, and legumes, such as beans, lentils, peanuts and soybeans. Many grains are capable of being stored for long periods of time, easily transported over long distances, processed into flour, oil, and gas, and consumed by animals and humans.
Most grain in the U.S. is used as animal feed, while slightly less is converted into ethanol. The smallest portion is consumed by humans. There has been recent debate about the health and ethics of grain feeding animals such as cows, goats, and sheep, animals biologically better suited to consuming grass. Though more cost effective than grass feeding, some argue this practice has an adverse effect on the quality of the meat as well as on the health of the animal and the consumer.
The use of grains in producing ethanol has increased significantly in recent years. Global ethanol production has tripled since the year 2000. Ethanol is a semi-renewable energy formed by the fermentation of a feedstock, often sugar cane or corn cobs. It can be mixed with gasoline and used as motor vehicle fuel. This hybrid motor fuel emits fewer pollutants than standard gasoline.