Vegetable was very dull, typically comprising mainly some staple product made from rice, rye, barley, wheat, millet or maize. The addition of vegetable matter provided some variety to the diet. The staple diet of the Aztecs in Central America was maize and they cultivated tomatoes, avocados, beans, peppers, pumpkins, squashes, peanuts, and amaranth seeds to supplement their tortillas and porridge. In Peru, the Incas subsisted on maize in the lowlands and potatoes at higher altitudes. They also used seeds from quinoa, supplementing their diet with peppers, tomatoes, and avocados. In Ancient China, rice was the staple crop in the south and
Vegetable oils as alternative energy Vegetable oils as alternative energy Vegetable oils are increasingly used as a substitute for fossil fuels. Vegetable oils are the basis of biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles, but straight vegetable oil needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity and surface tension. Another alternative is vegetable oil refining. The availability of biodiesel around the world is increasing, although still tiny compared to conventional fossil fuel sources. There is significant research in algaculture methods to make biofuel from algae. Concerns have