Fermenters are temperature-controlled tanks in which yeast is allowed to feed on the sugars in beer wort to make carbon dioxide and ethyl alcohol. The most commonly used fermenter design is a vertical, cylindrical tank with a conical bottom. Often the temperature of the sections of the fermenter can be controlled separately by admitting coolant to jackets surrounding that part of the tank. After fermentation, the yeast settles into the cone and can be reused for the next fermentation.