Technologically, the process of producing ethanol from sugar is simpler than converting corn into ethanol and uses about half the energy. While converting corn into ethanol requires additional cooking and the application of enzymes, sugar requires only a yeast fermentation process and the removal of water.
The process begins with cultivating and harvesting sugarcane at a cane field. Further processing is done at the sugar mill where the cane stalks are shredded and then crushed to extract the cane juice. The byproducts of this process are cane molasses, used in the production of alcoholic beverages, fuel alcohol and for direct human consumption and bagasse, which can be used to produce steam and generate electricity within the plant; excess electricity can be sold to utility grids.
The sugarcane juice is then transformed into alcohol at a distillery plant, usually adjoined to the mill, through a 4 to 12 hour fermentation process using yeasts and generates a significant amount of CO2 and heat. Much of the CO2 that is generated during the fermentation process can be captured and converted into marketable products, such as dry ice, liquid CO2 for soft drinks, fire-fighting foams, filtration products and various industrial uses.
After fermentation, the ethanol is distilled from other byproducts, resulting in an approximate 95% pure liquid called hydrous ethanol. Hydrous ethanol can be commercially used, but cannot be blended with gasoline because it contains 5% water. An additional reactant, such as cyclohexane, is then used to dehydrate the ethanol, by forming a tertiary azeotropic mixture with water and alcohol. Anhydrous ethanol is nearly 100% pure and can be blended with gasoline.
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