Steps of ethanol production...

Starchy or sugary raw materials (like corn, sugarcane, or potatoes) are first processed. Starchy materials undergo saccharification, where enzymes break down complex carbohydrates into simpler sugars (like glucose). Sugary materials can be used directly.

The prepared sugar solution is mixed with yeast (Saccharomyces cerevisiae) in large fermentation tanks. The yeast consumes the sugars and, in an anaerobic (oxygen-free) environment, converts them into ethanol and carbon dioxide. This process typically takes several days.

After fermentation, the mixture (called "beer" or "wash") contains about 10-15% ethanol along with water and other byproducts. This mixture is then heated in a distillation column. Since ethanol has a lower boiling point (78°C) than water (100°C), it vaporizes first, separating from the water and other impurities. The ethanol vapor is then condensed back into liquid form, resulting in a higher concentration of ethanol (around 95%).

For applications requiring pure, anhydrous ethanol (e.g., as a fuel), the remaining water from distillation must be removed. This is often done using molecular sieves or azeotropic distillation, which can achieve ethanol concentrations of 99.5% or higher.