How is alcohol made?

Ethanol is commercially produced using a process called fermentation. Many other alcohols can be made this way, but are more likely to be produced by synthetic routes - from natural gas, oil or coal.


Fermentation?
Fermentation is the process in which yeast breaks down sugar into alcohol and carbon dioxide. Yeast are tiny single-celled fungi that contain special enzymes responsible for this reaction.

The word equation for this process is:

 Glucose + yeast alcohol + carbon dioxide

Carbon dioxide gas bubbles out of the fermenting solution into the air leaving a mixture of ethanol and water. It's important that no air is present or the yeast will produce ethanoic acid - the chemical found in vinegar.

     
   

Beer and lagers

Barley, hops, water and live yeast produce beers and lagers. The sugar in the mix comes from the spouting barley. Bitter, stout and ale use top-fermenting yeast, while lager uses a variety that sinks to the bottom.

     
   

Wine

In wine making the sugars come from the flesh of the crushed grapes. The type of wine produced depends on the type of grape used in the process.

     
   

Spirits and distillation

Yeast cannot survive in high levels of alcohol, so to create stronger spirits an additional process, distillation, is required. Fermented drinks are distilled to create vodka, rum and other spirits. Distillation relies on ethanol having a lower boiling point than water. When the fermented drink is heated the ethanol vaporises at 78.5 degrees and the water is left behind (water boils or vaporises at 100 degrees). The ethanol gas is caught and cooled so it condenses into a stronger concentration of ethanol liquid.

     
   

Other uses of fermentation

Fermentation is also used in bread making; the yeast is mixed with the dough and kept warm. The carbon dioxide produced by fermentation makes the bread dough rise and the alcohol evaporates.