Ethanol Recovery - Recovery of ethanol from the fermentation broth is by distillation, which exploits the difference in boiling points of ethanol (87°C) and water (l00°C). As a result, when a water-ethanol mixture having < 95% ethanol is heated, the vapour has a greater concentration of ethanol than the liquid phase. Thus a dilute ethanol: water mixture can be repeatedly distilled to obtain more concentrated (up to 95%) ethanol solution.

When 95% ethanol is heated, the proportion of water present in the vapour phase is the same as that in the liquid phase. Therefore, simple distillation is no more helpful in further purification/concentration of ethanol. A small amount of benzene is added to 95% ethanol, which is then distilled.

The distillate is nearly 100% ethanol, and the benzene can also be recovered. Thus recovery of pure ethanol requires considerable amounts of energy, which raises its production cost; this has been the chief reason for the limited use of this valuable biofuel for transport purposes.