ABSTRACT
The two most commonly used biofuels are bioethanol and biodiesel. At a global scale bioethanol is the preferred biofuel (90 per cent). However, in Europe 75 per cent of the market is biodiesel. STATE-OF-THE-ART TECHNOLOGY
Bioethanol, also known as alcohol, is a renewable fuel made by fermenting sugars mainly from cereals such as wheat, maize, triticale, rye, barley and from sugar cane or sugar beet. Ethanol production from cereals containing starch takes place in fi ve stages (see Figure 12.1):
1 Milling: in the fi rst step the cereal is mechanically crushed in a milling process in order to release the starch component of the grain;
2 Saccharifi cation: the starch obtained through milling is converted into sugars in the second production step. This is done by heating and by adding water and enzymes, which break the starch up into fermentable sugars. The resulting fl uid is called mash;
3 Fermentation: the liquid mash is then treated with yeast, whereby the sugar is converted into CO2 and ethanol;
4 Distillation and rectifi cation: during this process the ethanol is concentrated and cleaned. Impurities are removed;
5 Dehydration: drying of ethanol to a purity of 99.7 percentage volume.
