This is a type C3 perennial herbaceous plant that grows in the cool season and has an excellent resistance to flooding. Its productivity is strongly influenced by high levels of nitrogen fertilizers, a feature that makes it very useful for the distribution of fertilizer from livestock.

1.6 Sugar cane (saccharum officinarum)

This plant only grows well in tropical and subtropical regions, which is why it is particularly common in Brazil. It has a 12-17% sugar content, 10% of which is glucose and the other 90% is saccharose. Milling can extract 95% of the total sugar content and the juice can subsequently be used to produce sugar or allowed to ferment to produce bioethanol. The bagasse (i. e. the solid residue remaining after milling) can be used as a source of energy and heat.

1.7 Sugar beet (beta vulgaris)

This plant generally grows in the cooler temperate regions, so it is abundant in Europe, North America and Asia. In the ethanol production process, the sugar beet is sliced and, while the juice is used to produce sugar or ethanol, the pulp is dried and used as animal feed or sold for pharmaceutical purposes.

1.8 Cereals

These must be ground to obtain starch, from which bioethanol is subsequently obtained. The cereals containing fewer proteins and more carbohydrates are preferable for distilling purposes because they have a higher bioethanol conversion rate. This means that the nitrogen content in the cereals can be adapted to facilitate starch accumulation instead of proteins synthesis, thereby improving both the energy yield and the quality of the fermentation process (Rosenberg et al., 2001). The principal cereals are:

1.8.1 Wheat

It grows mainly in temperate regions. The wheat treatment process is much the same as for the other cereals and it is best to use high-gravity fermentation to obtain the best performance in the fermentation process.

1.8.2 Barley

The most suitable is the so-called Winter variety, which is often underestimated as a foodstuff, despite the fact that it can tolerate drought and is highly adaptable.