Biological fuel that can be used as a fuel for vehicles, either in its pure form or added to gasoline.

Since it can be mixed in variable quantities, ethanol could play a decisive role in the transition from fuels produced from petroleum by-products to alternative fuels.

Ethanol can be mixed with gasoline at different quantities. The resultant fuel is distributed in common mixtures, such as the so-called gasohol or E10 (10% ethanol and 90% gasoline) or the increasingly popular E85 (85% ethanol and 15% gasoline). Pure ethanol (E100) can also be used in modified combustion engines.

Ethanol mixed with gasoline can be used even in motors without modifications, while the pure version reacts or dissolves certain types of rubber and plastic and should be used only in modified engines.

Three types of commodity are used to produce biological ethanol on a large scale:

• Substances with a high sugar content: mainly, sugarcane, sugar beets, molasses and sweet sorghum.
• Substances with a high starch: corn, potato and yucca.
• Celluloses: mainly wood and agricultural residues.

It is derived from plant sources, but there are problems with its use as a clean fuel: ethanol produces, during its combustion, more greenhouse gases than gasoline.

However, during their growth, the plants dedicated to its production absorb large quantities of dioxide from the atmosphere, so considering the entire cycle, its contamination levels are lower than those of conventional gasoline.

Three countries have developed significant programs to manufacture bioethanol as fuel: Brazil, the United States and Colombia.

While Brazil and Colombia have bet mainly on sugarcane, the United States uses huge quantities of genetically modified corn cultivated by the large cattle raisers of the Midwest.

These three countries all have large centralized cattle farms, as well as very extensive territories with populations concentrated on the coasts and in the main cities.

Large scale production of agricultural alcohol for fuel use requires significant quantities of arable land, making this alternative to gasoline less attractive for industrialized regions with a high population density, like Western Europe.

• More information on ethanol, in Wikipedia.