1.1 Background of the study

Yams (Discorea spp) of the family Diocoreaceae are members of the flowering plant. They are monocots, related to palms, grasses and archids. Most yam species grow in the tropics and subtropics area with fairly heavy total annual rainfall, but with a definite day season. During the rainy season, they produced one or more underground tubers to store food and water through the dry season the tubers are thickened stems. Most yam plant have small flower with one plant having only male or female flower (Kay, 1987).

The tubers of most species of yam are poisonous to humans. The cultivation of most yams is very labour intensive. Cultivated yams generally do not produce seed and so tubers or pieces of tuber must be planted in prepared soil, most often in wounds to grow new plants.

Yams are nutritious food, providing carbohydrate, some protein, and mineral like phosphorus and potassium besides the use as food, yams have been symbolically associated with culture and ritualism in some parts of Africa, Asia and Latin Americas.

According to Ogbuka (2005) Ethanol can be produce from starch –containing substances like maize, cassava and yam. Ethanol is a monohydric alcohol that is colourless and flammable, it is a 2 –carbon alcohol with molecular formular CH3 CH2 OH, its empirical formular is C2H6O. An alternative notation is CH3CH2 OH which indicates that the carbon of a methyl group (CH3) is attached to the carbon of an ethylene group (CH2-) which is attached to the oxygen  of a hydroxyl group (OH). Ethanol is a colourless liquid that burns with a smokeless blue flame. It has a choking smell and a boiling point of 780c. They are characterized by the possessing of phydroxyl group (OH) as their functional group. Alcohols can be classified as primary, secondary and tertiary. The primary alcohols have only one or no alkyl group attached to the hydroxyl bonded carbon atom, the secondary alcohol contain two alkyl group attached to the hydroxyl bonded carbon atom while the tertiary alcohol contains three alkyl groups but no hydrogen attached to the hydroxyl- bonded carbon atom while the tertiary alcohol contains three alkyl groups but no hydrogen attached to the hydroxyl-bonded carbon atoms:

According to West et.al (2007) ethanol is a principle fuel that can be used as petrol substitute for vehicles. It is a renewable energy source produced mainly by sugar fermentation process. It is used in preservation of specimen, food e.t.c and even as a raw material in the manufacturing of chemicals and pharmaceuticals like trichloromethane