Chapter II
Review of Related Literature

Calabash tree Fruit (crescentiacujete) Crescentiacujete is an evergreen tree reaching six to ten meters in height, broad and irregular crown composed of long, spreading branches which creates a moderate shade beneath the tree. The tree is most outstanding in the landscape for its year round production of flowers and fruit, both of which are unusual. The five centimeter flowers which bloom at night are yellow or green with red or purple veins , cup shaped, and appear to emerge directly from the branches. These are followed by the emergence of the large, round fruit, twelve to thirty centimeters in diameter with a smooth hard shell which hang directly beneath the branches. Inside there is pulp which has medicinal properties. The part of the tree that is used mostly is the fruit. Its uses are mainly in phytopharmaceuticals. The extract of the fruit is effective in treatment of diseases of the respiratory tract such as: bronchitis, cough, asthma and those related illnesses caused by cold(Pimentel, 2005). The tree grows in clayey soils with deficient drainage subject to frequent floods. It grows at elevations from sea level eight hundred meters and an annual rainfall between 1,500 to 1,300 millimeters and an annual temperature of twenty-six degrees Celsius (Olanu, 2011). The chemical constituents of the crescentiacujete; the crude carbohydrate found in the fruit is 18%. The fruit can be considered a good source of crude carbohydrate. Carbohydrate supplies energy to the cells. The mean value of sucrose content of the fruit is fifty-nine percent. The high carbohydrate and sucrose content of the fruit is 59% which makes the fruit a good source for ethanol production through fermentation. The mean energy value is high when compared with those of banana and other fruits. The value recorded for lead, chromium and nickel in the fruit sample were found to be 0.17, 0.07 and 0.10 ppm (Patzek, 2009)
Biofuel
There is growing interest in biofuels in many developing countries as a means of modernizing biomass use and providing greater acces to clean liquid fuels while helping to address energy costs, energy security and global warming concerns associated with petroleum fuels. Metrics for understanding and evaluating biofuel systems includes land use efficiency, net lifecycle, energy balance and economics. Biofuels are classified as 1stgeneration which are from seed grains or sugars and second generation biofuel from lignocellolusic biomass such as crop residues, woody crops or energy grasses (Jensen; Rutz, 2008). Biofuel production is a trend, the standard procedure in producing biofuel from biomass is the sampling of the biomass(fruit, seeds)then the pre-treatment of the biomass. The communication of the starches to the cellulose sugar is called saccarification then down to fermentation where ethanol is formed. The fermented biomass is distilled to extract the ethanol to be prepared for used (Prasetio, 2005). Properties of bioethanol are an essential topic for example the octane number of ethanol is higher than the octane number of conventional petrol. A high octane number stands for an anti-knocking fuel. Biofuel helps in preventing uncontrolled combustion which puts heavy mechanical and thermal loads on the engine. Ethanol has low pressure thus will have fewer evaporative emissions (Larson, 2008)