**5. Conclusion**

262 Sustainable Growth and Applications in Renewable Energy Sources

because higher extraction time above the optimum time cannot yield oil more than the

With ethanol as extraction solvent, the effect of factor B (particle size) has the highest dominance of 9.5213. The interaction of factor AC, temperature and extraction time has an effect of 0.7288, while temperature has the least effect of -0.3813. The 23 factorial analyses, give a model equation (Equation 8). From the statistical model, it can be seen that the extraction temperature, X1, is inversely proportional to the oil yield, the particle size X2 and the extraction time X3 are all directly proportional to the oil yield. The inverse proportion effect of temperature on the extraction of oil from moringa oleifera seed is an indication that a range of 65 – 70oC is adequate to give a better yield of oil. Above this temperature range, the effect of temperature on the oil yield is negative. Thus a reduction in the extraction temperature from the maximum will result in an increase in the yield of oil. Results obtained also shows that the oil yield is directly proportional to the particle size. Hence the effect of particle size on oil yield increases with an increase in the particle size this is because greater surface area of the oil molecules exposed to solvent for dissolution. In the same vein, increase in the extraction time leads to increase in the yield of from moringa oleifera seed

Production of ethanol from starch or sugar based feedstock is among man's earliest ventures into value added processing, while the basic steps remain the same, the process has been considerably refined in recent years, leading to a very efficient process. Bio-ethanol is an alcohol made by fermenting sugar components of biomass (Bailey and Ollis, 1986; Elba and Antenieta, 1996). Apart from food and pharmaceutical uses, bio-ethanol is finding alternative uses as motor fuel and fuel additive, ethanol as motor fuel is preferred to fossil fuel in that, it is environmentally friendly, comes from a renewable source and has a higher performance in engine (Eurasia, 2009).It can be mass-produced by fermentation of sugars or by hydration of ethylene from petroleum and other sources (Eurasia, 2009). Hence the need to produce bio-ethanol from relatively inexpensive and readily available raw materials like rice husks. In this study, rice husks were used to produce ethanol through hydrolysis and fermentation with Zymomonas mobilis. In the process of fermentation, the organism fermented the substrate (rice husk) to produce ethanol, Zymomonas mobilis possesses alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) which is key enzymes in ethanol fermentation from organic substrate as stated by Gunasegaram and Chandra (1998). Results obtained of bio-ethanol from rice husks as presented in Table 4.3 indicates that the volume of bio-ethanol is influence by the volume of hydrolysate. The maximum volume of bio-ethanol produced was 43cm3 from 150 cm3 of hydrolysate, while 25cm3 of bio-ethanol was produced from 350cm3 of the hydrolysate. The high yield of bio-ethanol from rice husk may be due to high carbohydrates contents of rice husk or the high ethanol tolerance of Zymomonas mobilis and the presence of alcohol dehydrogenase in Zymomonas mobilis which appears to facilitate ethanol formation even at high ethanol concentration. Presented in Table 4.2 are the properties of oil, such as viscosity, refractive index, density and flash point of the bio-ethanol produced from rice husk, which compared favorably with those of the commercially available methanol. The slight variation between the values of properties of bio-ethanol and that of the commercially available methanol can be attributed the sources of production and experimental methods employed. It can therefore be inferred that the bioethanol produced from rice husk cab be used as an alternative feedstock for the production

of biodiesel base on the properties of bio-ethanol presented in table 4.2.

maximum oil content in the seed kernel.

with ethanol as the solvent.

The need for alternative sources of energy other than fossil fuel gained momentum recently, and biofuel is considered perfect alternative sources of energy that is sustainable and reliable. However, the possibility of producing biofuel in commercial quantities is not certain; this is blame on the consequence effects of producing the biofuel from vegetable oil, as this can lead to food shortage. To achieve commercial availability of biofuel, it is therefore important to produce biofuel from non-edible oil or from the sources that are not popular sources of edible oil. To achieve commercial realisation of biodiesel production, this work focuses on the extraction and optimization of oil from moringa oleifera seed as an alternative feedstock for the production of biodiesel. Analysis of results indicates that when n-hexane was employed as the extraction solvent, the effect of particle size has the highest effect with magnitude of 2.50, followed by the extraction temperature with magnitude of 1.59, while the effects of extraction time was the lowest with the magnitude value of 0.53. With ethanol as the extraction solvent, particle size also has the highest dominance of 9.52, while the interaction of temperature and time has an effect of 0.73, while the extraction temperature was -0.3813. Based on these results it can be deduce that for an appreciable yield of oil to be achieved with ethanol as the solvent, the particle size and interaction of temperature and time are the factors which have high significance. Results obtained from the production of bio-ethanol from husk indicate that, it is possible to produced bio-ethanol from rice husk, which is also a major a feedstock in the production of biodiesel.
