Comparative Characterization Of Biodiesels Produced By Transesterification From Jatrpha Curcas And Thevetia Nerifolia Seeds

Comparative Characterization Of Biodiesels Produced By Transesterification From Jatrpha Curcas And Thevetia Nerifolia Seeds

Abstract

Increasing scarcity of fossil resources, increasing demand for petroleum fuels as well as increasing detrimental effects of extracting and using fossil fuels suggests alternatives. Biodiesel is a renewable, environmentally friendly, socially acceptable, technologically feasible and economically viable alternative fuel for diesel engines.

This study investigates the comparative characterization of biodiesels produced by transesterification from Jatrpha curcas and Thevetia nerifolia seed oil using ratio 1:5, 1:6, and 1:7 of methanol and oil and base catalyst (NaOH), at temperature of 60oC.

The percentage oil and biodiesel yield and the physco-chemical properties (PH, specific gravity, viscosity and flash point) of the methyl ester biodiesels were determined. The values of the biodiesel properties obtained were compared with America (ASTM) and European (EN) biodiesel standard. The data was analyzed using Randomized Complete Block Design (RCBD).

The result of this study shows that reaction ratio 1:5 has the highest biodiesel yield of 91%, 82% and 70% from Jatropha, Thevetia and the mixture respectively. There is a significant difference in the biodiesel yield among the three oil sources. The flash point increases with increase in the specific gravity of the biodiesels. The highest and lowest viscosity value (mm2/s) of 6.44 and 1.2 was recorded for mixture (1:7) and Jatropha (1:7) respectively. The biodiesel with the highest and lowest viscosity value and the biodiesels from thevetia (1:6 and 1:7) do not meet the ASTM and EN specifications which ranges between 1.9-6.0 and 3.5-5.0 respectively. Others meet the ASTM Specification (Table 4 and 5). Finally, the result of this study shows that Jatropha curcas and Thevetia nerifolia are good potential sources of oil for biodiesel production

Chapter One

Introduction

1. 1 General Introduction

Alternative fuel sources like bioethanol and biodiesel are being produced to combat the threats of global warming and high cost of fossil fuel. Emission of green house gases is on the increase everyday with rapid depletion of oil resources. Thus, biofuel like bioethanol provides numerous benefits in terms of environmental protection, economic development and national security (Artheet al., 2008). Biodiesel is a variety of ester-based oxygenated fuels derived from natural renewable biological sources such as vegetable oil. Through a process termed transesterification, in most developed countries, biodiesel is produced from rape seed, sun flower, soybeans, peanut which are essentially edible. More research is being geared towards finding an alternative renewable fuel through biological ways because of its positive environmental benefits (Bridgewater, 2006 and Artheet al., 2008).

Two approaches for transesterification of vegetable oils for the production of biodiesel have been suggested (Haas et al., 2002). The first is a chemical one in which alcoholysis of oil by methyl or ethyl alcohol in the presence of a strong acid or base produces biodiesel and glycerol (Fukuda et al., 2001). Chemical transesterification is efficient in terms of reaction time; however, the chemical approach to synthesize biodiesel from triglycerides has drawbacks, such as difficulty in the recovery of glycerol and the energyintensive nature of the process. The second approach is the enzymatic one, in which lipase-catalyzed transesterification is carried out in non aqueous environments.
A number of plant species including Jatropha curcas L. are being established as feedstocks, but in the case of Jatropha the seed cake is toxic and can only be used as a less valuable fertilizer or combusted as a fuel (Jongschaap, et al., 2007). Seed oil of Jatropha has been used as fuel substitute during world war 11. Enzyme-catalysed transesterification has more advantages over chemical method because of the reduced feedstock limitations, downstream processing and environmental impact (Rosenthal et al., 1996 and Jegannathanet al., 2008). A lot of research work has been reported on the benefits of oil transesterification using enzymatic methods (Nelson et al., 1996; Wu et al., 1999; Abigoret al., 2000; Kaideet al., 2001; Belafiet al., 2002; Oznuret al., 2002 and Shieh et al., 2003).

Today, enzymatic oil transesterification using commercially available enzymes like Lipzyme RMIM® and Lipozyme TLIM® which are lipases from microorgamism have emerged as a promising technique for transesterification of oil from plant materials (Rosenthal et al., 2001 and Sharma et al., 2002). In this present work, crude lipase from microorganism (Enterobacter aerogenes, Aspergillus niger and Aspergillus flavus) was screened for their ability to transesterifyJatropha seed oil, the most promising enzyme from the microorganism was characterised.

1.2 Statement of the Problem

The consumption and demand for petroleum products are increasing every year due to increase in population, standard of living and urbanization. In addition, limited and diminishing resources of fossil fuels, increasing prices of crude oil and environmental concerns have been the reasons for exploring the use of vegetable oil as an alternative to fossil fuel. Combustion of fuels such as coal, oil and natural gas has increased the concentration of carbon dioxide in the atmosphere thus increasing green house effects.

1.3 Justification of the Study

Since chemical approach to transesterification of biodiesel from triglycerides has drawbacks, such as difficulty in the recovery of glycerol and the energy-intensive nature of the process, there is therefore the need to source alternative methods of transesterification of vegetable oil. Therefore, transesterification of Jatropha oil and Thevetianerifoliacurcasoil to biodiesel would be of great advantage such as reduction of global warming by reducing sulfur/carbondioxide (CO2) emmision.

1.4 Aims and Objectives of the Study

The objective of the work is to optimize biodiesel production from Jatropha curcas and Thevetianerifoliaseed oil using lipases from microogamisms (Enterobacter aerogenes, Aspergillus niger, and Aspergillus flavus).

1.4.1 Specific Objective

1. To determine the percentage oil in some Jatropha seeds provenances.
2. To Screen some microorganism lipase activity for use in transesterification of Jatropha oil and Thevetianerifoliaoil.
3. To characterise the crude lipase from organism with high activity in transesterification of the seed oil.

Chapter Six

Summary, Conclusions and Recommendations

6.1 Summary

1. The Jatropha seed provenances reveal some variation in their oil yield (8.32-60.62%).
2. Ptentials of Biofuel has been recogmized in Jatropha curcas seed oil. Identified microbial species posses’ good lipase activity. Optimization using the crude lipases was achieved via transesterification process
3. Changes in fatty acids compositions were observed following lipase-catalyzed transesterification of the Jatropha seed oil using crude microbial lipases, where a significant alteration of fatty acid profile was observed from Aspergillus niger.
4. Altering the fatty acid profile can therefore improve fuel properties of biodiesel such as cold temperature (cloud and pour points), oxidative stability and nitrous oxide emissions (Timothy et al., 2008). Lipase-catalyzed transesterification of Jatropha oil and Thevetianerifoliaseed oil was found to improve the oil quality via reducing the saturated and unsaturated fatty acids of the seed oil.
5. Since enzyme are generally denatured by organic solvents, inability of some of the microbial lipases used in the transesterification reaction of the Jatropha seed oil could be as a result of inhibitory effect of the solvents on them.

6.2 Conclusions

1. The oil yield of Jatropha provenances varies with climatic conditions such as soil
   profile, rain fall.
2. The study also reveals some fatty acid profile of the Jatropha seed oil which could be useful as biodiesel and for other industrial applications.
3. Transesterification of Jatropha oil and Thevetianerifoliaseed oil by lipase from fungal origin should be utilized as better source for optimizing biodiesel production from seed oils.

6.3 Recommendations

1. Study on microbial enzymes (lipase) of different sources for their ability to catalyze transesterification of Jatropha oil and Thevetianerifoliaoil is recommended.
2. Optimizing biodiesel production using lipase-catalyzes transesterification of Jatropha oil and Thevetianerifoliaseed oil in the presence of different organic solvents, various reaction times and /or in a solvent free system is also recommended.

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