Chapter Four: Processes and Challenges
4.6 The Referral Process
There are specifications that govern biodiesel quality, and the differences in key performance parameters of biodiesels versus conventional diesel. ASTM International (www.astm.org) is a consensus-based standards group that comprises engine and fuel injection equipment companies, fuel producers, and fuel users whose standards are recognized in the United States by most government entities and in some other countries.
The specification for biodiesel (B100) is ASTM D6751. This specification is a compilation of efforts from researchers, engine manufacturers, petroleum companies and distributors, and many other fuel-related entities, and it is intended to ensure the quality of biodiesel used as a blend stock at 20% and lower blend levels. In the United States for example, any biodiesel used for blending should meet ASTM D6751 standards (ASTM D6751, 2009) Also, the German Institute of Standardization (DIN EN 14214) is another notable regulatory body that issues specifications for all biodiesels produced or sold for use in the European Union.
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The result of the elemental analyses carried out on the respective biodiesel fuels produced (except for the Spirogyra biodiesel where there was insufficient quantity to run the analyses) showed a significant reduction (p < 0.05) in the levels of all the elements that were assessed in the biodiesel compared to their corresponding parent biomass. The negative correlation observed between the percentage elemental composition of the biomasses and the biodiesel yield in the two transesterification processes (Table 4.7) indicates that an increase in the proportion of the elements in the biomasses results in the decrease of biodiesel yield after transesterification. This is in agreement with the findings of Gerpen et. al. (2004). There was also a significant decrease (p < 0.05) in the kinematic viscosity of the biodiesels when compared to their parent oils. This suggests a significant increase in the fluidity of the fuels and a greater performance in diesel engines in terms of fluid operability.
Table 3.1 shows the specifications made by ASTM and DIN EN. It can be seen from the table that the Phosphorus content of Moringa biodiesel clearly exceeded the 0.001% maximum limit set by both regulatory bodies. Palm kernel biodiesel slightly surpassed the limit but Thevetia biodiesels was within the maximum set value. The Calcium and Sodium levels of the biodiesels of Moringa, Palm kernel and Thevetia all considerably surpassed the EN standard for these elemental compositions in biodiesel fuels. However, the Sulphur content in all the biodiesel fuels were clearly within the guideline set by ASTM, except that they slightly exceeded the guideline set by DIN EN.
A minimum flash point for diesel fuel is required for fire safety. B100‟s flash point should be at least 93ºC (200ºF) to ensure it is classified as nonhazardous under the National Fire Protection Association (NFPA) code. The biodiesels from all the respective oils in this work were in definite conformity with both ASTM and DIN EN guidelines, indicating a good level of safety handling with much less danger of inflaming accidentally.
Aliyu et. al, (2013) reported 186oC as the flash point for moringa biodiesel, while Sanford et. al.
(2009) also reported a value of >160oC as the flash point for moringa biodiesel. Also, Alamu et.
al. (2008) reported 167oC, Atu et. al. (2011) reported 209oC,while Oghenejoboh and Umukoro, (2011) reported 152oC as the flash point of Palm kernel biodiesel respectively. In the same vein,
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Balusamy and Marappan (2007) reported a flash point value of 128oC for Thevetia biodiesel whereas Olisakwe et. al. (2009) and Chindo et. al. (2013) reported a flash point of 168oC and 175oC respectively.
The results of all the flash point values recorded in this work for the biodiesels from the different substrate oils clearly show all these biodiesels to have a significantly higher “ignitability point”
as compared to that of conventional diesel fuel as shown in Table 3.1, which compares certain parameters of B100 biodiesel to conventional petroleum-based diesel.
The low-temperature properties of biodiesel and conventional petroleum diesel are extremely important. Unlike gasoline, petroleum diesel and biodiesel can freeze or gel as the temperature drops.
If the fuel begins to gel, it can clog filters on dispensing equipment and may eventually become too thick to pump. Cloud point is the most commonly used measure of low-temperature operability; fuels are generally expected to operate at temperatures as low as their cloud point.
The B100 cloud point is typically higher than the cloud point of conventional diesel. Cloud point must be reported to indicate biodiesel‟s effect on the final blend cloud point. Thevetia oil had the lowest cloud point (8.5+0.1oC) amongst the three biodiesels indicating a substantially very good cold property while Moringa and Palm kernel biodiesel fuels were observed to start containing small solid crystals at 13.6+0.1oC and 14.1+0.1oC respectively. At the same time, Thevetia, Moringa and Palm kernel oils were observed to essentially become a gel/solid (i.e. Pour point) at 5.1+0.1oC, 6.5+0.0oC and 8.6+0.1oC respectively.
Balusamy and Marappan (2007) had reported a Cloud point value of -4oC and a Pour point of -7oC for Thevetia biodiesel while Olisakwe et. al. (2009) reported 8oC Pour point value for Thevetia biodiesel. Also, Alamu et. al. (2008) had reported a Cloud point value of 6oC and a Pour point value of 2oC for Palm kernel biodiesel, whereas Oghenejoboh and Umukoro (2011) reported a Cloud point value of 8oC and a Pour point value of-15oC. Furthermore, Igbum et. al.
(2012) reported -13.19oC as the Pour point value for Palm kernel biodiesel. These results generally show that the biodiesel from these substrate oils considerably conform to ASTM D6751 and/or EN 14214 standards.
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CHAPTER SIX
CONCLUSION AND RECOMMENDATIONS 6.1 Conclusion
The purpose of this study was to evaluate the biodiesel yielding potential of certain plant biomasses viz-a-viz the characteristics of the biomasses and their respective products (i.e.
extracted oil and biodiesel). The oils were extracted by Solvent extraction processes: Soxhlet extraction and Cold extraction respectively; while these oils were processed to biodiesel by transesterification reaction using two alcohol systems.
The results of the experimental work show that Thevetia seeds produced the highest oil yield across the different extraction processes utilized while Spirogyra biomass produced the lowest yields. In the same vein, Thevetia oil gave the highest biodiesel yield across the two transesterification reaction systems in this work while Spirogyra oil produced the least biodiesel yields.
The extraction of oil from the plant biomasses via Solvent system proved that a mixture of the organic solvent (n-hexane) with another non-polar solvent (pet ether) in ratio 1:1 was more effective than the use of one organic solvent alone. However, the transesterification experiment showed that the use of a single alcohol such as methanol alone proved to be more effective than the combination of two alcohol systems (such as methanol/ethanol mixture). The physical and chemical characteristics of the biomasses and their respective products showed that they conformed to set standards that are stipulated by some regulatory bodies such as ASTM and DIN EN.
There was significant reduction in the level of certain undesirable parameters in the extracted oils when they were processed to their respective biodiesels through the base-catalyzed transesterification process. This suggests that undesirable qualities of biodiesels (such as high viscosity and high content of certain elements) could be significantly reduced by processing the oils to biodiesels via the base-catalyzed transesterification process.
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The results of analyses that were carried out in this work also revealed that there was a significant difference (p<0.05) between the relative density of the oils and that of the biodiesels that were produced from the oils. In the same vein, there was a significant difference (p<0.05) between the pH of the oils and their respective biodiesels. There was also a significant difference (p<0.05) between the Kinematic viscosity of the oils and their respective biodiesels.
Conclusively, the biodiesels derived from the respective extracted oils are acceptable substitutes for petrodiesel based on the plausible results from the analyses that were carried out to assess certain physicochemical properties of the oils and biodiesels respectively. Although the analyses carried out were somewhat limited to the available resources, but the major physicochemical properties analyzed for in the oils make them an attractive alternative feedstocks for biodiesel production. However, same cannot be said for Spirogyra biomass due to its significantly low oil and biodiesel yield respectively.