ABSTRACT
Introduction As described in previous chapters, during the transesterification process, intermediate glycerols, mono-and diacylglycerols, are formed, small amounts of which can remain in the final biodiesel (methyl or other alkyl ester) product. In addition to these partial glycerols, unreacted triacylglycerols as well as unseparated glycerol, free fatty acids (FFA), residual alcohol, and catalyst can contaminate the final product. The contaminants can lead to severe operational problems when using biodiesel, including engine deposits, filter clogging, or fuel deterioration. Therefore, standards such as those in Europe (EN 14214; EN 14213 when using biodiesel for heating oil purposes) and the United States (ASTM D6751) limit the amount of contaminants in biodiesel fuel (see Appendix B). Under these standards, restrictions are placed on the individual contaminants by inclusion of items such as free and total glycerol for limiting glycerol and acylglycerols, flash point for limiting residual alcohol, acid value for limiting FFA, and ash value for limiting residual catalyst. A more detailed discussion of the rationale for quality parameters in biodiesel fuel standards is given in parts of this book and the literature (1-3). Some methods used in the analysis of biodiesel, including procedures for determination of contaminants such as water and phosphorus, which will not be dealt with here, were also described briefly (3). The determination of fuel quality is therefore an issue of great importance to the successful commercialization of biodiesel. Continuously high fuel quality with no operational problems is a prerequisite for market acceptance of biodiesel.
