In general, algal oils contain a higher degree of polyunsaturated fatty acids (PUFA) (i. e., more than four double bonds) than vegetable oil (Belarbi et al., 2000; Harwood and Guschina, 2009) and higher free fatty acid content (>2%). ASTM D6751 (United States) and EN 14214 (European Union) provide the specifications for pure biodiesel (B100, Table 7.1) and are used in many parts of world for comparing the fuel proper­ties of biodiesel. The biodiesel standards developed in many countries are based on the availability of region-specific biodiesel feedstocks. The specifications developed for ensuring biodiesel fuel quality are frequently subjected to modifications, and biodiesel-producing countries are required to update their specifications according to changes in ASTM — or EN-based biodiesel standards.

The lipid composition of algal oil is different from plant oils/animal fats, and it varies with species and growing conditions (Mutanda et al., 2011). Major fuel and chemical properties considered for the selection of an alternate diesel fuel are

kinematic viscosity (KV), higher heating value (HHV), Cetane Number (CN), den­sity, flashpoint, cold flow properties (cloud and pour points), carbon residue, oxi­dation stability, ash content, ignition quality, acid value (AV), saponification value (SV), and iodine value (IV). These properties can be compared with well-established international fuel standards for ensuring fuel quality for diesel engine applications. Properties such as SV, IV, and CN are considered more important for assessing alternate diesel fuels because they give basic information about the ignition quality of fuel, the presence of unsaturated fatty acids (UFAs), and the ignition properties of FAMEs, respectively. The higher iodine values of algal oil indicate the presence of higher UFAs, and heating these UFAs may be lead to the formation of deposits due to the polymerization of glycerides at high temperatures (Mittelbach, 1996; Ramos et al., 2009). The algal oils/FAMEs containing higher degrees of unsaturation are not recommended for biodiesel. The values of the SV, IV, and CN can be easily calcu­lated from the lipid profiles of algal oil using equations developed by Krisnangkura (1986) and Kalayasiri et al. (1996).

Based on the lipid profiles of identified strains/species grown on a laboratory scale, they can be easily screened for suitability in biofuel production. Based on cor­relations developed between fatty acid compositions and the fuel properties of oils, the fuel quality of biodiesel derived from selected algal oils can be predicted through the lipid composition. Hence, it is necessary to determine the fatty acid profiles of extracted algal lipids for suitability in biodiesel production and assess the fuel qual­ity. It is essential for biodiesel derived from microalgal oil to meet ASTM (2008) or EN (2003) biodiesel standards for ensuring fuel quality.