A preliminary study on some Chlorella spp. for biodiesel production

This paper describes a preliminary analysis of the possibility to use different algae species for biodiesel production. A lab scale cultivation of five Chlorella spp. was conducted to evaluate their potential for biodiesel production, with respect to their growth and fatty acids characterization, as an initial step to transferring them into the outdoor open ponds. The results of algal dry wt (mg/l), arranged in descending order, were Chlorella salina, 200 ± 0.02; Chlorella vulgaris , 192.28 ± 0.00; Chlorella stigmatophora , 162 ± 13.06; Chlorella capsulata , 101.08 ± 7.54; Chlorella marina , 86 ± 6.99, while the growth rates (mg/d) were Chlorella marina , 2 ± 0.17; Chlorella vulgaris , 1.78 ± 0.14; Chlorella stigmatophora , 1.52 ± 0.11; Chlorella capsulata , 1.51 ± 0.13; Chlorella salina , 1.16 ± 0.09. The highest lipid content (dry wt based) was recorded for Chlorella capsulata (446 ± 0.33 mg/g), while Chlorella vulgaris showed the lowest content (255 ± 2.5 mg/g). The amounts of the neutral lipids (dry wt and total lipid based) were found in the range of 14-28%, and 60-80%, respectively. Data showed that Chlorella salina was the oil-richest species, while C. capsulata was the poorest. The extracted oil was also characterized according to its acid and saponification values. Based on the analysis of fatty acid methyl esters (FAMEs), the carbon chain lengths ranged from C₆ to C₂₁, and most of them were of saturated types. The most important fractions for best quality biodiesel (C14 : 0, C16 : 0, and C18 : 0) were detected in all examined microalgae. The distribution patterns of fatty esters in C. salina , C. marina , and C. stigmatophora were the same. C18 : 1 was not present in C. capsulata , while C16 : 1 was completely absent from all species. However, no polyunsaturated fatty acids were detected in this study. The relative molecular weight of FAMEs and the percentage of the free fatty acids were also recorded for each microalga. The study was meant not only to enrich the Chlorella database, but it was also concerned with the potential of the three nonnative strains to adapt to the Egyptian habitats to be cultivated under the same conditions. The results of our studies are thus an important achievement.