Effects of Sun and Oven Drying Techniques on Quality of Oil Produced from Chlorella vulgaris (Microalgae) Biomass

Abstract

This study involved the molecular identification of Chlorella vulgaris microalgae obtained from Kaduna State University Fish Pond for biodiesel production potential. The DNA of Chlorella microalgae was extracted and subjected to PCR. The molecular weight of the PCR product obtained was 1.8kb using 18S rDNA primer sets and BLAST analyses revealed 95% identity with Chlorella vulgaris. The Chlorella vulgaris was cultured in open aquaria tanks at the Department of Biological Sciences, Nigerian Defence Academy. The biomass harvested was subjected to varying timings of sun and oven drying techniques (25-35ºC for 72hours and 60ºC for 12hours respectively) before extraction of oil from the biomass using solvent extraction method. The values for the density (0.854 and 0.867 cm3), specific gravity (0.875 and 0.876), acid value (0.414 and 0.384 mgKOH/g), saponification value (173.3 and 170.1 mgKOH/g), kinematic viscosity (5.200 and 3.870 mm2/g at 40ºC), flash point (114 and 115ºC) and cetane number (54.00 and 47.70) for the sun and oven dried biomass oil respectively were found to be in accordance with the ASTM standard values for biodiesel and fossil diesel. GC-MS analyses of the oil extracted using the two drying methods showed that the fatty acid profiling of the oil obtained from sun dried processed biomass had C14:0, C15:0, C16:0, C18:0, C18:1 cis9 and C22:1ω9 while the oven dried biomass oil had C14:0, C16:0, C19:0, C11:1, C18:1 cis9 and C22:1ω9. Drying methods, therefore, had influenced on the composition of saturated and unsaturated fatty acids. The oven dried biomass oil possesses high monounsaturated fatty acids when compared to sun dried biomass oil though the most important fatty acids (C14:0, C16:0 and C18:1) found in standard biodiesel were present in both. The results suggested that Chlorella vulgaris microalgae can be sustainably harvested for the production of biodiesel, both drying techniques can be employed for effective extraction but oven dried biomass oil was found to be of high quality because of the balanced in saturated and unsaturated fatty acid compositions and have an easy mode of operation but it required instrumentation.