Biodiesel Properties from Chlorella sorokiniana Bio-Oil Cultivated Heterotrophically with Industrial By-Products

The fatty acid (FA) distribution of bio-oil derived from Chlorella sorokiniana and the biodiesel basic properties were examined. C. sorokiniana was cultivated heterotrophically in two growth media: a) glycerol and inorganic salts (GLIN) and b) glycerol and anaerobic digestrate (GLAD). The cultivation took place in 42 L bioreactors. The bio-oil was extracted from the biomass collected. Extraction was performed using a mixture of n-hexane and isopropanol in a 3:2 ratio. The fatty acid (FA) distribution was determined in a gas chromatograph by converting the bio-oil in biodiesel. The fatty acid distribution covered chain lengths from C10 to C26. The great proportion of the FA were of medium chain FA C16-C18 constituting about 85% and 53% of the total fatty acids of the GLIN and GLAD treatments respectively. Also, the distribution of saturated, monounsaturated and polyunsaturated FA differed. The basic properties of the biodiesel such as the density, the kinematic viscosity, the acid value, the cetane number, the iodine value and the heating value were within the range of the respective values from biodiesel obtained from seed oils and differences in the properties of the two treatments were explained in terms of differences in FA distribution.