| Summary: | Biodiesel from microalgae is a viable alternative for replacing the global demand for petro-diesel. High biomass and lipid production are key desirable characteristics needed in a species to be used for biodiesel production. It has been demonstrated in literature that the increase in salinity can increase the lipid content of microalgae, but lower the growth rate of a species. Therefore the effect that salinity has on the growth and lipid content of ten microalgal species, isolated from a warm temperate solar saltworks, was investigated. The microalgae were cultivated at a temperature of 22°C and at salinities ranging from 17 to 70 psu. It was found that growth and lipid production for all species were influenced to some degree by the salinity. Growth rates greater than 0.6 d-1 showed a decrease with higher salinity. Most (71 percent) of the growth rates that exceeded 0.6 per day were exhibited by cultures exposed to normal salinity (35 psu). This shift is a good indication that salinity inhibits/slows down growth and that the species in general prefer lower salinity conditions. Growth rates ranged from 0.17 ± 0.05 to 1.19 ± 0.17 d-1. Lipid content for the diatoms (2.78 ± 0.36 to 10.86 ± 4.59 percent DW) were lower than expected, whereas the lipid content for the green flagellates (3.10 ± 1.56 to 22.64 ± 1.19 percent DW) was on par with that reported in literature. To bring results into perspective a production model was developed to simulate a production scenario at the Swartkops Saltworks. Lipid and productivity results obtained in this study were used to estimate how much oil and biomass can be produced within the ponds of the Swartkops Saltworks. The model showed that although microalgae cultivation for biodiesel is technically feasible, at present it is not economically viable to do so.
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