Lipid productivity, settling potential and fatty acid profile of 11 microalgal species grown under nitrogen replete and limited conditions

Microalgae are a promising alternative source of oil for biodiesel production. Identification of a species with desirable characteristics is a key component towards achieving economic feasibility for the process. This has been compromised by a lack of data allowing effective interspecies comparison. Eleven species of microalgae, selected on the basis of available literature data, were tested for lipid productivity, gravity sedimentation and the suitability of their fatty acid profiles for biodiesel production. The response to nitrogen limitation was species-specific. Lipid yields and productivity were higher at 150 mg L-1 nitrate than at 1,500 mg L-1 for all species tested except Spirulina platensis. The Chlorophyta, particularly Chlorella vulgaris and Scenedesmus, had the highest growth rates and showed the greatest increase in lipid content in response to nitrogen limitation. Cylindrotheca fusiformis, S. platensis, Scenedesmus and Tetraselmis suecica had the fastest settling rates and highest biomass recoveries after 24 h of gravity sedimentation. For most species, the fuel would need to be blended or culture conditions to be optimised to achieve the correct lipid profile in order for microalgal fuel to meet the European standards for biodiesel production (EN 14214). The most promising species overall were the freshwater algae Scenedesmus and C. vulgaris and the marine algae C. fusiformis and Nannochloropsis.