Biodiesel Production from Botryococcus sudeticus and Chlorella vulgaris: Assessment of Nitrogen Deficiency on Lipid, Fame Yield and Biodiesel Properties

Biodiesel production from microalgae is considered a sustainable alternative to fossil fuel sources. The economic feasibility of algae-based biodiesel is highly related to biomass, lipid and FAME yield of the species. Thus, optimization of the culture conditions plays an important role in biodiesel production. The aim of this study is to compare lipid and FAME yield and biodiesel quality of two green algae species, Chlorella vulgaris, and Botryococcus sudeticus, under nitrogen deficiency conditions. For this purpose, algae species were cultured under optimum conditions until the stationary phase, then in the second phase the effect of nitrogen stress on total lipid, FAME content, and biodiesel quality were assessed. Although nitrogen-deficiency had negative impact on the growth and survival of both species, complete nitrogen removal from the medium stimulated the total lipid and FAME yield and the level of enhancement varied among species. FAME yield increased by 21% in B. sudeticus and 28% in C. vulgaris cultures under nitrogen deficiency conditions. The biodiesel properties of both cultures met European standards, on the other hand the absence of nitrogen did not reveal a significant effect on the cetane number values of C. vulgaris. However, it caused a reduction in B. sudeticus cultures. Nitrogen deficiency had a negative impact on the oxidative stability of B. sudeticus, reducing its ability to resist oxidation. However, it enhanced the oxidative stability of C. vulgaris in long-term storage. The results highlighted the importance of species-specific approaches to maximize both lipid content and biodiesel quality.