Biodiesel Production from Nannochloropsis Oculata Cultured at High Illumination Associated with High CO2 Concentration
Date Issued
2009
Date
2009
Author(s)
Tsai, Wen-Yi
Abstract
The development of global economies is limited by two current problems, global warming and oil crisis, and dealing with these issues is a global goal. CO2 is the main greenhouse gas that results in the global warning, and is generated by burning fossil fuels, which are limited and non-regenerated resources that can be exhaust eventually used. icroalgae, which is grown by photosynthesis from light and CO2, can accumulate lipids inside cells and be converted to biodiesel, it can not only reduce atmospheric CO2 but also produce biodiesel which is belong to regenerated energy. However, the CO2 concentration discharged from power plants and factories is normally 10-15%, is too high for Nannochloropsis oculat growth. In order to solve high CO2 concentrations that result in the growth inhibition of N. oculata, intensity light and initial cell concentration are manipulated in this study. N. ocualata cultured under both high light intensity and high CO2 concentrations, not only improves growth rates, but also dramatically enhances cell lipid content. Results showed that cultured at 300 μmol m-2s-1 and 10% CO2, the cell concentration can reach about 9 × 107 cells mL-1 after culturing for 10 days from an initial cell concentration of 1 × 107 cells mL-1, with significant enhancement of lipid content in N. oculata. When 15% CO2 was supplied, the initial cell concentration of 108 cells mL-1 was required for growth because using 107 cells mL-1 as the inoculation concentration led to growth inhibition. The particle size of N. oculata was also increased when cultured with high CO2 concentration and high illumination. This might be due to lipid accumulation inside the cell, and was confirmed by performing fluorescent spectra of cells stained with Nile red. The cultivation of N. ocualat was further scaled up in a photobioreactor. Results revealed that N. oculata grown with high light intensity and high CO2 concentration can obtain the highest cell concentration and lipid, and use CO2 more efficiently. The cellular lipids were extracted and then converted to biodiesel by transesterification reaction. The microalgal biodiesel analyzed by gas chromatography revealed that high yield can be achieved by culturing N. oculata under stressful conditions – high CO2 concentration in combination of high illumination.
Subjects
CO2
Nannochloropsis oculata
Photoinhibition
Initial cell concentration
Biodiesel
Type
thesis
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