Abstract
Third generation biofuels which is biodiesel from microalgae has its share of problems such as high cultivation costs, expensive dewatering and drying process, lipid extraction and transesterification. Nannochloropsis sp. was cultivated indoor using pulse light emitting diodes LED, blue LED and red LED. Nannochloropsis sp. was cultivated for 12 d under LED pulsed at a constant frequency between 5and 100 kHz with various duty cycles (5 – 50 %) by changing the resistance compared with red and blue LED. The number of cells, lipid content and FAME composition were determined using cell counting, Nile red method and gas chromatography respectively. Results revealed that the pulse LED compared to other wavelength LED have a significant effect in the number of cell (pulse: 3.39; blue 2.83; red: 2.63 x 107 cell/mL) and exhibited a consistent lipid production stability curve compared with red and blue LED. The biodiesel produced under the pulse LED has the following characteristics: degree of unsaturation (80.41), density (881 kg/m3), viscosity (3.96 mm2/s), cetane number (61.03), iodine value (97.76), cloud point (7.1 oC), pour point (0.86 oC), CFPP (6.52 oC) and HHV (41.28 MJ.kg).
