Effect of pressure and carbon dioxide concentration on batch culture of microalgae chlorella sp

• Main Author: Tan, Wei Feng.
• Other Authors: Lau Wai Man
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Chemical engineering::Biotechnological production
• Online Access: http://hdl.handle.net/10356/39796
• Institution: Nanyang Technological University

An airlift photobioreactor was utilised to study the combined effects of carbon dioxide gas feed concentration and system pressure on the microalgae Chlorella sp. in 144-hr batch culture operations. Biomass growth, CO2 removal rate and energy content of the batch cultures were assessed based on applied conditions at three levels – different CO2 concentrations at atmospheric pressure, different total pressure at equal CO2 concentration, and equal dissolved CO2 partial pressures based on varied sets of CO2 concentration and total pressure. Maximum biomasses and biomass productivities achieved were 4.18-5.16g/L and 1.40-1.77 g/L.day respectively at 1%-4%VCO2 aerations and 1atm. Higher total pressures of 1.5-2atm at correspondingly equal %VCO2 were found to inhibit biomass growth by 14.3% for final biomass, and equal partial pressures induced by higher system pressures of 1.5-2atm produced biomass up to 21.1% lower. Average CO2 removal rates ranged from 0.375-1.221 g/hr for all runs, and were linearly proportional to applied CO2 concentrations. Increase in CO2 concentrations up to 3%VCO2 were found to increase calorific values of the culture by up to 3.7% respectively, while high pressure effect improved calorific values up to 2.4%. Calorific values per cell were found to increase with 1.5-2atm application, which indicates higher cellular lipid contentin the microalgae cells. With biomass productivity determined the dominating factor on the energy content productivity, optimising cell biomass growth over lipid content in the exponential growth phase of microalgae cultures was found to be a superior option.