Performance Evaluation of a Bubble Column Photobioreactor for Carbon Dioxide Sequestration by Chlorella vulgaris

Biosequestration of carbon dioxide is a promising technique for global warming reduction. The present work evaluates the performance of a bubble column photobioreactor for simulated industrial effluent treatment using Chlorella vulgaris. C. vulgaris was cultivated under various conditions of initial size inoculum and initial carbon dioxide feed percentages. The maximum growth rate constant achieved was equal to 0.056 h (-1) for the culture of an initial size of 0.01 g/L fed with 10% CO2. The mass of carbon fixed as a per cent of carbon sequestered was calculated for all cultures, and a maximum value of 40% was calculated for the culture of an initial size of 0.1 g/L fed with 5% CO2, indicating that not all carbon sequestered by the reactor is effectively fixed in biomass cells. The energy output (calculated as the higher heating value of produces biomass) as a per cent of light energy input was calculated to account for the energetic performance of the reactor, and the maximum calculated per cent was equal to 12.21% achieved for the culture of an initial size of 0.1 g/L fed with 5% CO2. Biomass subjected to a 16:8 and a 12:12 light/dark cycle yielded carbon fixation rate, which represents 86 and 18.8% of that obtained under continuous illumination respectively.