For example, hollow fibre membrane with porosity of 0.264 had CO2 fixation rate of 0.275 g/L/h, which was 20% higher compared to membrane with porosity of 0.280. In addition, it was also observed that by allowing high gas flow rate into the photobioreactor, the effect of fine bubbles in homogenizing CO2 transfer in the system was diminished due to the reduction in bubbles retention time. The CO2 fixation rate by Chlorella vulgaris was dropped by about 36% when gas flow rate increased from 1 L/min to 2.2 L/min.