CO₂ capture and lipid production performance of microalgae in the S-shaped photobioreactor under different culture...

An S-shaped photobioreactor was designed by adding grooves and baffles in the traditional photobioreactor to improve the culture efficiency of microalgae. After that, the parameters of the characterization of the S-shaped photobioreactor, such as the mixing time, gas holdup, and gas-liquid mass transfer coefficient, were determined. The biomass, lipid production rate, and average CO₂ capture rate of microalgae were then analyzed under different culture modes. Finally, the feasibility of using digested piggery wastewater combined with simulated flue gas was explored as a culture mode for the microalgae and the lipid properties of the microalgae were analyzed. The results revealed that, at a flow rate of 0.08 vvm, the mixing time was reduced by 8.5 s, the gas hold-up increased by 44.6% and the gas-liquid mass transfer ability was also improved. Improvements were also observed in the biomass values, lipid production rate, and average CO₂ capture rate of the microalgae under different culture conditions, with respective values reaching 0.23 g·(L·d)^-1, 70.28 mg·(L·d)^-1, and 0.43 g·(L·d)^-1 under the mixotrophic mode. Additionally, digested piggery wastewater combined with the simulated microalgae flue gas culture was determined to be feasible. The biomass, lipid production rate, and the average CO₂ capture rate of microalgae, the values of which were 0.22 g·(L·d)^-1, 52.55 mg·(L·d)^-1, and 0.41 g·(L·d)^-1, respectively. Lipid was observed to have the potential to produce high-quality biofuel.