The effects of medium salinity on the delivery of carbon dioxide to microalgae from capture solvents using a polymeric membrane system

Abstract

Efficient provision of carbon dioxide to microalgae is one of the major challenges to cost effective large-scale cultivation. Previously we have demonstrated the effectiveness of a novel membrane system in delivering CO2 to a marine strain of Chlorella sp. from CO2loaded solvents. In this approach, the solvent is pumped through a non-porous hollow fibre membrane immersed in a microalgae medium, allowing passive transfer of CO2 that is utilised by the microalgae to enhance their growth, while simultaneously regenerating the solvent. In this article, we compare the growth of both fresh water and marine strains of algae using this membrane delivery system. While the fresh water medium has less pH buffering capacity and can dissolve less CO2, it proves similarly effective in delivering CO2 to the growing algae. Both the freshwater and marine species of Chlorella have slightly higher growth rates than the other species tested-Dunaliella tertiolecta and Haematococcus pluvialis. However, due to the lower osmotic pressure of the fresh water medium, more water is drawn through the membrane into the solvent than when the salt water medium is used. In conclusion, while CO2 delivery through the membrane system is effective for both salt and fresh water media, better performance is obtained for the salt water medium.

Enhanced CO2 bio-utilization with a liquid–liquid membrane contactor in a bench-scale microalgae raceway pond

“…The medium pH influences enzyme activity in the cells and also affects the concentration of bicarbonate in the medium, thus indirectly influencing carbon assimilation by the microalgae [25]. In our prior work, the pH has not been controlled and this has led to poor algal growth in some cases [39]. In the present case, with no CO 2 addition at all, the pH in the control culture surged from 8.4 to 10.2 within three days (Figure 4(a)) as the carbon demand from the algae exceeded the supply from atmosphere.…”

Membrane Technology for Energy Saving: Principles, Techniques, Applications, Challenges, and Prospects

“…These membranes exhibit high porosity and hydrophilicity, contributing to significant algal permeation and antifouling properties. In algal culture systems, Zheng et al [ 181 ] achieved 100% carbon dioxide transfer utilization efficiency using a multimembrane carbonated carbon dioxide transfer system, eliminating energy consumption for gas compression and transport, and reducing energy loss during capturing solvent regeneration.…”