Efficient CO2 Delivery from Flue Gas to Microalgae Ponds through a Novel Membrane System

EFFICIENT CO2 DELIVERY FROM FLUE GAS TO MICROALGAE PONDS THROUGH A NOVEL MEMBRANE SYSTEM
Qi Zheng, Shirley Xu, Greg Martin, Sandra Kentish

During microalgae cultivation, carbon dioxide is supplied as the carbon source for photosynthesising microalgae. The traditional strategy is to directly bubble CO2 gas into photobioreactors or microalgae ponds. However, most CO2 is lost into the atmosphere. Several technologies, such as microbubbles, porous membrane spargers or non-porous membrane contactors, have been applied to reduce the CO2 losses. However, these CO2 delivery technologies cannot eliminate the energy associated with the compression and transportation of CO2.

In the present work, a novel system, consisting of chemical absorption, membrane separation and microalgae cultivation, was demonstrated to capture and transport CO2 from flue gas to microalgae. The novel approach can reduce energy requirements for the compression and transportation of CO2 and avoid energy penalty for the regeneration of solvents as incurred in the conventional chemical absorption process.

Chemical solvents studied in the current work were potassium carbonate (K2CO3), monoethanolamine and potassium glycinate. They were studied in combination with a marine strain of Chlorella sp., freshwater Chlorella vulgaris, and marine Dunaliella tertiolecta. Potassium glycinate was identified as the optimum solvent while marine algae gave slightly better results than freshwater. The work has established a novel method for CO2 delivery to microalgae, reducing the energy for compression and transportation of CO2. It represents important implications in CO2 capture and utilization.

Dr Qi Zheng has recently graduated, after a PhD thesis focussed on this topic. A new PhD student, Shirley Xu, has recently commenced to continue this work, with a focus on scaleup and pH control.