Integration of CO2 Absorption from Flue Gas with CO2 Assimilation by Microalgae Using a Coupled Chemical-Biological Model

Abstract

Integration of conventional amine-based CO2 capture systems with microalgae cultivation systems might be a promising strategy to overcome the challenges of energy requirement and the limitations in the utilization of captured CO2. However, integrating these two very different systems forms a more complex system. In this paper, a coupled chemical-biological model was developed to reduce the complexity of a proposed integrated system for a better understanding of the critical process parameters. The proposed system uses an aqueous tertiary alkanolamine solution to capture CO2 from flue gases and delivers part of the captured CO2 to microalgae after mixing the CO2-rich absorption solution with a nutrient solution. The model simulates the processes of CO2 absorption-desorption and microalgae CO2 assimilation by using chemical equilibrium principles and Monod kinetics in an integrated way and estimates biomass production rates and CO2 utilization efficiencies for a given set of process parameters. The sensitiviy analysis of the model revealed that the overall efficiency of the integrated system is primarily determined by the type of alkanolamine used in the absorption solution and the maximum alkanolamine concentration in the growth medium. The model predicted that among the four types of alkanolamine selected in this study, N-methyldiethanolamine could be a more favorable CO2 absorbing chemical for such systems, and thus deserves to be investigated more in future studies.