Optimization of CO₂ bio-fixation and utilization by microalgae in arid environment

In the ongoing efforts to combat the impact of climate change, microalgae cultivation is favored as agents for Biological Carbon Capture and Utilization in arid environment due to ability to thrive under high CO2 aeration, growth in saline and wastewater and high biomass and lipids productivities. The objective of this study is to design an effective and optimized cultivation system within a short time and with minimal experimental runs. Herein, we used response surface methodology to find the optimum decision variables that maximize CO2 fixation rate, algal biomass productivity, protein and lipids content. The main decision variables included in the study were process control variables such as temperature, light intensity, CO2 injection rate and mole fraction in inlet gas stream, and media composition. The solution of the multi-objective optimization indicates that 837.65 m³/hr of flue gas containing 0.7463 mole fraction of CO2 and wastewater containing 24.88 mmol/L of ammonium-nitrogen, 1.45 mmol/L of nitrate-nitrogen, 18.87 mmol/L inorganic carbon and 0.89 mmol/L of phosphate phosphorus under summer cultivation are required for optimum CO2 bio-fixation by microalgae. This study is useful as a vital tool for the scalability and optimum design of microalgae-based CO2 utilization plants in an arid environment.