Improvement of Photoautotrophic Algal Biomass Production after Interrupted CO2 Supply by Urea and KH2PO4 Injection

Byung Sun Yu,Young Joon Sung,Sang Jun Sim,Min Eui Hong

doi:10.3390/en14030778

Abstract

Microalgae-derived biomass is currently considered a sustainable feedstock for making biofuels, including biodiesel and direct combustion fuel. The photoautotrophic cultivation of microalgae using flue gas from power plants has been continuously investigated to improve the economic feasibility of microalgae processes. The utilization of waste CO2 from power plants is advantageous in reducing carbon footprints and the cost of carbon sources. Nonetheless, the sudden interruption of CO2 supply during microalgal cultivation leads to a severe reduction in biomass productivity. Herein, chemical fertilizers including urea and KH2PO4 were added to the culture medium when CO2 supply was halted. Urea (5 mM) and KH2PO4 (5 mM) were present in the culture medium in the form of CO2/NH4+ and K+/H2PO4−, respectively, preventing cell growth inhibition. The culture with urea and KH2PO4 supplementation exhibited 10.02-fold higher and 7.28-fold higher biomass and lipid productivity, respectively, compared to the culture with ambient CO2 supply due to the maintenance of a stable pH and dissolved inorganic carbon in the medium. In the mass cultivation of microalgae using flue gas from coal-fired power plants, urea and KH2PO4 were supplied while the flue gas supply was shut off. Consequently, the microalgae were grown successfully without cell death.

Highlights

The emissions of carbon dioxide (CO2 ) from the use of fossil fuels are increasingly raising the atmospheric levels of CO2
Choi et al developed an affordable bicarbonate buffer system applicable to large-scale microalgae processes by utilizing flue gas emitted from power plants [9]
To generate the bicarbonate buffer, air containing a high concentration of CO2 is injected into an alkaline solution to decrease the pH and increase the dissolved inorganic carbon (DIC) concentration

Summary

Introduction

The emissions of carbon dioxide (CO2 ) from the use of fossil fuels are increasingly raising the atmospheric levels of CO2. This increase in the levels of CO2 in the atmosphere is associated with climate change [1], rising sea levels [2] and direct risks to human health [3]. Biological conversion technologies that capture CO2 using only photosynthetic organisms and light as energy sources are promising technologies [7,8]. Bio-based CO2 conversion processes have a high potential as a sustainable carbon reduction technology, producing valuable products while simultaneously mitigating CO2 emissions [9,10,11,12]

Methods

Results

Conclusion