Microalgae-based biomass production for control of air pollutants

Abstract Global mechanization and urbanization have led to the increased release of toxic gases (CO2, CO, NOx, SOx, volatile organic compound, NH3, H2S, chlorofluorocarbon) into the biosphere, leading to environmental pollution and associated impacts such as global warming, which ultimately causing health problems in all life forms. In order to prevent from further deterioration of air quality there is a need for minimizing the emissions of harmful substances, performing pollution control and introducing solutions to reduce the concentrations of pollutants in the air. Moreover, chemical and physical processes could remove these air pollutants but they are expensive and can generate some toxic by-products. Biofiltration is an alternative to these processes and uses living microorganism or macroorganisms to degrade waste or harmful constituents and air pollutants that can be removed by this process. One of the biofiltration option is phycoremediation, which is the utilization of macroalgae and microalgae to remove pollutants (CO2, nutrients, metals, xenobiotics) and it gained popularity due to inexpensive growth requirements (solar light, CO2, and even salt water), no arable land, no competition with food crops, carbon mitigation and ecofriendly character. Macroalgae and microalgae are omnipresent and grow much faster than most terrestrial plants, thereby having higher CO2 fixation rates. Moreover, microalgae have been considered the most effective platform for combustion gases (CO2, NOx, SOx) reutilization, as the microalgal biomass is a very useful feedstock for the production of biofuels and bio-based chemicals, which proved their suitability in practical applications in bioremediation of gaseous pollutant from the source. Moreover, use of microalgae to reduce such air pollutant emissions is a promising approach that has both economic and environmental benefits. Algae and gaseous interaction have been extensively studied but not utilized in the real life. In this chapter, different techniques used in bioremediation of air pollutants especially CO2, NOx, SOx, and NH3 are presented, along with the ability and potential of microalgae species to utilize toxic gases and its biomass production for value-added purposes.