## 1 Introduction  
Electricity generation in Mexico has proven to be a significant source of air pollution at the national level [1]. In 2015, the electricity sector produced 124.85 million of tons of CO\({}_{2}\), 205,787 tons of NOx and 60,968 tons of CO [2, 3]. In general, steam boilers produce pollutant gases such as CO, NO, NO\({}_{2}\), hydrocarbons, SO\({}_{2}\), and solid particles or soot. Given the need to regulate the emissions of these gases, there is a wide variety of post-combustion treatments among which are the chemical absorption and biological fixation processes using microalgae [4, 5, 6]. One of the limitations for the use of CO and NO emissions in the cultivation of microalgae is its low solubility of 0.0068 and 0.0026 g\(\cdot\)L\({}^{-1}\), respectively [7]. That is why they must first be transformed into more soluble compounds, such as CO\({}_{2}\) and NO\({}_{2}\) (0.0386 mol\(\cdot\)L\({}^{-1}\cdot\)at\({}^{-1}\) and more than 1 mol\(\cdot\)L\({}^{-1}\) in water respectively). The CO and NO can be burned catalytically to CO\({}_{2}\) and NO\({}_{2}\), using a catalytic converter with noble metals or metal oxides as catalysts. These converters are composed of ceramic materials in the form of a honeycomb coated with alumina where metals like platinum are supported as active sites and other oxides such as CeO\({}_{2}\), TiO\({}_{2}\), ZrO\({}_{2}\), SiO\({}_{2}\)-Al\({}_{2}\)O\({}_{3}\)[8]. These converters can use the thermic energy of combustion gases to carry out the oxidation reactions [9]. Emissions from steam generators also contain volatile organic compounds (VOCs) such as polycyclic aromatic hydrocarbons, carcinogenic aldehydes or carbon in the form of soot. The conversion of unburned hydrocarbons to CO\({}_{2}\) is also carried out by the catalysts mentioned above. The presence of sulfur compounds such as SO\({}_{2}\) may also be present and depends on the quality of the fuel. In general, the diesel currently sold in Mexico City does not contain significant amounts of sulfur (\(<1\) vol.%), so it did not represent a problem in this study. To remove the soot formed by unburnt carbon particles, zeolite-based filters with Pt are used to retain and convert the particles to CO\({}_{2}\)[8]. Sequentially, it is necessary to place a catalytic converter for the treatment of diesel combustion emissions. In our previous study, we have observed that the removal of NO\({}_{2}\) can be carried out in microalgae bioreactors as part of its metabolism; however, this was not the case for SO\({}_{2}\) since this gas decreases its growth at a concentration of 60 ppm [10]. As is known, there are two types of bioreactors for cultivating algae to sequester CO\({}_{2}\) that include open raceway ponds and closed bioreactors [11,12]. The closed bioreactors allow better control of the operating conditions such as hydrodynamics, the sterilization process, and increase of the fixation efficiency. Among the closed bioreactors, there are the bubble columns (BC) and Airlift reactors (ALR), which consist of an inner tube (or riser) where the gas emission is bubbled at its base and an outer tube that surrounds the inner tube (or downcomer), where a flow of liquid or culture medium together with the gas flow forming a circular flow pattern avoiding the need for mechanical agitation, which decreases the energy requirements [13]. It is known that the ALR have shown better mixing, better heat transfer and mass than the BC, due to the presence of the draft tube or riser together with the advantage of simple construction without moving parts [14,15]. It is known that all nutrients in the culture medium, the mass transfer of CO\({}_{2}\), the intensity of the light, the gas holdup, and the circulation rate of the liquid in the ALR, have a decisive role in the growth of biomass observed. Therefore, the rate of inlet gas flow leads to gas holdup and the velocity of circulation of the liquid either in the riser or in the downcomer [16,17].