CO₂ capture of the gas emission, using a catalytic converter and airlift bioreactors with the microalga Scenedesmus dimorphus

A process composed by a catalytic converter and three sequential Airlift photobioreactors containing the microalga Scenedesmus dimorphus was studied to capture CO₂, NOx, and CO from emissions of a steam boiler which was burning diesel. The catalytic converter transformed to CO₂ a maximum of 78% of the CO present in the combustion gas. The effects of shear rate, light intensity, and light/dark cycles on the biomass growth of the algae were studied. It was observed that at low shear rates (Re ≈ 3200), a high productivity of 0.29 g_cel L^-1 d^-1 was obtained. When the microalga was exposed to 60.75 μmol·m^-2·s^-1 of intensity of light and a light/dark cycle of 16/8 h, a maximum productivity of 0.44 g_cel L^-1 d^-1 and a maximum CO₂ fixation rate 0.8 g CO₂ L^-1·d^-1 were obtained. The maximum CO₂ removal efficiency was 64.3%, and KLa for CO₂ and O₂ were 1.2 h^-1 and 3.71 h^-1 respectively.