Biomitigation of CO from flue gas by Scenedesmus obtusiusculus AT-UAM using a hybrid photobioreactor coupled to a biomass recovery stage by electro-coagulation-flotation.

The microalga Scenedesmus obtusiusculus AT-UAM efficiently captured CO from two flue gas streams in a hybrid photobioreactor located in a greenhouse. Uptake rates of CO, NO, and SO from a formulated gas stream were 160.7 mg L day, 0.73 mg L day, and 1.56 mg L day, respectively, with removal efficiencies of 100% for all gases. Exhaust gases of a motor generator were also removed with uptake rates of 111.4 mg L day, 0.42 mg L day, and 0.98 mg L day, obtaining removal efficiencies of 77%, 71%, and 53% for CO, NO, and SO, respectively. On average, 61% of the CO from both flue gas streams was assimilated as microalgal biomass. The maximum CO uptake rate of 182 mg L day was achieved for formulated flue gas flow rate above 100 mL min. The biomass recovery of 88% was achieved using a 20-L electro-coagulation-flotation chamber coupled to a settler with a low specific power consumption of 0.27 kWh kg. The photobioreactor was operated for almost 7 months without contamination of invasive species or a decrease in the activity. It is a very encouraging result for long-term operation in flue gas treatment.