Biomitigation of CO₂ from flue gas by Scenedesmus obtusiusculus AT-UAM using a hybrid photobioreactor coupled to a biomass recovery stage by electro-coagulation-flotation.

Abstract

The microalga Scenedesmus obtusiusculus AT-UAM efficiently captured CO2 from two flue gas streams in a hybrid photobioreactor located in a greenhouse. Uptake rates of CO2, NO, and SO2 from a formulated gas stream were 160.7 mg L-1 day-1, 0.73 mg L-1 day-1, and 1.56 mg L-1 day-1, 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-1 day-1, 0.42 mg L-1 day-1, and 0.98 mg L-1 day-1, obtaining removal efficiencies of 77%, 71%, and 53% for CO2, NOx, and SO2, respectively. On average, 61% of the CO2 from both flue gas streams was assimilated as microalgal biomass. The maximum CO2 uptake rate of 182 mg L-1 day-1 was achieved for formulated flue gas flow rate above 100 mL min-1. 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-1. 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.