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, NO_x, 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.