High-rate CO2 sequestration using a novel venturi integrated photobioreactor and subsequent valorization to microalgal lipids. Issue 22 (2nd November 2020)

• Record Type: Journal Article
• Authors: Dey, Saptarshi; Bhattacharya, Arghya; Kumar, Pushpendar; Malik, Anushree
• Is Part Of: Green chemistry. Volume 22:Issue 22(2020)
• Page Start: 7962
• Page End: 7973
• Publication Date: 2020-11-02
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/d0gc02552f
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : A novel microbubble assisted photobioreactor has been reported for high-rate online CO2 capture and co-optimized for application in enhanced microalgal growth, CO2 bio-fixation and increased production of microalgal lipids for 4 th generation biofuels. Abstract : Recovery of waste CO2 from flue gas involves two phase gas–liquid interactions for application in enhanced microalgal growth, CO2 bio-fixation and increased production of microalgal lipids for 4 th generation biofuels. Mineralized CO2 as bicarbonate between pH 10 and 7 constitutes the major inorganic carbon for phototrophic microalgae. Consolidating Carbon Capture and Usage (CCU) technology with microalgal lipid synthesis, the present work exhibits design and optimization of a microbubble assisted CO2 sequestration reactor to recover CO2 from low concentration sources (5% v/v) and maximize microalgal lipid productivity without any nutrient stress. A venturi microbubble generator was amalgamated with a bubble column and the Reynolds number was used to define the hydrodynamic flow regime. At a steady volumetric liquid flow rate Q L, corresponding to laminar flow conditions, the gas flow rate Q G was varied in the range 0.1–1 L min −1 to determine the volumetric mass transfer coefficient K L a and the CO2 mass transfer efficiency. K L a and Q G values were found to be linearly dependent in the Q G range 0.1–0.7 L min −1, while CO2 capture efficiencies in the range 86% to 98% were obtained. The optimized medium recirculation sufficed for culture agitation and further aeration for mixing was not required. A correlation coefficient was derived, relating the change in gas–liquid interfacial area with the change in Q G . The resultant system achieved a biomass yield of 0.454 g L −1 and a carbon content of 38.9% volatile suspended solids (VSS). Furthermore, a lipid accumulation of 35.9% on a dry cell weight basis and a lipid productivity of 11.64 mg L −1 d −1 exhibited feasible valorisation of sequestered carbon.