The urgent need to mitigate anthropogenic CO
2 emissions has spurred innovative approaches for CO
2 capture and utilization. In this study, we explore a novel method involving the capture of CO
2 using a functionalized deep eutectic solvents (DESs) [
1,
2] and subsequent bio-fixation through microalgae cultivation [
3]. The study focuses on the development of an integrated system that efficiently captures CO
2 and harnesses the photosynthetic capabilities of microalgae for sustainable CO
2 reduction.
Two DESs were compared: a binary DES, ChCl:MEA 1:8 (CM) and a ternary DES, ChCl:EG:MEA (CEM) 1:2:1 molar ratio. Choline chloride (ChCl) is a hydrogen bond acceptor, while ethylene glycol (EG) and monoethanolamine (MEA) are hydrogen bond donors. The CO
2 capture took place in a glass bubbler with ceramic diffuser. The desorption process involved immersing the DES in a stainless-steel container, subjecting it to a controlled temperature of 80 °C, and agitating at 12 RCF (Relative Centrifugal Force) within a full vacuum, ensuring effective desorption of CO
2 from the DES. The CO
2-enriched gas was introduced into a microalgae bioreactor series, where it served as a carbon source for photosynthesis [
4]. The microalgae culture,
Chlorella sp. NIVA-CHL137, was cultivated under controlled environmental conditions, including a day/night photoperiod (13/11 h) and BG-11 cultivation medium. The optical density (OD) and biomass yield were used to evaluate the microalgae development.
The microalgae cultivation in the bioreactor showed CO
2 fixation capabilities, resulting in a significant increase in the microalgal biomass and a corresponding reduction in CO
2 concentration within the system. Using the binary DES (CM) resulted in a significant 26% increase in OD of
Chlorella sp. compared to control and the bio-sequestration of 53 mg of carbon per liter, equivalent to an elevation of 194 mg CO
2 per liter of culture. The ternary DES (CEM), on the other hand, exhibited slightly higher CO
2 concentration removal than CM (+1.4%), leading to higher OD and biomass augmentation, compared to the control culture. Additionally, CO
2 desorbed from CEM positively influenced the biomass growth of
Chlorella sp. compared to control, with OD surging by 12% during the initial 7 days and a sustained 24.7% increase until day 14, surpassing the performance of the control group (
Figure 1).
Our study presents an approach for CO2 capture and bio-fixation using functionalized DES and microalgae cultivation. The CO2 desorption process, coupled with the prolific growth of microalgae, highlights the viability of this integrated system as an environmentally friendly and sustainable strategy for mitigating CO2 emissions. This innovative method has the potential to contribute significantly to the global efforts aimed at addressing climate change and advancing the utilization of captured CO2 in various applications, including biofuels and bioproducts.
Author Contributions
Conceptualization, F.O.; methodology, E.-G.B. and D.G.P.; validation, E.-G.B., D.G.P., D.C.-A. and C.M.; formal analysis, D.C.-A. and T.D.; investigation, E.-G.B. and D.G.P.; resources, C.M.; data curation, D.C.-A.; writing—original draft preparation, E.-G.B.; writing—review and editing, F.O.; visualization, E.-G.B.; supervision, F.O. and T.D.; project administration, F.O and E.-G.B.; funding acquisition F.O. All authors have read and agreed to the published version of the manuscript.
Funding
The research leading to these results has received funding from European Regional Development Fund (ERDF), the Competitiveness Operational Programme (POC), Axis 1, project POC-A1-A1.2.3-G-2015-P_40_352, My_SMIS 105684, “Sequential processes of closing the side streams from bioeconomy and innovative (bio)products resulting from it—SECVENT”, subsidiary project 1882/2020—AquaSTIM.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data is contained within the article.
Conflicts of Interest
The authors declare no conflict of interest and DFR Systems SRL has no conflict of interest.
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