CO2-Derived Carbon Capture Using Microalgae and Sodium Bicarbonate in a PhotoBioCREC Unit: Kinetic Modeling

Maureen Cordoba-Perez,Hugo De Lasa

doi:10.3390/pr9081296

Abstract

By converting bicarbonates via Chlorella vulgaris photosynthesis, one can obtain valuable biofuel products and find a route toward carbon-derived fossil fuel conversion into renewable carbon. In this research, experiments were carried out in the PhotoBioCREC prototype under controlled radiation and high mixing conditions. Sodium bicarbonate (NaHCO3) was supplied as the inorganic carbon-containing species, at different concentrations, in the 18 to 60 mM range. Both the NaHCO3 concentrations and the organic carbon concentrations were quantified periodically during microalgae culture, with the pH being readjusted every day to the 7.00 level. It was found that sodium bicarbonate was converted with a selectivity up to 33.0% ± 2.0 by Chlorella vulgaris. It was also observed that the reaction rate constant for inorganic carbon conversion was 0.26 ± 0.09 day−1, while the maximum reaction rate constant for organic carbon formation was achieved with a 28 mM NaHCO3 concentration and displayed a 1.18 ± 0.05 mmole L−1day−1 value.

Highlights

Innovative processes are required to reduce the use of fossil fuels and promote the consumption of anthropogenic carbon dioxide (CO2)
The present study focused on rigorously establishing phenomenologically based growth kinetics for CPCC90 Chlorella vulgaris
The green algae CPCC90 Chlorella vulgaris obtained from the Canadian Phycological Culture Centre (CPCC) of the University of Waterloo, Canada was used throughout the experiments

Summary

Introduction

Innovative processes are required to reduce the use of fossil fuels and promote the consumption of anthropogenic carbon dioxide (CO2). The culturing of microalgae in either an open pond or a closed photobioreactor requires the supply of inorganic carbon This can be done by using gaseous CO2 directly from a combustion process or alternatively by using soluble carbonates (i.e., bicarbonates). One should note that there may be other factors affecting microalgae growth, including: (a) nutrients (i.e., nitrogen and phosphorous), (b) visible light, (c) mixing, (d) pH, and (e) temperature [9] All these microalgae growth parameters must be carefully controlled to achieve maximum efficiency in the carbon conversion into microalgae. Regarding the microalgae growth rate, few studies have determined algae growth kinetic parameters, including the effect from inorganic carbon concentration from bicarbonate solutions. These growth kinetics were established for a wide range of bicarbonate concentrations They adequately predicted both bicarbonate and organic carbon concentrations at various culture times, while effectively determining the efficiency of inorganic carbon conversion into microalgae biomass

Microalgae Strain and Medium

Experimental Setup

Inorganic Carbon Conversion Efficiency

Microalgae Characterization

Findings

Modeling Algae Growth