Abstract
Climate change brought about by anthropogenic CO2 emissions has created a critical need for effective CO2 management solutions. Microalgae are well suited to contribute to efforts aimed at addressing this challenge, given their ability to rapidly sequester CO2 coupled with the commercial value of their biomass. Recently, microalgal biofilms have garnered significant attention over the more conventional suspended algal growth systems, since they allow for easier and cheaper biomass harvesting, among other key benefits. However, the path to cost-effectiveness and scaling up is hindered by a need for new tools and methodologies which can help evaluate, and in turn optimize, algal biofilm growth. Presented here is a novel system which facilitates the real-time in situ monitoring of algal biofilm CO2 sequestration. Utilizing a CO2-permeable membrane and a tube-within-a-tube design, the CO2 sequestration monitoring system (CSMS) was able to reliably detect slight changes in algal biofilm CO2 uptake brought about by light–dark cycling, light intensity shifts, and varying amounts of phototrophic biomass. This work presents an approach to advance our understanding of carbon flux in algal biofilms, and a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO2 sequestration.
Highlights
Over the past two centuries, human activity has had a pronounced effect on the natural environment [1]
The CO2 sequestration monitoring system (CSMS) used in this study comprises two distinct biofilm reactor (BR) modules
The gas flow in the annular space was continuous through both BRs (Figure 2), allowing the heterotrophic biofilm in BRprod to serve as a biotic source of CO2 to the photoautotrophic biofilm growing inside BRcons
Summary
Over the past two centuries, human activity has had a pronounced effect on the natural environment [1]. Microalgal biomass can be used as animal feed and fertilizer with minimal downstream processing required [6] It is a source of numerous valuable compounds such as pigments, cosmetic products, and nutraceuticals like omega-3 fatty acids [5,7,8], and the lipid-rich nature of algal cells makes them an attractive biodiesel feedstock [9,10,11]. CO2 uptake is assessed by weighing the algal biomass produced and, using an approximate algal cell carbon content of 40–50%, stoichiometrically calculating the amount of carbon sequestered [18,19] Since this is a destructive measurement, it provides little insight about a biofilm’s performance during active growth. The fact that many algal strains are able to metabolize organic carbon through mixotrophic growth can make such calculations problematic [20] Another means of quantifying algal CO2 sequestration is by measuring effluent pH. This work presents an approach to advance our understanding of carbon flux in algal biofilms, carbon exchange between autotrophic and heterotrophic biofilms, as well as a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO2 sequestration
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