Inorganic Carbon-Limited Freshwater Algal Growth at High Ph: Revisited with Focus on Alkalinity

Abstract

Highlights Non-carbonate components of BG11 media impact TIC calculation on average 4.00 mg/L at high pH. BG11 media non-carbonate alkalinity (NCA) varies with pH: NCA (meq/L) = 0.0393×e0.2075×pH + (2.086×10-9)e1.860×pH. Monod kinetic constants with CO2, HCO3 -, and CO3 2- as inorganic carbon sources are improved from a previous report. Kinetic constants continue to be the only known reports considering multiple inorganic carbon sources. Algal stoichiometric reactions are developed that account for variation in cell content and carbon source. Abstract. Due to increasing atmospheric CO2, algal growth systems at high pH are of interest to support enhanced diffusion and carbon capture. Given the interactions between algal growth, pH, and alkalinity, data from Watson and Drapcho (2016) were re-examined to determine the impact of the non-carbonate constituents in BG11 media on estimates of Monod kinetic parameters, biomass yield, and cell stoichiometry. Based on a computational method, non-carbonate alkalinity (NCA) in BG11 media varies with pH according to: NCA (meq/L) = 0.0393×e0.2075×pH + (2.086×10-9)e1.860×pH (R2 = 0.999) over the pH range of 10.3 – 11.5. Updated maximum specific growth rates were determined to be 0.060, 0.057, and 0.051 hr-1 for CO2, HCO3, and CO3, respectively. Generalizable stoichiometric algal growth equations that consider variable nutrient ratios and multiple inorganic carbon species were developed. Improved kinetic and stoichiometric parameters will serve as the foundation for a dynamic mathematical model to support the design of high pH algal carbon capture systems. Keywords: Algae, Alkalinity, Carbon Abatement, Carbon Capture, Kinetics, Stoichiometry, Total Inorganic Carbon.