Strategic evaluation of limiting factors affecting algal growth - An approach to waste mitigation and carbon dioxide sequestration

Abstract

This work outlines major critical physico-chemical parameters that play a key role in increasing the fixation of CO₂ from coal-fired flue gas CO₂ into green microalgae biomass. Nitrogen concentration, gas flow rate, initial medium pH, and incident light intensity were determined to be the most important process variables with significant impact on CO₂ fixation. Therefore, NaNO₃ (500-3000 mg L^-1), pH (6.8-8.0), light (50-200 mol m^-2 s^-1) and aeration (0.1-1.0 vvm) were varied to assess the biological assimilation potential of CO₂ from the flue gas. The parameters that resulted in maximal CO₂ fixation from raw flue gas, resulting in a maximum biomass density of 3.1 g L^-1, were NaNO₃ = 1500 mg L^-1, pH =7.2-7.5, incident light intensity = 133.33 mol m^-2 s^-1, and 0.5-0.75 vvm aeration without any cost-incurring flue gas pre-treatment step. The inductively coupled plasma-mass spectrometer (ICP-MS) was used to investigate heavy metals uptake from raw flue gas, and it was discovered that no net intake of trace metals had a significant influence on biomass production. The research lays the path for efficient large-scale microalgal cultivations for industrial uses, as well as bolstering the circular economy concept.

Keywords: CO(2) fixation; Chlorella; Coal-fired flue gas; Green microalgae; Heavy metals uptake; ICP-MS.