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.