Cultivation of Chlorella emersonii with flue gas derived from a cement plant

The present study reviews the options of cultivating the green alga, Chlorella emersonii, under photoautotrophic conditions with flue gas derived from a cement plant. It was conducted in the Lafarge Perlmooser plant in Retznei, Austria, where stone coal and various surrogate fuels such as used tyres, plastics and meat-and-bone meal are incinerated for heating limestone. During 30 days of cultivation, flue gas had no visible adverse effects compared to the controls grown with pure CO₂. The semi-continuous cultivation with media recycling was performed in 5.5-L pH-stat photobioreactors. The essay using CO₂ from flue gas yielded a total of 2.00 g L⁻¹ microalgal dry mass and a CO₂ fixation of 3.25 g L⁻¹. In the control, a total of 2.06 g L⁻¹ dry mass was produced and 3.38 g L⁻¹ CO₂ was fixed. Mean growth rates were between 0.10 day⁻¹ (control) and 0.13 day⁻¹ (flue gas). No accumulation of flue gas residues was detected in the culture medium. At the end of the experiment, however, the concentration of lead was three times higher in algal biomass compared to the control, indicating that cultures aerated with this type of flue gas should not be used as food supplements or animal feed.