NOx are among the most serious environmental issues in the world, particularly in present-day China. Unfortunately, because of legislation restrictions, NOx, which compose a significant portion of fossil fuel flue gases, must be removed in an additional costly gas treatment step. However, physico-chemical denox methods, which are the conventional NOx treatments, are expensive and produce secondary wastes that often require further treatment. A biological denox method that uses microalgae may be a noteworthy method for flue gas treatment to reduce NOx emissions and merit further studies.
In this study, the actual flue gas fixed salts in FGFS 1 medium was from the caprolactam production plant of Sinopec’s Shijiazhuang Refining & Chemical Company in China. By using actual flue gas fixed salts for the cultivation of algal cells, it is much more appropriate to evaluate the application of Chlorella sp. C2 for biological denox of industrial flue gases. Also, NO, the main component of NOx, is sparingly soluble in water, and the dissolution of NO into the microbial culture is the rate-limiting step for NO removal, so the fixation of actual flue gas for the cultivation of algal cells is a possible effective way of improving NO or NOx removal efficiency, and the calculation of the removal capacity could be more accurate.
By using an oil-producing green alga Chlorella sp. C2, a 60% nitrite removal efficiency was obtained together with the production of 33% algae lipids, which may provide a new insight into the economically viable application of microalgae in the synergistic combination of biological denox of industrial flue gas and biodiesel production. Also, it is hoped that the results of the present research will provide a useful reference for the usage and environmental control of NOx using microalgae.
Zhang X, Chen H, Chen W, Qiao Y, He C, Wang Q.
Environ Sci Technol. 2014 ;48(17):10497-504.
Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences , Wuhan 430072, Hubei China.
NOx, a significant portion of fossil fuel flue gases, are among the most serious environmental issues in the world and must be removed in an additional costly gas treatment step. This study evaluated the growth of the green alga Chlorella sp. C2 under a nitrite-simulated NOx environment and the removal rates of actual flue gas fixed salts (FGFSs) from Sinopec’s Shijiazhuang refinery along with lipid production. The results showed that nitrite levels lower than 176.5 mM had no significant adverse effects on the cell growth and photosynthesis of Chlorella sp. C2, demonstrating that this green alga could utilize nitrite and NOx as a nitrogen source. High concentrations of nitrite (88.25-176.5 mM) also resulted in the accumulation of neutral lipids. A 60% nitrite removal efficiency was obtained together with the production of 33% algae lipids when cultured with FGFS. Notably, the presence of nitrate in the FGFS medium significantly enhanced the nitrite removal capability, biomass and lipid production. Thus, this study may provide a new insight into the economically viable application of microalgae in the synergistic combination of biological DeNOx of industrial flue gases and biodiesel production.