Evaluation of an Oil-Producing Green Alga Chlorella sp. C2 for Biological DeNO_x of Industrial Flue Gases

Abstract

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.

The acclimation of Chlorella to high-level nitrite for potential application in biological NOx removal from industrial flue gases

“…Traditional physical or chemical methods of NOx removal are usually expensive and may produce secondary waste (Jin et al, 2005). As the main component of NOx aqueous solutions, nitrite is widely used to simulate the dissolved ingredients of NOx in water (Zhang et al, 2014a). Microalgae have been reported to take up nitrite as the nitrogen (N) source for biomass accumulation (Vilchez and Vega, 1995), and this may both greatly reduce the costs of algae cultivation and benefit the production of microalgae-based biodiesel.…”

“…Cells cultured with fullstrength BG11 were harvested at mid-logarithmic growth phase (OD 700 value approximately 0.8) by centrifuging the culture at 3000g for 3 min, at 20 • C; the pellet was then washed with N-free BG11 medium and re-suspended to OD 700 0.5 in either regular BG11 or N-free medium with sodium nitrite added as the nitrogen source at various concentrations (Zhang et al, 2013). For the nitrite treatment, the nitrite concentrations were 17.65, 35.3, 88.25, and 176.5 mmol L −1 (1 × , 2 × , 5 × , and 10 × NaNO 2 ) (Zhang et al, 2014a). Chlorella strains were cultivated at 25 • C with continuous illumination of 70 mol m −2 s −1 and continuously bubbled with filter-sterilized air.…”

“…As we described in a previous study, high levels of nitrite (176.5 mmol L −1 ) have an obvious inhibitory effect on microalgae growth (Zhang et al, 2014a). The screening of nitrite-tolerant microalgae species, therefore, becomes an unavoidable step towards an algal bio-DeNOx approach.…”

An informatics-based analysis of developments to date and prospects for the application of microalgae in the biological sequestration of industrial flue gas

“…However, although early in 1995 a laboratory study carried out by Zeiler et al (1995) using a green alga Monoraphidium minutum demonstrated that this alga could efficiently utilize simulated flue gas containing high levels of carbon dioxide, as well as sulfur and nitrogen oxides, as a feedstock to produce substantial biomass, the studies on bio-DeNOx of NOx by using microalgae were limited and mostly in a basic research level at lab scale (Arata et al 2013;Nagase et al 1997;Van Den Hende et al 2011;Yoshihara et al 1996;Zhang et al 2014).…”

“…Several chemical compounds (SOx, heavy metals, etc. ) have shown to be toxic to some microalgae (Napan et al 2015;Zhang et al 2014); the effects of all flue gas compounds on microalgae and the interaction of flue gas compounds and microalgae need to be assessed (Van Den Hende et al Fig. 4 Percentage distribution of the high-frequency keywords of published papers related to microalgal biosequestration of industrial flue gas 2012).…”