Study On Biological Fixation Of CO₂ Using Oil-Rich Scendesmus Obliquus

Beginning with Industrial Revolution, huge amouts of fossil fuel were consumeed and produced a great deal of CO₂, simutaneously bringed a lot of environmental problems caused by Greenhouse Effect. Biological fixation CO₂ using algae could be an efficient and practical process, where fat content may be rich and has a great economic value. In the paper, the factors which affect the carbon fixation rate and fat contents of Scendesmus obliquus were studied. The factors include initial inoculation volume, environmental conditions such as temperature and illumination intensity, nutrients as type and concentration of nitrogen and phosphorus.The research results showed that: (1) While vaccination density was 900×104 /ml (absorbency was 0.2), CO₂ fixation rate and fat yield of Scendesmus obliquus were maximal. The average of CO₂ fixation rate and fat yield separately were 0.065g/(L·d) and 15.14mg/(L·d). (2) CO₂ fixation rate could maintain a higher state with the optimum temperature in the range of 20℃and 30℃, and the maximal CO₂ fixation rate of Scendesmus obliquus was observed when the culture temperature was 25℃. (3) CO₂ fixation rate and fat yield could maintain a higher state with the optimum intensity of illumination in the range of 10000lux and 15000lux, and the maximal CO₂ fixation rate and fat yield of Scendesmus obliquus was observed when the culture temperature was 15000lux. The average CO₂ fixation rate and fat yield separately were 0.096g/(L·d),16.35mg/(L·d). (4) The feasible nitrogen source for Scendesmus obliquus was NaNO3 or NaNO2. CO₂ fixation rate and fat yield could maintain a higher state with the optimum concertration of nitrogen in the range of 0.2g/L and 1.60g/L. The best culturing concertration of nitrogen for Scendesmus obliquus was 0.2 g/L. (5) CO₂ fixation rate and fat yield could maintain a higher state with the optimum concertration of phosphorus in the range of 2mg/L and 30mg/L.In conclusion, the fitting conditions were,Vaccination density: 900×104 /ml, Culture temperature: 25℃, Intensity of illumination: 15000lux, The kind of nitrogen source and the concertration of nitrogen: NaNO3 or NaNO2,0.2g/L, Concertration of phosphorus: 2～30mg/L, Light Period :12h light /12h dark , CO₂ concertration and flow rate: 10%,0.6L/min.