Study On Biological Fixation Of Elevated Co₂ Concentration Using Chlorella Pyrenlidosa

Entering the 21st century,with the continuing growth of the forces of social production,the demand of fossil fuel was growing.The gases contained elevated CO₂ concentration(v/v＞5%),caused in the process of utilizing energy source,had caused a series of environmental problems and setted the progress of human society back.So how to deal with these gases not only had a bearing on the survival and development of the society,but also affected the human health.Biological fixation of CO₂ using algae could reduce the emission of CO₂,and the algae itself could be widespreadly used in many different areas,such as food and energy.So this economical and effective technique had an infinite potential for future development.This paper studied the CO₂ fixation rate of Chlorella pyrenlidosa through analysing the growth of Chlorella pyrenlidosa under different environment conditions,such as culture temperature and intensity of illumination and made sure the fitting conditions of CO₂ fixation of Chlorella pyrenlidosa,at the same time,analyzed the results using biological principle.The subsequent step in the process was on the premise of optimum conditions obtained from previous experiments.The results as follows:1)CO₂ concentration(%,v/v) was between 0.035%and 100%.When the CO₂ concentration was up to 10%,CO₂ fixation rate was maximal,but decreased as CO₂ concentration increased.Moreover,the further study result showed that this algae could survive when CO₂ concentration was 100%.2)Vaccination density(absorbency) was between 0.082 and 0.641.The study result showed that the maximal CO₂ fixation rate of Chlorella pyrenlidosa appeared when the vaccination density was 0.341.Subsequently,the variance ratio maintained relatively stabilization.3)Culture temperature was between 20℃and 50℃.CO₂ fixation rate could maintain a higher state with the optimum temperatures in the range of 25℃-30℃and the maximal CO₂ fixation rate of Chlorella pyrenlidosa was observed when the culture temperature was 25℃.Beyond 50℃,Chlorella pyrenlidosa could not survive and snuffed out before long. 4)Flow rate was between 100ml/min and 1500ml/min.The maximal CO₂ fixation rate of Chlorella pyrenlidosa was observed when the fiow rate was 1000ml/min.Besides,the study result showed that CO₂ fixation rate of Chlorella pyrenlidosa in lower flow rate(100ml/min,500ml/min)would be improved significantly if there was a stirring(200r/min).5)Initial pH was between 3 and 7.The study result showed that CO₂ fixation rate could maintain a higher state with the initial pH in the range of 5-7.The maximal CO₂ fixation rate of Chlorella pyrenlidosa was observed when the initial pH was 6.When the initial pH was 3,Chlorella pyrenlidosa could not survive.6)Intensity of illumination was between 30001ux and 90000lux.The study result showed that CO₂ fixation rate of Chlorella pyrenlidosa maintained a lower state with the intensity of illumination between 3000lux and 8000lux.When the intensity of illumination beyond 20000lux,CO₂ fixation rate increased and the maximal rate was observed when intensity of illumination was up to 25000lux,Beyond 90000 lux, Chlorella pyrenlidosa could not survive.7)The effects of three nitrogen source such as NaNO₃,NaNO₂ and NH₄Cl on the CO₂ fixation rate of Chlorella pyrenlidosa were investigated.The result showed that when NaNO₃ was used as the sole nitrogen source,CO₂ fixtion rate was maximal.NaNO₃ concertration was between 0 g/L and 10g/L.The study result showed that the maximal CO₂ fixtion rate was observed when NaNO₃ concertration was 5g/L,then, CO₂ fixtion rate decreased as the increasing NaNO₃ concertration.In conclusion,the fitting conditions were:CO₂ concentration:10%;Vaccination density:0.341;Culture temperature:25℃; Flow rate:1000ml/min;Initial pH value:6;Intensity of illumination:25000lux;The kinds of nitrogen source and the concertration of nitrogen source:NaNO₃,5g/L.Under the fitting conditions of culture,the maximal CO₂ fixation rate of Chlorella pyrenlidosa was 4.478 gCO₂/L·d.