Study On The Cultivation Of Chlorella Using Carbon Dioxide Under Simulated Microgravity

With the rapid development of industry,the increased CO₂ emission may accelerate global warming and lead to serious environmental problems.To sustain the development of human beings,high priority was given to the renewable energy,such as solar energy,wind energy,biomass energy and so on.Microalgae,renowned for its advantages of good environmental adaptability,short growth circle,and high productivity of the lipid,is an ideal raw material for biomass energy.Considering the high cost for artificial culture of microalgae limits the lipid production to industrial application,using wastewater and CO₂ in flue gas will not only capture the CO₂,but also lower the cost of microalgae cultivation.Using wastewater as culture media and CO₂ as extra carbon sources,and microalgae was cultured in the simulated micro-gravity system to enhance the growth rates and the lipid yields of microalgae.This thesis studied the lipid yields of the Chlorella pyrenoidosa in different types of wastewater and its removal efficiencies toward nitrogen,phosphorus and COD,and thus screening the water that is suitable for the Chlorella pyrenoidosa growth.Chlorella pyrenoidosa was cultured in simulated micro-gravity system and absorbed CO2 with high concentration.Meanwhile,the lipid yields,carbon fixation efficiency,fatty acid content and physiological structure were compared.Finally,the nitrogen,phosphorus and COD were also measured in the simulated microgravity system using wastewater as culture media.The main results are as followed:?1?Chlorella pyrenoidosa has good adaptability in different types of wastewater.It can efficiently absorb and degrade N,P and COD in water,especially for simulated livestock wastewater.In this type of condition,the removal of ammonia nitrogen,total nitrogen,total phosphorus,and COD is high to 86.59%,96.39%,79.83%and 76.48%,respectively,within 11 days.The production of the lipid in this system is also higher.?2?Under the condition of simulated microgravity,the input of the high concentration CO2 boost the growth of the Chlorella pyrenoidosa.Consuming the extra CO2 at night is a good method for pH regulating and thus promoting the growth rate.Meanwhile,it has higher lipid yield and carbon fixation efficiency.High purging of CO₂ may stimulate the increase of the unsaturated fatty acid,while the simulated micro-gravity inhibit its production.The high concentration CO2 enlarges the size of the Chlorella pyrenoidosa.?3?As culture media,the simulated livestock wastewater has obviously better performance than BG-11media,including Chlorella pyrenoidosa growth,N,P and COD removal,lipid production and so forth,demonstrating that livestock water is a good replacement for the artificial microalgae medium.The experiment results also exhibit that the simulated micro-gravity obviously promote the Chlorella pyrenoidosa growth,but has little effects to the removal of N,P and COD.Besides,the input of the CO₂ also shows the minor role for aspects of Chlorella pyrenoidosa growth.