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Modeling and Experimental Study of an Open Channel Raceway System to Improve the Performance of Nannochloropsis Salina Cultivati

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Modeling and Experimental Study of an Open Channel Raceway System to Improve the Performance of Nannochloropsis Salina Cultivati Modeling and Experimental Study of an Open Channel Raceway System to Improve the Performance of Nannochloropsis salina Cultivation DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Stephen Yoonbum Park, B.S. Graduate Program in Food, Agricultural and Biological Engineering The Ohio State University 2014 Dissertation Committee: Dr. Yebo Li, Advisor Dr. Jiyoung Lee Dr. Jay Martin Copyright by Stephen Yoonbum Park 2014 Abstract Lipid-rich microalgae are a potentially favorable alternative source of liquid fuels, and the use of open channel raceways has been proposed as a potential method for their mass cultivation. Studies on energy return on investment (EROI) show that open pond raceways are not feasible enough to be commercialized, but can be considered as a future commodity if energy can be recovered from both lipids and biomass residue. Analyses also show that the energy input in the form of CO2, nutrients, and mixing account for approximately 85% of the total energy consumption for algal biofuel production. Therefore, the conceptual framework of this study was mainly focused on the improvement of the open pond cultivation of the photosynthetic microalgae, Nannochloropsis salina, to increase the EROI of the process. The preexisting open pond cultivation process was hypothesized to be procedurally improved through modifications such as the conversion of algae biomass residue (ABR) via anaerobic digestion (AD) and the addition of phase-change material (PCM) to the open pond surface. A numerical approach was also employed by modeling the demonstration-scale cultivation systems using computational fluid dynamics (CFD) integrated with a kinetic model. The growth kinetics of N. salina was integrated into a 3-dimensional CFD model. Validation in a 120-m3 open channel raceway showed a good fit for the change in ii biomass, CO2, and nitrogen concentrations. The model also showed the characteristics of dead zones that tail off the bends and increase in biomass concentration. The light attenuation, which is dependent on pond depth and cell concentration, was also observed to drastically increase in the system as the biomass concentration increased. Sensitivity analysis showed that the model was particularly sensitive to the several species-specific parameters. In an attempt to improve the low biomass productivity in the open channel raceways, supposedly caused by excessive water evaporation, susceptibility to contamination, and sensitivity to ambient influences, hexadecane was introduced as a phase change material (PCM) to cover the pond surface. The existing model was modified to accommodate an immiscible secondary phase that flowed in conjunction with the pond medium. Simulated results were compared with the 150-d data acquisition of light intensity, temperature, nutrient concentration, and algal biomass acquired from a demonstration scale raceway pond constructed for the growth of N. salina and were observed to be in good agreement with one another. Additional energy can be generated from ABR by means of anaerobic digestion (AD), but is inhibited by the byproducts of excessive protein degradation. Fat, oil, and grease waste (FOG) from a local municipal waste receiving facility was co-digested with ABR to evaluate the effects on methane yield and degradation of carbohydrates, lipids, and proteins. Co-digestion of ABR and FOG allowed for an increased loading rate while increasing methane yield. Lipids were the key contributor to methane yields. iii The above results suggest that the production of N. salina in an open environment was substantially improved through the modeling and experimental studies. The knowledge gained from this study may serve as a valuable resource in understanding the issues in the scale up of algal biofuel production and may be applied to other fuel feedstock candidates. iv This dissertation is dedicated to Youji and Abigail, to whom I devote the rest of my life. v Acknowledgements My deepest appreciation goes my academic advisor, Dr. Yebo Li, who put his faith and motivation into me from our very first meeting. He encouraged my strengths, and helped me find my weaknesses. Even in the most difficult and frustrating times of my graduate career, he did not cease to encourage me and tell me that I can change to become a better person. Many thanks go to the members of my dissertation committee: Dr. Jiyoung Lee and Dr. Jay Martin for their insightful advice and efforts in reviewing this document. I would like to thank the valuable members of the Department of Food, Agricultural and Biological Engineering, including Mrs. Mary Wicks, for the great amount of time and effort to review my publications, Mrs. Candy McBride and Mrs. Peggy Christman, for their administrative support, and Mr. Michael Klingman, for his knowledge and effort in modifying and repairing our laboratory’s experimental apparata. I would also like to acknowledge the numerous colleagues that I had a chance to work with, Dr. Caixia Wan, Dr. Jiying Zhu, Dr. Yuguang Zhou, Dr. Zhifang Cui, Dr. Shengjun Hu, Dr. Xiaolan Luo, Dr. Xumeng Ge, Mrs. Ting Cai, Ms. Fuqing Xu, Mr. Johnathon Sheets, Mr. Ratanachat Racharaks Mr. Wee Fong Lee, and many more, for their wisdom, advice and friendship. Special thanks go to my parents and siblings, for their love and support, regardless of how far we are apart. Lastly, and most importantly, my utmost vi gratitude goes to my wife Youji Kim and daughter Abigail, as they are the ultimate driving force of my life. vii Vita 2008................................................................B.S. Biosystems Engineering, Virginia Polytechnic Institute and State University 2008 to 2009 ..................................................Engineer and Lab Technician, Novozymes Biologicals, Inc. 2009 to present ..............................................Graduate Research Fellow, Food Agricultural and Biological Engineering, The Ohio State University Publications Park. S., Li, Y. 2014. Integrated computational fluid dynamics model for open pond cultivation of Nannochloropsis salina using phase change material. Bioresour. Technol. (in preparation) Park, S., Li, Y. 2014. Integration of biological kinetics and computational fluid dynamics to model the growth of Nannochloropsis salina in an open channel raceway. Biotechnol. Bioeng. (submitted) Park, S., Li, Y. 2012. Evaluation of methane production and macronutrient degradation in the anaerobic co-digestion of algae biomass residue and lipid waste. Bioresour. Technol. 111: 42-48. Cai, T.*, Park, S.*, Li, Y. 2013. Nutrient recovery from wastewater streams by microalgae: status and prospects. Renew. & Sustain. Energy Rev.19: 360-369. (* - equal contribution). viii Sheets, J. P., Ge, X., Park, S., Li, Y. 2013. Effect of outdoor conditions on Nannochloropsis salina cultivation in artificial seawater using nutrients from anaerobic digestion effluent. Bioresour. Technol. 152: 154-161. Cai, T., Ge, X.,Park, S., Li, Y. 2013. Comparison of Synechocystis sp. PCC6803 and Nannochloropsis salina for lipid production using artificial seawater and nutrients from anaerobic digestion effluent. Bioresour. Technol. 144: 255-260. Cai, T. Park, S., Racharaks, R., Li, Y. 2013. Cultivation of Nannochloropsis salina in anaerobic digestion effluent for nutrient removal and lipid production. Appl. Energy. 108: 486-492. Li, Y., Zhu, J., Wan, C., Park, S. 2011. Solid-state anaerobic digestion of corn stover for biogas production. Trans. ASABE. 54(4): 1415-1421. Li, Y., Park, S., Zhu, J. 2010. Solid-state anaerobic digestion for methane production from organic waste. Renew. & Sustain. Energy Rev. 15(1): 821-826. Fields of Study Major Field: Food, Agricultural, and Biological Engineering Study in: Biological Engineering ix Table of Contents Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................ vi Vita .................................................................................................................................. viii Table of Contents ................................................................................................................ x List of Tables .................................................................................................................... xv List of Figures .................................................................................................................. xvi Chapter 1: Introduction ....................................................................................................... 1 1.1. Background ........................................................................................................... 1 1.2. Research Objectives .............................................................................................. 5 1.3. Contribution of the Dissertation ........................................................................... 6 Chapter 2: Literature Review .............................................................................................. 7 2.1. Introduction ........................................................................................................... 7 2.2. Microalgae Growth Factors ................................................................................ 10 2.2.1. Irradiance .................................................................................................
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