Improving Algal Biomass or Lipid Productivity for Increased Cultivation Feasibility

168 Pages·2015·4.4 MB·English

by  Everett Eustance

Assessing Outdoor Algal Cultivation in Panel and Raceway Photobioreactors
for Biomass and Lipid Productivity
by
Everett Eustance

A Dissertation Presented in Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy

Approved July 2015 by the
Graduate Supervisory Committee:

Milton Sommerfeld, Co-Chair
Peter Fox, Co-chair
Paul Westerhoff

ARIZONA STATE UNIVERSITY

August 2015
ABSTRACT
Over the past decade, there has been a revival in applied algal research and
attempts at commercialization. However, the main limitation in algal commercialization
is the process of cultivation, which is one of the main cost and energy burdens in
producing biomass that is economically feasible for different products. There are several
parameters that must be considered when growing algae, including the type of growth
system and operating mode, preferred organism(s), and many other criteria that affect the
process of algal cultivation. The purpose of this dissertation was to assess key variables
that affect algal productivity and to improve outdoor algal cultivation procedures. The
effect of reducing or eliminating aeration of algal cultures at night, in flat panel
photobioreactors (panels), was investigated to assess the reduction of energy
consumption at night. The lack of aeration at night resulted in anoxic conditions, which
significantly reduced lipid accumulation and productivity, but did not affect log phase
biomass productivity. In addition, the reduction in aeration resulted in lower pH values,
which prevented ammonia volatility and toxicity. Raceways are operated at deeper
cultivation depths, which limit culture density and light exposure. Experimentation was
accomplished to determine the effects of decreasing cultivation depth, which resulted in
increased lipid accumulation and lipid productivity, but did not significantly affect
biomass productivity. A comparison of semi-continuous cultivation of algae in raceways
and panels in side-by-side experiments showed that panels provided better temperature
control and higher levels of mixing, which resulted in higher biomass productivity. In
addition, sub-optimal morning temperatures in raceways compared to panels were a
significant factor in reducing algae biomass productivity. The results from this research
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indicate that increasing lipid productivity and biomass productivity cannot be completed
simultaneously. Therefore, the desired product will determine if lipid or biomass
productivity is more crucial, which also dictates whether the system should be operated in
batch mode to either allow lipid accumulation or in semi-continuous mode to allow high
biomass productivity. This work is a critical step in improving algal cultivation by
understanding key variables that limit biomass and lipid productivity.

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DEDICATION

This dissertation is dedicated to my family who I love dearly. To my parents Camie and
Randy Eustance and my sister Chanee Eustance who all showed me how to work hard
and made sacrifices so that I could pursue my dream. To my wife Jessica Eustance, who
has always supported me and has been amazing, as I have worked towards getting my
Ph.D. To my baby girl Brianne Eustance, who has been my inspiration during these last
few months.

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ACKNOWLEDGMENTS
I would like to thank my advisor Dr. Milton Sommerfeld. Without his guidance
and support, I would not have had the freedom to pursue the research that will help shape
the future of algal cultivation.
I would also like to thank my committee members, Dr. Peter Fox and Dr. Paul
Westerhoff, for their support and questioning during this process.
Additionally, I would like to thank Dr. Robert Gardner who initially mentored me
during my Master’s degree, as he taught me a strong foundation for conducting excellent
research.
I would also like to thank Joshua T. Wray, Shahrzad Badvipour, and Emil
Puruhito, who are excellent co-authors and colleagues, which provided a great
community for collaboration during this process.
Lastly, I would like to thank the technicians of the Arizona Center for Algae
Technology and Innovation for their help and support during this process. Specifically, I
would like to thank Sarah Arrowsmith for her help with the biochemical analysis that was
completed during this process.

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TABLE OF CONTENTS
Page
LIST OF TABLES ........................................................................................................... viii
LIST OF FIGURES ............................................................................................................ x
CHAPTER
1. INTRODUCTION ..................................................................................................... 1
1.1. Commercialization of Algae ......................................................................... 1
1.2. Limitations to Commercialization of Algae .................................................. 4
1.3. Project goal: Improving the Algal Cultivation Process ................................. 5
1.4. Overview of Dissertation .............................................................................. 6
2. BACKGROUND ..................................................................................................... 10
2.1. What is Required for Algal Growth ............................................................ 10
2.2. How are Algae Grown? ............................................................................... 23
2.3. What Affects Algal Growth? ....................................................................... 30
2.4. What are the Benefits of using Algae over Terrestrial Plants? ................... 31
3. MANUSCRIPT 1: THE EFFECTS OF LIMITING NIGHT TIME AERATION ON
PRODUCTIVITY AND LIPID ACCUMULATION OF SCENEDESMUS
DIMORPHOUS TO MINIMIZE AMMONIA VOLATILIZATION ..................... 34
3.1. Introduction: ................................................................................................ 36
3.2. Materials and Methods ................................................................................ 40
3.3. Results: ........................................................................................................ 45
3.4. Discussion: .................................................................................................. 54
3.5. Conclusions: ................................................................................................ 60
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CHAPTER Page
3.6. Acknowledgements ..................................................................................... 61
3.7. References ................................................................................................... 61
4. MANUSCRIPT 2: THE EFFECTS OF CULTIVATION DEPTH, AREAL
DENSITY AND NUTRIENT LEVEL ON LIPID ACCUMULATION OF
SCENEDESMUS ACUTUS IN OUTDOOR RACEWAY PONDS ........................ 66
4.1. Introduction: ................................................................................................ 68
4.2. Materials and Methods ................................................................................ 72
4.3. Results ......................................................................................................... 75
4.4. Discussion ................................................................................................... 84
4.5. Conclusions ................................................................................................. 87
4.6. Acknowledgments ....................................................................................... 88
4.7. References ................................................................................................... 88
5. MANUSCRIPT 3: BIOMASS PRODUCTIVITY OF TWO SCENEDESMUS
STRAINS OPERATED SEMI-CONTINUOUSLY IN OUTDOOR RACEWAY
PONDS AND FLAT-PANEL PHOTOBIOREACTORS ....................................... 91
5.1. Introduction: ................................................................................................ 93
5.2. Materials and Methods ................................................................................ 96
5.3. Results ......................................................................................................... 99
5.4. Discussion ................................................................................................. 109
5.5. Conclusions ............................................................................................... 116
5.6. Acknowledgments ..................................................................................... 117
5.7. References ................................................................................................. 118
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CHAPTER Page
6. SYNTHESIS CHAPTER: IMPROVING ALGAL CULTIVATION ................... 121
6.1. Lipid Accumulation Improves Lipid Productivity .................................... 122
6.2. Key Variables that Influence Biomass Productivity ................................. 124
6.3. Implications of the Research in the Field of Algal Cultivation ................. 129
7. SUMMARY CONCLUSION AND FUTURE RESEARCH ............................... 132
7.1. Key Findings from the Research Chapters ................................................ 132
7.2. General Conclusions and the Implications from Synthesis Chapter ......... 135
7.3. Future Research Recommendations .......................................................... 136
8. WORK CITED ...................................................................................................... 140

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LIST OF TABLES
Table Page
2.1 Modified from Williams and Laurens (2010) Highlighting the High Annual
Biomass Production Compared to Current Terrestrial Crops. .................................32
3.1 Timeline and Description of Experiments with Different Nighttime Aeration
Conditions and Ammonium Sources ........................................................................44
3.2 Biochemical Composition of Strain LB 0414 with and without Aeration at Night
During Different Growth Phases.. ............................................................................49
3.3 Biochemical Composition of Strain LB 0414 with Different Sparging
Frequencies at Night During Different Growth Phases. ..........................................51
3.4 Biochemical Composition of Strain LB 0414 with Low Aeration (Approximately
60% or 80% DO Saturation) at Night During Different Growth Phases .................54
4.1 Biochemical Composition of Scenedesmus acutus Strain 0414 during Different
Stages of Growth Under Different Nutrient Levels and the Same Depth ................78
4.2 Biochemical Composition of Scenedesmus acutus Strain 0414 during Different
Stages of Growth Under Different Depths and the Same Areal Nutrient
Concentration (mg-N/m2) .........................................................................................80
4.3 Average Culture Productivity During Log Phase, Stress Phase and Overall
Cultivation Time ......................................................................................................82
5.1 Description of Changes that Occurred During Experimentation from February
17th to March 27th .................................................................................................100
5.2 Average ± S.D. for Solar Irradiance, Biomass Productivity, and Photosynthetic
Efficiency for Experiments Completed in February and March ............................102
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Table Page
5.3 Description of changes that occurred during experimentation from April 2nd to
May 7th ..................................................................................................................105
5.4 Average ± S.D. for Solar Irradiance, Biomass Productivity, and Photosynthetic
Efficiency for Experiments Completed in April and May .....................................107

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