Lipid Productivity of Algae Grown on Dairy Wastewater as a Possible Feedstock for Biodiesel

87 Pages·2008·0.84 MB·English

by  Ian C. Woertz

LIPID PRODUCTIVITY OF ALGAE
GROWN ON DAIRY WASTEWATER
AS A POSSIBLE FEEDSTOCK FOR BIODIESEL

A Master’s Thesis Presented to the Faculty
California Polytechnic University, San Luis Obispo

In Partial Fulfillment
of the Requirements for the Degree
Master of Science in
Civil and Environmental Engineering

by

Ian Charles Woertz

December 2007
AUTHORIZATION FOR REPRODUCTION OF MASTER’S THESIS

I grant permission for the reproduction of this thesis in its entirety or any parts, without
further authorization from me, provided the author and major advisor are properly
referenced.

___________________________________
Signature

___________________________________
Date
ii
APPROVAL PAGE

LIPID PRODUCTIVITY OF ALGAE GROWN ON DAIRY WASTEWATER AS A
POSSIBLE FEEDSTOCK FOR BIODIESEL

IAN WOERTZ

SUBMITTED: _________________________

___________________________________ _________________________
Committee Chair: Yarrow Nelson, Ph.D. Date

___________________________________ _________________________
Committee Member: Tryg Lundquist, Ph.D. Date

___________________________________ _________________________
Committee Member: Andrew Kean, Ph.D. Date
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ABSTRACT
Lipid Productivity of Algae Grown on Dairy Wastewater as a Possible Feedstock for
Biodiesel
Ian Woertz
The objective of this thesis is to develop a biological wastewater treatment system that
utilizes algal growth to simultaneously create renewable energy in the form of biodiesel
and digester biogas, remove polluting nutrients, and abate greenhouse gases. Research
under the Department of Energy Aquatic Species Program during 1978-1996 concluded
that cultivating algae for biofuels was cost prohibitive at that time and that an integrated
approach should be studied that combined wastewater treatment with algal biofuel
production. Nutrient removal, in particular nitrogen and phosphorus, from wastewater is
a growing regulatory need and the use of algae cultivation could create a unique marriage
between waste treatment and biofuel production. To investigate this possible synergy,
bench-scale tests were conducted to determine potential algal lipid productivity with
mixed-cultures of algae grown on anaerobically-pretreated dairy wastewater in batch
mode. The total lipid content of the algae ranged from 8% to 29% of algal mass.
Maximum biomass concentration reached 920 mg/L, measured as volatile suspended
solids, on Day 13 of incubation. In contrast, maximum total lipid content was reached at
Day 6, corresponding to a lipid productivity of 2.8 g/m2/day, or 1,200 gallons/acre/year if
scaled up. Nutrient removal over 12 days of incubation was nearly complete. Total
ammonia (NH +NH +) was reduced 96% to 1.1 mg/L as N, and phosphate (PO 3-) was
3 4 4
reduced >99% from an initial concentration of 2.5 mg/L PO as P.
4
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ACKNOWLEDGMENTS
I would like to thank my thesis advisors for their support during the work of this thesis. I
would like to thank Dr. Yarrow Nelson for his inspiration, dedication and friendship
throughout the creation of this master’s thesis. Without Dr. Nelson I would not have
made it through the many late hours of experimentation and the countless drafts that it
took to get to this point. I would also like to thank Dr. Tryg Lundquist who made this
project possible with his endless knowledge of algae and wastewater. I feel incredibly
fortunate to have met someone as talented and passionate about algae as Dr. Lundquist
and I look forward to what the future of algae-biofuels will bring. In addition, I would
like to thank Dr. Andrew Kean for his support during all the presentations that led up to
my defense as well as his contribution in editing this thesis.

I would like to thank my co-workers and friends here at Cal Poly: Adam Feffer and Kyle
Poole for their analytical support and endless laughs in lab, Laleh Rastegarzadeh for her
enthusiasm and support in DC, and the rest of my friends here at school that always
believed in me.

And finally, I would like to thank my family for their love and sacrifice throughout my
college career and better part of two decades of education.

Joint funding for this project was provided by the U.S. Environmental Protection
Agency’s People, Prosperity, and Planet (P3) student competition and the U.S.
Department of Energy’s Small Business Innovative Research (SBIR) Program.
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TABLE OF CONTENTS

LIST OF FIGURES...........................................................................................................ix
LIST OF TABLES............................................................................................................xii
CHAPTER 1: INTRODUCTION.......................................................................................1
CHAPTER 2: BACKGROUND.........................................................................................6
2.1. Biofuels...............................................................................................................6
2.1.1. Renewable Energy.......................................................................................6
2.1.2. Biodiesel and the Feedstock Dilemma.........................................................9
2.2. Algae to Biodiesel History................................................................................12
2.3. Wastewater Treatment......................................................................................13
2.3.1. Algae-Based Wastewater Treatment vs. Traditional Methods..................13
2.3.2. Anaerobic Digestion and Biogas Production.............................................15
2.4. Other Algae Products and Commercial Algae Production...............................16
2.5. Lipid Chemistry................................................................................................19
CHAPTER 3: MATERIALS AND METHODS..............................................................21
3.1. Collection and Pretreatment of Dairy Wastewater...........................................21
3.2. Outdoor Algal Growth Containers....................................................................24
3.2.1. Operation of Initial Semi-Continuous experiments...................................26
3.2.2. Batch Experiment.......................................................................................28
3.3. Operating Conditions and Additional Testing..................................................29
3.4. Algae Analysis..................................................................................................30
3.4.1. Algae Identification...................................................................................30
3.4.2. Total Suspended Solids..............................................................................30
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3.5. Nutrient Analyses..............................................................................................31
3.5.1. Ammonia....................................................................................................31
3.5.2. Total Kjeldahl Nitrogen.............................................................................31
3.5.3. Nitrate, Nitrite, and Phosphate by Ion Chromatography...........................32
3.6. Total Lipid Analysis.........................................................................................34
3.7. Dissolved Oxygen Measurement......................................................................38
CHAPTER 4: RESULTS AND DISCUSSION................................................................39
4.1. Semi-Continuous Experiment...........................................................................39
4.1.1. Biomass Results for Semi-Continuous Experiment...................................39
4.1.2. Biochemical Oxygen Demand during Semi-Continuous Experiment.......40
4.1.3. Nutrient Removal Semi-Continuous Experiment......................................41
4.1.4. Initial Total Lipid Content during the Semi-Continuous Experiment......44
4.2. Batch Experiment Results.................................................................................45
4.2.1. Algae Identification...................................................................................45
4.2.2. Initial Conditions.......................................................................................48
4.2.3. Biomass Results for Batch Experiments and Growth Curves...................49
4.2.4. Total Lipid Percentages and Productivity..................................................52
4.2.5. Nutrient Removal.......................................................................................57
4.2.6. Dissolved Oxygen and pH Changes During Batch Experiments...............61
CHAPTER 5: CONCLUSIONS.......................................................................................63
5.1. Experimental Conclusions.........................................................................63
5.2. Future Research.........................................................................................65
REFERENCES.................................................................................................................68
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APENDIX A.....................................................................................................................73
Ammonia testing...........................................................................................................73
APPENDIX B...................................................................................................................74
Kjeldahl Nitrogen Testing.............................................................................................74
APPENDIX C...................................................................................................................75
Lipid Extraction Data....................................................................................................75

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LIST OF FIGURES
Figure 1.1 Combined dairy wastewater treatment and algae-biodiesel feedstock
production..........................................................................................................5

Figure 2.1: US energy use sector breakdown, 2005 (EIA, 2005).......................................7
Figure 2.2: U.S. renewable energy as share of total energy, (EIA, 2005)..........................8
Figure 2.3: U. S. Transportation sector energy consumption (EIA, 2005).........................9
Figure 2.4: Algae-bacteria symbiosis in wastewater treatment (Lundquist, 2007)..........14
Figure 2.5: High rate ponds for Spirulina.........................................................................18
Figure 2.6: Paddle wheel mixer in HRP for wastewater treatment Hilmar,
California (photo credit: T. Lundquist)............................................................18

Figure 3.1: Cal Poly Dairy, San Luis Obispo with...........................................................21
Figure 3.2: Wedge wire sloped screen at the Cal Poly Dairy...........................................22
Figure 3.3: Anaerobic digester..........................................................................................23
Figure 3.4: Algae bioreactors (and anaerobic digester in background)............................25
Figure 3.5: Diagram of an algae bioreactor......................................................................25
Figure 3.6 Algae bioreactor with air mixing and CO2 sparging.......................................26
Figure 3.7: Algae bioreactor media..................................................................................29
Figure 3.8: Lipid extraction diagram................................................................................36
Figure 3.9: Fume hood with lipid extraction equipment...................................................37
Figure 3.10: Dried lipid extract.........................................................................................37

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Figure 4.1: Biomass and pH for semi-continuous experiment for R1 tank......................40
Figure 4.2: Nitrite concentrations during the semi-continuous experiment.....................42
Figure 4.3: Nitrate removal during the semi-continuous experiment...............................43
Figure 4.4: Phosphate removal during the semi-continuous experiment..........................44
Figure 4.5: Photomicrograph of Scenedesmus at 1000x (phase contrast) at Day 45
of the semi-continuous experiment R5............................................................46
Figure 4.6: Photomicrograph of Micractinium at 100x (phase contrast) on Day 45
of the semi-continuous experiment R5............................................................46
Figure 4.7: Photomicrograph of Actinastrum at 1000x (phase contrast) on Day 27
of the semi-continuous experiment R1............................................................47
Figure 4.8: Photomicrograph of flocculated Scenedesmus at 400x (Dark Phase) on
Day 45 of the semi-continuous experiment R4................................................48
Figure 4.9 Biomass and pH for batch experiment for 25% WW dilution........................50
Figure 4.10 Biomass and pH for batch experiment for 25% WW dilution......................51
Figure 4.11 Log phase of biomass for 25% WW dilution algae growth reactor..............51
Figure 4.12 Log phase of biomass for 10% WW dilution algae growth reactor..............52
Figure 4.13: 25% WW Dilution algae growth and lipid content during batch run...........54
Figure 4.14: 10% WW Dilution algae growth and lipid content during batch run...........55
Figure 4.15: Nutrient reduction in 25% dilution culture...................................................58
Figure 4.16: Nutrient reduction in 10% dilution culture...................................................59
Figure 4.17: Dissolved oxygen and pH change in 25% dilution culture through
sunrise on March 24th, 2007.............................................................................62
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