The Production Of Algal Biodiesel Using Hydrothermal Carbonization And In Situ Transesterification.

230 Pages·2013·3.48 MB·English

by  Robert Levine

THE PRODUCTION OF ALGAL BIODIESEL USING HYDROTHERMAL CARBONIZATION
AND IN SITU TRANSESTERIFICATION

by

Robert Bernard Levine

A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
(Chemical Engineering)
in The University of Michigan
2013

Doctoral Committee:

Professor Phillip E. Savage, Chair
Brian Goodall, Valicor Renewables
Professor Nancy G. Love
Professor Henry Y. Wang
Distinguished University Professor Emeritus Walter J. Weber, Jr.
© Robert Bernard Levine 2013
DEDICATION

To my mother Rita.

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ACKNOWLEDGEMENTS
This work would not have been possible without the mentorship provided by my advisor
Phil Savage and the outstanding committee members who helped guide me towards its
final form. These individuals generously shared with me wisdom gained over many years
in their respective fields. I am grateful for their interest in my work as well as my
professional development, and I thank them for giving freely of their time and ideas.

I also wish to acknowledge my fellow graduate students, both in the Savage Group and
beyond, for creating a vibrant community of scholarship. In particular, my time at the
University of Michigan was influenced by fellow group members Shujauddin Changi, Jacob
Dickenson, Julia Faeth, Chad Huelsman, Tannawan Pinnarat, and Peter Valdez, as well as
Michael Hoepfner, Aaron Shinkle, Elizabeth Stuart, and Huanan Zhang. I also want to
thank the many undergraduates who I had the experience of working, including Alexandra
Bollas, Matthew Durham, Anna Jenks, and Sita Syal.

My sincere gratitude also goes to the excellent staff of the Chemical Engineering
Department. In particular, Pablo Lavalle was instrumental in helping me acquire much of
the instrumentation required to carry out this work, and his creativity, willingness to
share, and can-do attitude made working with him a pleasure. Likewise, Harald Eberhart,
our glassblower, never ceased to amaze me with new solutions to my problems and his
unwavering generosity. Finally, I wish to acknowledge the support of the administrative
professionals who helped me in countless ways (Pam Bogdanski, Susan Hamlin, Shelley
Fellers, Laurel Neff).

Finally, I acknowledge financial support from an NSF Graduate Research Fellowship, a
University of Michigan Graham Environmental Sustainability Institute Fellowship, and a
University of Michigan Rackham Graduate Fellowship. I also gratefully acknowledge
financial support from the University of Michigan College of Engineering and from the
U.S. National Science Foundation.
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TABLE OF CONTENTS
Dedication ............................................................................................................................ii
Acknowledgements ............................................................................................................. iii
List of Tables ....................................................................................................................... vi
List of Figures .................................................................................................................... viii
List of Abbreviations ........................................................................................................... xi
Abstract .............................................................................................................................. xii
CHAPTER 1 Introduction .................................................................................................. 1
1.1 The case for biofuels ............................................................................................ 1
1.2 Algae as a biofuel feedstock ................................................................................. 4
1.3 Process overview and chapter summaries .......................................................... 7
CHAPTER 2 Feedstock Production and Characterization ................................................. 9
2.1 Background ........................................................................................................... 9
2.2 Materials and methods ...................................................................................... 17
2.3 Results and discussion ........................................................................................ 25
2.4 Conclusions......................................................................................................... 38
CHAPTER 3 Hydrothermal Carbonization ...................................................................... 39
3.1 Background ......................................................................................................... 39
3.2 Materials and methods ...................................................................................... 45
3.3 Results and discussion ........................................................................................ 47
3.4 Conclusions......................................................................................................... 78
CHAPTER 4 Supercritical In Situ Transesterification ...................................................... 80
4.1 Background ......................................................................................................... 80
4.2 Materials and methods ...................................................................................... 84
4.3 Results and discussion ........................................................................................ 87
4.4 Conclusions....................................................................................................... 114
CHAPTER 5 Acid-catalyzed In Situ Transesterification ................................................. 115
5.1 Background ....................................................................................................... 115
5.2 Materials and methods .................................................................................... 116
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5.3 Results and discussion ...................................................................................... 117
5.4 Conclusions....................................................................................................... 129
CHAPTER 6 Triflate-Catalyzed In Situ Transesterification ............................................ 131
6.1 Background ....................................................................................................... 131
6.2 Materials and methods .................................................................................... 132
6.3 Results and discussion ...................................................................................... 134
6.4 Conclusions....................................................................................................... 147
CHAPTER 7 Algal Growth on the Aqueous Co-product of HTC .................................... 148
7.1 Backgrounds ..................................................................................................... 148
7.2 Materials and methods .................................................................................... 151
7.3 Results and discussion ...................................................................................... 154
7.4 Conclusions....................................................................................................... 170
CHAPTER 8 The Energy Balance of Algal Biodiesel Processes ..................................... 172
8.1 Background ....................................................................................................... 172
8.2 Methodology and model descriptions ............................................................. 176
8.3 Results and discussion ...................................................................................... 182
8.4 Conclusions....................................................................................................... 188
CHAPTER 9 Summary and Engineering Significance .................................................... 189
Appendix A. ..................................................................................................................... 192
References ...................................................................................................................... 195

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LIST OF TABLES
Table 1.1. Feedstock oil yield .............................................................................................. 5
Table 1.2. Fertilizer consumption and non-oil product generation related to producing
20% of US transportation fuels from algae without nutrient recycling ............................. 5
Table 2.1. The metabolisms of algae .................................................................................. 9
Table 2.2. Algae bioreactor apparatus .............................................................................. 17
Table 2.3. Media compositions ......................................................................................... 19
Table 2.4. Fatty acid profiles for relevant microalgae ...................................................... 35
Table 3.1. Characterization of biomass feedstock and hydrochars for C. vulgaris HTC at
250 °C ................................................................................................................................ 50
Table 3.2. Hydrochar characterization from C. vulgaris HTC at 250 °C ............................ 53
Table 3.3. Hydrochar elemental analysis and energy content for C. protothecoides
hydrochars at various temperatures and 60 min ............................................................. 57
Table 3.4. Lipid composition of hydrochars from HTC reactions containing C.
protothecoides with and without acetic acid ................................................................... 59
Table 3.5. The effect of solids loading on lipid composition of Chlorella hydrochars ...... 61
Table 3.6. Hydrothermal carbonization yields and hydrochar characteristics for
Nannochloropsis................................................................................................................ 69
Table 3.7. Hydrochar yields and lipid information from HTC (200 °C, 15 min) of algae
grown in bubble column reactors ..................................................................................... 71
Table 3.8. Hydrochar elemental composition and energy yieldsa .................................... 73
Table 3.9. Aqueous phase analysis from HTC of C. protothecoides biomass for 60 min at
various temperatures ....................................................................................................... 74
Table 3.10. Aqueous phase analysis from low-temperature HTC (200 °C x 15 min) with
various feedstocks ............................................................................................................ 76
Table 4.1. Characterization of algal hydrochars used in SC-IST ........................................ 88
Table 4.2. Crude biodiesel yield and composition from the SC-IST of hydrochar A ......... 90
Table 4.3. Fatty acid ethyl ester composition of biodiesel produced through SC-IST ...... 94
Table 4.4. Fatty acid ethyl ester yield from SC-IST ........................................................... 96
Table 4.5. Reaction conditions and total ester yields for factorial experiment ............. 102
Table 4.6. Second order regression model for supercritical in situ transesterification of
hydrochar A. .................................................................................................................... 103
Table 5.1. Characterization of algal hydrochars used in AC-IST ..................................... 118
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Table 5.2. Mineral acid-catalyzed in situ transesterification factorial experiment ........ 125
Table 5.3. Regression analysis of factorial experiment .................................................. 126
Table 6.1 Non-catalytic oleic acid esterification ............................................................. 138
Table 6.2 Triflate-catalyzed hydrolysis of ethyl oleate ................................................... 140
Table 6.3 Characterization of carbonized solids used in TC-IST ..................................... 142
Table 7.1. C, N, and P content in the aqueous phase co-product from hydrothermal
carbonization .................................................................................................................. 156
Table 7.2. Media N content, biomass growth, and N uptake for the growth experiment
shown in Figure 7.3 ......................................................................................................... 161
Table 7.3 Biomass and Lipid Productivities (mg/L-h) for Growth Experiments in Figure 7.6
......................................................................................................................................... 167
Table 7.4. Production model for algal biorefinergy using two-stage growth scheme to
produce about one million gallons of biodiesel annually ............................................... 168
Table 8.1. Model productivity assumptions and land requirements ............................. 177
Table 8.2. Elemental composition and estimated energy content of process materials 178
Table 8.3. Elemental yields ............................................................................................. 178
Table 8.4. Process energy input assumptions ................................................................ 179
Table 8.5. Homogenization, extraction, and transesterification process assumptions . 181
Table 8.6. Mass flows in model algal biorefinery for 5 BGY biodiesel production ......... 183
Table 8.7. Summary of energy use and generation ........................................................ 184
Table 8.8. Detailed summary of process energy inputs ................................................. 186
Table 8.9. Energy required for traditional wet hexane extraction and transesterification
......................................................................................................................................... 187

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LIST OF FIGURES
Figure 1.1. Shares of energy sources in total global primary energy supply in 2008. ........ 2
Figure 1.2. Consumption of N and P fertilizer by all of US agriculture in comparison to algal
biofuel production with varying amounts of nutrient recycling. ...................................... 6
Figure 2.1. C. vulgaris biomass density and media nitrate concentration over time.. ..... 26
Figure 2.2. Light microscopy of Chlorella vulgaris.. .......................................................... 27
Figure 2.3. Fatty acid profile of phototrophic and heterotrophic C. vulgaris................... 28
Figure 2.4. Biomass density and lipid content over time in sterile fermentation of C.
protothecoides. ................................................................................................................. 29
Figure 2.5. Biomass density and lipid content over time in non-sterile carboy fermentation
of C. protothecoides. ......................................................................................................... 30
Figure 2.6. Light microscopy of Chlorella protothecoides grown heterotrophically. ....... 31
Figure 2.7. Fatty acid profile of C. protothecoides over time during non-sterile
fermentation on glucose ................................................................................................... 31
Figure 2.8. Biomass density over time in shaker flasks containing C. protothecoides grown
in standard media containing glucose, glycerol, or cellulosic hydrosylate. . .................. 33
Figure 2.9. Change in fatty acid profile for developing marine bi-culture immediately
following introduction of metal stress.............................................................................. 34
Figure 2.10. Light microscope image of bi-culture. ........................................................ 36
Figure 3.1. The properties of liquid and supercritical water. . ......................................... 41
Figure 3.2. Hydrolysis of triglycerides ............................................................................... 44
Figure 3.3. Chlorella hydrochar obtained from reaction at 250° C for 30 min ................. 48
Figure 3.4. Lipid content of C. vulgaris biomass (time 0) and hydrochars . .................... 49
Figure 3.5. Lipid composition and lipid retention in C. vulgaris biomass and hydrochars
generated by reaction at 250 °C for various times.. ......................................................... 51
Figure 3.6. HT-GC-FID chromatogram showing FAs (9 to 12 min), MGs (13.5 to 16 min),
DGs (20 to 21 min), and TGs (22 to 24 min) of Chlorella hydrochars processed at 250 °C.
........................................................................................................................................... 52
Figure 3.7. Light microscopy of Chlorella biomass processed at 230 °C for (a) 0 min, (b) 5
min, (c) 15 min, or (d) 30 min. ......................................................................................... 54
Figure 3.8. HTC of C. protothecoides biomass at 220 °C, 235 °C, and 250 °C for 30, 60, and
90 min. . ............................................................................................................................ 56
Figure 3.9. Lipid retention for C. protothecoides hydrochars. ........................................ 56
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Figure 3.10. Solids yield in HTC reactions containing C. protothecoides with and without
acetic acid. ....................................................................................................................... 58
Figure 3.11. Lipid retention in hydrochars from HTC reactions containing C. protothecoides
with and without acetic acid ............................................................................................. 60
Figure 3.12. HTC of C. protothecoides at different solids contents at 235 °C for 60 min. 61
Figure 3.13. HTC of Nannochloropsis biomass at 215 °C for 15, 30 or 45 min. .............. 63
Figure 3.14. Filter cakes of Chlorella hydrochars reacted for 15 and 30 min at 215 °C. 63
Figure 3.15. Solids yield from low-temperature HTC of Nannochloropsis. ...................... 65
Figure 3.16. Lipid retention in hydrochars formed by low-temperature HTC of
Nannochloropsis................................................................................................................ 66
Figure 3.17. GC-FID analysis of Nannochloropsis hydrochar (200 °C x 30 min) compared to
unreacted biomass. .......................................................................................................... 67
Figure 3.18. GC-FID analysis of isomerization in commercial omega-3 ethyl ester product.
........................................................................................................................................... 68
Figure 3.19. FT-ICR-MS spectra showing molecular weight distribution of organic matter
in aqueous phase co-product obtained from reacting N. oculata biomass at 200 °C for 15
min. ................................................................................................................................... 77
Figure 3.20. van Krevelen plot of organic compounds detected by FT-ICR-MS. ............ 78
Figure 4.1. Representative GC-FID chromatogram of fatty acid ethyl esters from
supercritical in situ transesterification. ............................................................................ 87
Figure 4.2. Reaction water content (wt.%) for supercritical in situ transesterification of
hydrochars with various amounts of azeotropic ethanol (4.4 wt.% water).. ................... 89
Figure 4.3. Supercritical esterification of oleic acid at 275 °C with 12:1 EtOH:FA molar ratio.
........................................................................................................................................... 98
Figure 4.4. Supercritical in situ transesterification of wet and dry hydrochars at 275 °C.99
Figure 4.5. Supercritical in situ transesterification of dry hydrochar B at 275–295 °C (~20
MPa). . ............................................................................................................................ 100
Figure 4.6. Parity plot comparing experimental data with regression model.. .............. 104
Figure 4.7. Supercritical in situ transesterification of partially dried hydrochar at 275 °C..
......................................................................................................................................... 106
Figure 4.8. Comparing in situ transesterification under sub-critical and supercritical
conditions with methanol and ethanol. ......................................................................... 109
Figure 4.9. Proposed process flow diagram for supercritical in situ transesterification.111
Figure 5.1. Total fatty acid ethyl ester yield from hydrochars reacted at 80, 90, and 100 °C
for 15 to 120 min.. .......................................................................................................... 121
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