Using the greet model to analyze algae as a feedstock for biodiesel production

68 Pages·2012·1.32 MB·English

by  Christopher Tatum

USING THE GREET MODEL TO ANALYZE ALGAE

AS A FEEDSTOCK FOR BIODIESEL PRODUCTION

By

Christopher Tatum

Approved:

_____________________________ ______________________________
Tricia A. Thomas Neslihan Alp
Professor of Engineering Professor of Engineering
(Director of Thesis) (Committee Member)

_____________________________ ______________________________
Frank Jones Jim Henry
Professor of Engineering Professor of Engineering
(Committee Member) (Committee Member)

_____________________________ ______________________________
William H. Sutton A. Jerald Ainsworth
Dean, Engineering & Computer Science Dean of the Graduate School
USING THE GREET MODEL TO ANALYZE ALGAE

AS A FEEDSTOCK FOR BIODIESEL PRODUCTION

By

Christopher Tatum

A Thesis Submitted to the Faculty of the University
of Tennessee at Chattanooga in Partial
Fulfillment of the Requirements for the
Degree of Master of Science in Engineering

The University of Tennessee at Chattanooga
Chattanooga, Tennessee

December 2012

ii
ABSTRACT

There is a growing interest in renewable, carbon-neutral biofuels such as ethanol
and biodiesel. A life-cycle analysis is conducted in this study to determine the viability of
using algae as a feedstock for biodiesel. The method involves assessing energy use,
fossil fuel use, greenhouse gas emissions, and criteria pollutant emissions using a
simulation developed by Argonne National Laboratory. The energy and emissions of
algae-derived biodiesel are compared to those of soybean biodiesel, corn ethanol,
conventional gasoline, and low-sulfur diesel. Results show that there are sizeable
greenhouse gas emission benefits attributed to the production of both types of biodiesel
as compared to petroleum fuels. Energy expenditures are much larger when producing
algae biodiesel than compared to the other four fuels. The alternative scenario of
growing algae at a wastewater treatment plant is also evaluated and is proven to reduce
fossil fuel consumption by 17%. The results suggest that producing biodiesel from algae,
while not yet competitive regarding energy use, does have many benefits and is worthy of
further research and development.
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TABLE OF CONTENTS

LIST OF TABLES.........................................................................................................vi

LIST OF FIGURES......................................................................................................vii

LIST OF ABBREVIATIONS.........................................................................................ix

CHAPTER

I. INTRODUCTION...............................................................................................1

Why Alternative Fuels?.......................................................................................2
Types of Alternative Fuels...................................................................................3
Ethanol....................................................................................................3
Biodiesel..................................................................................................5
Algae as a Feedstock...........................................................................................6
Evaluating Algae as a Feedstock Using GREET..................................................8

II. METHODOLOGY............................................................................................10

Pathways in GREET..........................................................................................10
Petroleum...............................................................................................10
Electricity..............................................................................................10
Ethanol..................................................................................................11
Biodiesel................................................................................................12
Algae Process Description.................................................................................14
Carbon Dioxide Transportation..............................................................15
Growth and First Dewatering.................................................................16
Nutrients................................................................................................16
Second Dewatering................................................................................17
Oil Extraction........................................................................................17
Anaerobic Digestion (Recovery)............................................................18
Biogas Cleanup......................................................................................18
Soil Amendment Transportation.............................................................19
Conversion to Biodiesel.........................................................................19
Co-Product Treatment for Biofuels....................................................................20
Stochastic Simulation........................................................................................21

III. RESULTS.........................................................................................................25
iv
Energy Consumption.........................................................................................25
Greenhouse Gas Emissions................................................................................31
Pollutant Emissions...........................................................................................37

IV. DISCUSSION AND CONCLUSION

Wastewater Treatment Plant Scenario................................................................43
General Discussion............................................................................................46
Conclusion........................................................................................................48

REFERENCES.............................................................................................................49

APPENDIX

A. SUPPLEMENTARY DATA................................................................................52

VITA............................................................................................................................58

v
LIST OF TABLES

A1 Total energy and fossil fuel consumption for each stage of the corn-to-ethanol
process.........................................................................................................54

A2 Total energy and fossil fuel consumption for each stage of the soybean-to-
biodiesel process..........................................................................................54

A3 Total energy, fossil fuel, electricity, and thermal energy consumption for
each stage of the algae-to-biodiesel process.................................................55

A4 Well-to-pump (WTP) results for energy consumption and greenhouse gas
and pollutant emissions. Listed as mean over standard deviation in
BTU or grams/mmBTU of fuel available at the pump..................................56

A5 Well-to-wheels (WTW) results for energy consumption and greenhouse
gas and pollutant emissions. Listed as mean over standard deviation in
BTU or grams/mmBTU of fuel available at the pump..................................57

vi
LIST OF FIGURES

1 Flow Diagram of the algae-to-biodiesel process.................................................14

2 Sample points (100) on a unit square using four sampling techniques
(Subramanyan and Diwekar 2005)...............................................................23

3 The energy required to get one million units of energy of each fuel type to
the pump......................................................................................................26

4 The amount of fossil fuels consumed to get one million units of energy of
each fuel type to the pumps..........................................................................27

5 The total amount of fossil fuel energy consumed in a complete, well-to-
wheels life-cycle analysis.............................................................................29

6 The contributions to fossil fuel consumption occurring from the various
processes involved in the production of biodiesel from algae feedstock........30

7 The total amount of CO emitted while getting one million units of energy
2
of each fuel to the pumps.............................................................................31

8 The total amount of CH emitted while getting one million units of energy
4
of each fuel to the pumps.............................................................................33

9 The total amount of N O emitted while getting one million units of energy
2
of each fuel to the pumps.............................................................................34

10 The total amount of greenhouse gases emitted, in CO equivalent units,
2
while getting one million units of energy of each fuel to the pumps.............35

11 The total amount of greenhouse gases emitted, in CO equivalent units, for
2
a full well-to-wheel life-cycle analysis.........................................................36

12 The total emissions of CO, NO , and SO for the entire well-to-wheels
X X
life-cycle analysis........................................................................................37

13 The total emissions of VOCs, PM , and PM for the entire well-to-
10 2.5
wheels life-cycle analysis.............................................................................40

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14 The contributions to fossil fuel consumption occurring from the various
processes involved in the production of biodiesel from algae feedstock........44

15 The amount of fossil fuels consumed to get one million units of energy of
each fuel type to the pumps for the wastewater treatment plant
scenarios......................................................................................................45

A1 Process flow diagram for electricity generation at a typical power plant
with 35% efficiency.....................................................................................53

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LIST OF ABBREVIATIONS

AD Anaerobic digestion
ANL Argonne National Laboratory
BD Biodiesel
BD20 Mixture of 20% biodiesel and 80% diesel by volume
C Carbon
CD Conventional diesel
CH Methane
4
CHP Combined heat and power
CO Carbon monoxide
CO Carbon dioxide
2
DAP Diammonium phosphate
DDGS Distillers’ dry grains and solubles
DOE U.S. Department of Energy
EPA U.S. Environmental Protection Agency
EtOH Ethanol
E10 Mixture of 10% ethanol and 90% gasoline by volume
FAME Fatty acid methyl esters
GHG Greenhouse gas
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GREET Greenhouse gases, Regulated Emissions, and Energy use in Transportation
LSD Low sulfur diesel
MTBE Methyl tertiary butyl ether
N Nitrogen
NAAQS National Ambient Air Quality Standards
N O Nitrous oxide
2
NH Ammonia
3
NOx Nitrogen oxides

NREL National Renewable Energy Laboratory
O Oxygen
2
P Phosphorus
PBR Photobioreactor
PM Particulate matter with aerodynamic diameter of 10 micrometers or less
10
PM Particulate matter with aerodynamic diameter of 2.5 micrometers or less
2.5
RFG Reformulated gasoline
RFS Renewable Fuel Standard
SO Sulfur dioxide
2
SOx Sulfur oxides

VOC Volatile organic compound
WTP Well to pump
WTW Well to wheel
WWTP Wastewater treatment plant
x