Table Of ContentPROCESS SYNTHESIS
FOR FUEL ETHANOL
PRODUCTION
C. A. Cardona
Universidad Nacional de Colombia
Manizales, Colombia
Ó. J. Sánchez
Universidad de Caldas
Manizales, Colombia
L. F. Gutiérrez
Universidad de Caldas
Manizales, Colombia
Boca Raton London New York
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Library of Congress Cataloging‑in‑Publication Data
Cardona, C. A.
Process synthesis for fuel ethanol production / C.A. Cardona, Ó.J. Sánchez, L.F.
Gutiérrez.
p. cm. -- (Biotechnology and bioprocessing series ; 32)
Includes bibliographical references and index.
ISBN 978-1-4398-1597-7 (hardcover : alk. paper)
1. Ethanol as fuel. 2. Corn--Biotechnology. 3. Sugarcane--Biogtechnology. 4.
Biomass energy. I. Sánchez, Ó. J. II. Gutiérrez, L. F. III. Title. IV. Series.
TP339.C37 2010
662’.6692--dc22 2009035959
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© 2010 by Taylor and Francis Group, LLC
Contents
Preface.................................................................................................................xv
Acknowledgments .............................................................................................xvii
The Authors .......................................................................................................xix
Chapter 1 Biofuels ............................................................................................1
1.1 Biofuels Generalities ............................................................1
1.1.1 Solid and Gaseous Biofuels .....................................3
1.1.2 Liquid Biofuels ........................................................4
1.1.2.1 Biodiesel ..................................................4
1.1.2.2 Bioethanol ................................................5
1.2 Gasoline Oxygenation ..........................................................5
1.2.1 Tetraethyl Lead as Antiknocking Additive .............8
1.2.2 Ethers as Gasoline Oxygenates ...............................8
1.2.2.1 Methyl Tert-Butyl Ether (MTBE) ............9
1.2.2.2 Ethyl Tert-Butyl Ether (ETBE) ..............10
1.2.2.3 Tert-Amyl Methyl Ether (TAME)
and Tert-Amyl Ethyl Ether (TAEE) .......11
1.2.2.4 Di-Isopropyl Ether (DIPE) .....................11
1.2.3 Methanol ................................................................12
1.3 Ethanol as a Gasoline Oxygenate .......................................12
1.3.1 Advantages of Fuel Ethanol ..................................13
1.3.2 Drawbacks of Fuel Ethanol ...................................14
1.4 Gasoline Oxygenation Programs with Fuel Ethanol in
Some Countries ..................................................................17
References .....................................................................................22
Chapter 2 Process Design and Role of Process Synthesis .............................27
2.1 Conceptual Process Design ................................................27
2.2 Knowledge-Based Process Synthesis .................................30
2.2.1 Evolutionary Modification .....................................31
2.2.2 Hierarchical Decomposition..................................32
2.2.3 Phenomena-Driven Design ....................................33
2.2.4 Conflict-Based Approach ......................................33
2.2.5 Thermodynamics-Based Process Synthesis ..........33
2.2.6 Analysis of the Statics ...........................................34
2.3 Optimization-Based Process Synthesis ..............................35
2.3.1 Mathematical Aspects ...........................................36
2.3.2 Superstructures ......................................................38
vii
viii Contents
2.3.3 Hybrid Methods .....................................................39
2.4 Final Considerations ...........................................................40
References .....................................................................................40
Chapter 3 Feedstocks for Fuel Ethanol Production .......................................43
3.1 Sugars .................................................................................43
3.1.1 Sugarcane ..............................................................43
3.1.2 Cane Sugar ............................................................45
3.1.3 Sugar Beet .............................................................48
3.1.4 Beet Sugar .............................................................48
3.1.5 Sucrose-Containing Materials Used for
Ethanol Production ................................................50
3.1.5.1 Cane and Beet Juices .............................51
3.1.5.2 Sugarcane Molasses ...............................51
3.1.5.3 Beet Molasses ........................................52
3.1.5.4 Other Sugar-Containing Materials ........52
3.2 Starchy Materials ................................................................53
3.2.1 Starch .....................................................................53
3.2.2 Starch Sources for Ethanol Production .................55
3.2.2.1 Corn .......................................................56
3.2.2.2 Other Grains as Starch Sources .............59
3.2.2.3 Cassava ..................................................60
3.3 Lignocellulosic Materials ...................................................61
3.3.1 Structure of Lignocellulosic Complex...................62
3.3.2 Classification of Lignocellulosic Materials ...........63
3.3.2.1 Sugarcane Bagasse .................................68
3.3.2.2 Corn Stover ............................................69
3.3.2.3 Cereal Straws .........................................70
3.3.2.4 Municipal Solid Waste ...........................70
References .....................................................................................71
Chapter 4 Feedstock Conditioning and Pretreatment ....................................77
4.1 Conditioning of Sucrose-Containing Materials .................77
4.2 Pretreatment of Starchy Materials ......................................80
4.3 Pretreatment of Lignocellulosic Biomass ...........................83
4.3.1 Physical Methods of Pretreatment .........................84
4.3.2 Physical–Chemical Methods of Pretreatment .......85
4.3.3 Chemical Methods of Pretreatment ......................90
4.3.4 Biological Methods of Pretreatment......................95
4.3.5 Role of Pretreatment during Process
Synthesis ................................................................95
4.4 Detoxification of Pretreated Biomass .................................98
4.4.1 Physical Methods of Detoxification ....................100
Contents ix
4.4.2 Chemical Methods of Detoxification ..................100
4.4.3 Biological Methods of Detoxification .................105
References ...................................................................................108
Chapter 5 Hydrolysis of Carbohydrate Polymers ..........................................115
5.1 Starch Saccharification ......................................................115
5.2 Hydrolysis of Cellulose ......................................................117
5.2.1 Enzyme Systems for Cellulose Hydrolysis ...........118
5.2.2 Conversion of Cellulose to Glucose ....................122
5.2.3 Cellulose Hydrolysis Assessment for Process
Synthesis ..............................................................123
5.2.3.1 Efficiency of Cellulases .......................123
5.2.3.2 Modeling of Cellulose Hydrolysis .......124
References ...................................................................................126
Chapter 6 Microorganisms for Ethanol Production ......................................131
6.1 Metabolic Features of Ethanol Producing
Microorganisms .................................................................131
6.2 Nongenetically Modified Microorganisms for Ethanol
Production.........................................................................134
6.2.1 Yeasts ...................................................................136
6.2.2 Bacteria ................................................................138
6.3 Genetically Modified Microorganisms for Ethanol
Production.........................................................................140
6.3.1 Mutagenesis .........................................................140
6.3.2 Recombinant DNA Technology ...........................141
6.3.2.1 Recombinant Microorganisms for
Starch Processing ..................................143
6.3.2.2 Recombinant Microorganisms
for Processing of Lignocellulosic
Biomass ................................................148
References ...................................................................................151
Chapter 7 Ethanolic Fermentation Technologies .........................................155
7.1 Description of Main Fermentation Technologies for
Ethanol Production ...........................................................155
7.1.1 Features of Ethanolic Fermentation Using
Saccharomyces cerevisiae ...................................155
7.1.2 Fermentation of Sucrose-Based Media ...............156
7.1.2.1 Batch Fermentation ..............................157
7.1.2.2 Semicontinuous Fermentation .............158
7.1.2.3 Continuous Fermentation......................161
x Contents
7.1.2.4 Fermentation of Sugar Solutions
Using Immobilized Cells .....................163
7.1.3 Fermentation of Media Based on Starchy
Materials ..............................................................166
7.1.3.1 Conversion of Saccharified Corn
Starch into Ethanol ..............................166
7.1.3.2 Very High Gravity Fermentation .........167
7.1.4 Fermentation of Media Based on
Lignocellulosic Biomass ......................................168
7.1.4.1 Fermentation of Cellulose
Hydrolyzates ........................................168
7.1.4.2 Pentose Fermentation ............................170
7.1.4.3 Co-Fermentation of Lignocellulosic
Hydrolyzates .........................................171
7.2 Modeling of Ethanolic Fermentation for Process
Design Purposes ................................................................173
7.2.1 Modeling of Ethanolic Fermentation from
Sugars ...................................................................176
7.2.2 Modeling of Co-Fermentation of Hexoses and
Pentoses ...............................................................179
7.3 Analysis of Fed-Batch Ethanolic Fermentation ................181
7.4 Dynamics of Continuous Fermentation Systems .............182
References ....................................................................................191
Chapter 8 Analysis of Ethanol Recovery and Dehydration .........................199
8.1 Concentration and Rectification of Ethanol Contained
in Culture Broths ..............................................................199
8.2 Ethanol Dehydration .........................................................201
8.2.1 Pressure-Swing Distillation ................................202
8.2.2 Azeotropic Distillation ........................................202
8.2.3 Extractive Distillation .........................................206
8.2.4 Saline Extractive Distillation ..............................209
8.2.5 Adsorption ............................................................210
8.2.6 Pervaporation........................................................211
8.3 Evaluation of Separation and Dehydration Schemes ........213
References ....................................................................................217
Chapter 9 Integrated Processes for Fuel Ethanol Production ......................221
9.1 Process Integration ...........................................................221
9.2 Reaction–Reaction Integration for Bioethanol
Production.........................................................................224
9.2.1 Process Integration by Co-Fermentation.............224
Contents xi
9.2.2 Process Integration by SSF .................................225
9.2.2.1 SSF of Starch .......................................225
9.2.2.2 SSYPF of Starchy Materials ................230
9.2.2.3 SSF of Lignocellulosic Materials ........231
9.2.2.4 Modeling of SSF of Cellulose ..............235
9.2.3 Process Integration by SSCF ...............................240
9.2.4 Process Integration by Consolidated
Bioprocessing ......................................................241
9.3 Reaction–Separation Integration for Bioethanol
Production.........................................................................244
9.3.1 Ethanol Removal by Vacuum ..............................246
9.3.2 Ethanol Removal by Gas Stripping .....................246
9.3.3 Ethanol Removal by Membranes ........................249
9.3.4 Ethanol Removal by Liquid Extraction ...............263
9.4 Separation–Separation Integration for Bioethanol
Production.........................................................................275
References ...................................................................................276
Chapter 10 Environmental Aspects of Fuel Ethanol Production ...................285
10.1 Effluent Treatment during Fuel Ethanol Production ........285
10.1.1 Residues Generated in the Process of
Bioethanol Production .........................................285
10.1.2 Methods for Treatment and Utilization of
Stillage .................................................................286
10.1.2.1 Stillage Recycling ................................287
10.1.2.2 Stillage Evaporation .............................289
10.1.2.3 Solids Recovery ...................................289
10.1.2.4 Stillage Incineration .............................289
10.1.2.5 Fertilization .........................................290
10.1.2.6 Anaerobic Digestion ............................290
10.1.2.7 Composting ..........................................291
10.1.2.8 Stillage as a Culture Medium ..............292
10.1.2.9 Stillage Oxidation ................................292
10.1.2.10 Wastewater Treatment of Biomass-
to-Ethanol Process ...............................293
10.2 Environmental Performance of Fuel Ethanol
Production.........................................................................298
10.2.1 WAR Algorithm ..................................................299
10.2.2 Life Cycle Assessment of Bioethanol
Production ...........................................................304
10.2.3 Other Methodologies for the Environmental
Analysis of Bioethanol Production ......................306
References ...................................................................................307
xii Contents
Chapter 11 Technological Configurations for Fuel Ethanol Production in
the Industry ..................................................................................311
11.1 Ethanol Production from Sucrose-Containing
Materials ............................................................................311
11.2 Ethanol Production from Starchy Materials .....................322
11.2.1 Configuration Involving the Separate
Hydrolysis and Fermentation (SHF) of Corn
Starch ...................................................................322
11.2.2 Configuration Involving the Simultaneous
Saccharification and Fermentation (SSF) of
Corn Starch..........................................................325
11.2.3 Configuration for Production of Cassava
Ethanol ................................................................333
11.3 Ethanol Production from Lignocellulosic Materials ........336
11.3.1 Process Flowsheet Development for
Production of Biomass Ethanol ...........................337
11.3.2 Optimization-Based Process Synthesis for
Ethanol Production from Biomass ......................348
11.4 Role of Energy Integration during Process Synthesis .......351
References ...................................................................................353
Chapter 12 Food Security versus Fuel Ethanol Production ...........................359
12.1 Crop Potentials for Food and Energy ...............................359
12.1.1 Corn in the United States ....................................360
12.1.2 Sugarcane in Colombia .......................................361
12.1.3 Sugarcane in Brazil .............................................362
12.1.4 Sugarcane in Tanzania ........................................363
12.1.5 Lignocellulosics: Nonfood Alternative ...............364
12.2 Bioethanol and Fossil Oil Dependence ............................365
12.3 Bioenergy and Transgenics ...............................................366
12.4 Bioenergy and Food Market .............................................366
12.5 Bioenergy and Food Security Project ...............................368
12.5.1 The BEFS Project Is Developed in Basic
Phases ..................................................................369
12.5.2 Purposes and Activities of Modules ....................369
12.5.2.1 Module 1 ..............................................369
12.5.2.2 Module 2 ..............................................370
12.5.2.3 Module 3 ..............................................371
12.5.2.4 Module 4 ..............................................371
12.5.2.5 Module 5 ..............................................371
12.5.2.6 Module 6 ..............................................371
12.5.3 Preliminary BEFS Results for Tanzania .............372
Contents xiii
12.6 Concluding Remarks ........................................................375
References ...................................................................................376
Chapter 13 Perspectives and Challenges in Fuel Ethanol Production ...........379
13.1 Feedstocks ........................................................................379
13.2 Process Engineering .........................................................380
13.3 Food Security Impacts ......................................................384
13.4 Environmental Impacts ....................................................387
Index .................................................................................................................391
Preface
The mitigation of climate change, energy versus food security, and equity in rural
areas are some of the main global goals facing the world today. One of the real
options to achieving these goals is the development of cleaner and renewable
energy sources, such as biofuels. Fuel ethanol from sugarcane and corn is world-
wide the most important biofuel, followed by biodiesel from rapeseed. However,
speculations about the possible impacts of fuel ethanol production create confu-
sion about its convenience.
This book stresses the need to analyze and design accurately fuel ethanol pro-
duction systems based on a process engineering approach as the source of techni-
cal information for assessing the real impacts of this biofuel on energy, food, and
environmental balances. The processes for producing fuel ethanol from different
feedstocks are not all the same in terms of technologies, impacts, and benefits.
There is diversity among scientists, engineers, governments, or decision mak-
ers who try to analyze fuel ethanol projects. The book, through the 13 chapters,
describes a logic and structured strategy for further analysis and development
of fuel ethanol production from different feedstocks including energy crops and
lignocellulosic biomasses.
The authors aim to offer a comprehensive review as well as results from
more than 15 years in process engineering and ethanol research developed by
the Chemical and Biotechnological Processes Design Group at the National
University of Colombia, Manizales campus. Additionally, the process intensifica-
tion reached by integration of reaction and separation processes in fuel ethanol
production is analyzed in detail.
Chapter 1 discusses bioenergy focusing on liquid biofuels and describes the
development of biofuels production in the world. Chapter 2 discusses the role of
process synthesis and design as a key strategy for rapid and high-tech analysis
and design of complex biotechnological processes. Chapters 3 and 4 describe
the characteristics and technological implications of using different sugary and
starchy crops as well as lignocellulosic feedstocks. Chapter 5 emphasizes the
hydrolysis technologies for the saccharification of carbohydrate polymers as cel-
lulose and starch. Chapter 6 analyzes the microorganisms used in ethanol produc-
tion. Chapters 7 and 8 describe in detail the fuel ethanol production technologies
for different feedstocks. Chapter 9 analyzes the new technological innovations
based on process integration as a way for reducing energy consumption. Chapter
10 addresses the environmental issues regarding bioethanol production. Here,
environmental impacts are discussed in terms of waste reduction algorithm and
the life cycle assessment. Then, these impacts are calculated as a result of over-
all energy and material balances obtained from a process engineering approach.
Chapter 11 describes the technological configurations for fuel ethanol produc-
tion in the industry. Chapter 12 discusses the possible factors that could affect
food security when fuel ethanol production and consumption are encouraged in
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