EVALUATION OF THE ECONOMIC FEASIBILITY OF GRAIN SORGHUM, SWEET SORGHUM, AND SWITCHGRASS AS ALTERNATIVE FEEDSTOCKS FOR ETHANOL PRODUCTION IN THE TEXAS PANHANDLE

1. EVALUATION OF THE ECONOMIC FEASIBILITY OF
GRAIN SORGHUM, SWEET SORGHUM, AND
SWITCHGRASS AS ALTERNATIVE FEEDSTOCKS FOR
ETHANOL PRODUCTION IN THE TEXAS PANHANDLE
by
JNANESHWAR RAGHUNATH GIRASE
A Thesis Submitted in Partial Fulfillment
of the Requirements for the Degree
MASTER OF SCIENCE
Major Subject: Agricultural Business and Economics
West Texas A & M University
Canyon, Texas
August 2010

2. ABSTRACT
Economic, environmental and political concerns centered on energy use from
conventional fossil fuels have led to research on alternative renewable energy fuel such
as ethanol. The goal of this thesis is to evaluate the potential of grain sorghum, sweet
sorghum, and switchgrass for ethanol production in the Texas Panhandle Region using
three alternative ethanol production methodologies: starch based ethanol, sugar based
ethanol, and cellulose based ethanol respectively.
The study area includes the top 26 counties of the Texas Panhandle. The potential
of three feedstocks: grain sorghum, sweet sorghum, and switchgrass for ethanol
production in the Texas Panhandle Region is analyzed using yield and production costs
of feedstock, processing cost of feedstock, final demand for ethanol, farm to wholesale
marketing margin, and the derived demand price of feedstock.
The calculated farm-to-wholesale marketing margins per gallon of ethanol are
$0.57, $1.06, and $0.91 for grain sorghum, sweet sorghum, and switchgrass respectively.
Current price of ethanol in Texas is $1.81/ (E-100) gallon. Derived demand price is
calculated by subtracting farm-to-wholesale marketing margin from the price of ethanol.
The calculated derived demand price per gallon ethanol is $1.24, $0.75, and $0.90 for
grain sorghum, sweet sorghum, and switchgrass respectively. The estimated
ii

3. grain sorghum production cost per acre is $413.40 and $141.70 under irrigated and
dryland conditions respectively. The estimated production costs of sweet sorghum and
switchgrass are $462.70 and $349.05 respectively under irrigated condition and $193.07
and $102.32 respectively under dryland condition. The calculated total gross income per
acre of grain sorghum, sweet sorghum, and switchgrass are $478.00, $162.53, and
$308.88 respectively under irrigated condition and $128.41, $72.98, and $98.28
respectively under dryland condition. An economic return is calculated by subtracting
irrigated cash rent of $110.00 per acre and dryland cash rent of $25.00 per acre from net
return of the selected feedstocks. The calculated economic returns per acre of grain
sorghum, sweet sorghum, and switchgrass are -$45.37, -$410.19, and -$150.17
respectively under irrigated condition and -$38.25, -$145.09, and -$29.04 respectively
under dryland condition.
The evaluation in this study demonstrates that ethanol production from grain
sorghum, sweet sorghum, and switchgrass in the Texas Panhandle Region is not
economically feasible given the current price for ethanol in Texas. This is consistent with
the status of the ethanol industry in the Texas Panhandle. An increase in the price of
ethanol would seem to justify a reevaluation of the economic feasibility. However, since
any increase in the price of ethanol would occur only with an increase in the prices of
energy inputs to the production process, the economic feasibility is not assured.
Decreases in cost and increases in productivity may present possibilities for achieving
economic feasibility.
iii

4. ACKNOWLEDGMENTS
This work would not have been accomplished without the continuous support and
thoughtful insights of Dr. Arden Colette who has been instrumental in motivating me to
develop and complete this work. The views and guidelines provided by him were of
utmost importance with regard to the subject and application of learnt knowledge
throughout the time period involved in this study.
I consider myself privileged to have been guided by my learned committee
member Dr. Bob A Stewart who has been an inspiration during the study period and my
thesis development at West Texas A & M University. I also express my sincere gratitude
to Dr. Robert DeOtte for agreeing to provide useful guidance as a member of my thesis
committee and suggesting improvements that were extremely important in creating the
final shape of this research.
I am heartily thankful to my major advisor, Dr. Lal K. Almas for providing a
platform for the foundation of this research and whose encouragement, guidance and
support from the initial to the final level enabled me to develop an understanding of the
subject.
This research was supported in part by the Ogallala Aquifer Program, a
consortium between USDA Agricultural Research Service, Kansas State University,
iv

5. Texas AgriLife Research, Texas AgriLife Extension Service, Texas Tech University, and
West Texas A&M University.
Last but not the least; I would like to thank my parents Sushila and Raghunath B.
Girase and my brother Kishor for their never ending love, patience and belief in me.
v

6. Approved:
___________________________ _________________
Chairman, Thesis Committee Date
Dr. Lal K. Almas
___________________________ _________________
Member, Thesis Committee Date
Dr. Arden Colette
___________________________ _________________
Member, Thesis Committee Date
Dr. Robert DeOtte
___________________________ _________________
Member, Thesis Committee Date
Dr. Bob A. Stewart
________________________ ________________
Head, Major Department Date
Dr. Dean Hawkins
________________________ _________________
Graduate School Date
vi

7. TABLE OF CONTENTS
Chapter Page
I. INTRODUCTION .......................................................................................... 1
Research Objective ................................................................................... 6
II. LITERATURE REVIEW ............................................................................... 7
Ethanol Overview ..................................................................................... 7
U.S. Ethanol Production and Demand .................................................... 10
Ethanol Production Techniques .............................................................. 12
General Chemistry of Ethanol Production .............................................. 16
Cellulosic Ethanol ................................................................................... 19
Cellulosic Ethanol Production Process ................................................... 20
Sugar-based Ethanol ............................................................................... 24
Sugar-based Ethanol Production Process................................................ 25
Starch-based Ethanol .............................................................................. 27
Starch-based Ethanol Production Process ............................................... 28
Conventional Ethanol versus Cellulosic Ethanol .................................... 32
By-products of Ethanol Production ........................................................ 33
vii

8. Chapter Page
SWEET SORGHUM .............................................................................. 34
Introduction...................................................................................... 34
Importance and Uses........................................................................ 35
GRAIN SORGHUM ............................................................................... 40
Introduction...................................................................................... 40
Importance and Uses........................................................................ 40
SWITCHGRASS .................................................................................... 42
Introduction...................................................................................... 42
Importance and Uses........................................................................ 42
III. MATERIALS AND METHODS .................................................................. 44
Selection of Feedstock Source ................................................................ 47
Current Situation of Selected Feedstocks Production ............................. 49
Potential of Selected Feedstocks in Panhandle ....................................... 50
Price of Ethanol....................................................................................... 52
Feedstock Requirement ........................................................................... 52
Farm-to-Wholesale Marketing Margin ................................................... 54
Estimated Derived Demand Price for Feedstock .................................... 57
Current Production Costs of Feedstock .................................................. 58
IV. RESULTS AND DISCUSSION ................................................................... 60
Grain Sorghum ........................................................................................ 60
viii

9. Chapter Page
Sweet Sorghum ....................................................................................... 62
Switchgrass ............................................................................................. 64
V. CONCLUSION AND SUGGESTIONS ....................................................... 66
REFERENCES ....................................................................................... 68
APPENDIX A ......................................................................................... 76
APPENDIX B ......................................................................................... 83
APPENDIX C ......................................................................................... 85
ix

10. LIST OF TABLES
Table Page
1. Summary of Feedstock Characteristics ............................................................... 15
2. Physical, Chemical and Thermal Properties of Ethanol ..................................... 18
3. Cost Competitiveness of Cellulosic Ethanol....................................................... 24
4. Nutritional Content Variations of DDGS ........................................................... 33
5. Comparison of Sugarcane, Sugar beet, and Sweet sorghum .............................. 39
6. Harvested acres and Production of major crops: Corn, Wheat, Cotton,
and Grain Sorghum in the 26 counties in the Texas Panhandle,
2005 - 2009 ......................................................................................................... 46
7. Irrigated and Dryland Grain sorghum Acreages and Production in the
top 26 Counties in the Texas Panhandle, 2005-2009.......................................... 50
8. Yields of Selected Feedstocks used in the analysis for the Texas
Panhandle Region ............................................................................................... 51
9. Feedstock requirements of the three basic feedstocks for 20, 40, 60, 80,
and 100 MGY processing facilities..................................................................... 53
10. Irrigated and dryland acres of feedstock requirement for 20, 40, 60, 80,
and 100 MGY ethanol processing facilities ........................................................ 54
x

11. Table Page
11. Estimated Farm-to-Wholesale Marketing Margin for Grain Sorghum in
the Production of Ethanol using a 100MGY Processing Facility ....................... 55
12. Estimated Farm-to-Wholesale Marketing Margin for Switchgrass in the
Production of Ethanol using a 56MGY Processing Facility ............................... 56
13. Estimated Farm-to-Wholesale Marketing Margin for Sweet Sorghum in
the Production of Ethanol using a 40MGY Processing Facility ......................... 57
14. Farm-to-Wholesale Marketing Margin and Derived Demand Price
for three feedstocks in the Production of Ethanol ............................................... 58
15. Estimated Feedstock Production Cost per Acre in Texas Panhandle
Region ................................................................................................................. 59
16. Grain sorghum yield and economic returns per acre .......................................... 62
17. Sweet sorghum yield and economic returns per acre.......................................... 64
18. Switchgrass yield and economic returns per acre ............................................... 65
xi

12. LIST OF FIGURES
Figure Page
1. Role of Renewable Energy Consumption in the Nation’s
Energy Supply, 2008 ............................................................................................. 4
2. U.S. Ethanol Production in Billions of Gallons (1980-2009) ............................. 11
3. Ethanol Production Steps by Feedstock and Conversion Technique.................. 13
4. Ethanol Feedstocks and Production Process ...................................................... 14
5. Schematic Diagram of Ethanol Production from Switchgrass .......................... 22
6. General Process Flow: Production of Ethanol from Sweet Sorghum ................. 26
7. Diagrammatic Representation of Grain Feedstock to Ethanol ........................... 29
8. Graphical Representation of Alternative Processes to Convert
Sweet Sorghum to Energy Fuels ......................................................................... 38
9. Map of Texas with Panhandle Region indicated in box ..................................... 45
10. Grain Sorghum Production by State, 2009 ......................................................... 49
xii

13. CHAPTER I
INTRODUCTION
There is an increasing need for energy throughout the world. Given current
consumption trends, world energy demand is estimated to grow by 50% between 2005
and 2030 (EIA 2008). As the economy grows, the energy requirement also grows.
Traditional liquid fuels evolved from fossil resources are presently, and are predicted to
continue to be, a dominant energy source, given their remarkable role in the
transportation sector (EIA 2008). Presently, more than 90% of the energy used for
transportation is derived from petroleum fuels. More than 60% of the petroleum
consumption is directed towards the production of gasoline and diesel fuel (Research and
Innovative Technology Administration - Bureau of Transportation Statistics 2009).
Petroleum is a possible pollutant, non-renewable and geographically limited to a few
countries. Its use discharges huge amounts of greenhouse gases, mainly CO2, into the
atmosphere. This increase in CO2 is postulated to contribute to the greenhouse effect and
climate change. The transportation sector accounts for approximately 13% of global
anthropogenic greenhouse gas (GHG) emissions (IPCC 2007).
The rising prices of traditional energy fuels and increased scientific and political
1

14. discussions of evaluating alternative energy sources have resulted in growth of support
for developing ethanol as a replacement or substitute fuel. The goal is to develop an
energy structure for the future that is renewable, sustainable, convenient, cost-effective,
economically feasible, and environmentally safe. The availability of oil at low prices has
retarded the research study and interest in alternative fuels. Current geopolitical,
environmental, and economical changes have led to an increasing interest in an
alternative fuel source, preferably renewable and cost-effective.
The role of petroleum and oil based products in the U.S. economy is remarkable.
Oil is the major source of energy in the United States. The transportation sector in the
United States is almost totally dependent on gasoline and diesel fuel which are obtained
from petroleum. According to the Energy Information Administration (EIA); U.S.
gasoline consumption reached a record high of 9.30 million barrels a day (391 million
gallons/day) in 2007 before declining to about 9.00 million barrels a day in 2008. About
7% of the gasoline consumed in 2008 was actually ethanol mixed gasoline. According to
EIA U.S.A. statistics for 2008; net petroleum imports were 12.95 million barrels/day,
petroleum consumption was 19.50 million barrels/day, U.S. total petroleum exports were
1.81 million barrels/day, and dependence on net petroleum imports was 66.41% of the
total requirement.
Triggered by high oil prices, government subsidies and energy policies, a large
expansion in ethanol production, along with research and innovation to develop second
generation biofuels is underway in the United States. This increased focus on ethanol and
other biofuels is an important element of United States economic, energy, environmental,
2

15. and national security policies. The recent resurgence of interest in ethanol production has
spurred various stakeholders to request an unbiased analysis of the economic ethanol
production potential in Texas.
There has been increased interest in ethanol production recently for following
reasons:
1) The inconsistency in the political situation, the continued conflict in the Middle
East and the reliance on foreign oil has many in the United States looking for a
more dependable, renewable, and domestic fuel source.
2) Ethanol production would boost depressed commodity prices and provide
producers with ethanol feedstocks byproducts.
3) The finding that Methyl Tertiary Butyl Ether (MTBE), a widely used oxygenate
that has been linked to groundwater contamination and is likely to be banned
nationwide, increases interest in substituting ethanol as an oxygenating agent, and
4) Local, State, and Federal officials see ethanol production as a source of business
activity and tax base.
Ethanol is a clean burning, high octane, renewable fuel that can be made from
grains or other biomass sources such as sweet sorghum, switchgrass, wood chips, and
other plant residues. It can also be used as an effective octane boosting fuel additive,
which can replace MTBE (Methyl Tertiary Butyl Ether) as an oxygenating agent. Ethanol
use has been shown to reduce emissions, decrease the use of gasoline, and provide a fuel
which is free from MTBE (Wyman 1996). Ethanol, also known as an ethyl alcohol, is a
high proof form of grain alcohol.
3

16. Production of renewable fuels would contribute to our goal of reducing nation’s
dependence on imported oil. Achieving the production goals for bio-ethanol production
will require appropriate and promising bioenergy feedstocks with supplementation from
agricultural crop residues.
The overall contribution of renewable energy is only 7% of the whole energy
supply of the United States, Figure 1. Fifty-three percent of the renewable energy comes
from biomass. Petroleum energy (37%), natural gas (24%), and coal (23%) account for
the greatest contribution in the nation’s whole energy supply, Figure 1. Solar (1%),
geothermal (5%), wind (7%), and hydropower (34%) are other sources of renewable
energy contributes in the nation’s energy supply.
Source: U.S. Energy Information Administration, Annual Energy Review 2008.
Figure 1. Role of Renewable Energy Consumption in the Nation’s Energy Supply,
2008
4

17. These fossil fuels are a limited source of energy due to their depletion by time and
non-renewable characteristics. At this stage of increasing depletion of non-renewable
energy sources there is a great need to have an alternative renewable energy sources.
They play an important role in the supply of energy. When renewable energy sources are
used, demand for fossil fuels is reduced.
Biofuels have evolved as an alternative energy source to fossil fuels by
substituting bioethanol and biodiesel for gasoline and diesel respectively. They have been
considered as alternative sources of energy due to their capacity to offset the reliance on
foreign oil and potential to moderate climate change (Pacala and Socolow 2004).
Currently bioethanol is being produced on a large scale, especially in the US and Brazil.
Sugarcane is the major feedstock used in Brazil for ethanol production by using sugar to
ethanol technology, while the US uses corn as a major feedstock for ethanol production
by using starch to ethanol technology. In the United States there is ongoing technology
development to produce ethanol from sugar, and ethanol from cellulose based feedstocks.
This study analyses ethanol production potential by three alternative
methodologies for the Texas Panhandle: starch based ethanol, sugar based ethanol, and
cellulose based ethanol. To be a viable ethanol production methodology for the Texas
Panhandle, it needs to meet environmental as well as economic criteria.
Feasibility of any ethanol production methodology for the Texas Panhandle
Region will be determined on the basis of economics of selected feedstock used, current
situation of selected feedstock production, current production levels and yields of
selected feedstock, estimated net value residual to selected feedstock.
5

18. Research Objective
The research objective of this study is to evaluate the economic feasibility of three
ethanol production methods in the Texas Panhandle: starch to ethanol, sugar to ethanol,
and cellulose to ethanol. The three feedstocks associated with the three methods are grain
sorghum, sweet sorghum, and switchgrass respectively.
6

19. CHAPTER II
LITERATURE REVIEW
Research has been conducted on different aspects of the ethanol industry but there
has not been a study over the use of alternative methodologies: sugar based, starch based,
and cellulose based for ethanol production in the Texas Panhandle Region. The review of
literature provides an overview of previous literature on ethanol, different ethanol
production techniques, ethanol production and demand in the U.S., and sources of
feedstock for ethanol production.
Ethanol Overview
Ethanol is a renewable fuel made from starches, sugars, and cellulosic biomass.
Conventional starch feedstocks used for ethanol production include crops such as corn,
wheat, and sorghum. A large growth in ethanol production, along with research and
innovation to foster second-generation biofuels, is underway in the United States. These
are prompted by high oil prices and energy policies. This increased focus on ethanol and
other biofuels production is an important aspect of United States economic, energy,
environmental and national security policies (BR&DI 2000). The inconsistency in
7

20. political situation, the continued conflict in the Middle East and the reliance on foreign
oil by the United States has forced policy makers and researchers to look for a more
dependable, renewable and domestic fuel source. However, the volatile nature of oil
prices is an economic concern.
According to the United States Department of Energy (DOE 2007) the
importation of crude oil is increasing by period of time. Moreover, in 2005 crude oil
imports attained a record of more than 10 million barrels per day. The reduction of our
nation’s dependence on imported oil is identified as one of our greatest challenges. To
address this challenge, the United States needs a variety of alternative renewable fuels,
including ethanol produced from cellulosic materials like grasses, wood chips; sugar rich
materials like sugarcane, sweet sorghum, sugar beet; and starch based materials like corn
or sorghum grains. Fortunately, the United State has ample agricultural and forest
resources that can be easily converted into biofuels. Recent studies by the U.S.
Department of Energy (DOE) Biofuels suggest that these resources can be used to
produce 60 billion gallons of ethanol per year. This would replace about 30% of our
current gasoline consumption by 2030.
Ethanol can be used as an effective octane-boosting fuel additive or as a stand-
alone fuel (Salassi 2007). Ethanol has 30-35% of the energy value of gasoline. Bio-fuels
like bio-ethanol and bio-diesel, which are produced from renewable energy sources like
biomass, grains etc., are attaining an importance in the light of rising fossil fuel prices,
depleting oil reserves and concerns over the perceived ‘green house effect’ associated
with the use of conventional fossil fuels. The rising price of energy as well as the limited
8

21. oil and gas reserves around the world has created a need to improve the renewable energy
production. By the year 2025 world energy consumption is projected to increase by 57%
over 2002 levels. The resulting stress on the world’s energy supply requires the
expansion of alternative energy sources. Moreover, concern about the potential
association of increases in atmospheric CO2 due to the consumption of fossil fuels with
global warming; is providing an additional motivation for the development of biofuels
that can generate low net carbon emission (Rooney et al. 2007).
The American Coalition for Ethanol (ACE), an advocacy group promoting
ethanol use, suggests that ethanol is a cleaner fuel source due to its perceived
environmental friendly nature than the traditionally used nonrenewable fossil fuel
sources. As shown in Figure 2. the increasing cost of crude oil along with the United
States’s movement towards decreasing the reliance on imported oil has lead to a boom of
the biofuel industry. In addition, the government tax incentives and environmental
concerns also have contributed to this boom. The remarkable increase in United States
ethanol production is enhancing ability to supply a major portion of our transportation
fuel requirement. As of 2007 there were 180 completed ethanol production facilities with
20 more processing plants under construction (ACE 2007). The advanced technology of
ethanol production, increasing energy prices, concern over pollution from the use of
conventional fossil fuels, and tax incentives have prompted automobile manufacturers to
promote vehicles that can easily be converted to use ethanol and gasoline blends with
other future alternative energy sources (David et al. 2008).
9

22. David et al. (2008) noted that ethanol adds to the overall fuel supply of the United
States and contributes to maintaining competitive and affordable fuel prices. Cities
around the U.S. have been selling an ethanol blend (E85) and gasohol or E10 as
alternative fuel sources for automobiles (DOE 2007). E85 is a blend of 85% ethanol and
15% unleaded gasoline; whereas E10 is a blend of 10% ethanol and 90% unleaded
gasoline.
U.S. Ethanol Production and Demand
The fuel ethanol industry in the U.S. has grown to a total annual production
capacity of 13 billion gallons with an estimated 12 billion gallons per year of actual
production (RFA 2010). There are 201 ethanol plants operating in 27 states and 14 new
plants or plant expansions are underway (RFA 2010). New ethanol plant construction or
expansions are estimated to add 1.4 billion gallons of annual production, bringing U.S.
ethanol production capacity to 14.4 billion gallons per year (RFA 2010).
This increased trend in the annual U.S. ethanol production indicates increasing
scope and demand of ethanol usage over the use of conventional fossil fuels. Following
are the major factors that have driven demand for ethanol as an alternative renewable fuel
source (Hardy 2010):
• High oil prices
• National energy security
• Ethanol tax incentives
• Lower ethanol production costs with improved technology, and
• Climate change concerns.
10

23. United States ethanol production (in billions of gallons) from the year 1980 to
2009 is summarized in Figure 2. Ethanol production has increased from 175 million
gallons in 1980 to 10.6 billion gallons in year 2009 (ACE 2007, RFA 2010), Figure 2.
This is 60 times more than year 1980.
12
10.60
10
9.23
8
Billion Gallons
6.20
6
4.89
4.00
4
3.40
2.81
2.12
1.77
2 1.63
1.20 1.40
1.35 1.40 1.47
0.87 1.10 1.30
0.71 1.10
0.85 0.90 0.95
0.43 0.83
0.22 0.38 0.61
0.18 0.35
0
Years
Source: American Coalition for Ethanol 2007, Renewable Fuels Association 2010
Figure 2. U.S. Ethanol Production in Billions of Gallons (1980-2009)
11

24. Ethanol Production Techniques
Fermentation is the conversion process of an organic material from one chemical
form to another form using enzymes produced by living microorganisms (Soltes 1980). It
plays a vital role in the production of ethanol from alternate feedstocks such as starch
based feedstocks, sugar rich feedstocks, and cellulosic feedstocks. Ethanol is produced by
removing starch from carbohydrates with the action of yeasts. Carbohydrates are made up
of carbon, hydrogen, and oxygen with sugar and starch. Yeasts utilize fermentable sugar
to convert it into ethanol (Reidenbach 1981).
The steps in the ethanol production process by feedstock and conversion method
are summarized in Figure 3. The three major ethanol producing feedstocks: cellulose,
sugar, and starch have three different production techniques with different harvest
techniques for each feedstock. In crops such as sugar cane or sweet sorghum, stalks are
cut and hauled from the field to the ethanol processing plant. In grain crops such as corn,
grain sorghum, or wheat the grain is harvested and the stalks left in the field. In cellulosic
crops, such as trees, the full plants are harvested; with grasses several harvests are made
to allow for regrowth of the plant. There are variations in by-products from the different
feedstocks with respect to their ethanol production techniques. Heat, electricity, and
molasses are the by-products obtained from sugar based ethanol. Animal feed such as
distillers dried grain with solubles (DDGS) and wet distillers grain soluble (WDGS) are
the main by-products obtained from starch based ethanol. Heat, electricity, animal feed,
and bioplastics are the by-products obtained from cellulose based ethanol, Figure 3.
12

25. Source: International Energy Agency 2004
Figure 3. Ethanol Production Steps by Feedstock and Conversion Technique
13

26. Source of feedstock to produce ethanol and their production process is
summarized in Figure 4. Corn stover, switchgrass etc. are sources of cellulose. Whereas
corn, wheat, potatoes etc. are sources of starch and cane juice is a source of sugar.
Pretreatment, addition of enzymes and fermentation are the common steps involved in the
production of ethanol, Figure 4.
Source: Michael 2008
Figure 4. Ethanol Feedstocks and Production Process
14

27. A comparison of the characteristics of the alternative feedstocks is shown in Table 1.
Table 1. Summary of Feedstock Characteristics
Type of Processing Principal advantage Principal
feedstock needed prior to (s) disadvantage (s)
fermentation
Sugar crops (ex., Milling to extract Preparation is Storage may result in
sugar cane, sugar minimal loss of sugar
sweet sorghum,
sugar beets, High yields of Cultivation practices
Jerusalem ethanol per acre are not wide-spread,
artichoke) especially with
Crop co-products “nonconventional”
have value as fuel, crops
livestock feed, or soil
amendment
Starch crops: Milling, Storage techniques Preparation involves
liquefaction, and are well developed additional equipment,
Grains (ex., saccharification labor and energy costs
corn, sorghum, Cultivation practices
wheat, barley) are widespread with DDG from aflatoxin
grains contaminated grain is
Tubers (ex., not suitable as animal
potatoes, sweet Livestock co-product feed
potatoes) is relatively high in
protein.
Cellulosic: Milling and Use involves no No commercially cost-
hydrolysis of the integration with the effective process exists
Crop residues linkages livestock feed market for hydrolysis of the
(ex., corn stover, linkages
wheat straw) Availability is wide-
spread
Forages (ex.,
switchgrass,
alfalfa, forage
sorghum)
Source: Mother Earth Alcohol Fuel 1980
15

28. General Chemistry of Ethanol Production
The chemical equations describing the reactions which occur during ethanol
production from the alternative feedstocks: starch based, sugar based, and cellulose based
is described by Reidenbach (1981).
Conversion of Starch-based Feedstock into Ethanol
Hydrolysis (starch liquefaction)
Amylase
Starch + Water Sucrose
2N (C6H10O5) + N (H2O) N (C12H22O11)
(1 kg) + (0.056 kg) (1.056 kg)
In the conversion of starch to ethanol, first water is added into starch (C6H10O5) and
converted it into sucrose (C12H22O11) with the reaction of amylase. This process is called
hydrolysis or starch liquefaction.
Inversion (saccharification)
Invertase
Sucrose + Water Glucose
(C12H22O11) + (H2O) 2(C6H12O6)
(1 kg) + (0.053kg) (1.053 kg)
In this process of inversion, water is added into sucrose (C12H22O11) obtained from the
starch hydrolysis in the previous process and converted into glucose (C6H12O6) with the
reaction of invertase. This process also called saccharification.
Fermentation
Yeast
Glucose Ethanol + Carbon dioxide
(C2H12O6) 2(C2H5OH) + 2(CO2)
16

29. (1 kg) (0.511kg) + (0.489kg)
Fermentation is the last process of starch to ethanol conversion technique in which
glucose (C2H12O6) is converted into ethanol and carbon dioxide with the action of yeast.
Conversion of Sugar-based Feedstock into Ethanol
Fermentation
Yeast
Glucose Ethanol + Carbon dioxide
(C2H12O6) 2(C2H5OH) + 2(CO2) + Heat
(1 kg) (0.511kg) + (0.489kg)
In the conversion of sugar to ethanol, glucose (C2H12O6) is readily available in the form
of sugar and converted easily into ethanol and carbon dioxide with the action of yeast.
This process is called fermentation. Heat can be harvested to improve energy efficiency
of ethanol production plant.
Conversion of Cellulose-based Feedstock into Ethanol
Hydrolysis (cellulose conversion)
Cellulose + Water Acid or Glucose
Enzymes
N (C6H10O5) + N (H2O) N (C6H12O6)
(1 kg) + (0.11 kg) (1.11 kg)
In the conversion of cellulose to ethanol, first water is added into cellulose (C6H10O5) and
converted into glucose (C6H12O6) with the reaction of acid or enzymes. This process is
called hydrolysis or cellulose conversion.
Fermentation
Yeast
Glucose Ethanol + Carbon dioxide
(C2H12O6) 2(C2H5OH) + 2(CO2) + Heat
17

30. (1 kg) (0.511kg) + (0.489kg)
Then in the process of fermentation glucose is converted into ethanol and carbon dioxide
with the action of yeast. This process is called fermentation.
Physical, chemical and thermal properties of ethanol are listed in Table 2. Boiling
temperature of ethanol is 78.50C with a molecular weight of 46.1. Chemical formula of
ethanol is C2H5OH with 52.1%, 34.75, and 13.1% by weight of carbon, oxygen, and
hydrogen respectively, Table 2.
Table 2. Physical, Chemical, and Thermal Properties of Ethanol
Physical Properties of Ethanol
Specific gravity 0.79 gm/cm3
Vapor pressure (380) 50 mm Hg
Boiling temperature 78.50C
Dielectric constant 24.3
Water solubility ∞
Chemical Properties of Ethanol
Formula C2H5OH
Molecular weight 46.1
Carbon (wt) 52.1%
Hydrogen (wt) 13.1%
Oxygen (wt) 34.7%
C/H ratio 4.0
Stoichiometric ratio (Air/ETOH) 9.0
Thermal Properties of Ethanol
Lower heating value 6,400 kcal/kg
Ignition temperature 350C
Specific heat (kcal/kg-0C) 60
Melting point -1150C
Source: ISSAAS 2007.
18

31. Cellulosic Ethanol
Only a small percentage of a plant can be used in the form of sugar or starch,
consumed by animals or human beings, or fermented by yeast into ethanol. Most of the
rest of the plant is cellulose. Using the bulky portion of the plant may be more efficient
than using other portions of the plant. Some grasses have higher energy storage in the
form of cellulose when compared to corn in the form of grain, and can be grown
efficiently with less application of nitrogen based fertilizer, low pesticides use, and less
processed energy. Cellulosic ethanol is a second generation biofuel, as opposed to ethanol
made from corn which is considered a first generation biofuel. The important difference
is that the second generation biofuel uses non-food residual biomass including stems,
leaves, husks, wood chips etc., or they use non-food crops that can be grown without high
energy inputs.
Cellulosic feedstocks are under research and will be used for ethanol production
in the upcoming years. Crop byproducts like corn stover, grain straw, rice hulls, paper
pulp, and sugarcane bagasse; wood chips; and native grasses such as switchgrass are
major cellulose based feedstocks which can be converted easily into ethanol. Research in
advanced technology is directed to make cellulosic ethanol more economical so it can
attain a commercial level of production.
According to Rinehart (2006) switchgrass is not only the most suitable biomass
species to produce cellulosic based ethanol, it also bears some ecological characteristics
that makes it a very good competitor among all cellulosic feedstocks. Positive
characteristics of switchgrass include high cellulose yields, resistance to pests and
disease, superior wildlife habitat, low fertility requirements, can tolerate poor soils and
19

32. wide variations of soil pH, drought and flood tolerant, can use water efficiently in
grassland ecosystems, and cultivars that are locally adapted and relatively available.
Cellulosic Ethanol Production Process
Cellulose is a polymer of sugar (glucose), which is easily consumed by yeast to
produce ethanol (Mosier and Illeleji 2006). It is produced by every living plant on the
earth, which means that cellulose is the most abundant biological molecule on the planet.
According to a USDA study, at least one billion tons of cellulosic feedstocks like corn
stover, straw, forages, grasses, and wood wastes etc. could be feasibly collected and
processed in the U.S. each year. This could contribute approximately 67 billion gallons of
ethanol. Which could replace 30% of gasoline consumption in the U.S. by 2030 (U.S.
Department of Energy Biofuels 2010).
There are three basic types of cellulose-to-ethanol production designs: acid
hydrolysis, enzymatic hydrolysis, and thermo-chemical (Badger 2002). Cellulose can be
converted into ethanol by using current technology. The technology at the front end of
the process is the major difference between grain ethanol and cellulosic ethanol processes
(Mosier and Illeleji 2006). The technology used for the processes of fermentation,
distillation, and recovery of the ethanol are the same for both grain and cellulosic based
feedstocks (Mosier and Illeleji 2006). In order for cellulose based ethanol to be
competitive with grain based ethanol, there are some major challenges associated with
reducing the costs related to production, harvest, transportation, and pretreatment of the
cellulosic feedstock (Eggeman and Elander 2005). There are also some processing
challenges associated with the biology and chemistry of the processing steps of cellulosic
20

33. ethanol. Advances in biotechnology and engineering are expected to make substantial
gains toward attaining the goals of improving efficiency and yields in converting plant
cellulose to ethanol (Mosier 2006).
Although there are similarities between the cellulosic and grain ethanol
production techniques, there are three important steps (pretreatment, hydrolysis, and
fermentation) involved in the production of cellulosic ethanol that are different from
grain ethanol (Mosier 2006). The steps in the ethanol production process from
switchgrass are summarized in Figure 5.
Pretreatment is the process done to soften the cellulosic feedstock to make the
cellulose more susceptible to being broken down and accessible before it is broken down
into simple sugars. Thus the following hydrolysis step is more efficient because the
breakdown of cellulose into simple sugar is faster, higher in yield, and requires fewer
inputs like enzymes and energy (Mosier 2006). The leading pretreatment technologies
under development use a combination of chemicals (water, acid, caustics, and/or
ammonia) and heat to partially break down the cellulose or convert it into a more reactive
form (Mosier et al. 2005). According to Eggeman and Elander (2005), better
understanding of the chemistry of plant cell walls and the chemical reactions that occurs
during pretreatment processes is leading to improvements in these technologies which
can reduce the cost of ethanol production.
Hydrolysis is the process where the cellulose and other sugar polymers are broken
down into simple sugars through the action of biological catalysts called “enzymes”
(Mosier 2006). A combination of enzymes working together can best hydrolyze cellulose
21

34. in industrial applications (Mosier et al. 1999). Biotechnology has allowed these enzymes
to be produced more cheaply and with better properties for use in biofuel applications
(Knauf and Moniruzzaman 2004).
Figure 5. Schematic Diagram of Ethanol Production from Switchgrass
22

35. In the process of fermentation, the equipment and processing technology used to
produce ethanol from cellulose is the same as for producing ethanol from grain (Mosier
2006). In addition, yeast used in starch-based ethanol production can use glucose derived
from cellulose.
Distillation and recovery is the last step in cellulosic ethanol production similar to
ethanol production from grain. Since ethanol has a lower boiling point than water it can
be separated by a process called “distillation.” The conventional distillation or
rectification system has the ability to produce ethanol at 92-95% purity. The remaining
water is then removed by using molecular sieves that selectively absorb the water from an
ethanol or water vapor resulting in approximately pure ethanol (>99%) (Mosier and
Illeleji 2006).
Cost competitiveness of cellulosic ethanol with corn based ethanol is shown in
Table 3. According to Keith, 2007, the total production cost of cellulosic ethanol was
$2.65/gallon compared to corn based ethanol at $1.65/gallon. Department of Energy
(DOE) targeted total production cost of cellulosic ethanol for year 2010-12 to be
$1.10/gallon, which is far less than the production cost in 2007. This decline in the total
production cost of cellulosic ethanol between year 2007 and 2012 reflects decreased
feedstock cost and processing cost combined with increased production efficiency of
ethanol from 60 gallons/dry ton to 90 gallons/dry ton of cellulosic feedstock. In the DOE
target the cost of cellulose based feedstock declines from $60/dry ton in 2007 to $30/dry
ton in 2012 and cost of enzymes to produce one gallon of ethanol declines from $0.40 to
$0.10, Table 3.
23

36. Table 3. Cost Competitiveness of Cellulosic Ethanol
Cellulosic Cost
Cellulosic
Corn Based as of 2010-12
Cost as of 2007
(DOE target)
Feedstock Cost
$1.171 $1.002 $0.333
($/g of ethanol)
By-Product -$0.38 -$0.10 -$0.09
Enzymes $0.04 $0.40 $0.10
Other Costs** $0.62 $0.80 $0.22
Capital Cost $0.20 $0.55 $0.54
Total $1.65 $2.65 $1.10
Note: g = gallon, bu = bushel, dt = dry ton
1
= Cost of corn required to produce per gallon ethanol (2.75 g /bu @ $3.22/bu)
2
= Cost cellulosic feedstock required to produce per gallon ethanol as of 2007 (60 g/dt @ $60/dt)
3
= Cost cellulosic feedstock required to produce per gallon ethanol as of 2010-12 (90 g/dt @ $30/dt)
**
(includes preprocessing, fermentation, labor)
Source: Keith 2007
Sugar-based Ethanol
The production of ethanol from the sugar-based feedstocks was one of man’s
earliest pursuits into value-added processing. The technique used for the production of
ethanol from sugar-based feedstocks is the same as starch-based ethanol production
except for some of the pretreatments of feedstocks.
After harvesting, sugar rich stalks need to be processed through several steps to
get ethanol. The first step in this process is juice extraction. In this step juice is extracted
by a series of mills (Almodares and Hadi 2009) pressing the freshly harvested sugar rich
stalks. These stalks harvested fresh have a moisture content of about 75% (Cundiff and
Worley 1992). The primary goal of increasing ethanol production requires removing as
much sugar from the fresh stalks in the process of juice extraction as possible. Fifty to
one hundred tons of pressure should be applied on the fresh stalks when they pass
24

37. through rollers to extract the sweet juice. About 55 lbs. of juice will be extracted from
100 lbs. of whole sweet sorghum stalks in an efficient system (Mask and Morris 1991).
Ethanol production from sugar is quite simple compared to that for starch and
cellulose, because sugar is readily available from the sugar rich stalks to ferment into
ethanol. Whereas in starch and cellulose based ethanol they have to go through various
processes to get in the form of sugar to ferment into ethanol.
Sugar-based Ethanol Production Process
General process flow of ethanol production from sweet sorghum grain and stalk is
summarized in Figure 6. In the process of ethanol production from sugar rich stalks, the
first step is the milling of stalks to extract the sugar juice. The juice coming out of milling
section is first screened, then sterilized by heating up to 1000C, and then clarified
(Quintero et al. 2008). During clarification the muddy juice is sent to a rotary vacuum
filter. The filtrate juice is then sent to the evaporation section for concentration. The juice
can also be sent directly to fermentation to produce ethanol or it can be concentrated
using evaporators depending on the selected design. In case of sugar juice to ethanol
production it is recommended to increase the concentration of juice by 16 - 18 brix.
Syrup which will be stored for use during the off season needs to concentrate up to 65 -
85 brix (Almodares and Hadi 2009).
Fermentation is the next step after the juice extraction, Figure 6. Fermentation is
an internally balanced oxidation-reduction reaction (Kundiyana 2006; and Kundiyana et
al. 2006). In this process juice or syrup is converted into ethanol, carbon dioxide, yeast
biomass as well as minor end products like glycerol, fusel oils, aldehydes, and ketones by
25

38. the reaction of yeast, Saccharomyces cerevisiae (Almodares and Hadi 2009, Jacques et
al. 1999).
Distillation and dehydration is the last step in the sugar based ethanol production
process. During distillation, alcohol from fermented mash is concentrated up to 95
percent volume per volume (v/v). It is then further concentrated to a minimum
concentration of 99.6 percent to produce ethanol (Almodares and Hadi 2009). Vinasse
developed in the distillation step can be concentrated up to 20 - 25 percent solids
followed by press-mud-composting which further concentrates to 55 percent solids for
use as a liquid fertilizer (Almodares and Hadi 2009).
Source: ISSAAS 2007 (Modified)
Figure 6. General Process Flow: Production of Ethanol from Sweet Sorghum
26

39. Starch-based Ethanol
Presently, almost all the ethanol producing plants in the United States are based
on high starch content feedstock such as corn grain. Grain sorghum can also be used as a
source of starch for ethanol production. Commercial ethanol plants located in sorghum
production regions in the United States can easily rely on sorghum as their primary starch
source (RFA 2006).
In this category, ethanol is produced by fermenting and distilling simple sugars,
which are mostly derived from starch. There are two production processes of ethanol
from starch-based feedstocks: wet milling and dry milling.
In the United States, commercial production of ethanol from starch based grains
such as corn, grain sorghum, wheat etc. involves breaking down the starch into simple
sugars (glucose), feeding these sugars to yeast (fermentation), and then obtaining the
main product ethanol and byproducts like DDGS, carbon dioxide etc. (Mosier and Illeleji
2006). Starch content of corn varies between 70 to 72 percent. Sorghum varies between
68 to 70 percent starch (Shapouri et al. 2006). There is not much difference between corn
and sorghum starch content. Wet milling and dry milling are the two major industrial
methods used in the United States for producing fuel ethanol. Dry milling and wet
milling plant accounts for about 79 percent and 21 percent of total ethanol production
respectively (Shapouri et al. 2006).
Wet milling plants are more expensive to build than dry milling plants but more
flexible in terms of the products they can produce. Although they yield slightly less
ethanol per bushel than the dry mills, wet mills have more valuable byproducts.
27

40. Originally wet milling plants accounted for most of the ethanol production in the United
States, but because of the lower building costs of dry mills, the new construction has
shifted from wet mills to dry mills (Rendleman and Shapouri 2007). In 2004, 75 percent
of ethanol production came from dry milling plants and only 25 percent from wet milling
plants (RFA 2006). In fact, dry milling plants have higher yields of ethanol per bushel
grain than the wet milling plants (Rendleman and Shapouri 2007). As a result of all this,
most of the new technologies are being developed for dry-mill production plants. A dry
mill can have lower initial construction costs but also generates lower valued byproducts
such as distillers dried grain (DDG).
Mosier and Illeleji 2006 state that; it is called “wet” because the first step in the
wet milling process involves soaking the grain in water to soften the grain and make it
easier to separate the various components of the grain. During fractionation the various
components such as starch, fiber, and germ are separated to make a variety of products.
Starch-based Ethanol Production Process
General process flow of ethanol production from grain sorghum is summarized in
Figure 7. In the dry milling process, the whole grain is processed and the remaining
components are separated at the end of the process. There are six major steps: milling,
liquefaction, saccharification, fermentation, distillation, and recovery involved in the dry
milling method of ethanol production (Mosier and Illeleji 2006).
Milling is the first step in dry-grind method of ethanol production, Figure 7. It
involves processing grains through a hammer mill to produce grain flour. This whole
grain flour is then slurried with water and heat stable enzyme (α-amylase) is added.
28

41. Drying
Source: Viraj Alcohols Limited 2010
Figure 7. Diagrammatic Representation of Grain Feedstock to Ethanol
29

42. Liquefaction is the second step of dry-grind method of ethanol production, Figure
7. The slurry obtained from the previous step is cooked. This step is practiced by using
jet-cookers that inject steam into the grain flour slurry to cook it at temperatures above
1000C (2120F). The heat and mechanical shear of the cooking process breaks and separate
the starch granules present in the grain endosperm. The enzymes then break down the
starch polymer into small fragments. The cooked grain mash is allowed to cool to 80-
900C (175-1950F). Additional enzyme (α-amylase) is added and the slurry is allowed to
continue liquefying for at least 30 minutes (Mosier and Illeleji 2006).
Saccharification, the third step, comes after the liquefaction, Figure 7. The slurry,
now called “grain mash,” is cooled to around 300C (860F), and a second enzyme
(glucoamylase) is added. This glucoamylase completes the breakdown of the starch into
simple sugar called glucose. Saccharification occurs while the mash is filling the
fermentor in preparation for the next step (fermentation) and continues throughout the
next step (Mosier and Illeleji 2006).
Fermentation is the fourth step of dry-grind method of ethanol production. The
yeast grown in seed tanks is combined with the grain mash to begin the process of
fermentation, converting the simple sugars to ethanol. The other components of the grain
remain unchanged during the process of fermentation. In most of the dry-milling plants,
the process of fermentation occurs in batches. A fermentation tank is filled, and the batch
ferments completely before the tank is drained and refilled with a new batch. The up-
stream processes like grinding, liquefaction, and saccharification and the down-stream
processes like distillation and recovery occur continuously. During these processes grain
30

43. is continuously processed through the equipment. Dry-milling ethanol production plants
of this design commonly have three fermentation tanks. At any given time one tank is
filling, one tank is fermenting (usually for 48 hours) and one tank is emptying and
resetting for the next batch (Mosier and Illeleji 2006).
Carbon dioxide is also generated during the fermentation process. Usually it is not
recovered but is released from the fermentation tanks to the atmosphere. If it is recovered,
it can be compressed and sold for carbonation of soft drinks or can be frozen into dry ice
for cold product storage and transportation. After the completion of the fermentation
process, the fermented grain mash called “beer” is discharged into a beer well. After that,
this beer well stores the fermented beer between batches and supplies a continuous
stream of material for the distillation and recovery of ethanol (Mosier and Illeleji 2006).
Distillation and recovery is the last step of dry-grind method of ethanol
production. The liquid portion of the slurry remaining after the fermentation process has
8-12% ethanol by weight. Because ethanol has a lower boiling point than the water it can
be separated by a process called “distillation.” The conventional distillation or
rectification system has the ability to produce ethanol at 92-95% purity. The remaining
water is then removed with the help of molecular sieves that selectively absorb the water
from an ethanol or water vapor mixture resulting in approximately pure ethanol (>99%)
(Mosier and Illeleji 2006). The remaining water and grain solids remain after the process
of distillation is called “stillage.” This stillage is used to produce valued byproducts like
wet cake or distillers grains and distillers dried grain with solubles (DDGS).
31

44. Conventional Ethanol versus Cellulosic Ethanol
Although conventional (starch based) and cellulosic ethanol are produced by
using different feedstocks and techniques, the result is the same product. Ethanol
produced conventionally is derived from the starch contained in grains like corn,
sorghum, wheat etc.; where starch is converted to ethanol by either a dry milling process
or wet milling process. In the dry milling process, liquefied grain starch is produced by
heating grain meal and adding water and enzymes. These enzymes convert the liquefied
starch to sugars and finally the sugars are fermented by yeast into ethanol. In the wet
milling process the fiber, germ and protein are separated from the starch before it is
fermented into ethanol. On the other hand, conversion of cellulosic feedstocks to ethanol
requires three important processing steps: pretreatment, saccharification, and
fermentation (Burden 2009). Pretreatment requirements vary with the different
feedstocks.
Cellulosic ethanol displays three times higher net energy content than the
conventionally produced ethanol from corn, and also some of the cellulosic ethanol
production systems pass far lower net levels of greenhouse gases (GHG). Most
conventional (starch-based) ethanol production systems use fossil fuel to create heat for
fermentation and other processing steps and produces GHG emissions. Many cellulosic
ethanol production systems use some part of the input biomass feedstock rather than
fossil fuel to generate heat (Burden 2009).
32

45. By-products of Ethanol Production
Ethanol production from starch based feedstock has two major by-products:
distillers dried grain with solubles (DDGS) and carbon dioxide. One bushel of corn or
grain sorghum yields approximately 17 pounds of distillers grain, and 17 pounds of
carbon dioxide as by-products (Outlaw et al. 2003). DDGS contains all the nutrients from
the grain except starch. Generally, DDGS contains 27 percent protein, 11 percent fat, and
9 percent fiber (Outlaw et al. 2003). Nutritional content variations of DDGS summarized
in Table 4. It is a source of protein which can be sold either dry or wet. This DDGS can
be fed successfully to all major livestock species such as cattle, hogs, poultry etc.
Table 4. Nutritional Content Variations of Distillers Dried Grains with Solubles (DDGS)
Contents %
Protein 25.5-30.7
Fat 8.9-11.4
Fiber 5.4-6.5
Calcium 0.017-0.45
Phosphorus 0.62-0.78
Sodium 0.05-0.17
Chloride 0.13-0.19
Potassium 0.79-1.05
Amino acids % total amino acid
Methionine 0.44-0.56
Cystine 0.45-0.60
Lysine 0.64-0.83
Arginine 1.02-1.23
Tryptophan 0.19-0.23
Threonine 0.94-1.05
Source: Noll 2004
33

46. Fermentation of starch grain produces about equal amounts of carbon dioxide and
ethanol. A few ethanol producing plants catch and sell this CO2 on a commercial basis,
mostly to an organization that specializes in cleaning and pressurizing it. For an ethanol
producer to sell carbon dioxide it is very essential that a user must be nearby and the CO2
produced must be available long enough to justify the cost of the CO2 recovery and
purification equipment (McAloon et al. 2000).
Stillage or bagasse is the major by-product obtained from the conversion of sugar
based feedstocks such as sugar cane or sweet sorghum into ethanol. It is the biomass
remaining after the juice has been extracted from the stalks. It can be used to produce
electricity and steam for the refinery or for sale on the electricity grid (Gnansounou et al.
2005). Or it can be used as an excellent dry matter source for livestock as it is rich in
macro and micronutrients (Reddy et al. 2007). Heat, electricity, lignin, animal feed, and
bioplastics are the by-products obtained from the conversion of cellulose based
feedstocks into ethanol.
SWEET SORGHUM
Introduction
The term sweet sorghum is used to distinguish varieties of sorghum with high
concentration of soluble sugars in the plant sap or juice (Vermerris et al. 2007). It is a C-4
species plant having wide flat leaves and rounded head full of grain at the stage of
maturity. It can be grown and survive successfully in semi-arid tropics, where other crops
fail to thrive. It is highly suitable for tougher dry-land growing areas. It can produce very
high yields with irrigation. During very dry periods, sweet sorghum can go into
34

47. dormancy, with growth resuming when sufficient moisture levels return (Gnansounou et
al. 2005). It can be grown easily on all continents, in tropical, sub-tropical, temperate,
semi-arid regions as well as in poor quality soils. It is also known as the sugar cane of the
desert. Sweet sorghum is a short duration (4-5 months) crop, propagated by seeds;
requiring daily temperatures above 100C.
Importance and Uses
Around 60 percent of the world ethanol production uses sugar crops as the
primary feedstock, with the remaining 40 percent using grain crops as the primary
feedstock (Salassi 2007). Sweet sorghums are used as an alternative sugar source in areas
where sugarcane is not produced or failed to survive (Rooney 2004). Because of the high
sugar content of sweet sorghum, it may also be accessible to the sugar production for
conversion to ethanol, using the same methodology used in sugarcane for ethanol
production. It can be grown as an alternative to sugarcane and has been identified as a
promising dedicated energy crop; that can be grown as far north and south as latitude 450
(Rooney et al. 2007). This crop is appealing due to the easy accessibility of readily
fermentable sugars associated with very high yields of green biomass. The sap of this
crop is extracted by the process of milling. After extraction, the sugars from sweet
sorghum stalks can be fermented easily to produce ethanol. Syrup, molasses, and crystal
sugar are other products which can be produced from this crop (Vermerris et al. 2007).
Since the 1970s sweet sorghum has generated interest as an efficient feedstock for
the production of ethanol by using currently available conventional fermentation
technology. The byproducts, like bagasse (crushed stalks), that remains after removal of
35

48. juice from the sweet stalks can be burnt to create electricity or steam that can be a part of
co-generation strategy. Additionally, the bagasse available after juice removal could be
utilized as a feedstock for cellulosic ethanol production technology (Vermerris et al.
2007). According to the ICRISAT, the stillage obtained from sweet sorghum after the
extraction of sweet juice has a higher biological value than that of bagasse which is
obtained from sugarcane when used as forage for livestock, as it is rich in micronutrients
and minerals. Additionally, the level of pollution in sweet sorghum-based ethanol
production has one fourth of the biological oxygen demand (BOD) (19,500 mg/liter) and
lower chemical oxygen demand (COD) (38,640 mg/liter) compared to molasses–based
ethanol production (Reddy et al. 2007).
Traditional sweet sorghum varieties produce low grain yields. However, recently
varieties with more balanced grain as well as sugar production have been developed in
China and India. These varieties are the best example of dual-purpose crops, where grains
can be used for human or animal consumption, and sugars can be fermented to ethanol.
Alternatively, these varieties can be used as a dedicated bioenergy crop, where we can
use both sugars and grains for the production of ethanol (Vermerris et al. 2007). In
addition to sweet stalks, this crop gives grain yield of 2 to 2.5 tons/ha and this can be
used as food or feed (Reddy et al. 2007). While single-cut yields may be low, the
multiple cutting potential of this crop increases cumulative yields with an increased
growing season (Rooney et al. 2007).
The ICRISAT, headquartered in the Indian state of Andhra Pradesh, has found
that individual stalks of sweet sorghum grow up to 10 ft (3 m) in height in dry, saline, and
36

49. flooding conditions, tolerates heat, and can be used to produce both ethanol and food. In
comparison to corn where an individual stalk can be used only once to produce either
ethanol or food, with sweet sorghum the grain can be removed for food processing before
the stalk is crushed to extract the sugary liquid that is used to produce ethanol. Sweet
sorghum can be a potential feedstock for ethanol production due to the characteristics of
high fermentable sugars, low fertilizer requirement, high water use efficiency (1/3 of
sugarcane and 1/2 of corn), short growing period, and the ability to adapt well to diverse
climate and soil conditions (Wu et al. 2008).
Sweet sorghum has both advantages and disadvantages in producing ethanol. The
initial advantage is that sugars are directly available to fermentation without any
enzymatic treatment after simply extracting the sweet juice from biomass. The major
disadvantage is the requirement for fresh processing. The seasonal availability of the
fresh feedstock limits the sugar extraction period. In sugar based ethanol production
technique, efficiency of ethanol production depends on the fresh content of the biomass.
Most of the sugar crops such as sugarcane, sweet sorghum, sugar beet are seasonal crops
mostly available during specific seasons. These crops can’t be stored such as grains for
long period of time due to their high moisture content.
It is a promising crop for biomass production due to its high yield and potential to
generate high value added products like ethanol, DDG (distiller dried grain), electricity,
and heat. After harvesting it can be separated into grain (used for ethanol and DDG
production), sugar juice (used for ethanol production), and bagasse (used to generate
37

50. electricity and heat). Other by-products can be produced such as carbon dioxide from the
fermentation process, paper from bagasse or compost from leaves and roots, Figure 8.
Source: Chiramonti et al. 2004
Figure 8. Graphical Representation of Alternative Processes to Convert Sweet
Sorghum to Energy Fuels
38

51. General characteristics of sugarcane, sugar beet, and sweet sorghum are
summarized in Table 5.
Table 5. Comparison of Sugarcane, Sugar beet, and Sweet sorghum
Characteristics Sugarcane Sugar beet Sweet sorghum
Crop duration about 12 - 13 months about 5 – 6 months about 4 months
Growing season one season one season all season
Soil requirement grows well in drain grows well in sandy all types of drained
soil loam; also tolerates soil
alkalinity
Water requires water less water less water
management throughout the year requirement, 40 – 60% requirement; can be
compared to sugarcane grown as rain-fed crop
(14,600 m3/acre)
(7,300 m3/acre) (5,000 m3/acre)
Crop management requires good greater fertilizer little fertilizer
management requirement; requires required; less pest and
moderate management disease complex; easy
management
Yield per acre 25 – 30 tons 30 – 40 tons 20 – 25 tons
Sugar content on 10 – 12% 15 – 18% 7 – 12%
weight basis
Sugar yield 2.5 – 4.8 tons/acre 4.5 – 7.2 tons/acre 2 – 3 tons/acre
Ethanol 450 – 720 gallons/acre 740 – 1100 300 – 440 gallons/acre
production gallons/acre
directly from
juice
Harvesting harvested harvested very simple; both
mechanically manual and through
mechanically mechanical harvested
Source: Almodares & Hadi 2009; Prasad et al 2007
39

52. GRAIN SORGHUM
Introduction
Grain sorghum (Sorghum bicolor L. Moench) is known with a variety of names:
great millet and guinea corn in West Africa, kafir corn in South Africa, dura in Sudan,
mtama in eastern Africa, jowar in India and kaoliang in China (Purseglove 1972). In the
USA sorghum is usually referred to as milo, which belongs to the tribe Andropogonae of
the grass family Poaceae (FAO 1991). Sorghum is a genus with many species and
subspecies; with several types of sorghum, including grain sorghums (for food), grass
sorghums (for pasture and hay), sweet sorghums (for syrup), and Broomcorn. Similar to
corn, sorghum uses the C4 malate cycle. This is the most efficient form of photosynthesis
and also has greater water use efficiency than C3 plants. Grain sorghum needs less water
than corn, so it is likely to be grown as a replacement to corn and can produce better
yields than corn in hotter and drier areas. Because of sorghum’s high water-use efficiency
and drought tolerance ability it can be successfully grown in a wide range of
environments like hot and dry subtropical and tropical regions. However, under optimal
conditions, grain yield potential of sorghum is equal to or greater than other cereal grain
yields, except corn (Rooney et al. 2007).
Importance and Uses
Grain sorghum is the fifth leading cereal crop in the world after corn, wheat, rice,
and barley, and also the third most important cereal crop grown in the USA. The United
States is the world’s largest producer of grain sorghum followed by India and Nigeria.
Sorghum is a leading cereal grain produced in Africa and one of the important food
sources in India. The leading exporters of grain sorghum are the USA, Australia and
40

53. Argentina (U. S. Grains Council 2010). Sorghum grain constitutes the main food source
for over 750 million people who live in the semi-arid tropics of Africa, Asia, and Latin
America. Globally over half of all sorghum produced is used for human consumption
(FAO 2007; National Sorghum Producers 2006). Grain sorghum has the potential to offer
the best opportunity to satisfy the doubling demand for food in the developing world by
2020, by providing food for the poor and an alternative to corn for feed and food (Harlan
and de Wet 1972; Maunder 2005).
For the year 2005, total annual sorghum grain production was 58.6 million MT
from approximately 44.7 million ha. This represents an average yield of 1.31 MT/ha
(FAOSTAT 2006). The largest acreages of grain sorghum are centered in Sub-Saharan
Africa and India, where it plays a vital role of providing food grain, feed grain and
forage, and is even used as a fuel source (combustion) in industry. The highest average
sorghum grain yields are produced in countries like the USA, Mexico, Argentina, and
Australia where commercial agriculture has adopted sorghum hybrids and conditions are
more favorable to production. Presently, almost all the ethanol production plants in the
USA depend on starch conversion, primarily from corn grain. However, grain sorghum
can also be used as a starch source for the production of ethanol. Commercial ethanol
plants located in sorghum production regions in the USA can depend on sorghum as their
primary starch source (Rooney et al. 2007).
According to the USDA’s November, 2009 crop production report; corn
contributes 95.6 percent of the nation’s total feed grain production with 2.7 percent from
grain sorghum. From the national perspective, it is clear that corn will remain the
41

54. dominant feedstock for starch-based ethanol production plants, because it has greater
production potential than sorghum (Wisner 2009). However, certain parts of the U.S. can
use grain sorghum as an alternative feedstock for ethanol production due to the
availability of grains at low cost.
SWITCHGRASS
Introduction
Switchgrass (Panicum virgatum L.) is a perennial warm-season grass, native to
North America. It is a vigorous bunchgrass that grows throughout most of the United
States. It can adapt well to a variety of soil and climatic conditions. Switchgrass is most
productive on moderately well to well-drained soils of medium fertility with a soil pH at
5.0 or above (Garland 2008). With an extensive root system the plant can reach heights
up to 10 feet. Once established, switchgrass well-managed for biomass production should
have a productive life of 10-20 years. Within the stand, switchgrass is an extremely
strong competitor. However, it is not considered as an invasive plant (Garland 2008).
Importance and Uses
Switchgrass can act as exceptional forage for pasture and hay for livestock. It also
provides excellent cover for wildlife populations and seeds are a quality food source for
game birds. Switchgrass is most abundant and plays an important role as a forage and
pasture grass in the central and southern Great Plains.
Switchgrass has been identified as a promising bioenergy feedstock since the
1980s through the studies conducted by the US Department of Energy (DOE). It has been
under investigation in Canada as a bioenergy crop since 1991 (Samson 2007). It has been
researched in the United States as a mid-summer forage crop since 1940 and is most
42

55. commonly used for livestock forage in the south-central states. In the 1990’s it was
widely used in the Conservation Reserve Program (CRP) in the United States. To
enhance its erosion control and biodiversity value it is now recommended in the latest
Conservation Reserve Enhancement Program (CREP) to be used in mixtures with other
warm-season grasses (Samson 2007). Switchgrass, a perennial herbaceous plant, is being
evaluated as a cellulosic bioenergy crop (Schmer et al. 2007). Due to the high cellulosic
content of switchgrass it is a candidate as a feedstock for ethanol production. It is
estimated that it has the ability to yield adequate biomass to produce approximately 500
gallons of ethanol per acre (Garland 2008).
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56. CHAPTER III
MATERIALS AND METHODS
This study focuses on analyzing the economic feasibility of three ethanol
production methods in the Texas Panhandle Region: 1) starch to ethanol, 2) sugar to
ethanol, and 3) cellulose to ethanol. Since there is no market for sweet sorghum or
switchgrass in the Texas Panhandle Region, it is not possible to determine a price
directly. It is necessary to base the analysis on the final demand for ethanol. It is then
possible to estimate the maximum price that a rational processor would be willing to pay
for the feedstock input by subtracting the farm-to-wholesale marketing margin from the
final demand price to get the derived demand price for the feedstock used in the
production of ethanol. Total gross income from the production of the feedstock is then
calculated by measuring the yield per acre in gallons of ethanol produced by the
feedstock and multiplying by the derived demand price. The feasibility of ethanol
production from each feedstock is then determined by subtracting the total production
cost per acre from the gross income per acre to determine the return over specified costs
and economic return.
44

57. The study area includes the top 26 counties of the Texas collectively known as the
Texas Panhandle, Figure 9. The area is in a rectangular shape bordered by New Mexico
to the west and Oklahoma to the north and east. The crop growing season averages
between 200 to 217 days per year. The average annual rainfall averages between 17 to
20.5 inches.
Panhandle
Source: Texas County Map 2006
Figure 9. Map of Texas with Panhandle Region indicated in box
45

58. Corn, wheat, and grain sorghum are the important feed grain crops in the Texas
Panhandle. Cotton is the most important fiber crop in this region, Table 6. The five year
average (2005-2009) for harvested acres of corn, wheat, cotton, and grain sorghum in the
26 county area are 643,000 acres, 1,266,800 acres, 436,000 acres, and 357,700 acres
respectively. Average total production for the four major crops are 131,042,000 bushels
of corn, 45,755,250 bushels of wheat, 763,420 bales of cotton, and 21,558,600 bushels of
grain sorghum, Table 6.
Table 6. Harvested acres and Production of major crops: Corn, Wheat, Cotton, and
Grain Sorghum in the 26 counties in the Texas Panhandle, 2005 - 2009
Corn Wheat
Year Harvested Production Harvested Production
(1000 acres) (1000 bushels) (1000 acres) (1000 bushels)
2005 559.6 106,543 1,570.3 55,996
2006 523.1 101,202 545.3 14,061
2007 733.4 154,292 1,797.6 79,045
2008 686.7 141,228 1,153.9 33,919
2009 711.9 151,945 - -
Average 643.0 131,042 1,266.8 45,755
Cotton Grain Sorghum
Year Harvested Production Harvested Production
(1000 acres) (bales) (1000 acres) (1000 bushels)
2005 585.5 1,052,700 345.4 22,207
2006 574.2 1,019,700 294.4 14,636
2007 340.2 677,700 396.9 26,121
2008 337.2 503,700 431.2 23,514
2009 342.5 563,300 320.6 21,239
Average 436.0 763,420 357.7 21,559
Source: National Agricultural Statistics Service (2005-09)
46

59. Generally corn is the major starch based feedstock used to produce ethanol in the
United States. High water requirement in the production of corn and the impact of the
increased demand for corn on the price and availability of food are the main concerns that
lead to the search for an alternative starch based feedstock. Sugarcane is the predominant
sugar based feedstock used to produce ethanol in Brazil and the United States. The heavy
water use during the cultivation period and long season requirement of the crop are some
major concerns prompting the search for an alternative sugar based feedstock. Cellulosic
ethanol is considered a second generation biofuel. More research is needed on cellulosic
feedstocks to determine which will be economically feasible in production as well as in
the processing of the final product.
Selection of Feedstock Source
Since many kinds of agricultural products can be converted into ethanol, the
choice of feedstock selection is based on both biological and economic criterion. Since
the price of conventional gasoline fuel in the United States is not yet as high as the world
market price, the development of alternative fuels has been promoted by government
subsidies and research and development grants. Many alternative plant species and
technologies are being researched to determine the potential for alternative fuels.
Characteristics used in the evaluation of alternatives include production cost, selling price
of the main product and byproduct, processing cost, ethanol yield, and availability by
season and region, and procurement cost.
Feedstock suitable for use in ethanol production via fermentation process must
contain starches, sugars, or cellulose that can be readily converted to fermentable sugars.
47

60. Feedstocks are classified into three groups based on their contribution of starches, sugars,
or cellulose which can be used for the production of ethanol (Mathewson 1980; Mother
Earth Alcohol Fuel 1980).
The three groups include:
1) Saccharine (sugar) containing materials in which the carbohydrate is present as
directly fermentable sugar molecules such as glucose, fructose, or maltose. Crops
such as sugarcane, sweet sorghum, sugar beets, and fruits are the major sugar
producing crops.
2) Starchy materials contain complex carbohydrates. These carbohydrates must be
broken down into fermentable sugars by hydrolysis with acid or enzymes. Crops
such as grains, potatoes, and artichokes are the major starch producing crops.
3) Cellulosic materials contain a complex form of carbohydrates bonded by a
substance called lignin which must be broken down with acid and enzyme
hydrolysis. Cellulosic materials such as grasses, wood, stover, waste material,
paper, and straw are the major source of cellulose.
This study considers grain sorghum as a starch based ethanol, sweet sorghum as a
sugar based ethanol, and switchgrass as a cellulose based feedstock to evaluate the
economic feasibility of ethanol production in the Texas Panhandle Region. These have
been selected because of their characteristic of low water requirement compared to corn
or sugarcane and characteristic of shorter growing periods than other crops.
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61. Current Situation of Selected Feedstocks Production
According to the USDA crop production reports, Texas is the second largest
producer of grain sorghum in the United States with 101.2 million bu., Figure 10. It can
be processed into ethanol with the same type of facility that converts corn grain into
ethanol (Wisner 2009). Also the co-product from grain sorghum ethanol, called distillers
grain soluble (DGS), is considered to be equal with corn DGS in value. A new highly
efficient ethanol plant typically has an annual capacity to produce about 100 million
gallons of ethanol. At that volume of output, a single plant takes approximately 35 to 36
million bushels of grain.
Source: Wisner 2009
Figure 10. Grain Sorghum Production by State, 2009
49

62. Potential of Selected Feedstocks in Panhandle
The choice of feedstock used to produce ethanol is based primarily on the
availability, potential, and cost of alternative feedstock crops in the region. Presently corn
is the predominant feedstock being used in the ethanol production process. Corn accounts
for approximately 97 percent of the total ethanol produced in the United States.
Grain sorghum is an important grain crop in the Texas Panhandle Region. It can
be grown under both irrigation and dryland conditions, Table 7. Average harvested acres
of irrigated grain sorghum in the 26 counties in the Texas Panhandle Region for 2005-
2009 is 104,600 acres. Average total grain production under irrigation is 9,358,000
bushels, Table 7. Average harvested acres of dryland grain sorghum are 154,480 acres
with an average total grain production of 6,811,000 bushels.
Table 7. Irrigated and Dryland Grain sorghum Acreages and Production in the top
26 Counties in the Texas Panhandle, 2005-2009
Acres harvested (1,000) Production (1000 bu.)
Year Irrigated Dryland Irrigated Dryland
2005 104.6 192.7 9,205 10,116
2006 110.6 163.4 9,178 4,676
2007 166.9 194.5 15,447 8,843
2008 54.3 91.8 4,389 3,924
2009 86.5 130.0 8,572 6,495
Average 104.6 154.48 9,358 6,811
Source: National Agricultural Statistics Service (2005-09)
50

63. There are no published statistics reporting the production of either sweet sorghum
or switchgrass in the Texas Panhandle. Sweet sorghum and switchgrass production is in
the experimental stage in the Texas Panhandle and surrounding region. Switchgrass is
included in trials at the TAMU research stations at Etter, Texas, and at the New Mexico
State University research centers at Tucumcari, New Mexico, and at Roswell, New
Mexico. Sweet sorghum is included in trials at the TAMU research station at Bushland,
Texas; and at the New Mexico State University research program at Clovis, New Mexico.
Yield levels of selected feedstocks in the Texas Panhandle Region used in the
analysis are irrigated grain sorghum 134 bushels/acre and dryland grain sorghum 36
bushels/acre, Table 8. Switchgrass yields under irrigated and dryland condition are 4.4
dry tons/acre and 1.4 dry tons/acre respectively. Sweet sorghum yields under irrigated
and dryland condition are 25 wet tons/acre and 12.35 wet tons/acre, respectively.
Table 8. Yields of Selected Feedstocks used in the analysis for the Texas Panhandle
Region (Appendix B-Table 1 and 2)
Yield/acre
Feedstock
Irrigated Dryland
Grain sorghum 134 bushels 36 bushels
Switchgrass 4.4 dry tons 1.4 dry tons
Sweet sorghum 25 wet tons 12.35 wet tons
51

64. Price of Ethanol
The state price of ethanol varies from $1.65 to $2.15 / (E-100) gallon in the
United States (Kment 2010). The average price of ethanol in the United States is about
$1.80 / (E-100) gallon. Day to day fluctuation in the price of ethanol depends on
changing prices of raw inputs and alternative products. The price of ethanol varies
between different states depending on the level of state subsidy to produce ethanol and
the economic feasibility of ethanol production.
The current, June 2010, prices of ethanol are: Texas $1.81, Oklahoma $1.82,
Kansas $1.71 and Colorado $1.78 / (E-100) gallon (Kment 2010). The profitability of
ethanol production is highly variable. Due to the volatile nature of the ethanol price and
prices of the feedstock inputs, its profitability can change rapidly from month to month.
In addition the price variations of ethanol by-products such as distillers dried grains with
soluble (DDGS), stillage, heat, electricity, and natural gas adds to the variability in
ethanol profits.
Feedstock Requirement
It takes one bushel of sorghum grain to produce about 2.9 gallons of ethanol
(Trostle 2008). At this conversion rate a 20 MGPY plant would need 6.9 million bushels
of grain to operate. A 60 MGPY plant would need 20.7 million bushels of grain and a
100 MGPY plant would need 34.5 million bushels of grain, Table 9.
It takes one ton of sweet sorghum fresh stalks to produce about 8.7 gallons of
ethanol (Bean et al. 2009; Marsalis 2010). At this conversion rate a 20 MGY plant would
need 2.3 million tons of fresh stalks to operate. A 60 MGY plant would need 6.9 million
52