Economic Feasibility of Ethanol Production - Thesis (PDF)

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

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Economic Feasibility of Ethanol Production - Thesis (PDF)

  1. 1. EVALUATION OF THE ECONOMIC FEASIBILITY OF GRAIN SORGHUM, SWEET SORGHUM, ANDSWITCHGRASS AS ALTERNATIVE FEEDSTOCKS FORETHANOL 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. 2. ABSTRACT Economic, environmental and political concerns centered on energy use fromconventional fossil fuels have led to research on alternative renewable energy fuel suchas ethanol. The goal of this thesis is to evaluate the potential of grain sorghum, sweetsorghum, and switchgrass for ethanol production in the Texas Panhandle Region usingthree alternative ethanol production methodologies: starch based ethanol, sugar basedethanol, and cellulose based ethanol respectively. The study area includes the top 26 counties of the Texas Panhandle. The potentialof three feedstocks: grain sorghum, sweet sorghum, and switchgrass for ethanolproduction in the Texas Panhandle Region is analyzed using yield and production costsof feedstock, processing cost of feedstock, final demand for ethanol, farm to wholesalemarketing 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 iscalculated 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 forgrain sorghum, sweet sorghum, and switchgrass respectively. The estimated ii
  3. 3. grain sorghum production cost per acre is $413.40 and $141.70 under irrigated anddryland conditions respectively. The estimated production costs of sweet sorghum andswitchgrass are $462.70 and $349.05 respectively under irrigated condition and $193.07and $102.32 respectively under dryland condition. The calculated total gross income peracre 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 $98.28respectively under dryland condition. An economic return is calculated by subtractingirrigated cash rent of $110.00 per acre and dryland cash rent of $25.00 per acre from netreturn of the selected feedstocks. The calculated economic returns per acre of grainsorghum, sweet sorghum, and switchgrass are -$45.37, -$410.19, and -$150.17respectively under irrigated condition and -$38.25, -$145.09, and -$29.04 respectivelyunder dryland condition. The evaluation in this study demonstrates that ethanol production from grainsorghum, sweet sorghum, and switchgrass in the Texas Panhandle Region is noteconomically feasible given the current price for ethanol in Texas. This is consistent withthe status of the ethanol industry in the Texas Panhandle. An increase in the price ofethanol would seem to justify a reevaluation of the economic feasibility. However, sinceany increase in the price of ethanol would occur only with an increase in the prices ofenergy inputs to the production process, the economic feasibility is not assured.Decreases in cost and increases in productivity may present possibilities for achievingeconomic feasibility. iii
  4. 4. ACKNOWLEDGMENTS This work would not have been accomplished without the continuous support andthoughtful insights of Dr. Arden Colette who has been instrumental in motivating me todevelop and complete this work. The views and guidelines provided by him were ofutmost importance with regard to the subject and application of learnt knowledgethroughout the time period involved in this study. I consider myself privileged to have been guided by my learned committeemember Dr. Bob A Stewart who has been an inspiration during the study period and mythesis development at West Texas A & M University. I also express my sincere gratitudeto Dr. Robert DeOtte for agreeing to provide useful guidance as a member of my thesiscommittee and suggesting improvements that were extremely important in creating thefinal shape of this research. I am heartily thankful to my major advisor, Dr. Lal K. Almas for providing aplatform for the foundation of this research and whose encouragement, guidance andsupport from the initial to the final level enabled me to develop an understanding of thesubject. This research was supported in part by the Ogallala Aquifer Program, aconsortium between USDA Agricultural Research Service, Kansas State University, iv
  5. 5. Texas AgriLife Research, Texas AgriLife Extension Service, Texas Tech University, andWest 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. 6. Approved:___________________________ _________________Chairman, Thesis Committee DateDr. Lal K. Almas___________________________ _________________Member, Thesis Committee DateDr. Arden Colette___________________________ _________________Member, Thesis Committee DateDr. Robert DeOtte___________________________ _________________Member, Thesis Committee DateDr. Bob A. Stewart ________________________ ________________ Head, Major Department Date Dr. Dean Hawkins ________________________ _________________ Graduate School Date vi
  7. 7. TABLE OF CONTENTSChapter 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. 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. 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. 10. LIST OF TABLESTable 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. 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. 12. LIST OF FIGURESFigure 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. 13. CHAPTER I INTRODUCTION There is an increasing need for energy throughout the world. Given currentconsumption trends, world energy demand is estimated to grow by 50% between 2005and 2030 (EIA 2008). As the economy grows, the energy requirement also grows.Traditional liquid fuels evolved from fossil resources are presently, and are predicted tocontinue to be, a dominant energy source, given their remarkable role in thetransportation sector (EIA 2008). Presently, more than 90% of the energy used fortransportation is derived from petroleum fuels. More than 60% of the petroleumconsumption is directed towards the production of gasoline and diesel fuel (Research andInnovative Technology Administration - Bureau of Transportation Statistics 2009).Petroleum is a possible pollutant, non-renewable and geographically limited to a fewcountries. Its use discharges huge amounts of greenhouse gases, mainly CO2, into theatmosphere. This increase in CO2 is postulated to contribute to the greenhouse effect andclimate change. The transportation sector accounts for approximately 13% of globalanthropogenic greenhouse gas (GHG) emissions (IPCC 2007). The rising prices of traditional energy fuels and increased scientific and political 1
  14. 14. discussions of evaluating alternative energy sources have resulted in growth of supportfor developing ethanol as a replacement or substitute fuel. The goal is to develop anenergy structure for the future that is renewable, sustainable, convenient, cost-effective,economically feasible, and environmentally safe. The availability of oil at low prices hasretarded the research study and interest in alternative fuels. Current geopolitical,environmental, and economical changes have led to an increasing interest in analternative 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 theUnited States is almost totally dependent on gasoline and diesel fuel which are obtainedfrom petroleum. According to the Energy Information Administration (EIA); U.S.gasoline consumption reached a record high of 9.30 million barrels a day (391 milliongallons/day) in 2007 before declining to about 9.00 million barrels a day in 2008. About7% of the gasoline consumed in 2008 was actually ethanol mixed gasoline. According toEIA 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 were1.81 million barrels/day, and dependence on net petroleum imports was 66.41% of thetotal requirement. Triggered by high oil prices, government subsidies and energy policies, a largeexpansion in ethanol production, along with research and innovation to develop secondgeneration biofuels is underway in the United States. This increased focus on ethanol andother biofuels is an important element of United States economic, energy, environmental, 2
  15. 15. and national security policies. The recent resurgence of interest in ethanol production hasspurred various stakeholders to request an unbiased analysis of the economic ethanolproduction potential in Texas. There has been increased interest in ethanol production recently for followingreasons: 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 fromgrains or other biomass sources such as sweet sorghum, switchgrass, wood chips, andother 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. Ethanoluse has been shown to reduce emissions, decrease the use of gasoline, and provide a fuelwhich is free from MTBE (Wyman 1996). Ethanol, also known as an ethyl alcohol, is ahigh proof form of grain alcohol. 3
  16. 16. Production of renewable fuels would contribute to our goal of reducing nation’sdependence on imported oil. Achieving the production goals for bio-ethanol productionwill require appropriate and promising bioenergy feedstocks with supplementation fromagricultural crop residues. The overall contribution of renewable energy is only 7% of the whole energysupply of the United States, Figure 1. Fifty-three percent of the renewable energy comesfrom biomass. Petroleum energy (37%), natural gas (24%), and coal (23%) account forthe greatest contribution in the nation’s whole energy supply, Figure 1. Solar (1%),geothermal (5%), wind (7%), and hydropower (34%) are other sources of renewableenergy 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. 17. These fossil fuels are a limited source of energy due to their depletion by time andnon-renewable characteristics. At this stage of increasing depletion of non-renewableenergy 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 areused, demand for fossil fuels is reduced. Biofuels have evolved as an alternative energy source to fossil fuels bysubstituting bioethanol and biodiesel for gasoline and diesel respectively. They have beenconsidered as alternative sources of energy due to their capacity to offset the reliance onforeign 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 toethanol technology, while the US uses corn as a major feedstock for ethanol productionby using starch to ethanol technology. In the United States there is ongoing technologydevelopment to produce ethanol from sugar, and ethanol from cellulose based feedstocks. This study analyses ethanol production potential by three alternativemethodologies for the Texas Panhandle: starch based ethanol, sugar based ethanol, andcellulose based ethanol. To be a viable ethanol production methodology for the TexasPanhandle, it needs to meet environmental as well as economic criteria. Feasibility of any ethanol production methodology for the Texas PanhandleRegion will be determined on the basis of economics of selected feedstock used, currentsituation of selected feedstock production, current production levels and yields ofselected feedstock, estimated net value residual to selected feedstock. 5
  18. 18. Research Objective The research objective of this study is to evaluate the economic feasibility of threeethanol 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 grainsorghum, sweet sorghum, and switchgrass respectively. 6
  19. 19. CHAPTER II LITERATURE REVIEW Research has been conducted on different aspects of the ethanol industry but therehas 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 ofliterature provides an overview of previous literature on ethanol, different ethanolproduction techniques, ethanol production and demand in the U.S., and sources offeedstock 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 andinnovation to foster second-generation biofuels, is underway in the United States. Theseare prompted by high oil prices and energy policies. This increased focus on ethanol andother biofuels production is an important aspect of United States economic, energy,environmental and national security policies (BR&DI 2000). The inconsistency in 7
  20. 20. political situation, the continued conflict in the Middle East and the reliance on foreignoil by the United States has forced policy makers and researchers to look for a moredependable, renewable and domestic fuel source. However, the volatile nature of oilprices is an economic concern. According to the United States Department of Energy (DOE 2007) theimportation of crude oil is increasing by period of time. Moreover, in 2005 crude oilimports attained a record of more than 10 million barrels per day. The reduction of ournation’s dependence on imported oil is identified as one of our greatest challenges. Toaddress this challenge, the United States needs a variety of alternative renewable fuels,including ethanol produced from cellulosic materials like grasses, wood chips; sugar richmaterials like sugarcane, sweet sorghum, sugar beet; and starch based materials like cornor sorghum grains. Fortunately, the United State has ample agricultural and forestresources 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 toproduce 60 billion gallons of ethanol per year. This would replace about 30% of ourcurrent 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-fuelslike bio-ethanol and bio-diesel, which are produced from renewable energy sources likebiomass, 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’ associatedwith the use of conventional fossil fuels. The rising price of energy as well as the limited 8
  21. 21. oil and gas reserves around the world has created a need to improve the renewable energyproduction. 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 theexpansion of alternative energy sources. Moreover, concern about the potentialassociation of increases in atmospheric CO2 due to the consumption of fossil fuels withglobal warming; is providing an additional motivation for the development of biofuelsthat can generate low net carbon emission (Rooney et al. 2007). The American Coalition for Ethanol (ACE), an advocacy group promotingethanol use, suggests that ethanol is a cleaner fuel source due to its perceivedenvironmental friendly nature than the traditionally used nonrenewable fossil fuelsources. As shown in Figure 2. the increasing cost of crude oil along with the UnitedStates’s movement towards decreasing the reliance on imported oil has lead to a boom ofthe biofuel industry. In addition, the government tax incentives and environmentalconcerns also have contributed to this boom. The remarkable increase in United Statesethanol production is enhancing ability to supply a major portion of our transportationfuel requirement. As of 2007 there were 180 completed ethanol production facilities with20 more processing plants under construction (ACE 2007). The advanced technology ofethanol production, increasing energy prices, concern over pollution from the use ofconventional fossil fuels, and tax incentives have prompted automobile manufacturers topromote vehicles that can easily be converted to use ethanol and gasoline blends withother future alternative energy sources (David et al. 2008). 9
  22. 22. David et al. (2008) noted that ethanol adds to the overall fuel supply of the UnitedStates and contributes to maintaining competitive and affordable fuel prices. Citiesaround the U.S. have been selling an ethanol blend (E85) and gasohol or E10 asalternative fuel sources for automobiles (DOE 2007). E85 is a blend of 85% ethanol and15% unleaded gasoline; whereas E10 is a blend of 10% ethanol and 90% unleadedgasoline.U.S. Ethanol Production and Demand The fuel ethanol industry in the U.S. has grown to a total annual productioncapacity of 13 billion gallons with an estimated 12 billion gallons per year of actualproduction (RFA 2010). There are 201 ethanol plants operating in 27 states and 14 newplants or plant expansions are underway (RFA 2010). New ethanol plant construction orexpansions 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 increasingscope and demand of ethanol usage over the use of conventional fossil fuels. Followingare the major factors that have driven demand for ethanol as an alternative renewable fuelsource (Hardy 2010): • High oil prices • National energy security • Ethanol tax incentives • Lower ethanol production costs with improved technology, and • Climate change concerns. 10
  23. 23. United States ethanol production (in billions of gallons) from the year 1980 to2009 is summarized in Figure 2. Ethanol production has increased from 175 milliongallons 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 YearsSource: American Coalition for Ethanol 2007, Renewable Fuels Association 2010Figure 2. U.S. Ethanol Production in Billions of Gallons (1980-2009) 11
  24. 24. Ethanol Production Techniques Fermentation is the conversion process of an organic material from one chemicalform to another form using enzymes produced by living microorganisms (Soltes 1980). Itplays a vital role in the production of ethanol from alternate feedstocks such as starchbased feedstocks, sugar rich feedstocks, and cellulosic feedstocks. Ethanol is produced byremoving starch from carbohydrates with the action of yeasts. Carbohydrates are made upof carbon, hydrogen, and oxygen with sugar and starch. Yeasts utilize fermentable sugarto convert it into ethanol (Reidenbach 1981). The steps in the ethanol production process by feedstock and conversion methodare summarized in Figure 3. The three major ethanol producing feedstocks: cellulose,sugar, and starch have three different production techniques with different harvesttechniques for each feedstock. In crops such as sugar cane or sweet sorghum, stalks arecut 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 cellulosiccrops, such as trees, the full plants are harvested; with grasses several harvests are madeto allow for regrowth of the plant. There are variations in by-products from the differentfeedstocks with respect to their ethanol production techniques. Heat, electricity, andmolasses are the by-products obtained from sugar based ethanol. Animal feed such asdistillers dried grain with solubles (DDGS) and wet distillers grain soluble (WDGS) arethe 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. 25. Source: International Energy Agency 2004Figure 3. Ethanol Production Steps by Feedstock and Conversion Technique 13
  26. 26. Source of feedstock to produce ethanol and their production process issummarized in Figure 4. Corn stover, switchgrass etc. are sources of cellulose. Whereascorn, 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 theproduction of ethanol, Figure 4.Source: Michael 2008Figure 4. Ethanol Feedstocks and Production Process 14
  27. 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) fermentationSugar crops (ex., Milling to extract Preparation is Storage may result insugar cane, sugar minimal loss of sugarsweet sorghum,sugar beets, High yields of Cultivation practicesJerusalem ethanol per acre are not wide-spread,artichoke) especially with Crop co-products “nonconventional” have value as fuel, crops livestock feed, or soil amendmentStarch crops: Milling, Storage techniques Preparation involves liquefaction, and are well developed additional equipment,Grains (ex., saccharification labor and energy costscorn, sorghum, Cultivation practiceswheat, barley) are widespread with DDG from aflatoxin grains contaminated grain isTubers (ex., not suitable as animalpotatoes, sweet Livestock co-product feedpotatoes) is relatively high in protein.Cellulosic: Milling and Use involves no No commercially cost- hydrolysis of the integration with the effective process existsCrop residues linkages livestock feed market for hydrolysis of the(ex., corn stover, linkageswheat straw) Availability is wide- spreadForages (ex.,switchgrass,alfalfa, foragesorghum)Source: Mother Earth Alcohol Fuel 1980 15
  28. 28. General Chemistry of Ethanol Production The chemical equations describing the reactions which occur during ethanolproduction from the alternative feedstocks: starch based, sugar based, and cellulose basedis described by Reidenbach (1981).Conversion of Starch-based Feedstock into EthanolHydrolysis (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) andconverted it into sucrose (C12H22O11) with the reaction of amylase. This process is calledhydrolysis 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 thestarch hydrolysis in the previous process and converted into glucose (C6H12O6) with thereaction of invertase. This process also called saccharification.Fermentation Yeast Glucose Ethanol + Carbon dioxide (C2H12O6) 2(C2H5OH) + 2(CO2) 16
  29. 29. (1 kg) (0.511kg) + (0.489kg)Fermentation is the last process of starch to ethanol conversion technique in whichglucose (C2H12O6) is converted into ethanol and carbon dioxide with the action of yeast.Conversion of Sugar-based Feedstock into EthanolFermentation 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 formof 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 efficiencyof ethanol production plant.Conversion of Cellulose-based Feedstock into EthanolHydrolysis (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) andconverted into glucose (C6H12O6) with the reaction of acid or enzymes. This process iscalled hydrolysis or cellulose conversion.Fermentation Yeast Glucose Ethanol + Carbon dioxide (C2H12O6) 2(C2H5OH) + 2(CO2) + Heat 17
  30. 30. (1 kg) (0.511kg) + (0.489kg)Then in the process of fermentation glucose is converted into ethanol and carbon dioxidewith the action of yeast. This process is called fermentation. Physical, chemical and thermal properties of ethanol are listed in Table 2. Boilingtemperature of ethanol is 78.50C with a molecular weight of 46.1. Chemical formula ofethanol is C2H5OH with 52.1%, 34.75, and 13.1% by weight of carbon, oxygen, andhydrogen respectively, Table 2.Table 2. Physical, Chemical, and Thermal Properties of EthanolPhysical Properties of EthanolSpecific gravity 0.79 gm/cm3Vapor pressure (380) 50 mm HgBoiling temperature 78.50CDielectric constant 24.3Water solubility ∞Chemical Properties of EthanolFormula C2H5OHMolecular weight 46.1Carbon (wt) 52.1%Hydrogen (wt) 13.1%Oxygen (wt) 34.7%C/H ratio 4.0Stoichiometric ratio (Air/ETOH) 9.0Thermal Properties of EthanolLower heating value 6,400 kcal/kgIgnition temperature 350CSpecific heat (kcal/kg-0C) 60Melting point -1150CSource: ISSAAS 2007. 18
  31. 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 therest of the plant is cellulose. Using the bulky portion of the plant may be more efficientthan using other portions of the plant. Some grasses have higher energy storage in theform of cellulose when compared to corn in the form of grain, and can be grownefficiently with less application of nitrogen based fertilizer, low pesticides use, and lessprocessed energy. Cellulosic ethanol is a second generation biofuel, as opposed to ethanolmade from corn which is considered a first generation biofuel. The important differenceis 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 highenergy inputs. Cellulosic feedstocks are under research and will be used for ethanol productionin the upcoming years. Crop byproducts like corn stover, grain straw, rice hulls, paperpulp, and sugarcane bagasse; wood chips; and native grasses such as switchgrass aremajor cellulose based feedstocks which can be converted easily into ethanol. Research inadvanced technology is directed to make cellulosic ethanol more economical so it canattain a commercial level of production. According to Rinehart (2006) switchgrass is not only the most suitable biomassspecies to produce cellulosic based ethanol, it also bears some ecological characteristicsthat makes it a very good competitor among all cellulosic feedstocks. Positivecharacteristics of switchgrass include high cellulose yields, resistance to pests anddisease, superior wildlife habitat, low fertility requirements, can tolerate poor soils and 19
  32. 32. wide variations of soil pH, drought and flood tolerant, can use water efficiently ingrassland 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 toproduce ethanol (Mosier and Illeleji 2006). It is produced by every living plant on theearth, 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 cornstover, straw, forages, grasses, and wood wastes etc. could be feasibly collected andprocessed in the U.S. each year. This could contribute approximately 67 billion gallons ofethanol. 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: acidhydrolysis, enzymatic hydrolysis, and thermo-chemical (Badger 2002). Cellulose can beconverted into ethanol by using current technology. The technology at the front end ofthe 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 basedfeedstocks (Mosier and Illeleji 2006). In order for cellulose based ethanol to becompetitive with grain based ethanol, there are some major challenges associated withreducing the costs related to production, harvest, transportation, and pretreatment of thecellulosic feedstock (Eggeman and Elander 2005). There are also some processingchallenges associated with the biology and chemistry of the processing steps of cellulosic 20
  33. 33. ethanol. Advances in biotechnology and engineering are expected to make substantialgains toward attaining the goals of improving efficiency and yields in converting plantcellulose to ethanol (Mosier 2006). Although there are similarities between the cellulosic and grain ethanolproduction techniques, there are three important steps (pretreatment, hydrolysis, andfermentation) involved in the production of cellulosic ethanol that are different fromgrain ethanol (Mosier 2006). The steps in the ethanol production process fromswitchgrass are summarized in Figure 5. Pretreatment is the process done to soften the cellulosic feedstock to make thecellulose more susceptible to being broken down and accessible before it is broken downinto simple sugars. Thus the following hydrolysis step is more efficient because thebreakdown of cellulose into simple sugar is faster, higher in yield, and requires fewerinputs like enzymes and energy (Mosier 2006). The leading pretreatment technologiesunder development use a combination of chemicals (water, acid, caustics, and/orammonia) and heat to partially break down the cellulose or convert it into a more reactiveform (Mosier et al. 2005). According to Eggeman and Elander (2005), betterunderstanding of the chemistry of plant cell walls and the chemical reactions that occursduring pretreatment processes is leading to improvements in these technologies whichcan reduce the cost of ethanol production. Hydrolysis is the process where the cellulose and other sugar polymers are brokendown 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. 34. in industrial applications (Mosier et al. 1999). Biotechnology has allowed these enzymesto 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. 35. In the process of fermentation, the equipment and processing technology used toproduce ethanol from cellulose is the same as for producing ethanol from grain (Mosier2006). In addition, yeast used in starch-based ethanol production can use glucose derivedfrom cellulose. Distillation and recovery is the last step in cellulosic ethanol production similar toethanol production from grain. Since ethanol has a lower boiling point than water it canbe separated by a process called “distillation.” The conventional distillation orrectification system has the ability to produce ethanol at 92-95% purity. The remainingwater is then removed by using molecular sieves that selectively absorb the water from anethanol or water vapor resulting in approximately pure ethanol (>99%) (Mosier andIlleleji 2006). Cost competitiveness of cellulosic ethanol with corn based ethanol is shown inTable 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 totalproduction cost of cellulosic ethanol between year 2007 and 2012 reflects decreasedfeedstock cost and processing cost combined with increased production efficiency ofethanol from 60 gallons/dry ton to 90 gallons/dry ton of cellulosic feedstock. In the DOEtarget the cost of cellulose based feedstock declines from $60/dry ton in 2007 to $30/dryton in 2012 and cost of enzymes to produce one gallon of ethanol declines from $0.40 to$0.10, Table 3. 23
  36. 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 -$0.09Enzymes $0.04 $0.40 $0.10Other Costs** $0.62 $0.80 $0.22Capital Cost $0.20 $0.55 $0.54Total $1.65 $2.65 $1.10Note: g = gallon, bu = bushel, dt = dry ton1 = 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 2007Sugar-based Ethanol The production of ethanol from the sugar-based feedstocks was one of man’searliest pursuits into value-added processing. The technique used for the production ofethanol from sugar-based feedstocks is the same as starch-based ethanol productionexcept for some of the pretreatments of feedstocks. After harvesting, sugar rich stalks need to be processed through several steps toget ethanol. The first step in this process is juice extraction. In this step juice is extractedby a series of mills (Almodares and Hadi 2009) pressing the freshly harvested sugar richstalks. These stalks harvested fresh have a moisture content of about 75% (Cundiff andWorley 1992). The primary goal of increasing ethanol production requires removing asmuch sugar from the fresh stalks in the process of juice extraction as possible. Fifty toone hundred tons of pressure should be applied on the fresh stalks when they pass 24
  37. 37. through rollers to extract the sweet juice. About 55 lbs. of juice will be extracted from100 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 andcellulose, because sugar is readily available from the sugar rich stalks to ferment intoethanol. Whereas in starch and cellulose based ethanol they have to go through variousprocesses 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 issummarized in Figure 6. In the process of ethanol production from sugar rich stalks, thefirst step is the milling of stalks to extract the sugar juice. The juice coming out of millingsection 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 vacuumfilter. The filtrate juice is then sent to the evaporation section for concentration. The juicecan also be sent directly to fermentation to produce ethanol or it can be concentratedusing evaporators depending on the selected design. In case of sugar juice to ethanolproduction 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 isan internally balanced oxidation-reduction reaction (Kundiyana 2006; and Kundiyana etal. 2006). In this process juice or syrup is converted into ethanol, carbon dioxide, yeastbiomass as well as minor end products like glycerol, fusel oils, aldehydes, and ketones by 25
  38. 38. the reaction of yeast, Saccharomyces cerevisiae (Almodares and Hadi 2009, Jacques etal. 1999). Distillation and dehydration is the last step in the sugar based ethanol productionprocess. During distillation, alcohol from fermented mash is concentrated up to 95percent volume per volume (v/v). It is then further concentrated to a minimumconcentration of 99.6 percent to produce ethanol (Almodares and Hadi 2009). Vinassedeveloped in the distillation step can be concentrated up to 20 - 25 percent solidsfollowed by press-mud-composting which further concentrates to 55 percent solids foruse 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. 39. Starch-based Ethanol Presently, almost all the ethanol producing plants in the United States are basedon high starch content feedstock such as corn grain. Grain sorghum can also be used as asource of starch for ethanol production. Commercial ethanol plants located in sorghumproduction regions in the United States can easily rely on sorghum as their primary starchsource (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 ethanolfrom starch-based feedstocks: wet milling and dry milling. In the United States, commercial production of ethanol from starch based grainssuch as corn, grain sorghum, wheat etc. involves breaking down the starch into simplesugars (glucose), feeding these sugars to yeast (fermentation), and then obtaining themain product ethanol and byproducts like DDGS, carbon dioxide etc. (Mosier and Illeleji2006). Starch content of corn varies between 70 to 72 percent. Sorghum varies between68 to 70 percent starch (Shapouri et al. 2006). There is not much difference between cornand sorghum starch content. Wet milling and dry milling are the two major industrialmethods used in the United States for producing fuel ethanol. Dry milling and wetmilling plant accounts for about 79 percent and 21 percent of total ethanol productionrespectively (Shapouri et al. 2006). Wet milling plants are more expensive to build than dry milling plants but moreflexible in terms of the products they can produce. Although they yield slightly lessethanol per bushel than the dry mills, wet mills have more valuable byproducts. 27
  40. 40. Originally wet milling plants accounted for most of the ethanol production in the UnitedStates, but because of the lower building costs of dry mills, the new construction hasshifted from wet mills to dry mills (Rendleman and Shapouri 2007). In 2004, 75 percentof ethanol production came from dry milling plants and only 25 percent from wet millingplants (RFA 2006). In fact, dry milling plants have higher yields of ethanol per bushelgrain 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 drymill can have lower initial construction costs but also generates lower valued byproductssuch as distillers dried grain (DDG). Mosier and Illeleji 2006 state that; it is called “wet” because the first step in thewet milling process involves soaking the grain in water to soften the grain and make iteasier to separate the various components of the grain. During fractionation the variouscomponents 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 inFigure 7. In the dry milling process, the whole grain is processed and the remainingcomponents are separated at the end of the process. There are six major steps: milling,liquefaction, saccharification, fermentation, distillation, and recovery involved in the drymilling method of ethanol production (Mosier and Illeleji 2006). Milling is the first step in dry-grind method of ethanol production, Figure 7. Itinvolves processing grains through a hammer mill to produce grain flour. This wholegrain flour is then slurried with water and heat stable enzyme (α-amylase) is added. 28
  41. 41. DryingSource: Viraj Alcohols Limited 2010Figure 7. Diagrammatic Representation of Grain Feedstock to Ethanol 29
  42. 42. Liquefaction is the second step of dry-grind method of ethanol production, Figure7. The slurry obtained from the previous step is cooked. This step is practiced by usingjet-cookers that inject steam into the grain flour slurry to cook it at temperatures above1000C (2120F). The heat and mechanical shear of the cooking process breaks and separatethe starch granules present in the grain endosperm. The enzymes then break down thestarch 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 tocontinue 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 intosimple sugar called glucose. Saccharification occurs while the mash is filling thefermentor in preparation for the next step (fermentation) and continues throughout thenext step (Mosier and Illeleji 2006). Fermentation is the fourth step of dry-grind method of ethanol production. Theyeast grown in seed tanks is combined with the grain mash to begin the process offermentation, converting the simple sugars to ethanol. The other components of the grainremain 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 batchferments completely before the tank is drained and refilled with a new batch. The up-stream processes like grinding, liquefaction, and saccharification and the down-streamprocesses like distillation and recovery occur continuously. During these processes grain 30
  43. 43. is continuously processed through the equipment. Dry-milling ethanol production plantsof this design commonly have three fermentation tanks. At any given time one tank isfilling, one tank is fermenting (usually for 48 hours) and one tank is emptying andresetting for the next batch (Mosier and Illeleji 2006). Carbon dioxide is also generated during the fermentation process. Usually it is notrecovered 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 icefor cold product storage and transportation. After the completion of the fermentationprocess, 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 continuousstream 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 ethanolproduction. The liquid portion of the slurry remaining after the fermentation process has8-12% ethanol by weight. Because ethanol has a lower boiling point than the water it canbe separated by a process called “distillation.” The conventional distillation orrectification system has the ability to produce ethanol at 92-95% purity. The remainingwater is then removed with the help of molecular sieves that selectively absorb the waterfrom 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 processof distillation is called “stillage.” This stillage is used to produce valued byproducts likewet cake or distillers grains and distillers dried grain with solubles (DDGS). 31
  44. 44. Conventional Ethanol versus Cellulosic Ethanol Although conventional (starch based) and cellulosic ethanol are produced byusing different feedstocks and techniques, the result is the same product. Ethanolproduced 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 processor wet milling process. In the dry milling process, liquefied grain starch is produced byheating grain meal and adding water and enzymes. These enzymes convert the liquefiedstarch to sugars and finally the sugars are fermented by yeast into ethanol. In the wetmilling process the fiber, germ and protein are separated from the starch before it isfermented into ethanol. On the other hand, conversion of cellulosic feedstocks to ethanolrequires three important processing steps: pretreatment, saccharification, andfermentation (Burden 2009). Pretreatment requirements vary with the differentfeedstocks. Cellulosic ethanol displays three times higher net energy content than theconventionally produced ethanol from corn, and also some of the cellulosic ethanolproduction systems pass far lower net levels of greenhouse gases (GHG). Mostconventional (starch-based) ethanol production systems use fossil fuel to create heat forfermentation and other processing steps and produces GHG emissions. Many cellulosicethanol production systems use some part of the input biomass feedstock rather thanfossil fuel to generate heat (Burden 2009). 32
  45. 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 orgrain sorghum yields approximately 17 pounds of distillers grain, and 17 pounds ofcarbon dioxide as by-products (Outlaw et al. 2003). DDGS contains all the nutrients fromthe grain except starch. Generally, DDGS contains 27 percent protein, 11 percent fat, and9 percent fiber (Outlaw et al. 2003). Nutritional content variations of DDGS summarizedin Table 4. It is a source of protein which can be sold either dry or wet. This DDGS canbe 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 25.5-30.7Fat 8.9-11.4Fiber 5.4-6.5Calcium 0.017-0.45Phosphorus 0.62-0.78Sodium 0.05-0.17Chloride 0.13-0.19Potassium 0.79-1.05Amino acids % total amino acidMethionine 0.44-0.56Cystine 0.45-0.60Lysine 0.64-0.83Arginine 1.02-1.23Tryptophan 0.19-0.23Threonine 0.94-1.05Source: Noll 2004 33
  46. 46. Fermentation of starch grain produces about equal amounts of carbon dioxide andethanol. 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 ethanolproducer to sell carbon dioxide it is very essential that a user must be nearby and the CO2produced must be available long enough to justify the cost of the CO2 recovery andpurification equipment (McAloon et al. 2000). Stillage or bagasse is the major by-product obtained from the conversion of sugarbased feedstocks such as sugar cane or sweet sorghum into ethanol. It is the biomassremaining after the juice has been extracted from the stalks. It can be used to produceelectricity 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 inmacro and micronutrients (Reddy et al. 2007). Heat, electricity, lignin, animal feed, andbioplastics are the by-products obtained from the conversion of cellulose basedfeedstocks into ethanol.SWEET SORGHUMIntroduction The term sweet sorghum is used to distinguish varieties of sorghum with highconcentration of soluble sugars in the plant sap or juice (Vermerris et al. 2007). It is a C-4species plant having wide flat leaves and rounded head full of grain at the stage ofmaturity. It can be grown and survive successfully in semi-arid tropics, where other cropsfail to thrive. It is highly suitable for tougher dry-land growing areas. It can produce veryhigh yields with irrigation. During very dry periods, sweet sorghum can go into 34
  47. 47. dormancy, with growth resuming when sufficient moisture levels return (Gnansounou etal. 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 thedesert. 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 theprimary feedstock, with the remaining 40 percent using grain crops as the primaryfeedstock (Salassi 2007). Sweet sorghums are used as an alternative sugar source in areaswhere sugarcane is not produced or failed to survive (Rooney 2004). Because of the highsugar content of sweet sorghum, it may also be accessible to the sugar production forconversion to ethanol, using the same methodology used in sugarcane for ethanolproduction. It can be grown as an alternative to sugarcane and has been identified as apromising 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 readilyfermentable sugars associated with very high yields of green biomass. The sap of thiscrop is extracted by the process of milling. After extraction, the sugars from sweetsorghum stalks can be fermented easily to produce ethanol. Syrup, molasses, and crystalsugar 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 forthe production of ethanol by using currently available conventional fermentationtechnology. The byproducts, like bagasse (crushed stalks), that remains after removal of 35
  48. 48. juice from the sweet stalks can be burnt to create electricity or steam that can be a part ofco-generation strategy. Additionally, the bagasse available after juice removal could beutilized as a feedstock for cellulosic ethanol production technology (Vermerris et al.2007). According to the ICRISAT, the stillage obtained from sweet sorghum after theextraction of sweet juice has a higher biological value than that of bagasse which isobtained from sugarcane when used as forage for livestock, as it is rich in micronutrientsand minerals. Additionally, the level of pollution in sweet sorghum-based ethanolproduction has one fourth of the biological oxygen demand (BOD) (19,500 mg/liter) andlower chemical oxygen demand (COD) (38,640 mg/liter) compared to molasses–basedethanol production (Reddy et al. 2007). Traditional sweet sorghum varieties produce low grain yields. However, recentlyvarieties with more balanced grain as well as sugar production have been developed inChina and India. These varieties are the best example of dual-purpose crops, where grainscan 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 canuse both sugars and grains for the production of ethanol (Vermerris et al. 2007). Inaddition to sweet stalks, this crop gives grain yield of 2 to 2.5 tons/ha and this can beused as food or feed (Reddy et al. 2007). While single-cut yields may be low, themultiple cutting potential of this crop increases cumulative yields with an increasedgrowing season (Rooney et al. 2007). The ICRISAT, headquartered in the Indian state of Andhra Pradesh, has foundthat individual stalks of sweet sorghum grow up to 10 ft (3 m) in height in dry, saline, and 36
  49. 49. flooding conditions, tolerates heat, and can be used to produce both ethanol and food. Incomparison to corn where an individual stalk can be used only once to produce eitherethanol or food, with sweet sorghum the grain can be removed for food processing beforethe stalk is crushed to extract the sugary liquid that is used to produce ethanol. Sweetsorghum can be a potential feedstock for ethanol production due to the characteristics ofhigh fermentable sugars, low fertilizer requirement, high water use efficiency (1/3 ofsugarcane and 1/2 of corn), short growing period, and the ability to adapt well to diverseclimate and soil conditions (Wu et al. 2008). Sweet sorghum has both advantages and disadvantages in producing ethanol. Theinitial advantage is that sugars are directly available to fermentation without anyenzymatic treatment after simply extracting the sweet juice from biomass. The majordisadvantage is the requirement for fresh processing. The seasonal availability of thefresh feedstock limits the sugar extraction period. In sugar based ethanol productiontechnique, 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 cropsmostly available during specific seasons. These crops can’t be stored such as grains forlong period of time due to their high moisture content. It is a promising crop for biomass production due to its high yield and potential togenerate 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 DDGproduction), sugar juice (used for ethanol production), and bagasse (used to generate 37
  50. 50. electricity and heat). Other by-products can be produced such as carbon dioxide from thefermentation process, paper from bagasse or compost from leaves and roots, Figure 8.Source: Chiramonti et al. 2004Figure 8. Graphical Representation of Alternative Processes to Convert SweetSorghum to Energy Fuels 38
  51. 51. General characteristics of sugarcane, sugar beet, and sweet sorghum aresummarized in Table 5.Table 5. Comparison of Sugarcane, Sugar beet, and Sweet sorghumCharacteristics Sugarcane Sugar beet Sweet sorghumCrop duration about 12 - 13 months about 5 – 6 months about 4 monthsGrowing season one season one season all seasonSoil requirement grows well in drain grows well in sandy all types of drained soil loam; also tolerates soil alkalinityWater requires water less water less watermanagement 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 managementYield per acre 25 – 30 tons 30 – 40 tons 20 – 25 tonsSugar content on 10 – 12% 15 – 18% 7 – 12%weight basisSugar yield 2.5 – 4.8 tons/acre 4.5 – 7.2 tons/acre 2 – 3 tons/acreEthanol 450 – 720 gallons/acre 740 – 1100 300 – 440 gallons/acreproduction gallons/acredirectly fromjuiceHarvesting harvested harvested very simple; both mechanically manual and through mechanically mechanical harvestedSource: Almodares & Hadi 2009; Prasad et al 2007 39
  52. 52. GRAIN SORGHUMIntroduction 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 theUSA sorghum is usually referred to as milo, which belongs to the tribe Andropogonae ofthe grass family Poaceae (FAO 1991). Sorghum is a genus with many species andsubspecies; with several types of sorghum, including grain sorghums (for food), grasssorghums (for pasture and hay), sweet sorghums (for syrup), and Broomcorn. Similar tocorn, sorghum uses the C4 malate cycle. This is the most efficient form of photosynthesisand also has greater water use efficiency than C3 plants. Grain sorghum needs less waterthan corn, so it is likely to be grown as a replacement to corn and can produce betteryields than corn in hotter and drier areas. Because of sorghum’s high water-use efficiencyand drought tolerance ability it can be successfully grown in a wide range ofenvironments like hot and dry subtropical and tropical regions. However, under optimalconditions, grain yield potential of sorghum is equal to or greater than other cereal grainyields, 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 UnitedStates 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 foodsources in India. The leading exporters of grain sorghum are the USA, Australia and 40
  53. 53. Argentina (U. S. Grains Council 2010). Sorghum grain constitutes the main food sourcefor over 750 million people who live in the semi-arid tropics of Africa, Asia, and LatinAmerica. Globally over half of all sorghum produced is used for human consumption(FAO 2007; National Sorghum Producers 2006). Grain sorghum has the potential to offerthe best opportunity to satisfy the doubling demand for food in the developing world by2020, by providing food for the poor and an alternative to corn for feed and food (Harlanand de Wet 1972; Maunder 2005). For the year 2005, total annual sorghum grain production was 58.6 million MTfrom 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-SaharanAfrica and India, where it plays a vital role of providing food grain, feed grain andforage, and is even used as a fuel source (combustion) in industry. The highest averagesorghum grain yields are produced in countries like the USA, Mexico, Argentina, andAustralia where commercial agriculture has adopted sorghum hybrids and conditions aremore favorable to production. Presently, almost all the ethanol production plants in theUSA depend on starch conversion, primarily from corn grain. However, grain sorghumcan also be used as a starch source for the production of ethanol. Commercial ethanolplants located in sorghum production regions in the USA can depend on sorghum as theirprimary starch source (Rooney et al. 2007). According to the USDA’s November, 2009 crop production report; corncontributes 95.6 percent of the nation’s total feed grain production with 2.7 percent fromgrain sorghum. From the national perspective, it is clear that corn will remain the 41
  54. 54. dominant feedstock for starch-based ethanol production plants, because it has greaterproduction potential than sorghum (Wisner 2009). However, certain parts of the U.S. canuse grain sorghum as an alternative feedstock for ethanol production due to theavailability of grains at low cost.SWITCHGRASSIntroduction Switchgrass (Panicum virgatum L.) is a perennial warm-season grass, native toNorth America. It is a vigorous bunchgrass that grows throughout most of the UnitedStates. It can adapt well to a variety of soil and climatic conditions. Switchgrass is mostproductive on moderately well to well-drained soils of medium fertility with a soil pH at5.0 or above (Garland 2008). With an extensive root system the plant can reach heightsup to 10 feet. Once established, switchgrass well-managed for biomass production shouldhave a productive life of 10-20 years. Within the stand, switchgrass is an extremelystrong 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 alsoprovides excellent cover for wildlife populations and seeds are a quality food source forgame birds. Switchgrass is most abundant and plays an important role as a forage andpasture grass in the central and southern Great Plains. Switchgrass has been identified as a promising bioenergy feedstock since the1980s through the studies conducted by the US Department of Energy (DOE). It has beenunder investigation in Canada as a bioenergy crop since 1991 (Samson 2007). It has beenresearched in the United States as a mid-summer forage crop since 1940 and is most 42
  55. 55. commonly used for livestock forage in the south-central states. In the 1990’s it waswidely used in the Conservation Reserve Program (CRP) in the United States. Toenhance its erosion control and biodiversity value it is now recommended in the latestConservation Reserve Enhancement Program (CREP) to be used in mixtures with otherwarm-season grasses (Samson 2007). Switchgrass, a perennial herbaceous plant, is beingevaluated as a cellulosic bioenergy crop (Schmer et al. 2007). Due to the high cellulosiccontent of switchgrass it is a candidate as a feedstock for ethanol production. It isestimated that it has the ability to yield adequate biomass to produce approximately 500gallons of ethanol per acre (Garland 2008). 43
  56. 56. CHAPTER III MATERIALS AND METHODS This study focuses on analyzing the economic feasibility of three ethanolproduction methods in the Texas Panhandle Region: 1) starch to ethanol, 2) sugar toethanol, and 3) cellulose to ethanol. Since there is no market for sweet sorghum orswitchgrass in the Texas Panhandle Region, it is not possible to determine a pricedirectly. It is necessary to base the analysis on the final demand for ethanol. It is thenpossible to estimate the maximum price that a rational processor would be willing to payfor the feedstock input by subtracting the farm-to-wholesale marketing margin from thefinal demand price to get the derived demand price for the feedstock used in theproduction of ethanol. Total gross income from the production of the feedstock is thencalculated by measuring the yield per acre in gallons of ethanol produced by thefeedstock and multiplying by the derived demand price. The feasibility of ethanolproduction from each feedstock is then determined by subtracting the total productioncost per acre from the gross income per acre to determine the return over specified costsand economic return. 44
  57. 57. The study area includes the top 26 counties of the Texas collectively known as theTexas Panhandle, Figure 9. The area is in a rectangular shape bordered by New Mexicoto the west and Oklahoma to the north and east. The crop growing season averagesbetween 200 to 217 days per year. The average annual rainfall averages between 17 to20.5 inches. PanhandleSource: Texas County Map 2006Figure 9. Map of Texas with Panhandle Region indicated in box 45
  58. 58. Corn, wheat, and grain sorghum are the important feed grain crops in the TexasPanhandle. Cotton is the most important fiber crop in this region, Table 6. The five yearaverage (2005-2009) for harvested acres of corn, wheat, cotton, and grain sorghum in the26 county area are 643,000 acres, 1,266,800 acres, 436,000 acres, and 357,700 acresrespectively. Average total production for the four major crops are 131,042,000 bushelsof corn, 45,755,250 bushels of wheat, 763,420 bales of cotton, and 21,558,600 bushels ofgrain sorghum, Table 6.Table 6. Harvested acres and Production of major crops: Corn, Wheat, Cotton, andGrain 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 21,559Source: National Agricultural Statistics Service (2005-09) 46
  59. 59. Generally corn is the major starch based feedstock used to produce ethanol in theUnited States. High water requirement in the production of corn and the impact of theincreased demand for corn on the price and availability of food are the main concerns thatlead to the search for an alternative starch based feedstock. Sugarcane is the predominantsugar based feedstock used to produce ethanol in Brazil and the United States. The heavywater use during the cultivation period and long season requirement of the crop are somemajor concerns prompting the search for an alternative sugar based feedstock. Cellulosicethanol is considered a second generation biofuel. More research is needed on cellulosicfeedstocks to determine which will be economically feasible in production as well as inthe processing of the final product.Selection of Feedstock Source Since many kinds of agricultural products can be converted into ethanol, thechoice of feedstock selection is based on both biological and economic criterion. Sincethe price of conventional gasoline fuel in the United States is not yet as high as the worldmarket price, the development of alternative fuels has been promoted by governmentsubsidies and research and development grants. Many alternative plant species andtechnologies are being researched to determine the potential for alternative fuels.Characteristics used in the evaluation of alternatives include production cost, selling priceof the main product and byproduct, processing cost, ethanol yield, and availability byseason and region, and procurement cost. Feedstock suitable for use in ethanol production via fermentation process mustcontain starches, sugars, or cellulose that can be readily converted to fermentable sugars. 47
  60. 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; MotherEarth 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 asugar based ethanol, and switchgrass as a cellulose based feedstock to evaluate theeconomic feasibility of ethanol production in the Texas Panhandle Region. These havebeen selected because of their characteristic of low water requirement compared to cornor sugarcane and characteristic of shorter growing periods than other crops. 48
  61. 61. Current Situation of Selected Feedstocks Production According to the USDA crop production reports, Texas is the second largestproducer of grain sorghum in the United States with 101.2 million bu., Figure 10. It canbe processed into ethanol with the same type of facility that converts corn grain intoethanol (Wisner 2009). Also the co-product from grain sorghum ethanol, called distillersgrain soluble (DGS), is considered to be equal with corn DGS in value. A new highlyefficient ethanol plant typically has an annual capacity to produce about 100 milliongallons of ethanol. At that volume of output, a single plant takes approximately 35 to 36million bushels of grain.Source: Wisner 2009Figure 10. Grain Sorghum Production by State, 2009 49
  62. 62. Potential of Selected Feedstocks in Panhandle The choice of feedstock used to produce ethanol is based primarily on theavailability, potential, and cost of alternative feedstock crops in the region. Presently cornis the predominant feedstock being used in the ethanol production process. Corn accountsfor 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 canbe grown under both irrigation and dryland conditions, Table 7. Average harvested acresof 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 9,358,000bushels, Table 7. Average harvested acres of dryland grain sorghum are 154,480 acreswith an average total grain production of 6,811,000 bushels.Table 7. Irrigated and Dryland Grain sorghum Acreages and Production in the top26 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 6,811Source: National Agricultural Statistics Service (2005-09) 50
  63. 63. There are no published statistics reporting the production of either sweet sorghumor switchgrass in the Texas Panhandle. Sweet sorghum and switchgrass production is inthe experimental stage in the Texas Panhandle and surrounding region. Switchgrass isincluded in trials at the TAMU research stations at Etter, Texas, and at the New MexicoState University research centers at Tucumcari, New Mexico, and at Roswell, NewMexico. 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 theanalysis are irrigated grain sorghum 134 bushels/acre and dryland grain sorghum 36bushels/acre, Table 8. Switchgrass yields under irrigated and dryland condition are 4.4dry tons/acre and 1.4 dry tons/acre respectively. Sweet sorghum yields under irrigatedand 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 PanhandleRegion (Appendix B-Table 1 and 2) Yield/acreFeedstock Irrigated DrylandGrain sorghum 134 bushels 36 bushelsSwitchgrass 4.4 dry tons 1.4 dry tonsSweet sorghum 25 wet tons 12.35 wet tons 51

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