Ethanol May 1997

Transcription

1 Ethanol 93-5 May 1997

2 TABLE OF CONTENTS (Continued) TABLE OF CONTENTS I SUMMARY 1 A. TECHNOLOGY 1 1. Fermentation Ethanol 1 (a) Whole Kernel Dry Milling 1 (b) Tempered Degermination 1 (c) Wet Milling 1 2. Synthetic Ethanol 2 B. NEW TECHNOLOGY AND IMPROVEMENTS 4 1. Improved Microorganisms and Enzymes 4 2. Fermentation Design 4 3. Purification 5 4. Lignocellulosic Feedstocks: Biomass to Ethanol 6 C. ECONOMICS 8 D. COMMERCIAL ANALYSIS Demand Supply 13 II TECHNOLOGY 15 A. INTRODUCTION 15 B. STARCHES TO ETHANOL Process Chemistry 15 (a) Starch Hydrolysis 15 (1) Starch Hydration 17 (2) Gelatinization 17 (3) Starch Hydrolysis 17 (b) Fermentation Theory 19 (1) General 19 (2) The Embden-Meyerhof-Parnas Scheme 20 (c) Fermentation Variables 24 (1) Yield 24 (2) Recycle Stillage Tolerance 25 (3) Yeast Nutrition 26 (4) Fermentation Rates Corn to Ethanol: Whole-Kernel Dry Milling 29 (a) Corn Receiving 30

3 TABLE OF CONTENTS (Continued) (b) Milling and Hydrolysis 39 (c) Cooking and Saccharification 41 (d) Fermentation 42 (e) Distillation 42 (f) DDGS Separation and Drying Corn-to-Ethanol: Tempered Degermination Dry Milling 47 (a) Dry Milling 49 (1) Cleaning 49 (2) Degermination 49 (3) Separation 54 (b) Fine Milling and Hydrolysis 54 (c) Yeast and Gluten Separation and Drying Corn to Ethanol: Wet Milling Continuous Centrifugal Extraction (the Biostil Process) 59 (a) Dry Milling to Saccharification 60 (b) Fermentation and Yeast Separation 60 (c) Ethanol Purification Other Starch Feedstocks 63 (a) Cassava 63 (b) Sweet Sorghum 63 (c) Potatoes and Other Tubers 63 C. OTHER FERMENTATION FEEDSTOCKS Sugars and Other Carbohydrates Municipal Solid Wastes Cheese Whey 66 D. SYNTHETIC ETHANOL Process Chemistry Process Description 67 III NEW TECHNOLOGY AND IMPROVEMENTS 70 A. IMPROVED MICROORGANISMS AND ENZYMES Yeast Properties 70 (a) Genetic Manipulation of Enzyme Activity 70 (b) Thermophilic Operation Bacterial Fermentation 71 (a) General Principles 71

4 TABLE OF CONTENTS (Continued) (b) Process Advances 72 (1) Genetic Manipulation 72 (2) Process Manipulation 73 (3) Immobilized Bacteria Cornstarch Cooking 73 B. FERMENTATION DESIGN Vacuum Fermentation Flocculating Cells (Internal Recycle) 74 C. ETHANOL PURIFICATION Alternative Distillation Processes and Heat Recovery 75 (a) Dehydration Entrainer Choice 75 (b) Mechanical Vapor Recompression 76 (c) Vacuum Distillation Extraction and Adsorption 79 (a) Molecular Sieves 79 (1) Temperature-Swing Adsorption 79 (2) Pressure-Swing Adsorption 80 (3) Concentration-Swing Adsorption 81 (b) Pervaporation 83 D. DIRECT-CONTACT EXTRACTION Liquid/Liquid Extraction Gas/Liquid Extraction 91 E. LIGNOCELLULOSIC FEEDSTOCKS Process Chemistry 97 (a) Hydrolysis 97 (b) Pentose Fermentation 99 IV COMMERCIAL ECONOMICS 101 A. FEEDSTOCK AVAILABILITY AND PRICING Corn Price Corn Availability Corn Byproducts 103 B. PROCESS ECONOMICS Corn Whole-Kernel Dry Milling 104 (a) Corn and Byproduct Pricing 104 (b) Cost Estimate 105

5 TABLE OF CONTENTS (Continued) (c) Sensitivity Analysis 108 (1) Unit Prices 108 (2) Return on Investment 108 (3) Ethanol Concentration in Fermenters Corn Tempered Degermination Dry Milling 111 (a) Cost Estimate 111 (b) Sensitivity Analysis Synthetic Ethanol 113 C. NEW TECHNOLOGY ECONOMIC IMPACT Biomass to Ethanol Thermophilic Yeast Bacterial Fermentation Vacuum Fermentation Flocculating Cells Reactor Mechanical Vapor Recompression Molecular Sieves Membranes 123 D. COMPARATIVE ECONOMICS 123 V COMMERCIAL ANALYSIS 125 A. DEMAND North America 125 (a) Chemical Uses 125 (b) Solvent Uses 127 (c) Fuel Ethanol 128 (1) Ethanol-Gasoline Blends versus Gasoline 129 (2) Ethanol and Ethanol Derivatives as Oxygenated Additives133 (3) Renewable Resource-Based Fuel Incentives Western Europe 135 (a) Chemical Uses 136 (b) Solvent Uses 137 (c) Fuel 137 (d) E.C. Subsidies and Feedstock Pricing Japan Canada South America Asia 140

6 TABLE OF CONTENTS (Continued) B. SUPPLY United States 140 (a) Synthetic Ethanol 143 (b) Fermentation Ethanol Western Europe South America 145 REFERENCES 146

7 TABLES Table I.A.1 Recommended Process Conditions for Vapor Phase Catalytic Hydration of Ethylene 2 Table I.C.1 U.S. Gulf Coast Anhydrous Ethanol Plant Investment Costs, 1st Qtr Table I.C.2 U.S. Gulf Coast Ethanol Production Costs, 1st Qtr Table I.D.1 U.S. Ethanol Demand 12 Table I.D.2 West European Ethanol Demand excluding Beverage 12 Table I.D.3 Brazilian Transportation Fuel Demand 13 Table I.D.4 U.S. Ethanol Supply, Table II.B.1 Gelatinization Ranges of Selected Starches 17 Table II.B.2 Sugar Utilization in Fermentation 25 Table II.B.3 Inhibition Effects for S. cerevisiae 25 Table II.B.4 Yeast Nutrition Requirements 27 Table II.B.5 Ethanol Tolerance Grading 28 Table II.B.6 Typical Corn Analysis 29 Table II.B.7 Safe Corn Storage Life 30 Table II.B.8 Dry Milling degermination Product Distribution 48 Table II.D.1 Recommended Process Conditions for Vapor Phase Catalytic Hydration of Ethylene 68 Table III.B.1 Fermentation Product Distribution 75 Table III.C.1 Ethanol Dehydration Entrainer Choices 76 Table III.C.2 PVA Membrane PV Data 84 Table III.C.3 Ethanol-Selective Membrane PV Data 88 Table III.E.1 Composition of Selected Agricultural Residues 97 Table IV.A.1 Average Corn Price and GDP History 102 Table IV.A.2 Corn Production and Consumption 103 Table IV.A.3 Corn and Corn Byproduct Protein Content 104 Table IV.A.4 Corn and Corn Byproduct Prices 104 Table IV.B.1 Capital Cost Estimate of Whole Kernel Dry Milling 105 Table IV.B.2 Cost Estimate of Ethanol Production via Whole Kernel Dry Milling 106 Table IV.B.3 Cost Estimate of Ethanol Production versus Fermenter Ethanol Concentration, U.S. Midwest, 1st Qtr

8 Table IV.B.4 Capital Cost Breakdown of Tempered Degermination, U.S. Midwest, 1st Qtr Table IV.B.5 Cost Estimate of Ethanol Production via Tempered Degermination Dry Milling 112 Table IV.B.6 Cost Estimate of Ethanol Production via Ethylene Hydration 116 Table IV.C.1 Capital Cost Estimate for Biomass to Ethanol, U.S. Gulf Coast, 1st Qtr 1995, 54 million gallons per year 119 Table IV.C.2 Cost Estimate of Ethanol Production via Wood Fermentation 120 Table IV.D.1 U.S. Gulf Coast Anhydrous Ethanol Plant Investment Costs, 1st Qtr Table IV.D.2 U.S. Gulf Coast Ethanol Production Costs, 1st Qtr Table V.A.1 U.S. Ethanol Demand, Table V.A.2 U.S. Chemical Ethanol Demand, Table V.A.3 U.S. Solvent Ethanol Demand, Table V.A.4 U.S. Oxygenate Supply/Demand Balance, Table V.A.5 State Ethanol Incentives 136 Table V.A.6 West European Ethanol Demand Excluding Beverage, Table V.A.7 West European Chemical Ethanol Demand, Table V.A.8 West European Solvent Ethanol Demand, Table V.A.9 Ethanol Cost Comparison, Table V.A.10 Brazilian Transportation Fuel Demand, Table V.B.1 U.S. Ethanol Supply, Table V.B.2 U.S. Fermentation Ethanol Production, Table V.B.3 U.S. Synthetic Ethanol Production, Table V.B.4 Proposed U.S. Fermentation Ethanol Expansions, Table V.B.5 West European Ethanol Production,

9 FIGURES Figure I.A.1 Wet Milling versus Dry Milling 3 Figure I.B.1 Block Flow Diagram: Ethanol from Wood 7 Figure I.C.1 Ethanol COP Sensitivity to Corn Price 10 Figure I.C.2 Ethanol COP Sensitivity to Corn Price 10 Figure I.C.3 Ethanol COP Sensitivity to Ethylene Price 11 Figure I.C.4 Ethanol COP + ROI Sensitivity to Wood Price 11 Figure II.B.1 Structural and Fischer Projections of Glucose Structures 16 Figure II.B.2 Starch Linkages 16 Figure II.B.3 Embden-Meyerhof-Parnas Scheme 21 Figure II.B.4 Corn Receiving, Sotrage, and Milling: Whole Kernel Milling 31 Figure II.B.5 Milling and Hydrolysis: Whole Kernel Milling 32 Figure II.B.6 Saccharification: Whole Kernel Milling 33 Figure II.B.7 Fermentation: Whole Kernel Milling 34 Figure II.B.8 Beer Still: Corn Dry Milling 35 Figure II.B.9 Rectifier and Dehydration: Corn Dry Milling 36 Figure II.B.10 DDGS Drying: Whole Kernel Milling 37 Figure II.B.11 Ethanol Pasteurization and Vent Recovery: Whole Kernel Milling 38 Figure II.B.12 TakaTherm-II Temperature-Activity Curves 40 Figure II.B.13 Effect of ph on TakaTherm-II 40 Figure II.B.14 Baffle Tray Design: Disk-and-Donut Configuration 44 Figure II.B.15 Nutter V-Grid Tray Configuration 45 Figure II.B.16: Dry Milling through Corn Cleaning 50 Figure II.B.17 Dry Milling through Degermination 51 Figure II.B.18 Dry Milling through Final Product Separations 52 Figure II.B.19 Fine Milling and Hydrolysis 53 Figure II.B.20 Wet Milling versus Dry Milling 58 Figure II.B.22 The Biostil Process 61 Figure II.B.23 Biostil Centrifuge 62 Figure II.C.1 Sugar Crop to Ethanol Flow Diagram 65 Figure II.D.1 Ethanol Production via Direct Ethylene Hydration: Conventional Process 69 Figure III.C.1 Mechanical Vapor Recompresssion 77 Figure III.C.2 Concentration Swing Adsorption 82 Figure III.C.3 Ethanol Dehydration via Pervaporation 85 Figure III.C.4 Ethanol Purification via Pervaporation 87 Figure III.D.1 Liquid/Liquid Extraction of Ethanol 90 Figure III.D.2 Gas Stripping Tubular Reactor 93 Figure III.E.1 Aldopentose Fermentation in Yeasts 100

10 FIGURES Figure IV.B.1 Ethanol COP versus Corn Price, Whole Kernel Dry Milling 109 Figure IV.B.2 Ethanol COP versus DDG Price, Whole Kernel Dry Milling 109 Figure IV.B.3 Ethanol COP + ROI versus ROI, Whole Kernel Dry Milling 110 Figure IV.B.4 Ethanol COP versus Corn Price, Tempered Degermination 114 Figure IV.B.5 Ethanol COP versus Gluten Meal Price, Tempered Degermination 114 Figure IV.B.6 Ethanol COP + ROI versus ROI, Tempered Degermination 115 Figure IV.B.7 Ethanol COP versus Ethylene, Synthetic Ethanol 115 Figure IV.C.1 Block Flow Diagram: Ethanol from Wood 118 Figure IV.C.2 Figure IV.C.3 Ethanol COP + ROI versus Wood Price, Wood to Ethanol Process 121 Ethanol COP + ROI versus Initial Capital Investment, Wood to Ethanol Process 121 Figure V.A.1 Effect of Ethanol on RON of Various Base Stocks 130 Figure V.A.2 Effect of Ethanol on MON of Various Base Stocks 131