National Renewable Energy Laboratory Biofuels: Renewable Transportation Fuels from Biomass Cynthia Riley Biotechnology Division for Fuels and Chemicals National Bioenergy Center Utility Federal Technology Opportunities May 8, 2002 Operated for the U.S. Department of Energy by Midwest Research Institute Battelle Bechtel
Outline Energy for Transportation Biomass Resources Bioethanol Production Process Biomass Hydrolysis Chemical Enzymatic Fermentation Systems Analysis Future The Biorefinery
Biomass Energy Platforms Feedstock collection, handling & preparation Hydrolysis Acids, enzymes Gasification High heat, low oxygen Digestion Bacteria Pyrolysis Catalysis, heat, pressure Extraction Mechanical, chemical Sugars and Lignin Syngas Biogas Bio-Oil Carbon-Rich Chains Electricity Biofuels Biobased chemicals Biobased materials Separation Mechanical, chemical Plant Products Heat
U.S. Primary Energy Consumption - 1999 45 40 Quads/Yr 35 30 25 20 15 Nuclear Renewables Petroleum -- Imported Petroleum -- Domestic Nat. Gas -- Imported Nat. Gas -- Domestic Coal 10 5 0 Residential Commercial Industrial Transportation Sector of the Economy Just under 7% of all energy consumed in U.S. is for non-fuel purposes.
BioFuels Focus - Bioethanol Goals Ethanol production research Production Cost $1.07/gal by 2010 Enzyme research Purchase cost < 10 /gal ethanol Sugar Platform Production Cost < 6 /lb by 2010
What is bioethanol? Fuel ethanol made from non food biomass sources Requires new technology: To break down (hydrolyze) cellulose and hemicellulose to sugar To ferment unusual sugars in biomass
Biomass Resources and Issues Wood Residues Sawdust Wood waste Agricultural Residues Corn stover Rice hulls Sugarcane bagasse Animal waste Energy Crops Switchgrass Hybrid poplar Willow Quality Cost Composition Ease of Conversion Production Collection and Transportation Quantity Available Sustainability Land, Air and Water Resources
Potential Midterm U.S. Biomass Supply Millions Dry Tons per Year 600 500 400 300 200 100 0 Forest Residues Urban Wastes Ag Residues Mill Residues Energy Crops $20 $30 $40 $50 Delivered Price ($/dry ton) 42 million acres (10% of total cropland) switches to bioenergy crops, includes 13 million acres of CRP land 181 million dry tons of switchgrass per year at $50 per ton or less.
Biomass Composition Comparison 100% protein chlorophyll 80% 60% 40% soil acetyl Uronic acids ash extractives lignin galactan 20% arabinan mannan 0% poplar sawdust corn stover (fresh) bagasse (fresh) xylan glucan
Major Steps in Enzymatic Bioethanol Delivered feedstock Pre-processing Process Many different technology options exist for each step Pretreatment (hemicellulose extraction) Conditioning (if necessary) Enzymatic cellulose saccharification Biomass sugar fermentation Beer product to distillation
Goals of Biomass Pretreatment Acid-Catalyzed Process Solubilized Hemicellulose Hemicellulose Cellulose Oligomers Monomers Degradation Products Lignin Solubilized Cellulose All xylose, mannose, arabinose, galactose and portion of glucose released Remaining cellulose is highly digestible Cellulose Lignin Enzymes Oligomers Lignin Glucose Minimal sugar degradation products
Biomass Pretreatment Chemical partial hydrolysis prior to enzyme hydrolysis Reactor design is complex! Continuous processing High solids, erosive, corrosive High temperature, pressure Heterogeneous catalysis of complex substrate Many simultaneous reactions Tools for improving pretreatment Multiple reactor sizes and configurations Impeccable analytical process chemistry Kinetic and molecular modeling Computational fluid dynamics
Conversion of Biomass 100 g raw solids (dry) feedstock 60 g pretreated solids (dry) process intermediate 27 g residue solids (dry) lignin coproduct
Pretreatment Equipment 4 L Batch Steam Digester 2 ton/day Sunds Prehydrolyzer 200 kg/day Sunds Two-stage Countercurrent Reactor System
Mass Transfer Resistances The Boundary Layer Theory The hydrophobic surface of crystalline cellulose imparts a structuring to adjacent water molecules. 205 C Bulk density or below 25% above bulk density 50% above bulk density 75% above bulk density
Enzymatic Hydrolysis Enzymes offer greater opportunities for cost reduction in the long term compared to acid hydrolysis technologies currently focus of major efforts with Genencor and Novozymes Enzyme Biochemistry and specific activity Cellulase:Cellulose Interaction Cost of Enzyme Production +2 +1-1 -2 Y82 cellodextrin CBH1 from T. reesei E1 from A. cellulotiticus
Biomass Sugar Fermentation Ferment all Biomass Sugars Glucose, Xylose, Arabinose, Mannose, Galactose Resistant to toxic materials from pretreatment Furfural, HMF, Acetic, Uronic and other Acids, phenols, cations, sugar oligomers, Robust, able to out-compete contaminant microorganisms Thermo-tolerant Ethanol tolerant ph tolerant High fermentation rates Minimum metabolic byproducts
Pathways Required for Pentose Fermentation Pentose Metabolism Pathways D-Xylose L-Arabinose L-arabinose isomerase Xylose Isomerase L-Ribulose L-ribulokinase ATP D-Xylulose ADP Xylulokinase L-Ribulose-5-P ATP ADP L-ribulose-5-P 4-epimerase D-Xylulose-5-P Ribulose-5-P Ribose-5-P Transketolase Entner-Doudoroff Pathway D-Glucose ATP ADP Glucose-6-P Gluconolactone-6-P 6-P-Gluconate 2-Keto-3-deoxy-6-P-Gluconate Glyceraldehyde-3-P Sedoheptulose-7-P Glyceraldehyde -3-P Transaldolase 1,3-P-Glycerate ADP ATP 3-P-Glycerate Erythrose-4-P Fructose-6-P Fructose-6-P 2-P-Glycerate ADP Phosphoenolpyruvate ATP Pyruvate Transketolase Glyceraldehyde -3-P Acetaldehyde + CO 2 Ethanol
Life Cycle Assessment a framework for making choices that support a sustainable society Energy Crop, Waste, Residue Biomass Transport Hydrolysis and Fermentation Ethanol Feedstock Production Feedstock Transport Feedstock Conversion Fuel Distribution One Mile Traveled Crude Oil Production Crude Transport by barge, pipeline Oil Refining to Gasoline Gasoline
Avoiding fossil fuel use: bioethanol from corn stover
Simple Bioethanol Process Flow Diagram Feedstock Handling Pretreatment S/L Separation Corn Stover Steam & Acid Liquor Solids Enzyme Lime Steam Wastewater Treatment Lignin Residue Distillation & Ethanol Purification Saccharification & Fermentation Burner/Boiler Turbogenerator Conditioning
Corn Stover Case Normalized Cost by Area Capital Recovery Charge Raw Materials Process Electricity Grid Electricity Total Plant Electricity Fixed Costs Corn Stover 34% Feedstock Handling 5% Pretreatment and Conditioning 19% Saccharification and Fermentation Cellulase Distillation and Solids Recovery 8% 9% 11% (after ~10x cost reduction!) Waste Water Treatment 2% Boiler/Turbogenerator Utilities 4% 7% Storage 1% -20% -10% 0% 10% 20% 30% 40%
Processing of and Products from Lignin Intermediates Carbohydrate Hydrolysis Degree of lignin fractionation depends on upstream processing. Lignin Efforts Sugars Lignin Intermediates -Co-location studies: Bioethanol and biomass-fired or coal-fired power plants -EERC fuel evaluation of lignin intermediates (multiple projects) -Lignin upgrading to fuels and higher value products Combustion Gasification Depolymerization Hydroprocessing Recovery and Upgrading Power, Heat Syn-gas Liquid Fuels Residual solids to combustion or gasification Lignin Products Residual solids to combustion or gasification
The Costs of Cellulosic Conversion 2.50 Process with Existing Industrial Enzymes 2.00 Cost, $/gallon Ethanol 1.50 1.00 Existing corn ethanol and pioneer plant bioethanol technology Cost Reduction Enabled Through Enzyme Research and Pretreatment Improvements $1.07 target for first commercial enzyme biorefinery by 2010 0.50 Long term target as bulk fuel 0.00 1990 2000 2010 2020 2030 2040 2050 2060
Impact of Bioethanol on U.S. Gasoline 140 125 120 Billions of Gallons per Year (Gasoline Equivalents) 100 80 60 40 34.3 75 20 0 U.S. Gasoline Market @ 20.5 MPG Ethanol - Midterm Technology Ethanol - Improved Technology
DOE Bioethanol Commercialization Projects Company Project location BCI Jennings, LA Masada Middletown, NY Gridley Gridley, CA Sealaska Southeast Alaska BCI/Collins Pine Chester, CA Expected Startup Pending financing Technology Feedstock Ethanol Million Two-stage dilute acid 2003 Concentrated acid Evaluating approaches Evaluating approaches Gallons/Year Bagasse 20 MSW 10 TBD Rice straw 20 TBD Mill residues 6-8 2005? Enzymatic Forest thinnings and mill residues 20 Note: DOE is also sponsoring numerous RD&D projects for other products from biomass power, chemicals, and materials.
The New Industrial Biorefinery USES Fuels: Ethanol Renewable Diesel Biomass Feedstock Trees Grasses Agricultural Crops Agricultural Residues Animal Wastes Municipal Solid Waste Cargill Dow Dedicates PLA Refinery April 2002 Conversion Processes - Enzymatic Fermentation - Gas/liquid Fermentation - Acid Hydrolysis/Fermentation - Gasification - Combustion - Co-firing Power: Electricity Heat Chemicals Plastics Solvents Chemical Intermediates Phenolics Adhesives Furfural Fatty acids Acetic Acid Carbon black Paints Dyes, Pigments, and Ink Detergents Etc. Food and Feed
Acknowledgments Funding Provided by U.S. Department of Energy, Office of Transportation Technologies, Office of Fuels Development Operated for the U.S. Department of Energy by Midwest Research Institute Battelle Bechtel