Initial Comparative Process Economics of Leading Biomass Pretreatment Technologies Richard T. Elander, National Renewable Energy Laboratory Charles E. Wyman, Dartmouth College Bruce E. Dale, Michigan State University Mark Holtzapple, Texas A&M University Michael R. Ladisch, Purdue University Y.Y. Lee, Auburn University Tim Eggeman, Neoterics International The International Symposia on Alcohol Fuels and Other Renewables XV San Diego, CA September 28, 2005 Biomass Refining CAFI

Pretreatment in a Biomass Conversion Process Context Biomass Refining CAFI

Cellulosic Biomass Pretreatment Needs High cellulose accessibility to enzymes High sugar yields from hemicellulose Low capital cost – low pressure, inexpensive materials of construction Low energy cost Low degradation Low cost and/or recoverable chemicals A large number of pretreatment technologies have been studied, but only a few show promise Biomass Refining CAFI

Project Background: CAFI Biomass Refining Consortium for Applied Fundamentals and Innovation organized in late 1999 Included top researchers in biomass hydrolysis from Auburn, Dartmouth, Michigan State, Purdue, NREL, Texas A&M, UBC, Univ. Sherbrooke Mission: Develop information and a fundamental understanding of biomass hydrolysis that will facilitate commercialization, Accelerate the development of next generation technologies that dramatically reduce the cost of sugars from cellulosic biomass Train future engineers, scientists, and managers Biomass Refining CAFI

CAFI Approach Developing data on leading pretreatments using: Common feedstocks Shared enzymes Identical analytical methods The same material and energy balance methods The same costing methods Goal is to provide information that helps industry select technologies for their applications Also seek to understand mechanisms that influence performance and differentiate pretreatments Provide technology base to facilitate commercial use Identify promising paths to advance pretreatment technologies Biomass Refining CAFI

CAFI USDA IFAFS Project Overview Multi-institutional effort funded by USDA Initiative for Future Agriculture and Food Systems Program for $1.2 million to develop comparative information on cellulosic biomass pretreatment by leading pretreatment options with common source of cellulosic biomass (corn stover) and identical analytical methods Aqueous ammonia recycle pretreatment - YY Lee, Auburn University Water only and dilute acid hydrolysis by co-current and flowthrough systems - Charles Wyman, Dartmouth College Ammonia fiber explosion (AFEX) - Bruce Dale, Michigan State University Controlled pH pretreatment - Mike Ladisch, Purdue University Lime pretreatment - Mark Holtzapple, Texas A&M University Logistical support and economic analysis - Rick Elander/Tim Eggeman, NREL through DOE Biomass Program funding Completed in 2004 Biomass Refining CAFI

Non-structural Sugars CAFI USDA Project Corn Stover NREL supplied corn stover to all project participants (source: BioMass AgriProducts, Harlan IA) Stover washed and dried in small commercial operation, knife milled to pass ¼ inch round screen Component Composition (wt %) Glucan 36.1 % Xylan 21.4 % Arabinan 3.5 % Mannan 1.8 % Galactan 2.5 % Lignin 17.2 % Protein 4.0 % Acetyl 3.2 % Ash 7.1 % Uronic Acid 3.6 % Non-structural Sugars 1.2 % Biomass Refining CAFI

Hydrolysis Stages Cellulase enzyme Stage 2 Stage 1 Residual solids: Pretreatment Stage 2 Enzymatic hydrolysis Residual solids: cellulose, hemicellulose, lignin Biomass Solids: cellulose, hemicellulose, lignin Chemicals Dissolved sugars, oligomers Dissolved sugars, oligomers, lignin Stage 3 Sugar fermentation Biomass Refining CAFI

Dilute Acid Pretreatment Stage 1. Pretreatment Stage 2. Enzymatic hydrolysis Glucose and lignin Biomass Cellulose and lignin Mineral acid Hemicellulose sugars and oligomers Mineral acid gives good hemicellulose sugar yields and high cellulose digestibility Sulfuric acid usual choice because of low cost Requires downstream neutralization and conditioning Typical conditions: 120-200oC, 50 to 85% moisture, 0-1% H2SO4 Some degradation of liberated hemicellulose sugars

Schematic of Flowthrough Pretreatment System Sample

Controlled pH Liquid Hot Water Pretreatment pH control through buffer capacity of liquid No fermentation inhibitors, no wash stream Minimize hydrolysis to monosaccharides thereby minimizing degradation

The AFEX/FIBEX Process Reactor Explosion Ammonia Recovery Biomass Treated Liquid Gaseous • Liquid “anhydrous” ammonia treats and explodes biomass Ammonia is recovered and reused • • Ammonia can serve as N source downstream • Batch process is AFEX; FIBEX is continuous version • Conditions: 60-110oC, moisture 20-80%, ammonia:biomass ratio 0.5-1.3 to 1.0 (dry basis) • Moderate temperatures, pH prevent/minimize sugar & protein loss • No fermentation inhibitors, no wash stream required, no overliming • Only sugar oligomers formed, no detectable sugar monomers • Few visible physical effects

Ammonia Recycle Percolation (ARP) Vent Temp. monitoring system (DAS) PG N2 Gas C.W. Aqueous Ammonia PG TG Water TG Pump Oven (Preheating Coil and Reactor) Holding Tank PG : Press. Gauge TG : Temp. Gauge C.W.: Cooling Water

Lime Pretreatment Typical Conditions: Temperature = 25 – 55oC Biomass + Lime Gravel Air Typical Conditions: Temperature = 25 – 55oC Time = 1 – 2 months Lime Loading = 0.1 – 0.2 g Ca(OH)2/g biomass

Process Modeling in CAFI 1 Project Thermodynamics Process Analogies Chemistry Pretreatment Model Aspen Plus Design Methods CAFI Researcher Bioethanol Plant Model 2001 NREL Design Case 2000 Metric Ton (dry)/Day Stover Stover Cost: $35/ton Enzyme Cost: ~$0.15/gal ethanol Biomass Refining CAFI

General Process Flow Diagram Biomass Refining CAFI

Hydrolysis Stages Cellulase enzyme Stage 2 Stage 1 Residual solids: Pretreatment Stage 2 Enzymatic hydrolysis Residual solids: cellulose, hemicellulose, lignin Biomass Solids: cellulose, hemicellulose, lignin Chemicals Dissolved sugars, oligomers Dissolved sugars, oligomers, lignin Stage 3 Sugar fermentation Biomass Refining CAFI

Pretreatment Yield Comparisons at 15 FPU/g Glucan System Xylose yields* Glucose yields* Total sugars* Stage 1 Stage 2 Total xylose glucose Combined total Maximum possible 37.7 62.3 100.0 Dilute acid 32.1/31.2 3.2 35.3 3.9 53.2 57.1 36.0/35.1 56.4 92.4/91.5 Flowthrough 36.3/1.7 0.6/0.5 36.9/2.2 4.5/4.4 55.2 59.7/59.6 40.8/6.1 55.8/55.7 96.6/61.8 Controlled pH 21.8/0.9 9.0 30.8 3.5/0.2 52.9 25.3/1.1 61.9 87.2 AFEX 34.6/29.3 59.8 94.4/89.1 ARP 17.8/0 15.5 33.3/15.5 56.1 71.6 89.4/71.6 Lime 9.2/0.3 19.6 28.8/19.9 1.0/0.3 57.0 58.0/57.3 10.2/0.6 76.6 86.8/77.2 Increasing pH *Cumulative soluble sugars as total/monomers. Single number = just monomers. Biomass Refining CAFI

Pretreatment Yields at 15 FPU/g Glucan Maximum possible Dilute acid Flowthrough Controlled pH ARP AFEX Lime

Pretreatment Yields at 15 FPU/g Glucan

Pretreatment Yield Comparisons at 15 FPU/g Glucan—Alternative Basis System Xylose Yields, % of Theoretical* Glucose Yields, After Pretreatment After Enzymatic Hydrolysis Dilute Acid 90.2 / 89.7   95.6 / 95.1    8.0 / 7.5 85.1 / 84.6   Controlled pH 50.8 / 7.3 81.8 / 38.3 4.5 / 2.0 90.5 / 88.0 AFEX 0 / 0 92.7 / 77.6 95.9 ARP 47.2 / 0 88.3 / 41.1 1.4 90.1 Lime 24.3 / 0.8 75.3 / 51.8 1.6 / 0.5 92.4 / 91.3 No Pretreatment 8.5 15.7 Ideal Pretreatment - 100 *Cumulative soluble sugars as (oligomers+monomers) / monomers. Single number = just monomers. Biomass Refining CAFI

Capital Cost Estimates Pretreatment System Pretreatment Direct Fixed Capital ($MM) Pretreatment Breakdown, (% Reactor/% Other) Total Fixed Capital ($MM) Ethanol Production (MM gal/yr) Total Fixed Capital ($/gal Annual Capacity) Dilute Acid 25.0 64/36 208.6 56.1 3.72 Hot Water 4.5 100/0 200.9 44.0 4.57 AFEX 25.7 26/74 211.5 56.8 ARP 28.3 25/75 210.9 46.3 4.56 Lime 22.3 19/81 163.6 48.9 3.35 No Pretreatment - 200.3 9.0 22.26 Ideal Pretreatment 162.5 64.7 2.51 Biomass Refining CAFI

Minimum Ethanol Selling Price (MESP) Biomass Refining CAFI

Effect of Oligomer Conversion Biomass Refining CAFI

Solids Loading and Ethanol Concentration—Energy Impacts Pretreatment System Pretreatment Effluent (wt % Liquid) Fermentation Titer (wt % Ethanol in Liquid) Process Steam Usage Electrical Power HP Steam (kg/hr) LP Steam (kg/hr) VLP Steam (kg/hr) Total Generated (Mwe) Process Needs (Mwe) Dilute Acid 66.8 5.07 14,663 83,377 16,426 42.1 14.0 Hot Water 83.7 3.09 34,281 146,580 48,374 42.2 13.5 AFEX 61.2 4.62 154,980 31,932 35.6 17.4 ARP 74.5 5.06 112,330 56,972 11,469 38.0 11.9 Lime 80.0 3.16 160,540 42,265 14.4 No Pretreatment 0.92 59,697 51,477 88.8 13.9 Ideal Pretreatment 5.86 71,230 20,160 45.2 32.4 Biomass Refining CAFI

Key Findings from USDA CAFI Project Initial set of comparative pretreatment data has been developed 1st generation economic models developed Significant differences in pretreatment and enzymatic hydrolysis yields observed Especially, when and to what extent xylan is converted Pretreatment capital costs more similar than anticipated High costs for catalyst recovery or regeneration Findings to be published in a special issue of Bioresource Technology (December, 2005) Data gaps remain (addressed in current CAFI DOE Project) Optimal enzyme types for each pretreatment Hydrolyzate fermentability at relevant sugar concentrations Rigor of economic models (esp. pretreatment area capital costs) Biomass Refining CAFI

DOE Office of the Biomass Program Project: April 2004 Start Funded by DOE Office of the Biomass Program for $1.88 million through a joint competitive solicitation with USDA Using identical analytical methods and feedstock sources to develop comparative data for corn stover and poplar Determining more in-depth information on: Enzymatic hydrolysis of cellulose and hemicellulose in solids Conditioning and fermentation of pretreatment hydrolyzate liquids Predictive models Added University of British Columbia to team through funding from Natural Resources Canada to Capitalize on their expertise with xylanases for better hemicellulose utilization Evaluate sulfur dioxide pretreatment along with those previously examined: dilute acid, controlled pH, AFEX, ARP, lime Augmented by Genencor Int’l to supply enzymes Biomass Refining CAFI

Objectives of CAFI DOE Project Cellulosic biomass will be pretreated by leading technologies to improve cellulose accessibility to enzymes. Conditioning methods will be developed as needed to maximize fermentation yields by a recombinant yeast, the cause of inhibition will be determined, and fermentations will be modeled. Cellulose and hemicellulose in pretreated biomass will be enzymatically hydrolyzed, as appropriate, and models will be developed to understand the relationship between pretreated biomass features, advanced enzyme characteristics, and enzymatic digestion results. Capital and operating costs will be estimated for each integrated pretreatment, hydrolysis, and fermentation system and used to direct research. The proposal team will work with an Industrial and Agricultural Advisory Board and others to evaluate these findings; identify opportunities to utilize the pretreatment technologies; define opportunities to improve coupled pretreatment, fermentation, and enzymatic hydrolysis; and disseminate the results widely. Biomass Refining CAFI

Acknowledgements US Department of Agriculture Initiative for Future Agricultural and Food Systems Program, Contract 00-52104-9663 US Department of Energy Office of the Biomass Program, Contract DE-FG36-04GO14017 Natural Resources Canada Genencor International Our team from Dartmouth College; Auburn, Michigan State, Purdue, and Texas A&M Universities; the University of British Columbia; and the National Renewable Energy Laboratory Biomass Refining CAFI