Characteristics of Biomass Pretreatments Studied by the CAFI Bruce E. Dale, Richard T. Elander, Mark T. Holtzapple, Michael R. Ladisch, Yoon Y. Lee and Charles E. Wyman ISAF XV International Symposia on Alcohol Fuels September 26-28, 2005 San Diego, CA Biomass Refining CAFI

Brief History of Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) Pretreatment researchers working together in a coordinated, disciplined way to understand the fundamentals underlying lignocellulosic biomass pretreatment and hydrolysis Organized in late 1999, early 2000 CAFI recognizes that pretreatment operates as part of a system that includes hydrolysis and fermentation—pretreatment effects on downstream processes must be better understood Biomass Refining CAFI

One Source of 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 Glucan36.1 % Xylan21.4 % Arabinan3.5 % Mannan1.8 % Galactan2.5 % Lignin17.2 % Protein4.0 % Acetyl3.2 % Ash7.1 % Uronic Acid3.6 % Non-structural Sugars1.2 %

Pretreatment system Temperature, o C Reaction time, minutes Chemical agent used Percent chemical used Other notes Dilute acid Sulfuric acid0.4925% solids concentration during run in batch tubes Flowthrough none0Continuously flow just hot water at 10mL/min for 24minutes Partial flow pretreatment none0Flow hot water at 10mL/min from 4-8 minutes, batch otherwise Controlled pH none016% corn residue slurry in water AFEX 4 905Anhydrous ammonia % solids in reactor (60% moisture dry weight basis), 5 minutes at temperature ARP 5, ammonia15Flow aqueous ammonia at 5 mL/min without presoaking Lime weekslime0.08 g CaO/g biomass Purged with air. Characteristics of CAFI Pretreatments

Dilute Acid Pretreatment 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: o C, 50 to 85% moisture, 0-1% H 2 SO 4 Some degradation of liberated hemicellulose sugars Mineral acid Biomass Stage 1. Pretreatment Stage 2. Enzymatic hydrolysis Glucose and lignin Cellulose and lignin Hemicellulose sugars and oligomers

Glucose and Xylose Yields in Pretreatment and Enzymatic Hydrolysis

Schematic of Flowthrough Pretreatment System Sample

Xylose Fate for Batch, FT, and SFS Runs with Water at 200 o C

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

Stepwise Process Yields & Mass Balance for 15 FPU Spezyme (168 hrs) Controlled pH Liquid Hot Water Treated Stover Slurry Hydrolysis Cellulase Enzyme 2209 FPU per lb stover (30 FPU/ml) Water Stover Residual Solids Hydrolyzate Liquid Fermentation 62.8 lb undissolved solids 37.2 lb dissolved solids 620 lb water 100 lb (dry basis) 36.1 lb glucan 21.4 lb xylan lb glucose lb xylose Ethanol 90.5% total glucan conversion (raw stover basis) 81.8% total xylan conversion (raw stover basis) 88% of theoretical ethanol yield from glucose + xylose 620 lb 22.0 lb 25.2 lb Cellobiase Enzyme 5891 IU per lb stover (309 IU/ml)

The AFEX/FIBEX Process 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: o C, moisture 20-80%, ammonia:biomass ratio to 1.0 (dry basis) No fermentation inhibitors, no wash stream required, no overliming Only sugar oligomers formed, no detectable sugar monomers Few visible physical effects ReactorExplosion Ammonia Recovery Biomass Treated Biomass Liquid Ammonia Gaseous Ammonia ReactorExplosion Ammonia Recovery Biomass Treated Biomass Liquid Ammonia Gaseous Ammonia Moderate temperatures, pH prevent/minimize sugar & protein loss

AFEX Process Mass Balance Hydrolysis Enzyme (15 FPU/g of Glucan) Residual Solids Hydrolyzate Liquid AFEX System Treated Stover Ammonia Stover lb 100 lb (dry basis) 36.1 lb glucan 21.4 lbxylan 39.2 lb 95.9% glucan conversion to glucose, 77.6% xylan conversion to xylose 99% mass balance closure includes: (solids + glucose + xylose + arabinose ) Wash 2 lb 99.0 lb Solids washed out 38.5 lb glucose 18.9 lbxylose (Ave. of 4 runs) Very few solubles from pretreatment—about 2% of inlet stover

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

Preliminary Mass Balance for ARP Pretreatment Biomass Ammonia recycling Fermention ARP Reactor Soluble sugar Ammonia Washing 100 lb (dry basis) G:36.1 lb X: 21.4 lb O: 7.8 lb G: Glucan X: Xylan O: Other sugar Liquid G: 0.5 lb X: 10.6 lb Lignin12.1 lb Residual solid19.3 lb G: 35.6 lb X:10.8 lb Treated stover Hydrolysis Hydrolyzate Glucose 34.9 lb Xylose 17.0 lb SSF Ethanol 23.4 lb Conversion Efficiency: 87% glucan + 70% xylan conversion at 15 FPU/g of gulcan 3.56 gallons ethanol (90% of theoretical yield, glucan+xylan) 95% mass balance closure (solids + G + X + EtOH + Others) Other sugar is excluded for Ethanol production Others 20.8 lb Residual solids 18.9 lb

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

Lime System Solids Liquid Hydrolysis Enzyme Lime + air Stover Residual Solids Hydrolyzate Liquid Fermentation 43 lb carb. 4 lb lignin 100 lb (dry basis) 58 lb carb. 19 lb lignin Ethanol 3.8 – 4.1 gal 27 lb To date: 80 – 90% overall carbohydrate conversion 15 lb sugars 15 lb lignin lb sugars 15 lb lignin Mass Balance for Lime Pretreatment

Pretreatment Yields-Stage 1 and Overall* Pretreatment system Xylose yields (38% max)Glucose yields (62% max)Total sugars (100% max) Stage 1Total xyloseStage 1Total glucoseStage 1Combined Dilute acid / / / /91.5 Flowthrough / / / / / /61.8 Partial flow pretreatment / / / / / /60.6 Controlled pH / / / / / /63.0 AFEX 4 nil 34.6/ nil 94.4/89.1 ARP 5,6 17.8/0 33.3/ /0 89.4/71.6 Lime 7 9.2/ / / / / /77.2 * Soluble oligomers plus monomers/monomers only

Pretreatment system Temperature, o C Reaction time, minutes Chemical agent used Percent chemical used Other notes Dilute acid Sulfuric acid0.4925% solids concentration during run in batch tubes Flowthrough none0Continuously flow just hot water at 10mL/min for 24minutes Partial flow pretreatment none0Flow hot water at 10mL/min from 4-8 minutes, batch otherwise Controlled pH none016% corn residue slurry in water AFEX 4 905Anhydrous ammonia % solids in reactor (60% moisture dry weight basis), 5 minutes at temperature ARP 5, ammonia15Flow aqueous ammonia at 5 mL/min without presoaking Lime weekslime0.08 g CaO/g biomass Purged with air. Characteristics of CAFI Pretreatments

Acknowledgments US Department of Agriculture Initiative for Future Agricultural and Food Systems Program, Contract 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 First group publication: Bioresource Technology vol. 96 #18 pgs December 2005 Biomass Refining CAFI

IFAFS Project Institutions Purdue University

Some Distinctive Features of AFEX NOT MUCH CHANGE IN APPEARANCE- DRY PROCESS Stover hydrolysis- 15 zero hrs. NOT MUCH EXTRACTED FROM TREATED STOVER HPLC at 168 hours Glucose, xylose, arabinose, Not much else CLEAN SUGAR STREAMS FOR FERMENTATION AFEX treatedUntreated

Cellulose Digestibility of Pretreated Corn Stover 190C – 15 minute