Ammonia Fiber Explosion (AFEX) for Pretreatment of Corn Stover: Recent Research Results Farzaneh Teymouri, Hasan Alizadeh, Lizbeth Laureano-Perez and Bruce E. Dale Department of Chemical Engineering & Materials Science Michigan State University AIChE Annual Meeting San Francisco, California November 20, 2003 Biomass Refining CAFI

What is AFEX/FIBEX? ReactorExplosion Ammonia Recovery Biomass Treated Biomass Liquid Ammonia Gaseous Ammonia ReactorExplosion Ammonia Recovery Biomass Treated Biomass Liquid Ammonia Gaseous Ammonia Liquid ammonia treats, explodes biomass, 99% of ammonia is recovered & reused, remainder serves as N source downstream? No 1) fermentation inhibitors, 2) wash stream required, 3) overliming Conditions: C, moisture 20-60%, ammonia:biomass ratio :1.0 (dry basis), pressure up to 250 psig give theoretical yields for glucose and nearly 80% of theoretical for xylose Few visible effects of pretreatment, material is left dry and can be fed at very high solids loadings, stable for long periods Biomass Refining CAFI

The “Big Four” Process Parameters Yield (mass desired product(s) per mass purchased raw material) Concentration (mass desired product(s) per unit reactor volume) Purity (ratio of desired product concentrations to undesired products in the final reaction mixture) Rate (desired product(s) produced per unit reactor volume per unit time) How does AFEX stack up on the “Big Four?” Biomass Refining CAFI

AFEX Parameters Affecting Sugar Yields Primary focus of IFAFS project, these are: –Ammonia:biomass ratio –Temperature (also affects pressure) –Moisture content of biomass –Enzyme loading (FPU per gram glucan) Approximate “optimal” conditions for corn stover: 1:1 ammonia:biomass ratio, 90 degrees C, moisture content 60% dwb Enzyme loading is highly variable—we get effective hydrolysis at 7.5 FPU gram glucan We need better enzymes; especially for alkaline pretreatments Lots of data—we only show part of it Biomass Refining CAFI

Conversion of Glucan and Xylan vs. AFEX Treatment Temperature Biomass Refining CAFI

Effect of Ammonia Loading on Glucan & Xylan 60 FPU/gm glucan Biomass Refining CAFI

Conversion of Glucan and Xylan vs. Moisture Content at 90 0 C Biomass Refining CAFI

Treatment Conditions: 90 °C, 60% Moisture, 1:1 Ammonia:Biomass 5 minutes treatment Hydrolysis of Stover Glucan & Xylan At Two Enzyme Levels Biomass Refining CAFI

AFEX Process Yields & 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 38.7 lb 95.9% glucan conversion, 77.6% xylan conversion 94% mass balance closure includes (corrected for water of hydrolysis): (solids + glucose + xylose + arabinose ) Wash 2 lb 99.0 lb Solids washed out 38.5 lb glucose 18.9 lbxylose (Ave. of 4 runs) Biomass Refining CAFI

The “Big Four” Process Parameters Yield (mass final product per mass purchased raw material) Concentration (mass product per unit reactor volume) Purity (ratio of primary product concentration to other products in the reaction mixture) Rate (product produced per unit reactor volume per unit time) How does AFEX stack up on the “Big Four?” Biomass Refining CAFI

AFEX Process Yields & 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 38.7 lb 95.9% glucan conversion, 77.6% xylan conversion 94% mass balance closure includes (corrected for water of hydrolysis): (solids + glucose + xylose + arabinose ) Wash 2 lb 99.0 lb Solids washed out 38.5 lb glucose 18.9 lbxylose (Ave. of 4 runs) Biomass Refining CAFI

PretreatmentWater:Solids Ratio % Solids Solubilized Dilute acid>536 Flowthrough> Controlled pH AFEX ARP>540.0 Lime Water Loadings and Stover Solids Made Soluble by Pretreatments

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 Biomass Refining CAFI

Fed Batch SSF of AFEX Treated and Untreated Corn Stover (15 IU/gm glucan) AFEX treated stover in fed batch SSF at 24% solids loading Untreated stover in SSF 24% solids loading Flows very easily Doesn’t flow worth a dang Dark appearance is deceptive- caused by autoclaving & media Biomass Refining CAFI

The “Big Four” Process Parameters Yield (mass final product per mass purchased raw material) Concentration (mass product per unit reactor volume) Purity (ratio of primary product concentration to other products in the reaction mixture) Rate (product produced per unit reactor volume per unit time) How does AFEX stack up on the “Big Four?” Biomass Refining CAFI

Kinetics of Glucan Hydrolysis Biomass Refining CAFI

Treatment Conditions: 90 °C, 60% Moisture, 1:1 Ammonia:Biomass 5 minutes treatment Hydrolysis of Stover Glucan & Xylan At Two Enzyme Levels Biomass Refining CAFI

AFEX Process Yields & 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 38.7 lb 95.9% glucan conversion, 77.6% xylan conversion 94% mass balance closure includes (corrected for water of hydrolysis): (solids + glucose + xylose + arabinose ) Wash 2 lb 99.0 lb Solids washed out 38.5 lb glucose 18.9 lbxylose (Ave. of 4 runs) Biomass Refining CAFI

A Few More Words on Yield Yield (mass final product per mass purchased raw material) Sugar is an intermediate product, but not the final product we desire We have fermentation yield information on AFEX-treated materials, here is some of it Biomass Refining CAFI

Ethanol from Enzyme Hydrolyzates of AFEX Pretreated Corn Fiber Glucose & xylose were both well-utilized by all three organisms Hydrolyzates were fermented “as is” without dilution No removal of degradation products (none were detected) Work done by Dr. M. Moniruzzaman in conjunction with Dr. Nancy Ho, Dr. Lonnie Ingram and Dr. Rod Bothast’s group Organism Maximum Ethanol (g/L) Ethanol Yield (g/g sugar) % Theoretical Ethanol Yield E. Coli SL E. Coli KO Saccharomyces strain 1400 (pLNH 32) Biomass Refining CAFI

Some Conclusions & Observations I Maximum glucose yield to date approx. 100% of theoretical, xylose yield approx. 80% from AFEX corn stover Very high solids “concentrations” achievable during hydrolysis and fermentation of AFEX material Both glucose and xylose are converted to ethanol at high yields by engineered yeast and bacteria Not much difference between 60 & 15 FPU/gm; difference diminishes with increasing temperature Biomass Refining CAFI

Some Conclusions & Observations II Have not “tuned” AFEX pretreatment for lower enzyme levels, or better enzyme mixtures Increasing ammonia loadings, temperatures, moisture loadings all enhance effects of AFEX; therefore less need for enzyme Xylanase seems much less effective than glucanase—at least on this substrate for this pretreatment Developing enzyme mixture(s) for specific pretreatments & specific substrates deserves much more attention—enzyme, pretreatment and fermentation development should proceed together Biomass Refining CAFI

Future Work AFEX studies: –Tune AFEX for 7.5 IU/gram glucan –Complete SSF studies on stover –Begin looking at other enzyme cocktails –Begin participation in CAFI 2 Continue analytical work & modeling to develop fundamental insights on pretreatment effectiveness: –X Ray diffraction –Infrared analysis –Fluorescence studies Biomass Refining CAFI

Acknowledgements The USDA Initiative for Future Agricultural and Food Systems Program through contract National Renewable Energy Laboratory Biomass Refining CAFI

Questions ?? Biomass Refining CAFI

Specific Goals at Michigan State Better understand performance of AFEX system Investigate interplay between treatment conditions (temperature, moisture content, ammonia:biomass levels, time) Analyze AFEX pretreated corn stover and evaluate its digestibility by enzymatic hydrolysis & fermentation Optimize AFEX pretreatment for corn stover based on sugar yields from glucan & xylan Provide analysis to the IFAFS group for cellulose crystallinity, fluorescence and IR to enhance our fundamental understanding of pretreatment effectiveness Biomass Refining CAFI

AFEX Process Yields & Mass Balance Hydrolysis Enzyme (60 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 35 lb 99.4% glucan conversion, 79.4% xylan conversion (up-dated on 9/10/03) 98% mass balance closure includes: (solids + glucose + xylose + arabinose ) Wash 2 lb 98.5 lb Solids washed out 39.9 lb glucose 19.3 lbxylose (Ave. of 3 runs) Biomass Refining CAFI

AFEX Process Yields & Mass Balance Hydrolysis Enzyme (7.5 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 TBD 85.3% glucan conversion, 59.3% xylan conversion (up-dated on 9/10/03) Wash 2 lb 98.5 lb Solids washed out 34.2 lb glucose lb xylose (Ave. of 2 runs) Biomass Refining CAFI

Ammonia Fiber Explosion (AFEX) System Biomass Refining CAFI