A UBURN U NIVERSITY Pretreatment and Fractionation of Corn Stover with Aqueous Ammonia Tae Hyun Kim †, Changshin Sunwoo* and Y.Y. Lee † † Department of Chemical Engineering, Auburn University, AL 36849, U.S.A. * Chemical Engineering, Chonnam National University, Gwangju, Korea AIChE Annual Meeting Indianapolis, Indiana November 4, 2002

A UBURN U NIVERSITY Tasks of Auburn Research in IFAFS Project: Pretreatment by Aqueous Ammonia 1.Optimize the proposed pretreatment technology (reaction & operating conditions) 2.Characterize resulting fluid and solid streams 3.Close material and energy balances for each pretreatment process 4.Determine cellulose digestibility and liquid fraction fermentability 5.Compare performance of pretreatment technologies on corn stover

A UBURN U NIVERSITY Features of the ARP Process Aqueous ammonia is used as the pretreatment reagent:  Efficient delignification.  Volatile nature of ammonia makes it easy to recover. Flow-through column reactor is used. (Ammonia Recycled Percolation) Versatility of the products.  Ethanol  Low-lignin cellulose; “filler-fiber” in paper making  Uncontaminated lignin; value-added chemicals

A UBURN U NIVERSITY Processes Options Based on Aqueous Ammonia 1.ARP 2.Low-liquid ARP 3.Two-stage processing (Hot Water-ARP) - Fractionation of corn stover

A UBURN U NIVERSITY Material and Methods Material and Methods Corn stover supplied by NREL (1st batch used). –Common feedstock for IFAFS Project Ground and sieved (10 ~35 mesh). Flow-through column reactor (SS-316, 9/10 in ID  10 in L, internal volume of cm 3 ) is used. Component1 st batch2 nd batch Glucan Xylan Lignin 37.5 Unit [%]

A UBURN U NIVERSITY ARP Laboratory Reactor N2 Gas PG Vent Holding Tank Pump PG : Press. Gauge TG : Temp. Gauge C.W.: Cooling Water Aqueous Ammonia Water 3-way v/v #1 : For ARP #2 : For Water or Acid #1#2 PG C.W. Oven (Preheating Coil and Reactor) Temp. monitoring system (DAS) TG

A UBURN U NIVERSITY Reactor and System ReactorSystem All reactions are carried out in a Bed-Shrinking Flow-Through (BSFT) Reactor.

A UBURN U NIVERSITY Results of ARP Untreated [min] [%] Glucan Xylan Deligni- fication Solid Reaction Time 20 Digestibility 60FPU15FPU Glucan Xylan Liquid Pretreatment conditions: 15wt% of ammonia, 170  C, 5mL/min of flow rate, 325psig Note. All sugar and lignin content based on the oven-dry untreated biomass. [%] FPU : FPU/g-glucan

A UBURN U NIVERSITY Effect of Reaction Time in ARP Pretreatment Pretreatment conditions: 15wt% of NH 3, 170  C, 5mL/min flow rate, 325psig Digestibility Lignin

A UBURN U NIVERSITY XRD Diagram of ARP Treated Samples Pretreatment conditions: 15wt% of NH 3, 170  C, 5mL/min, 325psig  -cellulose Untreated

A UBURN U NIVERSITY FTIR Spectra of ARP Treated Samples (1) (2) (3) Untreated (Red line) 1) IR band of C-O in guaiacyl or syringyl ring 2) IR band of aromatic skeletal vibration + C=O stretching 3) IR band of aromatic skeletal vibration Pretreatment conditions: 15wt% of NH 3, 170  C, 5mL/min, 325psig This task was performed at Michigan State University (Courtesy of Professor Bruce Dale and his coworkers)

A UBURN U NIVERSITY SEM and Lignin Staining (a) Untreated (X50)(b) ARP 90min (X50) (d) ARP 90min (X300) (c) Untreated (X300) Untreated By phloroglucinol-HCL ARP 90min

A UBURN U NIVERSITY Low-Liquid ARP Pretreatment conditions Liquid throughput: 3.33mL of 15wt% NH 3 per g of corn stover Air dried corn stover is used without presoaking. Air dried corn stover is used without presoaking. 50 ml of 15wt% Aqueous NH3 170  C Reactor (15g of Corn Stover) Reactor Volume:70.9 cm 3 Reactor Void Volume: 45.0 cm 3 Flow rate; 5ml/minReaction time; 10 min Aq. NH 3

A UBURN U NIVERSITY Composition of Treated Low-Liquid ARP Samples Reaction time of 10 ~ 12.5 minutes [ml/min] [%] Glucan Xylan Lignin S.R. 2 Delig. 1 SolidFlow rate 4.0 Digestibility 60FPU15FPU Note. 1. Delignification 2. Solid remaining after reaction 3. All sugar and lignin content based on the oven-dry untreated biomass. [%] Untreated

A UBURN U NIVERSITY Economic Factors of ARP (Process Eng. Analysis by NREL) In direct comparison to NREL dilute-acid pretreatment Advantage: No need for neutralization of effluent (reduction of wastewater treatment cost). Disadvantage: Higher steam consumption. Overall Cost: Slightly lower than NREL base case.

A UBURN U NIVERSITY ARP Process Diagram Crystallizer Biomass Ammonia recycling To Fermentor (SSF) Steam Reactor Liquid Soluble sugar Make-up water Washing Lignin (Fuel) Steam Evaporator Ammonia Lignin & Other sugar Solid water Washing Steam

A UBURN U NIVERSITY Fractionation of Corn Stover Background ARPdelignificationARP is effective in delignification. hemicellulose hydrolysis.Neutral & Acidic pretreatments are effective in hemicellulose hydrolysis. Selective removal of hemicellulose and lignin is a feasible concept. ARP can be applied in conjunction with another pretreatment.

A UBURN U NIVERSITY Summary of Water-ARP Treatment Water only [°C] Y XYL 1 Glucan Xylan Lignin S.R. LiquidSolid [%]Temp 180 Digestibility [%] 60FPU10FPU Water + ARP Increase Decrease Increase Decrease Increase Optimum Note 1. Xylan yield in liquid [%] 2. All sugar and lignin content based on the oven-dry untreated biomass. Untreated

A UBURN U NIVERSITY Net effect of two-stage treatment 82.4% of cellulose Treated Solid contains 82.4% of cellulose Second Stage (ARP) 75.2% of Delignification First Stage (Hot Water Treeatment) 83.4% of Xylan recovery

A UBURN U NIVERSITY Relationship Between Lignin and Digestibility Enzymatic digestibilities (at 10FPU/g glucan) are affected by lignin content.

A UBURN U NIVERSITY The Fate of Lignin Residual lignin after water-ARP increase as the temperature of water treatment increases. Explanations condensationrepolymerization becoming insoluble 1)Lignin undergoes condensation and repolymerization, becoming insoluble (Lora, 1978, Genco, 1997, Xu, 1999). 2)Lignin bonded to the cellulose 2)Lignin become bonded to the cellulose at high temperature (Karlsson, 1997).

A UBURN U NIVERSITY Conclusions above 85% digestibilitywith 15 FPU/g-glucanPretreatment of corn stover by ARP renders near quantitative enzymatic digestibility with 60 FPU/g- glucan and above 85% digestibility with 15 FPU/g-glucan. delignification (70-85%)It gives a high and adjustable degree of delignification (70-85%). Lignin content affecting the enzymatic hydrolysis Lignin content is one of the major factors affecting the enzymatic hydrolysis. Crystallinity index of corn stover increasesCrystallinity index of corn stover increases by ARP treatment due to removal of amorphous component of corn stover. Crystallinity of the glucan in corn stover is unaffected by treatment by aqueous ammonia. ARP

A UBURN U NIVERSITY Conclusions (cont’d) Amount of liquid throughput major cost factorsAmount of liquid throughput is one of the major cost factors in the ARP. as effective asthe conventional ARPLow-liquid ARP is as effective as the conventional ARP: % delignification % 15FPU/g- glucan Low-Liquid ARP

A UBURN U NIVERSITY Conclusions (cont’d) Two-stage processing of corn stover can effectively fractionate corn stoverTwo-stage processing of corn stover (hot water treatment followed by ARP) can effectively fractionate corn stover into three main constituents. Theend product of two-stage processing 82% glucanThe end product of two-stage processing contains 82% glucan, a product equivalent to a “filler fiber” used in papermaking. Two-stage treatment

A UBURN U NIVERSITY Conclusions (cont’d) Hot water treatment aloneat o C unusually high digestibilityHot water treatment alone at o C gives unusually high digestibility. Two-stage processing lignin recondensation lignin-carbohydrate complexTwo-stage processing above 200 o C increases the residual “Klason lignin”, an indication that lignin recondensation and/or lignin-carbohydrate complex may occur.

A UBURN U NIVERSITY Future Work Fundamental Study on ARP: Lignin interaction with cellulase Physico-chemical change of ARP samples Lignin recondensation and complex formation with carbohydrate Develop an effective method of separating lignin from the ARP reactor effluent Determine the ultimate ethanol yield for the ARP samples by the simultaneous saccharification and fermentation (SSF) experiments Design and test a proof-of-concept continuous ARP reactor.

A UBURN U NIVERSITY Acknowledgement The United States Department of Agriculture Initiative for Future Agricultural and Food Systems Program through Contract

A UBURN U NIVERSITY Question?