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Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd and Charles E. Wyman Thayer School of Engineering Dartmouth College Hanover, New Hampshire 03755 AIChE Annual Meeting San Francisco, CA November 20, 2003 Biomass Refining CAFI

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Page 1: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Overall Sugar Yields from Corn Stover via Thermochemical

Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis

Todd A. Lloyd and Charles E. Wyman

Thayer School of EngineeringDartmouth College

Hanover, New Hampshire 03755

AIChE Annual Meeting San Francisco, CA November 20, 2003

Biomass Refining CAFI

Page 2: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Objectives

• Determine pretreatment conditions that lead to highest overall sugar yields

• Develop comparitive information on a consistent basis

• Identify opportunities to lower production costs while maintaining high yields

Page 3: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Corn Stover Composition• 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 screen

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

Page 4: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Hydrolysis

Enzyme

BatchPretreatment

H2O or H2SO4(aq)

Corn Stover

Overall Flow Diagram for Dilute Acid Pretreatment

Fermentation

Ethanol

Pretreatment Sugars

Residue

Digestion Sugars

Stage 1 Stage 2

Page 5: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Stage 1 – Summary of Pretreatment Conditions

• Steam Gun-no added acid– 150-220 oC– ~25% solids

• Dilute Acid– 140-200 oC– 0.22-1.0 % H2SO4

– 5-25% solids– Heated in sand bath

Biomass Refining CAFI

• Batch Reaction Systems1. NREL steam gun

2. ½”o.d. batch tubes

3. 1l stirred autoclave

Page 6: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

NREL Steam Gun

Biomass Refining CAFI

Page 7: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Batch Tube Experimental Apparatus for Dilute Sulfuric Acid

4 ”Biomass Refining CAFI

Page 8: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Parr Reactor Experimental Apparatus for Dilute Sulfuric Acid

Biomass Refining CAFI

Page 9: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Stage 2 – Enzymatic Digestion

• Spezyme from Genencor - used by all investigators

• NREL LAP-009 used to evaluate digestibility– 60 FPU/g original glucan used to determine

ultimate digestibility– 15 FPU/g tests done on selected samples

Page 10: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Severity Parameter• For no acid addition applied approach used by Overend

and Chornet

CS = t*Anexp[(T-100)/14.75]CS = Combined SeverityA = Added Acid, %n = Arbitrary exponentT = Reaction Temperature, oC

Biomass Refining CAFI

• Modified equation including acid addition has the form:

Ro = t*exp[(T-100)/14.75]

• Provides useful tools to compare results from a broad range of conditions

Page 11: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Combined Stage 1 and 2 Steam Gun Results - No Acid

Biomass Refining CAFI

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

3.2 3.4 3.6 3.8 4 4.2 4.4 4.6

Log (Ro)

Yie

ld, (X

/Xo +

G/G

o) Combined Xylose

Combined Glucose

Overall Combined

60 FPU/g original glucan

190 oC210 oC

Ro=t*exp((T-100)/14.75)

Page 12: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Stage 1 Pretreatment Yield for 0.49% H2SO4 Addition in Batch Tubes

Biomass Refining CAFI

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.00 1.50 2.00 2.50 3.00 3.50 4.00

Log CS

Yie

ld,

X/X

o o

r G

/Go

180 C Xylose Yield

180 C Glucose Yield

160 C Xylose Yield

160 C Glucose Yield

140 C Xylose Yield

140 C Glucose Yield

Batch Tube

CS=t*[aH+]0.5*exp((T-100)/14.75)

Page 13: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

Stage 2 Digestion Yield for 0.49% H2SO4 Addition in Batch Tubes

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.00 1.50 2.00 2.50 3.00 3.50 4.00

Log CS

Yie

ld,

X/X

o o

r G

/Go

180 C Glucose Yield

180 C Xylose Yield

160 C Glucose Yield

160 Xylose Yield

140 Glucose Yield

140 Xylose Yield

CS=t*[aH+]0.5*exp((T-100)/14.75)

60 FPU/g Original Glucan

Batch Tube

Page 14: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

Combined Stage 1 and Stage 2 Yield for 0.49% H2SO4 Addition in Batch Tubes

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.00 1.50 2.00 2.50 3.00 3.50 4.00

Log CS

Yie

ld,

(X+

G)/

(Xo

+ G

o)

180 C Combined Yield160 C Combined Yield140 C Combined Yield15 FPU/g glucan loading

Batch TubeCS=t*[aH+]

0.5*exp((T-100)/14.75)

60 FPU/g glucan enzyme loading

Page 15: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

Combined Stage 1 and Stage 2 Yield for 0.98% H2SO4 Addition in Batch Tubes

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.00 1.50 2.00 2.50 3.00 3.50Log CS

180 C Combined Yield

160 C Combined Yield

140 C Combined Yield

15 FPU/g glucan loading

Batch Tube

CS=t*[aH+]0.5*exp((T-100)/14.75)

60 FPU/g glucan enzyme loading

Page 16: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

84.2% glucan to glucose + 54.5% xylan to xylose conversion at 15FPU/g glucan

89.7% mass balance closure ( all solids + G + GO + X + XO)92% theoretical ethanol yield from glucose + xylose

Hydrolysis

Enzyme@ 15 FPU/g of glucan, 48h

Residual Solids

HydrolyzateLiquidParr Reactor

Pretreatment

1 wt% H2SO4

Corn Stover100 lb(dry basis)

21.4 lb xylan

0.2 lb gluco-oligomer (GO)

21.8lb xylose (X)

64.0 lb

36.1 lb glucan

Fermentation

4.08 galEthanol

1.3 lb xylose (X)30.9 lb glucose (G)

0.1 lb xylo-oligomer (XO)3.0 lb glucose (G)

32.4 lbTreated Solids

2.1 lb xylan33 lb glucan

2.29 gal ethanol

1.79 gal ethanol

140 oC

Mass Balance for Dilute Acid Pretreatment with Digestion (15 FPU/ g of glucan) in Parr Reactor

Page 17: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Summary of Batch Tube Dilute Acid

Performance at 15 FPU/g Glucan

Biomass Refining CAFI

T, oC A, % t, min X Yield, % G Yield, %

140 0.98 40

Stage 1 - 85

Stage 2 - 8

Total - 93

Stage 1 - 8

Stage 2 - 82

Total - 90

160 0.49 20

Stage 1 - 85

Stage 2 - 9

Total - 94

Stage 1 - 6

Stage 2 - 85

Total - 91

Page 18: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Understanding Role of Dilute Acid and Oligomer Release

• Why does acid enhance performance?

• What is the role of oligomers in sugar release?

Biomass Refining CAFI

Page 19: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Understanding Role of Dilute Acid and Oligomer Release

• Why does acid enhance performance?

• What is the role of oligomers in sugar release?

Biomass Refining CAFI

Page 20: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Predicting pH at Elevated Temperature

442

1

HSOHSOHK

44

2

SOHHSOK

(1)

(2)

][

]][[

4

42

HSO

SOHK (3)

Biomass Refining CAFI

][

][

4

42

SON

SOHM

2

8][ 2

222 MKNMKNMK

H

(4)

(Amount of Acid Neutralized)

Assume reaction (1) goes to completion

(Amount of Added Acid)

Page 21: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

I

I

IAzi 2.0

1log 2

Expression Empirical Davies'

molarity ion

charge ionic

tcoefficien activity ionic

m

z

T

TxA

zmI

i

ii

208.88.132

10825.1

2

1

5.16

2

*Marshall and Jones

444

41

)10(1 )0065./9.2307log9.199.56(

222

SO

TTT

SO

th

SOH

HSOth KKK

)0065./9.2307log9.199.56(log* ][

]][[2

4

42

4

4 TTTKHSO

SOHK th

HSO

SOHth

Predicting pH at Elevated Temperature

Page 22: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

HHHapH ][loglog

H

MKNMKNMKpH

2

8log 2

222

Predicting pH at Elevated Temperature

• Similar to approach used by Bienkowski et al. to predict the sulfuric acid degradation of glucose at elevated temperature and of Springer and Harris for the hydrolysis of wood

Page 23: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Predicted pH vs. Temperature

Biomass Refining CAFI

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20 40 60 80 100 120 140 160 180

T emperature, oC

pH

0.98% H2SO 4

0.45% H2SO 4

0.22% H2SO 4

5% solidsNo Neutralization

Page 24: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Predicted pH vs. Temperature

Biomass Refining CAFI

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20 40 60 80 100 120 140 160 180

Temperature, oC

pH

0.98% H2SO4

0.45% H2SO4

0.22% H2SO4

5% solids10 mg/g Biomass Neutralization

Page 25: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Predicted pH vs. Temperature

Biomass Refining CAFI

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20 40 60 80 100 120 140 160 180

Temperature, oC

pH

0.98% H2SO4

0.45% H2SO4

0.22% H2SO4

5% solids20 mg/g Biomass Neutralization

Page 26: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Predicted pH vs. Temperature

Biomass Refining CAFI

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20 40 60 80 100 120 140 160 180

Temperature, oC

pH

0.98% H2SO4

0.45% H2SO4

0.22% H2SO4

25% solids20 mg/g Biomass Neutralization

Page 27: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Understanding Role of Dilute Acid and Oligomer Release

• Why does acid enhance performance?

• What is the role of oligomers in sugar release?

Biomass Refining CAFI

Page 28: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Typical Stage 1 Yield vs Time Data

0

20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200

Reaction Time, min

% M

axim

um

Po

ten

tial

Xylo

se

Residual Xylan

Soluble Monomers and Oligomers

Soluble Xylooligomers

Batch Tube Reactors

140 oC

0.49% Sulfuric Acid

Page 29: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Models to Predict Hemicellulose Hydrolysis

• Abundance of literature data• Most kinetic studies neglect oligomers• Saeman model:

H M Dk h k d

Hf M D

Hs

k f

k s

k d

Biomass Refining CAFI

• Have also added consideration of two fractions of hemicellulose in biphasic reaction (Kobayashi et al.)

Page 30: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Hemicellulose Hydrolysis Kinetics

• A few models in literature include oligomers

• These treat oligomers as only one or possibly two species

• In fact, we would expect a number of different species of oligomers with varying chain lengths

• Some inconsistencies among models

Hf O MH s

k f

k s

k h

Dk d

Biomass Refining CAFI

Page 31: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Hemicellulose Hydrolysis Kinetics

• A few models in literature include more than one species of oligomer and suggest that oligomers may react directly to degradation products without first forming xylose monomer

Biomass Refining CAFI

XOH

MH s

k fk s k h

Dk d

XO L

k Od

Garrote et. al, 2000, Process Biochemistry, 36/571-78

Page 32: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Structure of Hemicellulose

p-Coumaric Acid

Xylose

Acetyl

Arabinose

Ferulic Acid

Glucuronic Acid

Fragmentation Products

+ H2O

Biomass Refining CAFI

Page 33: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Polymer Degradation1

N-mer

dCN/dt = -kh(N-1)CN

CN = CN0exp[-kh (N-1) t]

Assumes random bond scission and uniform rate constant

1 Simha, R., (1941), Journal of Applied Physics, 12:569-578

Biomass Refining CAFI

Page 34: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Generalized Form for j-mer Distribution

dCj/dt = 2kh Ci - kh(j-1)Cji=j+1

N

Cj = CN0 [1 – ](j-1)[ 2 + (N-j-1) ] 1< j < N-1

Where = 1 - exp[ -kht ]

@ t=0, CN=CN0; Cj=0

Biomass Refining CAFI

hd

tktk

hd

tktkh

kk

eeN

kk

eeN

N

kC

dhdh

2

212 2

1

For reactive monomer:

Page 35: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFIBiomass Refining CAFI

Depolymerization Model 140 oC, 0.49% Added Acid

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140 160 180 200

Pretreatment Time, min

Yie

ld,

X/X

0

Residual Xylan

Total Xylose and Xylooligomers

Xylooligomers

kh=0.126

kd=0.0016 AssumptionsOriginal DP = 100Cutoff DP = 8

Page 36: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Modified Depolymerization Model

n

mi

kaa0

1X e wher;i

iX

C

Ce

n:mj for

1)Ca(jkCa2kdt

dCjh

n

1jiih

j

• Assumes a change in activation energy with conversion

Page 37: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Modified Depolymerization Model 140 oC, 0.49% Added Acid

Biomass Refining CAFI

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140 160 180 200Pretreatment Time, min

Yie

ld, X

/X0

Residual Xylan

Soluble Xylooligomers

Soluble Xylose + Xylooligomers

Kh=.516 min-1

Ka=7.9

Ko=.094 min-1

Kf=.0016 min-1

Assumptions:

Cutoff DP = 8Original DP = 100

n:mj for

1)Ca(jkCa2kdt

dCjh

n

1jiih

j

mj1 for

j)C-(1kC2kCa2kdt

dCjo

1-m

iio

n

iih

1

2m

1 for

jm

CkC2kCa2kdt

dC1d

1-m

iio

n

iih

1

2

Xkaea

Page 38: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Conclusions

• Water only hydrolysis with a steam gun produced a maximum yield of about 60% X+G with 60 FPU/g glucan.

• For dilute acid pretreatment conditions for >95% yield of glucan and xylan ranged from 140oC with 0.98% added acid for 40 minutes to 180oC with 0.49% added acid for 5 minutes

• Xylanase activity in stage 2 enhances xylose yields • Neutralization of added acid can have a significant

effect on pH• Hydrolysis can be viewed as a depolymerization

process

Biomass Refining CAFI

Page 39: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Acknowledgements The United States Department of Agriculture Initiative for

Future Agricultural and Food Systems Program through Contract 00-52104-9663 for funding our research

The United States Department of Energy Office of the Biomass Program and the National Renewable Energy Laboratory

Our partners from Auburn University, Michigan State, Purdue, and Texas A&M Universities and the National Renewable Energy Laboratory

The National Institute of Standards and Technology for funds to purchase some of the equipment used in this research

The Thayer School of Engineering at Dartmouth College

Biomass Refining CAFI

Page 40: Biomass Refining CAFI Overall Sugar Yields from Corn Stover via Thermochemical Hemicellulose Hydrolysis Followed by Enzymatic Hydrolysis Todd A. Lloyd

Biomass Refining CAFI

Questions?

Biomass Refining CAFI