ammonia fiber explosion (afex) for pretreatment of corn stover: recent research results

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 MeetingSan Francisco, California

November 20, 2003Biomass Refining CAFI

What is AFEX/FIBEX?

Reactor Explosion

AmmoniaRecovery

BiomassTreatedBiomass

LiquidAmmonia

GaseousAmmonia

Reactor Explosion

AmmoniaRecovery

BiomassTreatedBiomass

LiquidAmmonia

GaseousAmmonia

• 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: 60-100 C, moisture 20-60%, ammonia:biomass ratio 0.5-1.0:1.0 (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?”


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 itBiomass Refining CAFI

0

10

20

30

40

50

60

70

80

90

100

60ºC 70ºC 80ºC 90ºC 100ºC Untreated

Glu

ca

n o

r X

yla

n C

on

ve

rsio

n (

%) Glucose yield

Xylose yield

Conditions:60% Moisture, 5 minutes Treatment1:1 Ammonia:Biomass168hr of Hydrolysis@15FPU

Conversion of Glucan and Xylan vs.AFEX Treatment Temperature


0

10

20

30

40

50

60

70

80

90

100

60%, 90ºC, 0.7:1 60%, 90ºC, 1:1 60%, 90ºC, 1.3:1

Moisture Content, Temperature, Ammonia:Biomass

Glu

can

or

Xyla

n C

on

ve

rsio

n %

Glucan Conversion

Xylan Conversion

Effect of Ammonia Loading on Glucan & Xylan Conversion @ 60 FPU/gm glucan


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

0

10

20

30

40

50

60

70

80

90

100

40%, 90ºC, 1:1 40%, 90ºC, 1:1 60%, 90ºC, 1:1 60%, 90ºC, 1:1

Moisture Content, Temperature, Ammonia:Biomass

Glu

can

or

Xyla

n C

on

vers

ion

%

Glucan Conversion @ 60FPU

Glucan Conversion @ 15FPU

Xylan Conversion @ 60FPUXylan Conversion @ 15FPU


0

10

20

30

40

50

60

70

80

90

100

0 24 48 72 96 120 144 168 192

Hydrolysis Time (hr)

Glu

ca

n a

nd

Xy

lan

Co

nv

ers

ion

(%

)

AFEX Treated at 15FPU


AFEX Treated at 7.5FPU

AFEX Treated at 7.5

Untreated at 15FPU

Untreated at 15FPU

Untreated at 7.5FPU

Untreated at 7.5FPU

Glucan Conversion

Xylan Conversion

Treatment Conditions:90 °C, 60% Moisture, 1:1 Ammonia:Biomass5 minutes treatment

Hydrolysis of Stover Glucan & Xylan At Two Enzyme Levels


AFEX Process Yields & Mass Balance

Hydrolysis

Enzyme (15 FPU/g of Glucan)

ResidualSolids

HydrolyzateLiquidAFEX

SystemTreatedStover

Ammonia

Stover

101.0 lb100 lb

(dry basis)36.1 lb glucan21.4 lb xylan 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 glucose18.9 lb xylose (Ave. of 4 runs)



• 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)




Hydrolysis


ResidualSolids


SystemTreatedStover

Ammonia

Stover

101.0 lb100 lb




Wash

2 lb

99.0 lb

Solids washed out



Pretreatment Water:Solids

Ratio

% Solids

Solubilized

Dilute acid >5 36

Flowthrough >10 29.3

Controlled pH 6.2 37.7

AFEX 0.6 2.0

ARP >5 40.0

Lime 10.0 23.0

Water Loadings and Stover Solids Made Soluble by Pretreatments

Some Distinctive Features of AFEXNOT MUCH CHANGE

IN APPEARANCE- DRY PROCESS

Stover hydrolysis- 15 FPU @ zero hrs.

NOT MUCH EXTRACTED FROM TREATED STOVER

HPLC at 168 hours

Glucose, xylose, arabinose,Not much else

CLEAN SUGAR STREAMS FOR FERMENTATION

AFEX treated UntreatedBiomass Refining CAFI

Fed Batch SSF of AFEX Treated and Untreated Corn Stover (15 IU/gm glucan)

AFEX treated stover in fed batchSSF 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



• 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)



Kinetics of Glucan Hydrolysis

0

10

20

30

40

50

60

70

80

90

100

0 24 48 72 96 120 144 168 192

Hydrolysis Time(hr)

Glu

can

Co

nve

rsio

n (

%)

90ºC

100ºC

Untreated

Conditions:60% Moisture1:1 Ammonia:Biomass5 Minutes Treatment@15FPU


0

10

20

30

40

50

60

70

80

90

100

0 24 48 72 96 120 144 168 192

Hydrolysis Time (hr)

Glu

ca

n a

nd

Xy

lan

Co

nv

ers

ion

(%

)



AFEX Treated at 7.5FPU

AFEX Treated at 7.5

Untreated at 15FPU

Untreated at 15FPU

Untreated at 7.5FPU

Untreated at 7.5FPU

Glucan Conversion

Xylan Conversion

Treatment Conditions:90 °C, 60% Moisture, 1:1 Ammonia:Biomass5 minutes treatment

Hydrolysis of Stover Glucan & Xylan At Two Enzyme Levels



Hydrolysis


ResidualSolids


SystemTreatedStover

Ammonia

Stover

101.0 lb100 lb




Wash

2 lb

99.0 lb

Solids washed out



A Few More Words on Yield


• 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


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 40 26.6 0.46 90 E. Coli KO 11 27.1 0.47 92 Saccharomyces

strain 1400 (pLNH 32)

21.0

0.50

95


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


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


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


Acknowledgements

• The USDA Initiative for Future Agricultural and Food Systems Program through contract 00-52104-9663

• National Renewable Energy Laboratory


Questions ??


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



Hydrolysis


ResidualSolids


SystemTreatedStover

Ammonia

Stover

100.5 lb100 lb

(dry basis)36.1 lb glucan21.4 lb xylan 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




Hydrolysis

Enzyme (7.5 FPU/g of Glucan)

ResidualSolids


SystemTreatedStover

Ammonia

Stover

100.5 lb100 lb

(dry basis)36.1 lb glucan21.4 lb xylan TBD

85.3% glucan conversion, 59.3% xylan conversion (up-dated on 9/10/03)

Wash

2 lb

98.5 lb

Solids washed out



Ammonia Fiber Explosion (AFEX) System


ammonia fiber explosion (afex) for pretreatment of corn stover: recent research results

Documents

biomass refining cafiwhat

glucan xylan conversion

glucan conversion

biomass ratiotemperature

xylan conversion94

unit timehow

mass balance closure

xylan vs