ammonia fiber explosion (afex) for pretreatment of corn stover: recent research results farzaneh...
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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?”
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 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
Biomass Refining CAFI
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
Biomass Refining CAFI
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
Biomass Refining CAFI
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 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
Biomass Refining CAFI
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)
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)
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)
Biomass Refining CAFI
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
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
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
Biomass Refining CAFI
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 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
Biomass Refining CAFI
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)
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 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
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 00-52104-9663
• 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)
ResidualSolids
HydrolyzateLiquidAFEX
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
39.9 lb glucose19.3 lb xylose (Ave. of 3 runs)
Biomass Refining CAFI
AFEX Process Yields & Mass Balance
Hydrolysis
Enzyme (7.5 FPU/g of Glucan)
ResidualSolids
HydrolyzateLiquidAFEX
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
34.2 lb glucose14.42 lb xylose (Ave. of 2 runs)
Biomass Refining CAFI
Ammonia Fiber Explosion (AFEX) System
Biomass Refining CAFI