enzyme sugar-ethanol platform project national renewable energy laboratory operated for the u.s....
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Enzyme Sugar-Ethanol Platform Project
National Renewable Energy Laboratory
Operated for the U.S. Department of Energy by Midwest Research Institute • Battelle • Bechtel
Project Goal
• Objective: Develop and demonstrate economical bioethanol technology based on enzymatic cellulose hydrolysis
• Feedstock Constraint: Develop the technology for an abundant biomass resource that can support production of at least 3 billion gallons of ethanol per year
Approach• Select corn stover as feedstock
– Most abundant, concentrated domestic biomass resource
– Potential to leverage existing corn harvesting and processing (esp. to produce fuel ethanol) infrastructure and “bridge” industrial contacts
• Utilize low cost enzymes now being developed
– Genencor International and Novozymes Biotech Inc. are leading enzyme development work through cost-shared subcontracts from the USDOE. Lower cost enzymes are anticipated in 2003-2004.
• Demonstrate compelling process economics
– Validate improved process performance and identify potentially attractive commercialization scenarios.
Project Scope
Process Development
DetailedInvestigation
Prelim.Studies
Testing andValidation
CommercialLaunch
Stage 1 Stage 3Stage 2 Stage 4 Stage 5
Gov. & Univ. & Corp. R&D
Industry-led deployment
Increasing Cost & Industrial Involvement
NREL-ledDevelopment
Industry-ledCommercialization
Strategic Fit
• The project demonstrates enabling technology for a lignocellulose-based biorefinery
• The project focuses on the core steps needed to produce sugars, fractionated lignin, and ethanol
• Industry is focusing on the application of this technology to make new products
Pretreatment Enzymatic Hydrolysis
Ethanol Production
Glucose to BioProducts
Lignin to Electricity
C5 Sugars to BioProducts
Key:
Enabling Technology
Energy Technology
Industry Technology
Fractionated Lignin to BioProducts
Ethanol Recovery
External Drivers or Showstoppers
• Price of Oil and Gasoline (Transportation Fuels)– Global supply and demand issue
– Contingent on fuel standards and energy policy
• Price and Availability of Starch (Grain) Ethanol– Existence of renewable fuel standard
– Markets for starch ethanol co-products
• Price and Availability of Corn Stover– How much can be removed and what does it cost?
– What infrastructure needed for collection, storage and delivery?
– Are there alternative markets that will out compete ethanol?
• Environmental Regulations and Policies– Greenhouse gas mitigation, carbon tax, etc.
Simplified Process Schematic
Feed Handling
Utilities
FermentationPretreatment
Burner/BoilerTurbogenerator
ConditioningWaste WaterTreatment
Distillation &StillageTreatment
Storage
Corn Stover
Hydrolyzate BrothRecycle &Condensate
Waste Water
Ethanol
Cake
Biogas & Sludge
Waste Water
Enzyme
Recycle Water
Steam
Electricity
Steam
Steam & Acid
S/L SepSolids
Liquor
Waste Water
S/L SepSyrup
Relative Cost Contribution by Area
Biomass Feedstock
Feed Handling
Pretreatment / Conditioning
SSCF
Cellulase
Distillation and Solids
Recovery
Wastewater Treatment
Boiler/Turbogenerator
Utilities
Storage
(0.30) (0.20) (0.10) - 0.10 0.20 0.30 0.40
Capital Recovery Charge Raw Materials Process ElectricityGrid Electricity Total Plant Electricity Fixed Costs
33%
5%
18%
12%
9%
10%
4%
4%
4%
1%
(after ~10x cost reduction)
Process Economics
• Production costs dominated by– Feedstock– Enzymes - cellulases– Capital equipment throughout the plant
The focus of the project is to work closely with USDOE, ORNL, USDA, and others, to decrease these key cost factors.
Key Cost Reduction Strategies• Minimize feedstock cost
– Work with ORNL, USDA, and others to reduce the cost of corn stover by developing policies and infrastructure for efficient collection, storage and delivery
• Minimize enzyme cost
– Exploit anticipated thermo-stability of lower cost enzymes being developed by Genencor and Novozymes to reduce enzyme and capital costs for process
• Reduce processing plant capital cost
– Demonstrate improved integrated process performance
– Use process engineering techno-economic models to explore potential benefits of co-location and co-products
Market Goals
• The project targets achieving a commercial production cost of $1.10 per gallon by 2010
• This target is based on a combination of technical conversion process performance goals and market considerations
• The market for ethanol is driven by refinery demand for ethanol as a gasoline blend stock
Ethanol Value-Demand Curve
• Oak Ridge National Lab’s linear programming model for a generic oil refinery used to estimate ethanol value as a function of demand (usage)
• Results quantify how the value of ethanol decreases as more of it is used
Refiner Ethanol Demand CurveReference conditions Higher ethanol
demand scenario
From G. Hadder (ORNL, 1999)
Demand Curve Findings
• At $1.10 per gallon, refiners can afford to use 1-5 billion gallons per year of ethanol, depending on the future price of petroleum
• This estimate does not include the effect of a tax incentives
• If the tax incentive continues at $0.50 per gallon ethanol, refiners can afford to use 10-11 billion gallons per year
Possible ProcessPossible Process ScenarioScenario
Feedstock Handling
CO2
Ethanol
LigninResidue
Enzyme
Corn Stover
Steam
Electricity
Steam & Acid SolidsLiquor
Pretreatment S/L Separation
ConditioningSaccharification&
FermentationDistillation &Ethanol Purification
WastewaterTreatment
Burner/BoilerTurbogenerator
Lime
Steam
Gypsum
Feedstock – Corn StoverFeedstock – Corn Stover
Model Parameter Value
Feedstock Cost $35/dry ton
Cellulose Fraction 37.1%
Xylan Fraction 19.9%
Arabinan Fraction 2.5%
Mannan Fraction 1.3%
Galactan Fraction 1.7%
Lignin Fraction 20.7%
* Composition is average of 5 stover pretreatment runs at NREL
Feedstock – Corn StoverFeedstock – Corn Stover
Rationale for data:
• Feedstock Cost: – Walsh, et.al. (ORNL)
– Demonstrated at Harlan, IA
• Feedstock Composition:– Averaged stover data (NREL)
– Research underway to improve analysis methods and understand major sources of compositional variance
Model Parameter Value
Feedstock Cost $35/dry ton
Cellulose Fraction 37.1%
Xylan Fraction 19.9%
Arabinan Fraction 2.5%
Mannan Fraction 1.3%
Galactan Fraction 1.7%
Lignin Fraction 20.7%
Feedstock – Corn StoverFeedstock – Corn StoverLarge Cost Impact
Feedstock Cost Impact
$0.83
$1.28
$1.48
$0.00
$0.50
$1.00
$1.50
Process Case
Min
imu
m E
than
ol S
ellin
g P
rice
($/
gal
eto
h)
$0.65/gal
$0 / BDT
$35 / BDT
$50 / BDT
Feedstock HandlingFeedstock Handling• Brings biomass into facility
• Prepares biomass for pretreatment
• Subcontract work to develop less expensive handling systems
Pretreatment - ExamplePretreatment - Example• Converts hemicellulose to monomeric sugars
• Makes cellulose more susceptible to enzymatic hydrolysis
Conditions:
Technology Dilute Acid
Reactor Solids Concentration
30 %
Residence Time 2 min
Acid Concentration 1.1 %
Temperature 190 °C
Reactor Metallurgy Incoloy 825-clad
Pretreatment - ExamplePretreatment - Example• Converts hemicellulose to monomeric sugars
• Makes cellulose more susceptible to enzymatic hydrolysis
Conditions:
Technology Dilute Acid
Reactor Solids Concentration
30 %
Residence Time 2 min
Acid Concentration 1.1 %
Temperature 190 °C
Reactor Metallurgy Incoloy 825-clad
Rationale for Data:
• Corn stover steam gun expts
• Hot wash process expts
• Prior research on hardwood feedstocks
Pretreatment - ExamplePretreatment - ExampleReactor Solids Cost Impact:
Prehydrolysis Solids Concentration Sensitivity
$1.20
$1.25
$1.30
$1.35
$1.40
$1.45
$1.50
10% 15% 20% 25% 30% 35% 40%
Prehydrolysis Solids Concentration inside Reactor
Min
imu
m E
tha
no
l S
ell
ing
Pri
ce
($
/ga
l)
Pretreatment - ExamplePretreatment - ExampleXylose Yield Cost Impact:
Xylose Yield Cost Impact
$1.23
$1.50
$1.28
$0.00
$0.50
$1.00
$1.50
Process Case
Min
imu
m E
than
ol
Sel
lin
g P
rice
($/
ga
l et
oh
)
$0.27/gal
50% xylose
85% xylose
95% xylose
Solid/Liquid SeparationSolid/Liquid Separation
Conditions:
Equipment Pressure Filter
Separation Temp 135 °C
Separation Pressure 5 atm
Conditioning Overlime only
Wash / Hydrolysate Ratio 0.58 kg/kg
• Separate pretreated solids from liquor
• Countercurrent hot water wash increases enzymatic digestibility and solubilizes recoverable lignin
Solid/Liquid SeparationSolid/Liquid Separation
Rationale for Data:– Lower acetylation of corn
stover hemicellulose means IX not needed to reduce acetic acid levels
– Hot wash process expts
– Harris subcontract
– Working towards pilot scale demonstration at NREL
Conditions:
Equipment Pressure Filter
Separation Temp 135 °C
Separation Pressure 5 atm
Conditioning Overlime only
Wash / Hydrolysate Ratio 0.58 kg/kg
• Separation of pretreatment solids from liquor
• Countercurrent hot water wash increases enzymatic digestibility and solubilizes recoverable lignin
Solid/Liquid SeparationSolid/Liquid SeparationCost Impact:
Conditioning Sensitivity
$1.20
$1.25
$1.30
$1.35
$1.40
$1.45
$1.50
OL only IX / OL
Process Case
Min
imu
m E
tha
no
l S
ell
ing
Pri
ce
($
/ga
l e
toh
)
$0.08 / gal
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Saccharification:
Enzyme Source purchased
Enzyme Cost $0.11/gal EtOH
SHF vs. SSF Hybrid
Temperature 65 °C
Residence Time 1.5 days
Cellulose to Glucose Yield
90%
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Saccharification:
Enzyme Source purchased
Enzyme Cost $0.11/gal EtOH
SHF vs. SSF Hybrid
Temperature 65 °C
Residence Time 1.5 days
Cellulose to Glucose Yield
90%
Rationale for Data:• Enzyme Cost is 10x-reduction
from Glassner-Hettenhaus parameters
• 10x-reduction is goal of enzyme subcontracts
• Hybrid design advantageous for more thermotolerant enzyme system
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Fermentation:
Residence Time 2 days
Temperature 37 °C
Nutrient Requirement 0.25% CSL
0.33 g/L DAP
Effective Solids Conc. 20%
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Fermentation:
Residence Time 2 days
Temperature 37 °C
Nutrient Requirement 0.25% CSL
0.33 g/L DAP
Effective Solids Conc. 20%
Rationale for Data:• Previous work based on
conversion of hardwood hydrolyzates using Z. mobilis
– Nutrients
• Strain improvements
– 2nd Gen. ethanologen projects at NREL
– Literature search
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Yields:
Glucose to Ethanol Yield 92%
Xylose to Ethanol Yield 85%
Arabinose to Ethanol Yield 85%
Contamination Loss 5%
Saccharification & FermentationSaccharification & Fermentation
• Enzymatic hydrolysis of cellulose to glucose
• Microbial conversion of sugars to ethanol
Yields:
Glucose to Ethanol Yield 92%
Xylose to Ethanol Yield 85%
Arabinose to Ethanol Yield 85%
Contamination Loss 5%
Rationale for Data:• Initial work based on
glucose and xylose cofermenting Z. mobilis
• Improved strains constructed with broader pentose and hexose substrate ranges
– rDNA yeast
– Ingram et al. constructs
Saccharification & FermentationSaccharification & FermentationEnzyme Cost Impacts:
Enzyme Cost Impact
$1.23
$1.67
$2.24 $1.07 / gal
$0.00
$0.50
$1.00
$1.50
$2.00
Process Case
Min
imu
m E
than
ol S
ellin
g P
rice
($/
gal
eto
h)
$1.01/gal
$0.06 / gal
$0.11 / gal
$.50 / gal
$1.28
Saccharification & FermentationSaccharification & FermentationCost Impacts:
Fermentation Residence Time Cost Impact
$1.25
$1.32
$1.28
$1.20
$1.25
$1.30
$1.35
$1.40
$1.45
$1.50
Process Case
Min
imu
m E
tha
no
l S
ell
ing
Pri
ce
($
/ga
l e
toh
)
$0.07/gal
1 day
3.5 days
7 days
Saccharification & FermentationSaccharification & FermentationCost Impacts:
Fermentation Yield Cost Impact
$1.23$1.28
$1.33
95%
92%
70%
$1.20
$1.50
$1.80
$2.10
$2.40
glucose only add 85% xylose add 85% arabinose all other sugars85%
Min
imu
m E
than
ol S
ellin
g P
rice
($/
gal
)
Saccharification & FermentationSaccharification & FermentationCost Impact:
Contamination
5% 7% equates to $0.02/gal increase
Nutrient Cost
$0.035/gal
89% CSL, 11% DAP
Distillation & Ethanol PurificationDistillation & Ethanol Purification• Separation of ethanol and CO2 from “beer”
Wastewater TreatmentWastewater Treatment• Anaerobic and aerobic treatment
• Reduce Biochemical Oxygen Demand (BOD)
• Recycle water
Burner/Boiler/TurbogeneratorBurner/Boiler/Turbogenerator• Biomass boiler generates steam from lignin residue
• Excess electricity from generator sold to power grid ($0.04/kWh credit)
• High capital cost area
Current Status
• Completing Stage 2– Compelling scenario identification
• Technology selection
– Stage 3 plan development
• Next step: Gate 3 review– Planned for January 2002
Conversion-relatedCost Reduction Opportunities
• Stage 2 technology selection focus– Is a better pretreatment technology available?
• Higher yields, lower capital or operating costs
– Is a better fermentation strain available?• Broader sugar utilization range, higher ethanol yields,
better compatibility with enzyme
• Stage 3 technology improvement focus– Are better cellulases available and how do they
benefit integrated process economics?
Technology Selection
• Tiered screening approach being applied to ensure best options will be studied in Stage 3– 1st screen: Efficacy– 2nd screen: Readiness and availability
• Stage 2 focus:– Pretreatment technology
– Fermentation strain
Co-location-relatedCost Reduction Opportunities
• Better feedstock price– Proximity to transportation– Farmer cooperative
• Reduce capital cost– Utilize existing utilities and processing
infrastructure within site constraints
Cost Reduction Strategies, cont.
• Reduce conversion plant capital cost– co-locate into a dry mill expansion– co-locate with a coal-fired power plant– co-locate with both a dry mill and power plant
• Reduce capital cost through better financing– Loan guarantee?– City/county/state/federal support or tax benefits?
Cost Reduction through Co-products
• New process case potentially enables “sugar platform” and “lignin platform” co-products– Value-added co-products can increase upside of
process commercialization and mitigate overall risk
• While we can explore the possibilities, development of prospective co-products must be led by industry!
Potential Bioethanol Co-products
Soluble Lignin (Low/Medium MW Phenolics)
Hemicellulose Hydrolyzate
(Xylose)
Cellulose Hydrolyzate
(Glucose)
Insoluble Lignin (High MW Phenolics)
1o EnzymaticCellulose
Hydrolysis
PretreatmentHemicellulose
Hydrolysis
2o EnzymaticHydrolysis &Fermentation
EthanolRecovery &Purification
Cell Mass, Enzymes
(Protein, etc.)
Process Residue Solids
Process Residue Liquids
Biomass EtOH
Concentration & Purification of
Sugar Product(s)
Sugar & Lignin Platform Biorefinery
Sugar-rich HydrolyzateFeedstock
HandlingBiomass
Fractionation
Waste WaterTreatment
Renewable Biomass
Feedstock
WasteWater
Residual Solids & Syrup
Biogas& Sludge
Sugar Product(s)
RecycleWater
Steam
Steam
CatalystSteam, Acid,Enzyme, etc.)
SteamGeneration
PowerProduction
(Turbogenerator)
Ethanol Production& Recovery
Hydrolyzate& Residual
Solids FuelEthanol
Make-up Water
Waste Water
Unrecovered Sugars
Electricity
SteamWater
RecoveredLignin Purification
& Drying ofLignin Product(s)
LigninProduct(s)
SteamWater
Unrecovered Lignin
UnrecoveredLignin