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