Energy, Greenhouse Gas Emissions and Water Use of Fuel Ethanol

Michael WangCenter for Transportation ResearchArgonne National Laboratory

Governors’ Ethanol Coalition MeetingChicago, IL, April 28, 2008

Well to Wheels

The GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) Model

Fuel Cycle GREET 1.8

Vehi

cle

Cyc

le G

REE

T 2.

7

More than 100 fuel production pathways from various feedstocks

More than 75 vehicle/fuel systemsGREET and its documents are available at Argonne’s

website at http://www.transportation.anl.gov/software/GREET/The most recent GREET version (GREET 1.8b) was

released in March 2008

3

Oils for Biodiesel/Renewable Diesel

SoybeansRapeseedPalm oilJatrophaWaste cooking oilAnimal fat

Sugar Crops for EtOHSugar caneSugar beetSweet sorghum

GREET Includes Some of the Potential Biofuel Production Pathways

Starch Crops for EtOH CornWheatCassavaSweet potato Cellulosic Biomass for EtOH

Corn stover, rice straw, wheat strawForest wood residueMunicipal solid wasteEnergy cropsBlack liquor

The feedstocks that are underlined are already included in the GREET model.

Butanol Production CornSugar beet

Cellulosic Biomass via Gasification

Fischer-Tropsch dieselHydrogenMethanol

4

Key Issues Affecting Biofuel WTW ResultsNitrogen fertilizer plants

Energy useNatural gas vs. coal as feedstock

FarmingCrop and biomass yieldsEnergy and chemical inputs

Energy use in biofuel plantsThe amount of process fuelsThe type of process fuels

Credits of co-products of biofuelsDistillers grains and solubles for corn ethanol: 0-50%Electricity for cellulosic and sugarcane ethanolSoy meals and glycerin for biodieselAcetone for butanol

N2O conversion factors of nitrogen fertilizerIPCC: 1.325% (GREET adopts it; equivalent to 1.77% of Crutzen factor) Crutzen et al.: 3-5% (equivalent to 2.24-3.74% of IPCC factor)Background vs. N fertilizer-induced N2O emissions in fields

Land use changes and resulted CO2 and CH4 emissionsSome of the issues are affected heavily by the scale of biofuel production

Corn Ethanol GHG Reductions Under Different N2O Conversion Factors

5

GH

G C

hang

e R

elat

ive

to G

asol

ine

N2O Conversion Rate

Energy Use in Ethanol Plants Has Reduced by More Than 50% in the Past 20 Years

Ethanol Plant Type Natural Gas (Btu)

Coal (Btu)

Renewable Process Fuel (Btu)

Electricity (kWh)

1. Plant with natural gas (NG) 33,330 None None 0.75

2. Plant with NG and wet DGS 21,830 None None 0.75

3. Plant with coal None 40,260 None 0.90

4. Plant with coal and wet DGS None 26,060 None 0.90

5. Plant with wood chips None None 40,260 0.90

6. Plant with DGS as fuel None None 40,260 0.75

Corn ethanol plants in early 1980s consumed 70,000 Btu per gallon of ethanol produced.

Current and Near-Future Ethanol Plant Energy Use (per gallon of ethanol)

Co-Products with BiofuelsTypes of co-products

Corn ethanol: animal feeds (distillers grains and solubles, DGS)Sugarcane ethanol: electricityCellulosic ethanol: electricityBiodiesel and renewable diesel from soybean and rapeseed: animal feeds, glycerin, and other chemicals

Ways of dealing with co-productsDisplacement method (or the system boundary expansion approach)Allocation methods• Mass based• Energy content based• Economic revenue based

Production plant process purpose basedScale of biofuel production (and resultant scale of co-product production) can affect the choice of methods

Proper Accounting for Animal Feed Is Key to Corn Ethanol’s Lifecycle Analysis

Allocation Method Wet milling Dry milling Weight 52% 51% Energy content 43% 39% Process energy 36% 41% Market value 30% 24% Displacement ~16% ~20%

Argonne uses the displacement method.

DG S Market Shares In 2006

GHG Emission Implications of Potential Land Use Change by Large-Scale Biofuel Production Needs to Be Examined

Potential land use changesDirect land use change: regional or national scaleIndirect land use change: global scaleBoth can be simulated with global computational general equilibrium (CGE) modelsThe resolution level of global CGE models could be a key factor

Carbon profiles of major land typesModels in the U.S. and Europe are availableCarbon profiles of land types in other parts of the world (South America, Asia, Africa) may be less understood

Time horizon of biofuel programs; “for-ever biofuels” can mathematically result in zero GHG emission changes from land use changesThere are some limited simulation results as of now; further efforts in this area are underwayAt present, GREET includes the following soil CO2 sources/sinks for ethanol

Corn ethanol: CO2 source of 73 grams/gal. EtOH from soil C reductionCellulosic ethanol

• Fast growing trees: CO2 sink of 1,250 g/gal. EtOH from soil C increase• Switchgrass: CO2 sink of 540 g/gal. EtOH from soil C increase

Up to 2007, U.S. Biofuel Production Does Not Seem to Significantly Impact U.S. Export of Corn and Soybeans

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On the Other Hand, U.S. Has Increased DGS Export Significantly

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1000 MT of DGS are equivalent to at least 39,000 bushels of corn; 2007 U.S. DGS export is equivalent to export of at least 117 million bushels of corn.

Cellulosic Ethanol Plants Potentially Produce Electricity Together With Ethanol

Key Issues Affecting Cellulosic Ethanol ResultsCellulosic biomass feedstock types

Fast growing trees • Soil carbon could increase • Fertilizer may be applied

Switchgrass and other native grass • Soil carbon could increase• Fertilizer will be applied

Crop residues• soil carbon could decrease• Additional fertilizer will be needed to supplement nutrient removal

Forest wood residues: collection effort could be extensiveCo-production of ethanol and electricity

The amount of electricity producedThe types of conventional electric generation to be displaced

Relative to corn ethanol, land use changes should have less effects on cellulosic ethanol’s GHG results

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Fuel-Cycle GHG Emission Shares for Corn-Based Ethanol

Shares of GHG Emissions for Corn Ethanol: Total of 5,795 grams/gallon (with Co-Product Credits)

Nitrogen31%

Corn Transportation3%

Corn Farming16%

Ethanol Transportation

2%

EtOH Production35%

Other Chemicals11%

Farming Machinery2%

Shares of GHG Emissions for Corn Ethanol: Total of 7,171 grams/gallon (without Co-Product Credits)

Nitrogen25%

Farming Machinery1%

Other Chemicals9%

EtOH Production48%

Ethanol Transportation

2%Corn Farming

13%Corn Transportation

2%

Energy Benefits of Ethanol Lie in Fossil Energy and Petroleum Energy

WTW Total Energy ResultsWTW Fossil Energy Results

WTW Petroleum Energy Results

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GHG Emissions of Corn Ethanol Vary Considerably Among Process Fuels in Plants

WTW GHG Emissions Per Million Btu

GHG Emission Reductions By Ethanol

Caution: effects of land use changes, especially indirect land use changes, are not included.

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Addressing Consumptive Water Use in Fuel Production

Developing a baseline characterization of current consumptive water use in production of biofuels and petroleum fuelsUnderstanding current practices in water conservation in the fuel industryEstimating consumptive water use in major life cycle steps for:

Current bioethanol production from cornFuture cellulosic bioethanol production from switchgrassGasoline production from conventional crude and oil sands

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Sources of Water Supply for Farming and Ethanol Production

Corn farmingRain fallSurface water irrigationGround water irrigation

Switchgrass farmingMay require little water to grow in U.S.Studies suggested that a yield of 4 - 8 dry tons per acre can be achieved without irrigation

Ethanol ProductionGround water withdrawal

Ground water in deep aquifers is non-renewable, its over consumption could lead to resource depletion

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Water Analysis for Corn Production

Adapted from Energetics, 2007

1

2

34

5

67

8

9

10 1

2

34

5

67

8

9

10

Based on ten farm production regions as designated by the USDA Considered corn growing states:

Regions 5, 6, and 7; including Iowa, Indiana, Illinois, Ohio, Missouri, Minnesota, Wisconsin, Michigan, North Dakota, South Dakota, Nebraska, Kansas88% of total U.S. corn production95% of total U.S. ethanol production

Included net water consumption from irrigation (i.e., water returning to water body not accounted)Estimated regional variations

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0

1000

2000

3000

4000

5000

6000

Region 7 Region 6 Region 5USDA Regions

Corn produced (MM bushels/y), 2003

Total ground water use (billion gallons/yr)

91%

3% 6%

59%

18%22%

Significant Regional Variations in Irrigation Water Use

Data source: USDA NASS, 2003 crop year; USDA Farm and Ranch Irrigation Survey, 2003

In U.S. …

Within the regions…

760 gal/bu

18 gal/bu29 gal/bu

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The ethanol industry maintains that zero net water consumption in ethanol plants is achievable with current technology and extra capital investment.

Water Use in Existing Dry Mill Corn Ethanol Plants

5.84.7 4.2 4.0 3.5

0.0

2.0

4.0

6.0

8.0

Dry mills,average(NREL)

USDA survey MN dry mills MN dry mills RFA survey

1998 2003 2005 2006 2007

Con

sum

ptiv

e w

ater

use

(G

allo

n w

ater

/gal

lon

fuel

eth

anol

)

Design value 3.63 gal/gal

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Consumptive Water Use from Corn Farming to Ethanol Production

USDA Regions 5 6 7

Share of ethanol production capacity in U.S. 52% 14% 30%

Corn farming, ground water 6.7 10.7 281.2

Corn farming, surface water 0.4 3.2 39.4

Ethanol production 3.5 3.5 3.5

Total 10.5 17.3 324.1

Unit: gallons water consumed per gallon of ethanol produced

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Consumptive Water Use of Cellulosic Ethanol Production

0 4 8 12

BioChemical,current

BioChemical,future

Thermochemical,optimized

Syngas-to-ethanol,future

Consumptive water use (gal water/gal ethanol)

Feedstock Ethanol production

Assume there is no irrigation for switchgrass farming

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Consumptive Water Use from Crude Production to Crude Refining

0.00 2.00 4.00 6.00 8.00 10.00 12.00

SAGD(Athabasca)

CSS (ColdLake)

Multi-scheme(PeaceRiver)

PADD II

PADD III

PADD V

Oil

Sand

sSu

rface

Min

ing

Oil

Sand

s In

-Situ

US

On-

Shor

eE&P (gal/gal crude) Refining (gal/gal crude)

Oil Sands Production Shares

US On-shore Crude Production Shares

34%

43%

13%

1.2%

21%

22%

55.6%

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SummarySo far, corn ethanol has achieved moderate GHG reductions; future GHG effects of corn ethanol are unclear

The unclear future of corn ethanol’s GHG effects is from the potential land changes by the rapid expansion of U.S. corn ethanol production

Cellulosic ethanol will achieve significant GHG reductions

Corn ethanol requires a significant amount of water, primarily due to irrigation for corn farming

Significant regional variations of water use for corn ethanol production are attributable to irrigation requirements in different regions