Susan E. Powers, PhD, PEClarkson University, Potsdam NY

Research funded by LLNL, NREL, USDA

Perspectives on the Lifecycle Environmental Impacts of

Ethanol Fuels

Expected Growth in Ethanol Use

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1980 1990 2000 2010 2020

Mill

ions

Gal

lons

EtO

HPr

oduc

ed

EPact’057.5BgalBy 2012

2007 State of the Union –35 billion gallons renewable and

alternative fuels by 2017 to displace 5% current imported gasoline

2008 2008 –– projected 12 projected 12 BgalBgal

History of Env. Considerations

VOCsVOCsNOxNOxSOxSOxPMPM1010

COCO……..

19801980’’ss System Boundary ConsideredSystem Boundary Considered

Solution – change fuel compositionFuel Oxygenates added to improve air quality (CAAA 1990)

• Petroleum lobby MTBE used

1990’s

MTBE ubiquitous in groundwaterMTBE banned, ethanol reconsidered (corn lobby)New system boundary now includes groundwater impacts

System Boundary ConsideredSystem Boundary Considered

UFT

MTBEEthanol ??

2000’s – New Priorities Added

Reduce dependence on foreign oilFuels Security Act of 2003

• U.S. Senator Tom Daschle (D-SD) “Triple the use of domestic renewable fuels over the next 10 years”

Energy Policy Act of 2005

State of Union Addresses 2006, 2007 promote ethanol ands other biofuels

Current White House Policies include reducing Greenhouse gases

Changes in Lifecycle Perspective

Single impactconsidered

Air quality

Impacts only during product use

Multiple impacts considered

Air qualityGroundwater qualityPetroleum consumptionGreenhouse gases

Impacts throughout lifecycle considered

raw materials acquisition through ultimate product “disposal”

Combustion Combustion byproducts, byproducts,

NN22O, NOO, NOx,x,NHNH33

Runoff Runoff pesticides, pesticides,

NONO33--, P, P

EnergyEnergy

Fertilizers & Fertilizers & PesticidesPesticides

Water, COWater, CO22

CO, COCO, CO22, , NONOxx, , SOSOxxVOCsVOCs……..

Energyraw materials

water

Ethanol,DDGS,Other

by-products

A Lifecycle A Lifecycle PerspectivePerspective

A lot of potential impacts…

Focus today:Groundwater impacts• During Ethanol fuel use only

Surface water impacts• corn and other feedstocks• production and conversion to ethanol

Greenhouse gas emissionsPerspectives –• Benefits in carbon cycling• Detriments in nitrogen cycling• Variability among feedstocks

UFT

Ethanol ??BTEX??

gasolinegasoline

EtOHEtOH

• Nitrates – much of GW in Iowa already above MCL for NO3

• Pesticides

Groundwater Quality

Key Question –How will ethanol impacts on groundwater compare to MTBE?

CH3 - (CH2)4- CH3

Hexane

CH3 - CH2-OH

CH3-O-C-CH3

CH3

CH3

MTBE

Ethanol

..

..

..

..

Water....OH H

Potential Spill Scenarios

EtOH gasolinediesel

Ethanol-blended fuels from LUFTsand trucks

Denatured ethanol at bulk storage terminals

Ethanol partitions completely and rapidly into the aqueous phase

Ethanol readily biodegradable

Ethanol in Groundwater

Ethanol-RFG gasoline

Water Water+ ethanol

Ethanol not a problem (??)

Can the presence of ethanol affect

contamination by other gasoline constituents?

Cosolvency - C2 gasoline

Volume Fraction of Ethanol in the Aqueous Phase

Aqu

eous

Pha

se C

once

ntra

tion

(mg/

L)

10

100

1000

10000

100000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

BenzeneToluenexylenes

Ethanol-RFG

Water

gasoline

Water+ ethanol

+BTEX ?

BTEX Plume

BTEX degradation

Biodegradation Impacts

Gasoline: Natural attenuation of BTEX importantmechanism that limits the distance contaminated

groundwater can travel.

Stable length of BTEX plumeStable length of BTEX plume

BTEX Plume

Ethanol Degradation

Effective BTEX degradation “Lag Length”Oxygen and other electron acceptors consumed, reduced BTEX degradation

Biodegradation ImpactsDegradation half-life of ethanol in groundwater

ranges between 1.3 and 7 days, depending on electron acceptor used.

Reduced natural attenuation,BTEX plume travels farther

Biodegradation Modeling Predictions

Three independent assessments - benzene plumes may increase 24 – 150 % in the presence of ethanol.Net result – a small number of increased GW consumers may be exposed to BTEX through their drinking waterThese impacts are LOCAL

Summary - MTBE vs. Ethanol

Highly solubleLow biodegradation ratesNo impact on BTEX dissolutionNo impact on BTEX transport

Infinitely solubleHigh biodegradation ratesSome increases in BTEX concentrationReduction in BTEX biodegradation ratesAnaerobic GW chemistry

MTBE difficult to treat BTEX easier to treat

MTBE is problem BTEX is problem

OtherEnvironmental Impacts:Nitrogen and Carbon Cycling

Choice of Feedstock

Goal: Quantify environmental impacts associated with agricultural activities for corn and other waste feedstock resources

Greenhouse gas emissions

Eutrophication

Potential Alternatives

Dedicated cellulosic feedstocksSwitchgrassWillow / poplar

Waste materialsCorn stoverWood products waste

• chips, sawdustFood products waste

• cheese whey, fruit pommace…Paper pulp sludge

Production process includes co-generation of heat and power from ethanol processing wastes

UFT

Ethanol ??gasolinegasoline

EtOHEtOH

Waste materialsWaste materials

Ethanol impact - The Nitrogen CycleLots of N used to increase corn yieldsNatural cycles affected with conversion of N2to NH3, NO3

-

Excess reactive nitrogen responsible for many environmental problems

NHNH33

NONOxx

NONO33--

NN22OO

AcidificationAcidification

Smog FormationSmog Formation

Human HealthHuman Health

Eutrophication/HypoxiaEutrophication/Hypoxia

Global WarmingGlobal Warming

Nutrients in water Excess nutrients Excess nutrients discharged to waterdischarged to water

•• Algal BloomsAlgal Blooms

•• Excess aquatic Excess aquatic plant growthplant growth

EutrophicationEutrophication

Mutation in frogs from Mutation in frogs from excess N and P in aquatic systemsexcess N and P in aquatic systemshttp://www.nrel.gov/biomass/photos.html

National Scale Issues - HypoxiaToo many nutrients - extreme eutrophication algae growth/decay

Oxygen concentrations reduced lethal

Gulf of Mexico along Louisiana coast D.O. < ~2-3 mg/L (~8 mg/L equilibrium)

First observed in mid-1980s

~15,000 km2 (~50 x 300 km) (~ size of Massachusetts)

Detrimental to ecosystem and economy

Sources: Canter (1997), deVries (2003), Blackmer (1987)

Soil/plant system

Soil

mineralization immobilization

Constraint: Steady state over long term

LCA Inventory Generate Model for Nitrogen Flows

Plants

nitrificationFN applied NH3

food / feed / energy

uptake

NO3

Sources: Canter (1997), deVries (2003), Blackmer (1987)

Soil/plant system

Constraint: Steady state over long term

Model for Nitrogen Flows

Soil

Plants

Atmosphericsystem

GW

river

Gulf

aqueous system

deni

trific

atio

n

NN22

NN22OONONO

NHNH33

food / feed / energy

NHNH3 NONO3

FN applied

APEX - Nutrient Fate (farm only)

0

5

10

15

20

25

30

35

40

45

CC

CT

CSC

T

CSN

T

stov

er-5

0%

stov

er-7

5%

switc

hgra

ss

Nut

rient

Flo

ws

(kg/

ha/y

) N to SWP to SW

CSNT

Significance - Eutrophication

1988 1990 1992 1994 1996 1998 20000

100

200

300

400

500

600

700

800

900

1000

Dis

char

ge fr

om E

. IA

to M

SR (1

000

mtN

O3

eq.) base case est., C-S only

backgroundmaximum load - WQSactual - 30% reduced TN load

Surface water

Nutrient loads to surface water presently much higher than acceptable in MidwestNitrogen on corn primary culpritBut, can reduce this impact

Change to no-till operationsHarvest stover for ethanol feedstockGrow switchgrass

APEX - Annual Soil Loss

0123456789

10

CC

CT

CSC

T

CSN

T

stov

er-5

0%

stov

er-7

5%

Switc

hgra

ss

Soil

Loss

(t/h

a/y) These recommended changes do These recommended changes do not adversely impact soil not adversely impact soil

retention. Switch to retention. Switch to nono--till most influentialtill most influential

Long-term soil carbon losses

-2

-1

0

1

2

3

4

5

CC

CT

CSC

T

CSN

T

stov

er-5

0%

stov

er-7

5%

Switc

hgra

ss

16-y

Soi

l Car

bon

Loss

(t/h

a) These recommended changes do These recommended changes do not adversely impact soil carbon. not adversely impact soil carbon.

Switchgrass increases carbonSwitchgrass increases carbon

Global Warming PotentialGlobal Warming Potential

COCO22 UptakeUptake

COCO22 EmittedEmittedDuring Fuel During Fuel CombustionCombustion

Upstream Chemical and EnergyUpstream Chemical and EnergyProduction and DistributionProduction and Distribution

CHCH44 , CO, CO22

releaserelease

NN22OO

Global Warming Potential

-2

-1

0

1

2

3

Corn

Stover A

Stover B

Wood Res

idue

Paper

Sludge

kg C

O2

eq/ L

Upstream chemical productionUpstream electricity and fuel productionProcessing

Transportation

Feedstock farming / collection

Emissions Only

(CO(CO22, CH, CH44, N, N22O)O)

Global Warming Potential

-2

-1

0

1

2

3

Corn

Stover A

Stover B

Wood Res

idue

Paper

Sludge

kg C

O2

eq/ L

Atmospheric CO2 credit

Electricitydisplacement credit

Co-product credit

Emissions

Credits

Global Warming Potential

-2

-1

0

1

2

3

Corn

Stover A

Stover B

Wood Res

idue

Paper

Sludge

NET

(modified GREET Model, does not include fuel combustion stage)(modified GREET Model, does not include fuel combustion stage)

kg C

O2

eq/ L

Summary –

Aspects of ethanol impactsGood – generally for Carbon related impactsBad – generally related to Nitrogen impacts

ultimately a trade off between priorities

Various impacts occur over entire life cycleCan mitigate many of the problems

No-till farming practicesAlternative feedstocks, including waste materialsWhen fermentation wastes utilized for heat and power co-generation

Uncertainties

Data on waste feedstocks from models, not plant operationCo-product credits – concepts and methodologies fraught with uncertaintiesSignificant variability in environmental emissions, especially from farming

GeographicClimateExtreme events

Next Steps…

Even broader system boundaries and environmental impacts

Human toxicity not considered yetWater resourcesLand use changes

Solutions that extend beyond new fuelsCAFE standardsOther means of transportation

Human toxicity, Smog need local scale

Geographic distribution of impacts for corn ethanolGeographic distribution of impacts for corn ethanol

Powers, S.E., D. Rice, B. Dooher P.J.J. Alvarez, “Replacing MTBE with Ethanol as a Gasoline Oxygenate –How May Ground Water Resources Be Impacted?” Environ. Sci. Technol. 35(1), 24A-30A, 2001.

Powers, S.E., “Quantifying Cradle-to-Farm Gate Life Cycle Impacts Associated with Fertilizer used for Corn, Soybean, and Stover Production.” NREL/TP-510-37500, May, 2005 (http://www.nrel.gov/docs/fy05osti/37500.pdf

Powers, S.E., “Integrating Variability into Inventory Estimates of Non-point Source Nutrient Loads from Energy Crop Production.” Int. J. LCA, 12(6): 391-398, 2007.

Lavigne, A., S.E. Powers, “Valuing fuel ethanol feedstock options from multiple energy perspectives: corn and corn stover feedstocks.” Energy Policy, 35: 5918–5930, 2007.

Powers, S.E., L.A Deer-Ascough, R. Nelson, “Soil and Water Quality and Other Environmental Implications Associated With Corn Stover Removal and Herbaceous Energy Crop Production in Iowa.” technical report - National Renewable Energy Laboratory, 2007.

Extra Slides

Energy Security and Resource Conservation

Fossil Energy UsedFossil Energy Used

RenewableRenewableBioenergyBioenergy

Diesel FuelDiesel Fuel

Natural GasNatural Gas

Electricity (coal)Electricity (coal)

Metrics – Energy Issues

Current – Net energy valueNEV = Energy out – “consumer” energy in

Alternatives – National Energy PoliciesEnergy Security• % energy inputs that are imported

Energy Resource Conservation• % energy inputs that are renewable

Global warming• % energy inputs from fossil fuels

All quantified over lifecycle

Reported Corn Ethanol NEVs

-12.0

-8.0

-4.0

0.0

4.0

8.0

12.0

1975 1980 1985 1990 1995 2000 2005 2010YEAR

NEV

(MJ/

L)

-12.0

-8.0

-4.0

0.0

4.0

8.0

12.0

1975 1980 1985 1990 1995 2000 2005 2010YEAR

NEV

(MJ/

L)

Pimentel References

Corn vs. Other feedstocks

Net Energy Value (MJ/L)

Corn 6Stover 23Wood residue 19Paper pulp 9

Calculation to move beyond NEV

Corn Farm

Ethanol ProcessDirect Input

= 4.0 MJ/L 3.6 MJ/L Nat

ura

l Gas

0.4 MJ/L

Calculation to move beyond NEV7.

3 M

J/L

Tota

l Inp

ut Corn Farm

Ethanol ProcessDirect Input

= 4.0 MJ/L (55%)

0.4 MJ/L

3.6 MJ/L

0.7 MJ/L

2.2 MJ/L

Upstream= 3.3 MJ/L (45%)

Fuel

Pr

oduc

tion

Chemical Production

Elec

tric

ityPr

oduc

tion

0.4

MJ/

L

(3%)

(54%)

P2O5

K2O

Pesticide

N(94%)

(43%)

Nat

ura

l Gas

Upstream

0

2

4

6

8

10

12

14

Farm

Direct

Trans

Ener

gy C

onsu

med

MJ/

L

Farm Trans Process

Coal

Gasoline

Diesel

Coal

Gasoline

Diesel

Upstream for Chemicals

Upstream for Electricity

Upstream for Fuels

Upstream for Chemicals

Upstream for Electricity

Upstream for Fuels

LPG

Natural GasBiomass

LPG

Natural Gas

Corn Stover

Process

73% NG

Categorize by Fuel Type

Farm Trans. Process.0

2

4

6

8

10

12

Farm Trans. Process.

MJ/

L

Renewable

Other Fossil Fuels

Petroleum

Renewable

Other Fossil Fuels

Petroleum

Corn Stover

Summary Energy Issues

Stover superior for all energy related metrics

Lower NEVMuch more renewable resourcesMuch less imported oil

Acidification Potential

Electricity displacement credit

Co-product credit

Upstream chemical productionUpstream electricity and fuel productionProcessing

Transportation

Feedstock farming / collection

-2

0

2

4

6

8

10

Corn

Stov

er A

Stov

er B

Woo

d Re

sidue

Pape

r Slu

dge

g SO

2 eq

/ L

Experimental Spill

Beginning stages of a gasoline spill, dominated by gravity and capillary forces

Capillary height

Ethanol spill- Gasoline is dissolved and displaced ahead of the advancing ethanol front

Ethanol front just entering existing NAPL pool

Ethanol does not spread by capillary action

Gasoline continues to spread ahead of advancing ethanol front

Significant reduction of gasoline in vadose zone

Spreading of gasoline into saturated zone

Capillary fringe depressed

As ethanol concentrations decrease, capillary fringe begins to rebound

Increase in NAPL saturation at the capillary fringe

Smearing of NAPL in the saturated zone

Spill Summary

Increased saturation of gasoline poolIncreased pool mobilityTemporary depression of capillary fringeReduced contamination of residual gasoline in unsaturated zone

Significance of ethanol1.2

0

0.2

0.4

0.6

0.8

1

1.2

Area Contact Length Length Height Capillary Depression

Nor

mal

ized

Dat

a (X

/Xin

t)

NormalizedSpill 1Spill 2Spill 3Spill 4Spill 5

Conclusions

Ethanol spill eventsLowered interfacial tension greatly affects distribution of NAPL

Cosolvency effects result in significant increase in BTEX following ethanol spill

Reduced biodegradation of BTEX