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Biofuels as an alternative to traditional transportation fuels: Chemist's Perspective

Ole John Nielsen and Vibeke Friis Andersen

Department of Chemistry, University of Copenhagen

Copenhagen June 10th 2011

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Acknowledgements

• Tim Wallington (FORD)• Sherry Mueller (FORD)• Jim Anderson (FORD)• Mads Andersen (NASA)• The CCAR group

• $$$: Danish Natural Science Research Council• $$$: Villum Kahn Rasmussen Foundation• $$$: EUROCHAMP2

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What features do we desire in a vehicle fuel?1. Cheap, either already abundant in nature, or easy to make2. Fuel and spent fuel should be easy and safe to handle (i.e.,

liquid or gas [not solid] over “typical” temperature operation range of -20 to +40 oC and no reaction with air or water under ambient conditions)

3. For a chemical fuel we need at least two reactants. Inefficient to carry more than one reactant on vehicle/plane, best to use atmosphere as second reactant. Atmosphere is 78% N2, 21% O2, 1% Ar. N2 is poor reactant (N≡ N bond too strong), Ar is unreactive, leaves O2

4. Fuel should have highly exothermic reaction with O2 but not at ambient temperature (kinetics and thermochemistry)

5. High energy density.6. Environmentally benign, renewable and the oxide(s) should

be benign

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Periodic Table

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Periodic Table

Exclude elements that: (i) have solid oxides

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Periodic Table

Exclude elements that: (i) have solid oxides, (ii) do not have highly exothermic reaction with oxygen

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Periodic Table

Exclude elements that: (i) have solid oxides, (ii) do not have highly exothermic reaction with oxygen, (iii) have toxic oxides

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Periodic Table

Conclusion: hydrogen and carbon are likely to be the two most important elements in transportation fuels.

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Periodic Table

Conclusion: hydrogen and carbon are likely to be the two most important elements in transportation fuels and oxygen will do no harm

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2. Motivation for biofuels - Sustainability

Sustainabilty:

•Economic,

•Environmental

•Social sustainability

•Biofuels address:

• Energy security

• Climate Change

• Support for rural communities

Year1880 1900 1920 1940 1960 1980 2000 2020

Ave

rage

glo

bal l

and

surf

ace

air

tem

pera

ture

(oC

)

13.5

14.0

14.5

15.0 Jan- Oct 2010

Warmest five years: 2005, 2007, 2009, 1998, 2002

Data source: NASA (2010)

Proven oil reserves. Source: BP

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3. Biofuel History- Biofuels are not new

Ford’s vision was to “build a vehicle affordable to the working family and powered by a fuel that would boost the rural farm economy.”

1908 – Ford Model T introduced

Around 1915 - First Flexible Fuel Model T Vehicle - (low compression engine, adjustable carburetor, and spark advance allowed use of gasoline, ethanol, or blends)

1916 - "All the world is waiting for a substitute for petrol. The day is not far distant when, for every one of those barrels of petrol, a barrel of ethanol must be substituted.”

– Henry Ford

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1920s Gasoline was motor fuel of choice; 6-12% ethanol added for anti-knock

www.jgi.doe.gov

Vehicle Ethanol: Rise and Fall

1940s Low-priced, Middle-East oil

1937 Ford supported ethanol for fuel. Ethanol blends account for 25% of sales in Midwest

1920s Tetraethyl lead added for anti-knock

2000s MTBE phased-out due to environmental concerns;Crude oil price more than doubled (~$30/bbl to $80+/bbl)

2005 U.S. oil imports accounted for 70% of consumption, U.S. Energy Policy Act mandated 7.5 billion gallons of renewable fuel use by 2012

2007 President Bush announced 35 billion gallons alternative fuel goal (2017). Ethanol production capacity was 10-12 billion gallons by 2010.

1970s World energy crisis; Leaded gas phased-out; US subsidies for ethanol blends

1978 MTBE became oxygenate of choice;1980s Excess oil capacity caused drop in crude oil price

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Biofuel are many different things

first, second and third generation…

/ butanols

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aOECD-SG/SD/RT(2007)3

4. Will biofuels survive this time?

• 2005: 0.8 EJ (1% of the total road transportation fuel)• 2010: 2-3% of rtf• 2050: 20 EJ from first generation biofuels (11% rtf)a

• 2050: 23 EJ from second generation biofuels (12% rtf)a

Says 27% in 2050 (a ref – but no ref….)

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460 Mha(Tot land 0.8 Gha)

520 Mha(Tot land 2 Gha)

730 Mha(Tot land 1.6 Gha)

620 Mha(Tot land 1 Gha)

730 Mha(Tot land 2 Gha)

1290 Mha1290 Mha(Tot land 3.4 Gha)(Tot land 3.4 Gha)

140 Mha(Tot land 0.3 Gha)

360 Mha(Tot land 1.9 Gha)

Assumptions:• 100 EJ from energy crops (0.5 Gha, 10 t/ha, 20 GJ/t)• 100 EJ from waste material (e.g. straw, sawdust, manure, MSW)

Global biomass supply potential converted into biofuel could satisfy approximately 20-30% of projected global transportation energy needs in 2050

Global total land ~13 GhaGlobal arable and pasture land ~4.85 Gha

Source: Maria Grahn, Chalmers University (2007)

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5. The Atmospheric Chemistry

• One example: iso-butanol

• Reaction with OH radicals is the most important atmospheric reaction

• Determine the OH rate constant and the degradation products

V. F. Andersen, T. J. Wallington, O. J. Nielsen: “Atmospheric Chemistry of i-butanol”, J. Phys. Chem. A 114, 12462-12469 (2010)

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Experimental Techniques

Smog chamber with FTIR

1.Cl2+hν→2Cl

2.CH3ONO+hν CH3O + NO CH3O + O2 HCHO + HO2

HO2 + NO OH + NO2

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OH radical kinetics•OH + (CH3)2CHCH2OH → products (9)•OH + C3H6 → products (10)•OH + C2H4 → products (11)

•Linear least squares analysis gives •k9/k10 = 0.41±0.04 and k9/k11 = 1.41±0.10.

•Using k10 = 2.63 x 10-11 and k11 = 8.52 x 10-12

•gives k9 = (1.08 ± 0.11) x 10-11 and (1.20 ± 0.09) x 10-11 cm3 molecule-1 s-1.

•Hence k9 = (1.14±017) x 10-11

•Reaction with OH radicals is the major atmospheric loss process for (CH3)2CHCH2OH

•Combined with [OH]=1x106

•Gives lifetime ~ 1 day

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OH radical kinetics

Oxidation kinetics of i-butanol are well established.

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OH radical oxidation products

OH radical initiated oxidation gives CH3C(O)CH3 in a molar yield of 61 ±4%.

Experimental data are indistinguishable from the result (57%) predicted using structure activity relationships and assumed in atmospheric models.

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57%

61%

4% 37%SAR:

Results are consistent with model assumptions

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Conclusions• Biofuels can address climate change and energy security.

– Biofuels not a wonder solution, but could make an important 10-30% contribution to the transportation sector.

– Incorporating biofuels into transportation fuels requires adherence to fuel specifications.

– Implementing a biofuels strategy requires the consideration of vehicle compatibility for optimal performance

– Provide support for rural communities (i.e. social benefit)

• Second and “third” generation biofuels needed.– Many ways to make biofuels, good ways and bad ways, encourage

the good ways (certification perhaps?)– Modern biofuel science in its infancy – future contribution of biofuels

to transportation fuel pool is unclear

• Environmental impacts (atm chem) of potential biofuels must be quantified/investigated

• Food vs Fuel issues?• Need to address CO2 from all sectors

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We have a lot to roar about

Thank you for your attention

Transportation biofuels present interesting questions -

It’s a great time to be an atmospheric chemist

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Extra slides

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Food vs Fuel?

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Ethanol or butanol from lignocellulose (grasses, wood) via hydrolysis & fermentation

Bio-gasoline from plant oils via catalytic cracking

Biomass-to-liquid (BTL) processes

- Alkanes via gasification + Fischer-Tropsch synthesis (CI, SI)

- Methanol via gasification + synthesis (SI)

- Bio-oil via anhydrous pyrolysis (CI)

- Bio-oil via hydrothermal upgrading (CI)

Alkanes from plant oils via hydrotreating

Butanol from sugar crops via fermentation

2nd

(10+ yr)

Fatty acid methyl esters (FAME) from plant oils (soy, canola, palm) via transesterification

Ethanol from starch/sugar crops (corn, sugar cane) via fermentation

Biogas from organic matter via anaerobic degradation

1st

(Now)

CI Biofuels

(Diesel, Cetane)

SI Biofuels

(Gasoline, Octane)Generation

Ethanol or butanol from lignocellulose (grasses, wood) via hydrolysis & fermentation

Bio-gasoline from plant oils via catalytic cracking

Biomass-to-liquid (BTL) processes

- Alkanes via gasification + Fischer-Tropsch synthesis (CI, SI)

- Methanol via gasification + synthesis (SI)

- Bio-oil via anhydrous pyrolysis (CI)

- Bio-oil via hydrothermal upgrading (CI)

Alkanes from plant oils via hydrotreating

Butanol from sugar crops via fermentation

2nd

(10+ yr)

Fatty acid methyl esters (FAME) from plant oils (soy, canola, palm) via transesterification

Ethanol from starch/sugar crops (corn, sugar cane) via fermentation

Biogas from organic matter via anaerobic degradation

1st

(Now)

CI Biofuels

(Diesel, Cetane)

SI Biofuels

(Gasoline, Octane)Generation

Many potential second generation biofuels – need research.

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Externalities of biomass growth and biofuel production will be magnified as scale increases.

Many factors must be considered for scale-up of first generation and development of second generation.

• Economics– Feedstock price and transport– Processing– Land use changes

• Food prices• Natural habitat, biodiversity

• Environmental properties (LCA)– Petroleum reduction– Greenhouse gas reduction– Other resources

• Properties as fuels

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Need to address CO2 in all sectors.

On-road light-duty car and trucks contribute about 20% of US, 17% of EU-15, and 11% of global fossil fuel CO2 emissions.

2004 Global CO2 Emissions

2004 USA Sectors 2004 USA Transportation 2004 USA Passenger Cars

Other, 23%

USA, 22%

China, 17%

Europe, 17%

Russia, 6%

Japan, 5%

India, 4%

Canada, 2%

S. Korea, 2%

S. Africa, 2%

Electricity Generation,

41%

Transport

33%Passenger Cars

33%

Light-duty

Trucks

27%

Other Trucks, 20%

Buses Other Rail Ships Aircraft

1% 3% 3% 3% 10%

2004 EU-15 Sectors 2004 EU-15 Transportation 2004 EU-15 Passenger cars

Vehicle Stock

95%

Vehicle Stock

93%

New Cars

7%

New Cars

5%

Passenger Cars

52%

Light Duty

Vehicles

14%

Heavy Duty

Vehicles

24%

Other Buses Rail Ships Aircraft

1% 3% 1% 3% 3%

Electricity Generation

37%

Manufacturing

17%

Commercial

5%Residential

13%Other

2%

Transport

26%

Distribution of CO2 Emissions from Fossil Fuel Combustion

Industrial, 15%

Commercial Residential 4% 7%

T. J. Wallington, J. L. Sullivan, and M. D. Hurley, Emissions of CO2, CO, NOx, HC, PM, HFC-134a, N2O and CH4 from the Global Light Duty Vehicle Fleet, Meteorol. Z., 17, 109 (2008)

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Energy content

MJ/kg• Gasoline 43.4 • Diesel 42.8 • Methanol 20.1• Ethanol 27.0• 1-Butanol 33.1• Propane 46.3• Methane 55.6• DME 28.4• Hydrogen 121.5• Biodiesel (FAME) 37.5

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31

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4. Experimental apparatus and setup

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FTIR SMOG CHAMBERSFTIR SMOG CHAMBERS

140 L Pyrex chamber

black-lamps

296 K

1-760 Torr

FTIR-detection

100 L Quartz chamber

UVA, UVA and sunlamps

245-325 K

1-760 Torr

FTIR-detection

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UV irradiation of:

– compound X/reference/CH3ONO/NO/air

(reference = C2H2 or C2H4)

CH3ONO + hν CH3O + NO

CH3O + O2 HCHO + HO2

HO2 + NO OH + NO2

OH + compound X products

OH + reference products

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Biodiesel model compound• CH3(CH2)7CH=CH(CH2)7C(O)OCH3 from oleic acid,

C15H31C(O)OCH3 from palmitic acid

• Energy density

• Biodiesel is composed of esters of fatty acids (typically methyl esters) and is made via a relatively simple trans-esterification process from tri-acyl-glycerides. Esters because of cold flow properties.

• Prior to the use of such acylated glyercine derivatives, information on their atmospheric chemistry and hence environmental impact is required.

• CH3C(O)O(CH2)2OC(O)CH3, ethylene glycol diacetate, as a model compound for such acylated glycerine molecules.

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CH3C(O)O(CH2)2OC(O)CH3

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OH + CH3C(O)O(CH2)2OC(O)CH3 → products (4)OH + C2H4 → products (5)OH + C2H2 → products (6)

Linear least squares analysis gives k4/k5 = 0.28 ± 0.03 and k4/k6 = 2.8 ± 0.3.

Using k5 = 8.7 x 10-12 and k6 = 8.45 x 10-13, we derive k4 = (2.4 ± 0.3) x 10-12 cm3molecule-1s-1.Atmospheric lifetime of approx. 5 days

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CH3C(O)OH

CH3C(O)OH

CH3C(O)OC(O)H

CH3C(O)OC(O)CH2OC(O)CH3

Closed symbols: 5 Torr O2

Open symbols: 700 Torr O2

Mechanism?

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UV irradiation of:

– CH3CH2CHOHCH2CH3/reference/CH3ONO/NO/air

(reference = C2H2 or C2H4)

CH3ONO + hν CH3O + NO

CH3O + O2 HCHO + HO2

HO2 + NO OH + NO2

OH + CH3CH2CHOHCH2CH3 products (4)

OH + reference products (5/6)

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Ln([reference]t0/[reference]t)

0,0 0,2 0,4 0,6 0,8 1,0

Ln

([C

H3C

H2C

H(O

H)C

H2C

H3] t0

/[C

H3C

H2C

H(O

H)C

H2C

H3] t)

0,0

0,2

0,4

0,6

C2H4

C3H6

OH + CH3CH2CHOHCH2CH3 → products (4)OH + C2H4 → products (5)OH + C3H6 → products (6)

Linear least squares analyses give k4/k5 = 1.6 ± 0.05 and k4/k6 = 0.46 ± 0.03

Using k5 = 8.52 x 10-12 and k6 = 2.68 x 10-11, we derive k4 = (1.3 ± 0.1) x 10-11 cm3molecule-1s-1.Gives an atmospheric lifetime for 3-pentanol of around 1 day.

Previously published value k = (1.2 ± 0.3) × 10‑11 cm3molecule‑1s‑1. Structure activity relationship (SAR) prediction of 1.13 x 10-11 cm3molecule-1s-1 with 90% of the predicted reactivity is on the central carbon atom. No product studies have been reported.

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3-Pentanone

3-Pentanol / [3-Pentanol]o

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

3-P

enta

none

/ [3

-Pen

tano

l]o

0,00

0,05

0,10

0,15

0,20

0,25

0,30

As in the case of OH, a significant fraction of the Cl reactivity is expected to take place at the central C atom:

CH3CH2CHOHCH2CH3 + Cl → α(CH3CH2C.OHCH2CH3) + HCl (1)

CH3CH2C.OHCH2CH3 + O2 → CH3CH2C(O)CH2CH3 + HO2 (100%)

We expect to observe a significant yield of 3-pentanone as one of the products in the reaction of 3-pentanol with Cl atoms in the presence of O2. 3-pentanone also reacts with Cl atoms, kCl=8.1x10-11 cm3molecule-1s-1. The corresponding rate equation can be solved analytically to relate the concentration of 3-pentanone to the conversion of 3-pentanol. The curve through the data is a fit of the expression above to the data which gives α = 42%.

There is some fundamentals to be learned!

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Biofuel – future

• 2005: 0.8 EJ (1% of the total road transportation fuel)• 2050: 20 EJ from first generation biofuels (11% rtf)• 2050: 23 EJ from second generation biofuels (12% rtf)

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Biofuel – future Energy security/availability• US consuming and importing more energy than ever before• Shrinking petroleum reserves• Political unrest in oil-producing regions• High (and unstable) petroleum prices

Source: EIA0

2

4

6

8

10

12

14

16

18

20

1950 1960 1970 1980 1990 2000 2010 2020 2030 2040

Cru

de

Oil

(m

illi

on

bar

rels

per

day

)

2005 Proven Reserves (Thousand million barrels)

Asia Pacific 40North America 59S. & C. America 103

Africa 114Europe & Eurasia 140

Middle East 743

U.S. Consumption

U.S. Production

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20% of the US corn harvest in 2006 was used to produce ethanol, but that ethanol replaced only 2.4% of gasoline consumption (equivalent

to an average blend of E3.6).

Second-generation biofuels are needed.

First-Generation Biofuel: Corn Ethanol

1980 1990 2000 2010 2020 2030

Fu

el

eth

an

ol

(bil

lio

n g

al/

yr)

0

10

20

30

40

50

Actual EPA Renewable Fuels Std (2007)

Proposed Renewable Fuel Std (2007)

DOE/EIA Projection (2007)

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Displacement of substantial fraction of petroleum requires development of second generation biofuels.

Biofuels are not likely to replace petroleum entirely, but they could displace 10, 20, or 30% of U.S. gasoline use in next few decades through use of B5, E10, and E85.

Biofuels are generally more expensive than fossil fuels. Mandates/subsidies will probably be required.

0

20

40

60

80

100

2000 2010 2020 2030

Fu

el e

tha

no

l (B

ga

l/ye

ar)

10% (E10 + 4% E85)Actual

Proposal in 2007 State of the Union speech

% of projected US LDV fuel demand

20% (E10 + 18% E85)

30% (E10 + 32% E85)

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Biofuels close the carbon cycle by recycling atmospheric CO2.

Degree of closure depends on fuel and process (lifecycle analysis).

Solar energy

Biomass growth

Biofuel production

Use in vehicle

Land use changesFood pricesResource use (energy, water, chemicals)Biodiversity

Corn Corn Corn Corn Corn Sugar cane Switchgrass(coal) (current) (nat. gas) (DGS) (biomass) (current) (future)

-100

-80

-60

-40

-20

0

20

Cha

nge

in G

HG

em

issi

ons

(% o

f gas

olin

e)

Corn Corn Corn Corn Corn Sugar cane Switchgrass(coal) (current) (nat. gas) (DGS) (biomass) (current) (future)

-100

-80

-60

-40

-20

0

20

Cha

nge

in G

HG

em

issi

ons

(% o

f gas

olin

e)

All biofuels are not created equal

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Proven oil reserves at end 2004

Source: 2005 BP Energy review

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Population Growth to 10 - 11 Billion People in 2050

Per Capita GDP Growthat 1.6% yr-1

Energy consumption perUnit of GDP declinesat 1.0% yr -1

492005: 14 TW 2050: 28 TW

Total Primary Power vs Year

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PrerequisitesThe stone age did not end for the lack of stoneAnd the oil age will end long before we run out of oil

• Transportation biofuels are going to be around – for what ever reasons

• What are transportation biofuels going to be ? -(if you read the papers)Bioethanol and biodiesel ?

• But look at what plants are made of ?

Biorefinery at College Station, Texas makes mixed alcohols from biomass

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The big pictureAtmospheric

chemistry

Ozone and secondary

organic aerosols

CH3 + CO2

CH3OCO

CH3OCHO + HO2

O2

HO2

O2

O2

CH3OCHO + H

CH3OCH2O

CH3OCH2OONO2CH3OCH2O2CH3OCH2OOH

CH3OCH2.

CH3OCH3

Atmospheric degradation of CH3OCH3

Decomp/h

h h

OH.

NO2NO

OH

NO2HO2

H2OThe Chemist’s pictureLight harvesting

Mircroorganisms

Enzymes (Artificial)

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Would it be possible to getbio C3, C4, C5 oxygenatedcompounds and burn then in engines?BP and Dupont initiative

Vehicle manufactures wouldlike oxygenates that do notrequire big changes

Bioethanol?But look at what plants are made of?

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Regardless, commitment from government, industry, and consumers is needed to ensure long-term viability of modern biofuel industry.

Year

1960 1970 1980 1990 2000 2010

[CO

2]

(pp

m)

300

320

340

360

380

Ave

rag

e G

lob

al T

emp

erat

ure

, oC

13.8

14.0

14.2

14.4

14.6

14.8

15.0

15.2

2005 2006 2007

380

385

Agriculture• Biofuels can benefit rural economies

Will biofuels survive this time?Climate change• Biofuels can reduce GHG emissions

by recycling atmospheric CO2

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Conclusions (2)• Biofuels should be derived from “non-food crops”

– Second and “third” generation biofuels needed.– There will always be indirect energy-food competition

through the competition for land.

• If the climate issue is more important than the energy security issue- then biomass should be burned and not converted

• Potential unintended consequences should be avoided (Crutzen, ACPD 7 (2007) 11191)

• Different numbers are flying all over the place– Biofuel “science” is “new”

• Time of great uncertainty and great opportunity, more research and development needed.

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