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Lecture 1:Energy and Global Warming

MCB 11313 March 2007

Note: Some of the material in this talk was donated by Chris Somerville.

Mean Global Energy Consumption, 1998(Total 12.8 TW)

Gas Hydro Renew

4.52

2.7 2.96

0.286

1.21

0.2860.828

0

1

2

3

4

5

TW

Oil Coal Biomass Nuclear

Nate Lewis, Caltech

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Consumption of Energy Increased by 85% between 1970 and 1999

20202015201020051999199519901985198019751970

700

600

500

400

300

200

100

0

Quadrillion Btu

History Projections

By 2020, Consumption will Triple

2002 US Energy Flows

3

World marketed energy use by fuel type

Source: Energy Information Administration

Net Petroleum Imports as a Percent of U.S. Petroleum Consumption

4

Hubbert Peak Theory for crude oil production

World Oil Production

Note: NGL = Natural Gas LiquidsSource: info.energyscenariosireland.com

Billions of barrels per year

5

World Oil Production

Historical Price of Oil

6

N. Lewis, Caltech

Atmospheric CO2 is rising rapidly

The world is warming

Source: Ken Caldeira, AtulJain, and Martin Hoffertpublished on "Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission", in the March 28, 2003 issue of science

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N. Lewis Caltech

CO2 release rises with per capita GDP

Carbon emissions per capita

8

Predicted effects on rainfall

www.metoffice.com/research/hadleycenter

CO2 concentration, temperature, and sea level continue to rise long after emissions are reduced

9

CO2 neutral options Estimated consumption 25 TW in 2050

• Nuclear– 1 new plant every 2 days for next 45 y

• Wind– 4 TW worldwide (~ 2 million windmills)

• Hydro, ocean, thermal• Photovoltaics• Sequestration• Biomass

The Sleipner Experiment1 million tons/y; capacity 600 B tons

7000 such sites needed

www.agiweb.org/geotimes

1000

M

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Basis for a “hydrogen economy”

Hoffert et al. Science 298,981

Why Biofuels?

• Reduce dependency on imports– Strategic issues– Balance of payments– Economic development

• Global climate changeImported Domestic

6.4 bbl/year

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Potential of underused renewable energy sources

Hydro Tides &currents

Wind Geothermal Solar Current use0.1

1

10

100

1000

10000

100000

1000000

TW

How much would every roof contribute?

• 7x107 detached single family homes in U.S.• ≈2000 sq ft/roof = 180 m2/home• = 1.2x1010 m2 total roof area• Hence can (only) supply 0.25 TW, ≈7.5% U.S. Primary Energy Consumption

Nate Lewis, Caltech

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~160,000 km2 of photovoltaic devices would meet US energy needs

3.3 TW

N. Lewis, Caltech

(in the U.S. in 2002)

1-4¢ 2.3-5.0¢ 6-8¢ 5-7¢

Production Cost of Electricity

6-7¢

25-50¢

Cos

t, ¢/

kW-h

r

0

5

10

15

20

25

Coal Gas Oil Wind Nuclear Solar

Courtesy of Nate Lewis, Caltech

No storage

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How Biomass is Used for Energy

Biomass

Burn produce electricity

Thermochemicalconversion to

syngas products

Biochemicalconversion toethanol and other fuels

Mature Semi-mature(Capital intensive

ineficient)

In development

Current Bioenergy and Bioproduct Facilities

NREL

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Chemical structure of starch

http://www.scientificpsychic.com/fitness/carbohydrates1.html

http://www.ucmp.berkeley.edu/monocots/corngrainls.jpg

STARCH

Corn yield averages 4.5 tons/acre at ~$77/ton

Ethanol from Cornstarch

Source: www.ethanol.org

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A. E. Farrell et al., Science 311, 506 -508 (2006)

Net energy and net greenhouse gases for gasoline, six studies, and three cases

A DOE Ethanol Vision

Grain

Cellulose

0

10

20

30

40

50

60

70

2000 2005 2010 2015 2020 2025

Year

Eth

an

ol (B

illio

ns

of

gal/

yr)

EXISTING EMERGING

SugarPlatform-New Enzymes-Pretreatment-Fermentation

ADVANCED

FundamentalAdvances inLignocelluloseProcessingand fermentation

Modified from Richard Bain, NREL

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Plants are mostly composed of sugars

Section of a pine board

3 nm

Polymerized glucose

Possible packing structures of cellulose

6(2x2) 6x6

R. Atalla, unpublished

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Cellulose is recalcitrant to hydrolysis

NREL

Cellulase hydrolyzing cellulose

cellulose

NREL

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Scale model of a cell wall

Cellulose

Hemicellulose+ Lignin

Cellulose is occluded by other polymers

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Linocellulose to ethanol process

Conc. H 2SO4

Water

Gypsum

Water

PurifiedSugar Solution

Lignin Utilization

Ethanolrecovery

Fermentor

Neutralization Tank

Acid Reconcentration

Acid/Sugar Separation

DecrystallizationHydrolysis

Hydrolysis

Biomass

Ethanoldehydration

The challenge is efficient conversion

• Burning switchgrass (10 t/ha) yields 14.6-fold more energy than input to produce*

• But, converting switchgrass to ethanol calculated to consume 45% more energy than produced

Biomass

Transport

Other

Steam

Electricity

Grinding

Energy consumption

*Pimentel & Patzek, Nat Res Res 14,65 (2005)

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Linocellulose to Hydrophobe Process

Conc. H 2SO4

Water

Gypsum

Water

PurifiedSugar Solution

Lignin Utilization

Hydrophobe

Fermentor

Neutralization Tank

Acid Reconcentration

Acid/Sugar Separation

DecrystallizationHydrolysis

Hydrolysis

Biomass 69 kt Ca, K, Mg, P66 kt lipids, waxes171 kt protein

Ethanol from glucose or xylose

Jeffries & Shi Adv Bioch Eng 65,118

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Conversion of sugar to alkanes

Huber et al., (2005) Science 308,1446

Relative cost factors of cellulosic ethanol

Biomass Feedstock

Feed Handling

Pretreatment / Conditioning

Saccharification and fermentation

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%

NREL Analysis

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Cost/gallon = (Y + aX)/X

GALLONS (X)

Feedstock, energy,Transportation, etc

capitalCost

Y

Y1

Plot of Cost/gal = (Y + aX)/X

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10

Gallons (X)

Cos

t/Gal

At 15 t/a, 300 Mgal ~ 30% of all land in 20 mile radius1 mi x 0.5 mi x 35 ft

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Is there enough land?

Estimated net primary productivity

University of Montana

90,000 TW of energy arrives on the earths surface from the sun

5% of land650 MHa

Land29.0%

Water70.9%

Amount of land needed for 13 TW at 1% efficiency

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>2% yield is feasibleYield of 26.5 tons/acre observed by Young & colleagues

in Illinois, without irrigation

Cou

rtesy

of S

teve

Lon

g et

al

Why is photosynthetic efficiency so low?

• Visible portion of spectrum• Active areas of plants• Photo-inhibition

– Antenna length• Electron transfer losses

Wes Hermann, Stanford

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Julian day 1993

100 150 200 250 300 350

PAR

inte

rcep

tion

(%)

0

20

40

60

80

100

Miscanthus x giganteus

Spartinacynosuroides

Zea mays

Courtesy of Steve Long, University of Illinois

Perennials have more photosynthesis

Harvesting Miscanthus

http://bioenergy.ornl.gov/gallery/index.html

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Land Usage

Forest & Savannah

Cereal4.6% Pasture & Range

23.7%

30.5%

Other crops6.9%

Nonarable

34.4%

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995Year

0

500

1000

1500

2000

M H

ecta

res

Actual1950 equivalent

Data from Worldwatch database 1996, 1997

Hectares of Grain With and Without Yield Improvements

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Limiting factors for global NPP

Baldocchi et al. 2004 SCOPE 62

Land use is fungible

• High plant productivity is equally important for food and energy production

• Plant productivity is a function of many aspects of growth and development so a broad approach to knowledge creation is essential

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US Biomass inventory = 1.3 billion tons

Forest12.8%

Urban waste2.9%

Manure4.1%

Grains5.2%

Crop residues7.6%

Soy6.2%

Wheat straw6.1%Corn stover

19.9%

Perennial crops35.2%

From: Billion ton Vision, DOE & USDA 2005

~ 3 tons/acre

The 1.3 Billion Ton Biomass Scenario

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Geographic distribution of biomass crops

Wright et al DOE-ORNL-EERE

Economics of Perennials are Favorable

33219352515 tonsMiscanthus

212138**35010 tonsSwitchgrass

170193*362160 buCorn

Profit$

Cost$

Value $@$35/t

Yieldper Acre

CROP

*USDA economic research service 2004**50% as much fertilizer, no chemicals

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Conclusions

• We can meet a significant proportion of our fuel needs from plants– If pressed, we could meet all our needs

• Productivity of energy crops is not yet optimized

• The industrial processing of energy crops to fuels is not yet optimized

• There are no insurmountable problems to achieving cost-effective, carbon-neutral solar energy production from plants

Comments

• Energy crops are expected to be more environmentally benign than production agriculture– Low fertilizer and chemical inputs– Late-harvest supports biodiversity– Mixed cultures possible– Many species can be used