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Major Roles for Fossil Fuels in an Environmentally Constrained World. Robert H. Williams Princeton University Sustainability in Energy Production and Utilization in Brazil: The Next Twenty Years Universidade Estadual de Campinas Campinas Sao Paulo, Brazil 18-20 February 2002.

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major roles for fossil fuels in an environmentally constrained world

Major Roles for Fossil Fuels in an Environmentally Constrained World

Robert H. Williams

Princeton University

Sustainability in Energy Production and Utilization in Brazil: The Next Twenty Years

Universidade Estadual de Campinas

Campinas

Sao Paulo, Brazil

18-20 February 2002

outline of presentation
OUTLINE OF PRESENTATION
  • Climate change context to motivate considerations of:

--electricity + hydrogen economy

--relative roles of renewables and decarbonized fossil energy

  • Prospects for geological storage of CO2
  • H2 production technology, with focus on coal
  • H2 costs as automotive fuel
  • Is decarbonization of natural gas worthwhile?
  • Conclusions and implications for Brazil
slide3

CLIMATE CLIMATE CHALLENGE

(IS92a “BAU” Scenario of IPCC)

Increase in global energy use/capita, 1997-2100:

For primary energy up 2.0X ( 1/3 US level in 1997)

For electricity up 2.6X (½ US level in 1997)

For “fuels used directly” up 1.4X (¼ US level in 1997)

Global CO2 emissions:

Total:

6.2 GtC (1997, actual, 37% coal) 20 GtC (2100, 88% coal)

From electricity generation:

1.9 GtC (1997)  5 GtC (2100)

From “fuels used directly”:

4.3 GtC (1997)  15 GtC (2100)

Cumulative emissions, 1990-2100: 1500 GtC

slide5

Renewables/Decarbonized Fossil Energy Competition,

Carbon-Constrained World

For electricity:

·Renewables will be strong competitors for decarbonized fossil fuels—esp. wind (central station), PV (distributed, grid-connected)

·Electric storage problem “solved” at large scales (CAES)

For fuels used directly (2/3 of CO2 emisions today):

·Biomass--regionally important but limited global potential relative to challenge

·Poor near-term and long-term economic prospects for making H2 via water-splitting (electrolysis or thermochemical cycles) from renewables—relative to H2 from fossil fuels with CO2 removal and sequestration

slide6

GLOBAL PERSPECTIVE ON BIOMASS

According to World Energy Assessment, long-term biomass energy potential

~ 100 – 300 EJ/y (for comparison: global primary energy use~ 400 EJ/y, 1997)

Biomass contributions to energy in IS92a:

·~ 130 EJ/y in 2050 (compared to 655 EJ/y from fossil fuels)

·~ 205 EJ/y in 2100 (compared to 865 EJ/y from fossil fuels)

Although it can make important regional contributions, biomass alone

cannot adequately decarbonize fuels used directly to the extent needed

to solve climate change problem

implications of renewable fossil energy competition for carbon management
Implications of Renewable/Fossil Energy Competition for Carbon Management
  • No carbon problem if fossil fuels = conventional oil/NG
  • Most of climate change challenge posed by coal [and, to lesser extent, unconventional oil (e.g., tar sands, heavy oils)]
  • Most of climate change challenge posed by “fuels used directly” and will be severe even if electricity is 100% decarbonized in this century
  • But gasification-based H2 production/CO2 sequestration technologies offer good prospects for decarbonizing low-quality fossil energy feedstocks at attractive costs
  • Are there options for storing the CO2 byproduct of H2 production that are adequate to raise the decarbonization/CO2 sequestration strategy to the status of a major contender in the energy race to achieve near-zero emissions of greenhouse gases?
slide8

OPTIONS FOR CO2 DISPOSAL

Deep Ocean Disposal (> 3 km)

·Most discussed option

·Reduces rapid transient CO2 buildup in atmosphere

·Significantly reduces long-term atmospheric CO2 concentration (> 50%)

·Many environmental concerns (e.g., ocean life impacts of pH changes, impacts of CO2

hydrate particles on benthic organisms, ecosystems)

Depleted Oil & Natural Gas Fields

·Large capacity (~ 500 GtC)

·Most secure option if original reservoir pressure not exceeded

·Some opportunities for enhanced oil/natural gas resource recovery

·Geographically limited option

Deep Beds of Unminable Coal

·CO2 injection can be used for enhanced methane recovery from unminable coal beds

·CO2 will remain in place (adsorptivity of CO2 on coals much higher than for CH4)

·Geographically limited option

Deep Saline Aquifers

·Deep saline aquifers (> 800 m) widely available geographically

·Enormous potential if closed aquifers with structural traps are not required

·Uncertainties about storage security, but time scales for reaching near-surface fresh-water aquifers

are long (~ 2000 y)

slide9

GLOBAL CAPACITY FOR CO2 STORAGE

IN DEEP SALINE AQUIFERS

If aquifers with structural traps are needed:

~ 50 GtC (C. Hendriks, Carbon Dioxide Removal from Coal-Fired Power Plants, Dept. of

Science, Technology, and Society, Utrecht University, The Netherlands, 1994)

If large open aquifers with good top seals can also be used:

Up to 2,700 GtC (IEA GHG R&D Programme)

~13,000 GtC (C. Hendriks, Carbon Dioxide Removal from Coal-Fired Power Plants, Dept. of

Science, Technology, and Society, Utrecht University, The Netherlands, 1994)

For comparison:

Projected emissions from fossil fuel burning, 1990-2100, IS92a: ~ 1500 GtC

Reasonable target for sequestration, 21st century ~ 600 GtC

Carbon content of remaining exploitable fossil fuels (excluding methane hydrates):

~ 5,000 - 7,000 GtC

slide10

EXPERIENCE WITH CO2 DISPOSAL

ENHANCED OIL RECOVERY: 74 projects worldwide; often profitable in mature

oil-producing regions; 4% of US oil so produced—mostly using CO2 from

natural reservoirs piped up to 800 km, but Weyburn (Canada) uses 1.5 million

tonnes/y of CO2 piped 300 km from North Dakota coal gasification plant

ENHANCED COAL BED METHANE RECOVERY: 1 commercial project in

San Juan Basin (US)

ACID GAS DISPOSAL: 31 acid gas (H2S + CO2) disposal projects in Canada

TWO PROJECTS FOR AQUIFER DISPOSAL OF CO2 ASSOCIATED

WITH OFF-SHORE NATURAL GAS PRODUCTION:

·Sleipner Project in North Sea (since 1996)

·Natuna Project in South China Sea (planned for 2005-2010)

slide11

NG Field

Firm

CO2 in gas (%)

Disposal Rate

Destination of CO2

On-Stream

t CO2/y

t C/y

Sleipner West,

Norway, North Sea

Statoil

($50-$80 million project)

9.5%

1 M

0.3 M

Sleipner East, Utsira Formation

(800 m depth)

1996

(20 y life)

Natuna, Indonesia,

South China Sea

Pertamina & Exxon/

Mobil

71%

> 100 M

> 30 M

Two aquifers north of

Natuna field

~ 2005?

EXPERIENCE WITH & PLANS FOR AQUIFER CO2 DISPOSAL AT LARGE SCALES

slide12

CAN NEAR-ZERO GHG/AIR POLLUTANT EMISSIONS BE REALIZED AT ACCEPTABLE COST?

Plausibly yes, if H2 major energy carrier complementing electricity—(CO2recovery costs low in H2 manufacture)

Requirements:

· Large, widely available, secure, and environmentally acceptable storage

capacity for CO2—geological storage options promising

· Technology for manufacturing H2 from abundant fossil fuel sources

· H2 competitive as energy carrier need technologies that:

—put high market value on H2 (e.g., fuel cells in transport)

—provide H2 at competitive costs

·H2 must be produced centrally to minimize cost of CO2 disposal

slide13

WHY COAL?

Coal resources abundant globally:

Recoverable coal ~ 200,000 EJ

(580 y supply at current fossil energy use rate)

Recoverable natural gas

Conventional ~ 12,000 EJ

Unconventional ~ 33,000 EJ

Coal prices low [1997 NG price for US electric generators: 2.1 X

coal price; projected (2020): 3.7 X coal price]; not volatile

Environmental issues  need radical technological innovation

Gasification  near-zero emissions of air pollutants/GHGs

Residual environmental, health, safety problems of coal mining

slide14

MAKING H2 FROMFOSSIL FUELS

Begin with”Syngas” Production:

Oxygen-Blown Coal Gasification: Steam-Reforming of Natural Gas

CH0.82O0.07 + 0.47 O2 + 0.15 H2O  CH4 + H2O  CO + 3H2

 0.56 H2 + 0.85 CO + 0.15 CO2

Followed by Syngas Cooling & Water-Gas Shift Reaction:

CO + H2O  H2 + CO2,

Net Effect:

CH0.82O0.07 + 0.47 O2 +1.00H2O CH4 + 2 H2O  CO2 + 4 H2

 1.40 H2 + 1.00 CO2

Followed by CO2/H2 Separation via Physical or Chemical Process

HHV efficiency [(H2 output)/(Total primary fuel input)]:

~ 70% for coal ~ 80% for natural gas

Separated CO2 Can Be Disposed of at Relatively Low Incremental Cost

slide16

With CO2 venting, cost of H2 from NG SMR always lower than H2 from coal

  • But, even at today’s low NG prices (2.44 $/GJ), H2 from coal with CO2-sulfur co-sequestration is comparable to H2 from NG
  • Note: 70 bar conventional technology is commercially available today
slide17

At NG prices (3.4 $/GJ) likely to be typical 20 y from now, cost of H2 from coal with CO2-sulfur co-sequestration is significantly lower than H2 from NG SMR

slide18

Consumer Fuel Costs for Gasoline ICE Cars and H2 Fuel Cell Cars

(excluding retail fuel taxes)

Fuel cost (¢/liter, gasoline equivalent)

Cost of driving (¢/km)

Production cost

Cost to consumer

Gasoline ICE

(6.7 l/100km)

H2 fuel cell car

(2.9 l/100 km ge)

Gasoline

23

30

2.0

-

H2 from coal, CO2 vented

21

50

-

1.4

H2 from coal, CO2 seq.

27

56

-

1.6

slide20

Carbon Tax Needed to Induce CO2 Sequestration

in the Production of H2 and Electricity

($/tC)

Energy Carrier

Feedstock for Producing

Energy Carrier

Natural Gas with CO2 Sequestered

Coal with CO2:

Sequestered

Cosequestered

H2

~ 100

~ 50

~ 30

Electricity

~ 250

~ 80

~ 50

slide21

Remaining Global NG & Conv. Oil Resources

Energy Resources

(103 EJ)

Carbon Content

(GtC)

Low

Med

High

Low

Med

High

Conv. oil

9.4

11.1

13.7

179

211

260

Conv. NG

8.7

11.9

16.5

118

162

224

Subtotal

18.1

23.0

30.2

297

373

484

Unconv. NG

33.2

452

Total

56.2

824

conclusions
CONCLUSIONS
  • Stabilizing atmospheric CO2 at 450-550 ppmv requires decarbonizing both electricity and fuels used directly.
  • Although there are many uncertainties, potential CO2 storage capacity in geological media is probably large enough to make fossil fuels decarbonization/CO2 sequestration a major energy option for a GHG-emissions-constrained world.
  • In electricity markets renewables and decarbonized energy systems will be strong competitors; renewables might well win the economic race to near-zero emissions.
  • Biofuels will be regionally important but the global potential is inadequate for biofuels to make more than a modest contribution in addressing the climate change challenge posed by fuels used directly.
conclustions continued
CONCLUSTIONS (continued)
  • H2 will probably be needed as a major energy carrier in markets that use

fuels directly.

  • By a wide margin, the least costly route to providing H2 in a GHG

-emissions-constrained world will be from carbonaceous feedstocks.

  • Making H2 from coal will probably be less costly than making it from NG

at typical feedstock prices in 2020 timeframe.

  • If a concerted effort can be directed to decarbonizing coal, it might not be

necessary to decarbonize NG energy systems.

  • The production of H2 from water via electrolysis or complex thermochemical

cycles will play at most marginal roles in providing H2 unless geological

sequestration of CO2 turns out to be a fatally flawed idea.

implications for brazil
IMPLICATIONS FOR BRAZIL
  • Prospect of H2 economy as necessary major component of climate mitigation strategy has major implications for all countries.
  • Brazil has opportunity to support demonstration projects for H2 fueled vehicles with H2 derived from offpeak hydropower.
  • Additional H2 supplies might be provided by gasification of petroleum residuals at refineries—e.g., petcoke gasification at Brazilian refineries could support more than 1 million fuel cell cars.
  • Brazil is one of few places where biomass-derived H2 might eventually become major option—and if CO2 coproduct were sequestered (so that CO2

emissions would be negative), Brazil could thereby plausibly sell profitably emission rights to the atmosphere under a global cap-and-trade regime.

slide25

Evolving CO2 Plume Front in a Vertical Cross Section of a Disposal AquiferModeling from: Eric Lindeberg, Escape of CO2 from aquifers, Energy Conversion and Management, 38 Suppl: 235-240.

slide26

Escape of CO2 from an Aquifer with a Spill Point Located 8 km from the InjectorModeling from: Eric Lindeberg, Escape of CO2 from aquifers, Energy Conversion and Management, 38 Suppl: 235-240.