Major Roles for Fossil Fuels in an Environmentally

Constrained WorldRobert H. WilliamsPrinceton University

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

Universidade Estadual de CampinasCampinas

Sao Paulo, Brazil 18-20 February 2002

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

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

Allowable Cumulative Carbon Emissions to Reach Various Targets

0

200

400

600

800

1000

1200

1400

1600

1980 2000 2020 2040 2060 2080 2100 2120

Gt

C

WRE350a

WRE450a

WRE550a

WRE650a

WRE750a

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

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

• 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?

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)

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. ofScience, 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. ofScience, 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

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)

EXPERIENCE WITH & PLANS FOR AQUIFER CO2 DISPOSAL

AT LARGE SCALES 

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?

 

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

 Plausibly yes, if H2 major energy carrier complementing electricity—

(CO2 recovery 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

WHY COAL? 

Coal resources abundant globally:

Recoverable coal ~ 200,000 EJ (580 y supply at current fossil energy use rate)

Recoverable natural gasConventional ~ 12,000 EJUnconventional ~ 33,000 EJ

 

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

MAKING H2 FROM FOSSIL 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 + 1.00 H2O 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

 

H2 Production from Coal with CO2/H2S Cosequestration

Gas turbine

HRSG

High temp.WGS

reactor

Quench +scrubberGasifier

Airseparation

unit

Syngascooling

Low temp.WGS

reactor

Solventregeneration

Syngasexpander

steam

coal slurry

leansolvent

richsolvent

H2- andCO2-rich syngas

CO-richraw syngas

oxygen

air

CO2 + H2Sto storage

air

CO2-leanexhaustgases

CO2/H2Sdrying and

compression

CO2/H2Sphysical

absorption

N2 for NOx control

Steamturbine

Pressureswing

adsorption

H2 product

compressedpurge gas

Conventional hydrogen 2 (1-7-02)

• 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

Hydrogen Cost vs. Carbon Tax

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

0 20 40 60 80 100

Carbon Tax ($/tonne C)

Hyd

roge

n C

ost

($/G

J H

HV

)

Fig. L2ab

Coal, conventional technologyNatural gas, steam reforming

70 bar

CO2 venting

CO2 -sulfurco-sequestration

NG price:2.44 $/GJ HHV

• 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

Hydrogen Cost vs. Carbon Tax

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

0 20 40 60 80 100

Carbon Tax ($/tonne C)

Hyd

roge

n C

ost

($/G

J H

HV

)

Fig. L2ac

Natural gas, steam reformingCoal, conventional technology

70 bar

CO2 venting

CO2 -sulfurco-sequestration

NG price:3.4 $/GJ HHV

 

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

 

Electricity Production via Coal IGCC with CO2/H2S Cosequestration

Gas turbine

HRSG

High temp.WGS

reactor

Quench +scrubberGasifier

Airseparation

unit

Syngascooling

Low temp.WGS

reactor

Solventregeneration

Syngasexpander

steam

coal slurry

leansolvent

richsolvent

H2- and CO2-rich syngas

CO-richraw syngas

oxygen

air

CO2 + H2Sto storage

air

CO2-leanexhaustgases

CO2/H2Sdrying and

compression

CO2/H2Sphysical

absorption

N2 for NOx control

H2-rich syngas

Conventional electricity 2 (1-7-02)

Steamturbine

 

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

 

 

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

• 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)

• H2 will probably be needed as a major energy carrier in markets that usefuels 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 NGat typical feedstock prices in 2020 timeframe.

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

• 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.

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.

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.