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Title: Major Roles for Fossil Fuels in an Environmentally Constrained World


1
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

2
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

3
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
4
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5
Renewables/Decarbonized Fossil Energy
Competition, Carbon-Constrained World   For
electricity       Renewables will be strong
competitors for decarbonized fossil fuelsesp.
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 renewablesrelative
to H2 from fossil fuels with CO2 removal and
sequestration
6
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
7
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?

8
OPTIONS FOR CO2 DISPOSAL   Deep Ocean Disposal (gt
3 km)        Most discussed option       
Reduces rapid transient CO2 buildup in
atmosphere        Significantly reduces
long-term atmospheric CO2 concentration (gt
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 (gt 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)
9
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 RD 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
10
EXPERIENCE WITH CO2 DISPOSAL     ENHANCED OIL
RECOVERY 74 projects worldwide often profitable
in mature oil-producing regions 4 of US oil so
producedmostly 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)
11
EXPERIENCE WITH PLANS FOR AQUIFER CO2 DISPOSAL
AT LARGE SCALES  
 
12
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 CO2geological
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
13
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
14
   
MAKING H2 FROM FOSSIL FUELS Begin withSyngas
Production Oxygen-Blown Coal Gasification Stea
m-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
 
15
  • H2 Production from Coal with CO2/H2S
    Cosequestration

16
  • With CO2 venting, cost of H2 from NG SMR always
    lower than H2 from coal
  • But, even at todays 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

17
  • 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

18
 
 
19
Electricity Production via Coal IGCC with CO2/H2S
Cosequestration
20
 
 
21
 
 
22
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.

23
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.

24
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
    refineriese.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 optionand 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.

25
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.
26
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.
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