Title: Major Roles for Fossil Fuels in an Environmentally Constrained World
1Major 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
2OUTLINE 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
3CLIMATE 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(No Transcript)
5Renewables/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
6GLOBAL 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
7Implications 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?
8OPTIONS 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)
9GLOBAL 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
10EXPERIENCE 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)
11EXPERIENCE WITH PLANS FOR AQUIFER CO2 DISPOSAL
AT LARGE SCALES
12CAN 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
13WHY 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 19Electricity Production via Coal IGCC with CO2/H2S
Cosequestration
20 21 22CONCLUSIONS
- 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.
23CONCLUSTIONS (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.
24IMPLICATIONS 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.
25Evolving 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.
26Escape 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.