1. Stabilization Wedges: Mitigation Tools for the Next Half-Century Robert Socolow Princeton University World Bank Washington, DC March 6, This talk is based on a paper by Stephen Pacala and Robert Socolow, published in the August 13, 2004, issue of Science, 305 (5686), pp , and its Supporting Online Material, available at

2. What if the fossil fuel future is robust, but the Greenhouse problem is severe?
Will the fossil fuel system wither away?
YES NO
Will the case for Greenhouse damage wither away?
A nuclear or renewables world unmotivated by climate.
Most people in the fuel industries and most of the public have been here.
Environmentalists, nuclear advocates are often here.
OUR WORKING ASSUMPTIONS

3. Outline of Talk
The Wedges Model: A simple quantification of carbon mitigation as the need for seven wedges
Some specific wedges
The challenge of meeting Basic Human Needs is at most 0.2 wedges.
4. Parting thoughts.

4. Past Emissions Billion of Tons of Carbon Emitted per Year Historical14
Billion of Tons of Carbon Emitted per Year 7
Historical
emissions
1.9 
1955
2005
2055
2105

5. Stabilization Triangle
The Stabilization Triangle 14
Billion of Tons of Carbon Emitted per Year
Currently projected path = “ramp”
Stabilization Triangle
Interim Goal O 7
Historical
emissions
Flat path
The “currently projected path,” is a ramp that rises linearly from 7 GtC/y and intersects 14 GtC/y in It is near the center of the cloud of estimates of Business As Usual (BAU) – a world oblivious to global carbon management.
The Flat Path is an Idealization of Stabilization below Doubling. Stabilization below doubling ( ppm) is the century-scale carbon management goal recommended by many environmental scientists.
This century-scale goal is broadly consistent with the Interim (50-year) goal: 7 GtC/y in 2055, as in 2005
Uncertainty of ± 3 GtC/y in land plus ocean sink.
Further emissions cuts are required after 2055.
1.9 
1955
2005
2055
2105

6. Stabilization Triangle
Beat doubling or accept tripling 14
Billion of Tons of Carbon Emitted per Year
Easier CO2 target
~850 ppm
Currently projected path = “ramp”
Stabilization Triangle
Interim Goal O 7
Historical
emissions
Flat path
Tougher CO2 target
~500 ppm
1.9 
1955
2005
2055
2105

7. The Interim Goal is Within Reach
Reasons for optimism that global emissions in 2055 need not exceed today’s emissions:
The world today has a terribly inefficient energy system.
Carbon emissions have just begun to be priced.
Most of the 2055 physical plant is not yet built

8. Wedges O Seven “wedges” Billion of Tons of Carbon Emitted per Year14
Billion of Tons of Carbon Emitted per Year
14 GtC/y
Currently projected path
Seven “wedges” O 7
Historical
emissions
7 GtC/y
Flat path
1.9 
1955
2005
2055
2105

9. What is a “Wedge”?
A “wedge” is a strategy to reduce carbon emissions that grows in 50 years from zero to 1.0 GtC/yr. The strategy has already been commercialized at scale somewhere.
1 GtC/yr
50 years
Total = 25 Gigatons carbon
Cumulatively, a wedge redirects the flow of 25 GtC in its first 50 years. This is 2.5 trillion dollars at $100/tC.
A “solution” to the CO2 problem should provide at least one wedge.

10. Fill the Stabilization Triangle with Seven Wedges
Methane Management
Energy Efficiency
Forests & Soils
14 GtC/y
Fuel Displacement by
Low-Carbon Electricity
Stabilization
Decarbonized
Electricity
Triangle
7 GtC/y
2004
2054
Decarbonized Fuels

11. Humanity Already Has The Tools
READINESS: All wedge technologies are already deployed somewhere at commercial scale.
PORTFOLIO: No single wedge technology can do the whole job, or even half the job.
CHOICE: Not every wedge technology is needed.

12. Outline of Talk
The Wedges Model: A simple quantification of carbon mitigation as the need for seven wedges
Some specific wedges
The challenge of meeting Basic Human Needs is at most 0.2 wedges.
4. Parting thoughts.

13. Allocation of 6.2 GtC/yr includes coal for heating and cooking Heating
Electricity
Transportation
Heating
Allocation of 6.2 GtC/yr
includes coal for heating and cooking

14. Efficient Use of Fuel lifestyle transport
Effort needed by 2055 for 1 wedge:
2 billion cars at 60 mpg instead of 30 mpg.

15. Efficient Use of Electricity
buildings
industry
power
Effort needed by 2055 for 1 wedge: .
25% - 50% reduction in expected 2055 electricity use in commercial and residential buildings

16. Wind Electricity Effort needed by 2055 for 1 wedge:
One million 2-MW windmills displacing coal power.
Today: 50,000 MW (1/40)
Prototype of 80 m tall Nordex 2,5 MW wind turbine located in Grevenbroich, Germany
(Danish Wind Industry Association)

17. Nuclear Electricity Effort needed by 2055 for 1 wedge:
700 GW (twice current capacity) displacing coal power.
Nuclear
Electricity
Phase out of nuclear power creates the need for another half wedge.
Graphic courtesy of NRC

18. Power with Carbon Capture and Storage
Effort needed by 2055 for 1 wedge:
Carbon capture and storage at 800 GW coal power plants.
Graphics courtesy of DOE Office of Fossil Energy

19. IGCC plants are nearly coal CCS plants
Steam plant by river
Gasifier
Oxygen plant
Coal feeder ramp
Gas turbine
powered
by CO + H2
BP will use petcoke and add at Carson refinery, California, USA:
CO2 capture [CO + H2O  CO2 + H2, CO2 - H2 separation, CO2 absorption ];
H2 to turbine for power; 3) CO2 pressurization and export off site for EOR.
Graphics courtesy of DOE Office of Fossil Energy

20. Carbon Storage Effort needed by 2055 for 1 wedge:
3500 MtCO2/yr
100 x U.S. CO2 injection rate for EOR
A flow of CO2 into the Earth equal to the flow of oil out of the Earth today
Sleipner project, offshore Norway
Graphic courtesy of Statoil ASA
Graphic courtesy of David Hawkins

21. Already, in the middle of the Sahara!
At In Salah, Algeria, natural gas purification by CO2 removal plus CO2 pressurization for nearby injection
Separation at amine contactor towers

22. The Future Fossil Fuel Power Plant
Shown here: After 10 years of operation of a 1000 MW coal plant, 60 Mt (90 Mm3) of CO2 have been injected, filling a horizontal area of 40 km2 in each of two formations.
Assumptions:
10% porosity
1/3 of pore space accessed
60 m total vertical height for the two formations.
Note: Plant is still young.

23. Biofuels Effort needed by 2055 for 1 wedge:
Two billion 60 mpg cars running on biofuels
250 million hectares of high-yield crops (one sixth of world cropland)
Usina Santa Elisa mill in Sertaozinho, Brazil (

24. Coal-based Synfuels with CCS* *Carbon capture and storage
Effort needed for 1 wedge by 2055
Capture and storage of the CO2 byproduct at plants producing 25 million barrels per day of coal-based synfuels
Assumption: half of C originally in the coal is captured, half goes into synfuels.
(from the SOM, footnote 26) “The equality of these two carbon flows, 1 GtC/y and million barrels of reference crude oil per day (mbd) links the unit of our carbon discussion with perhaps the world’s most widely used unit of bulk energy flow. This equality requires only two assumptions about reference crude oil: Its specific gravity is assumed to be (APIo = 33.0o), and it is assumed to be 85.0% carbon by weight. Also, 1 barrel = 42 gallons = 159 liters. Multiplying by days per year, an alternate form of this equality is that 1 GtC is the carbon in billion barrels of reference crude oil.”
Graphics courtesy of DOE
Office of Fossil Energy
Result: Coal-based synfuels have no worse CO2 emissions than petroleum fuels, instead of doubled emissions.

25. Possible 14 GtC/y and 7 GtC/y worlds in 2055
Total: 14 GtC/y
Total: 7 GtC/y
You can play too!

26. Summary: What’s appealing about stabilization wedges?
The stabilization triangle:
Does not concede doubling is inevitable.
Shortens the time frame to within business horizons.
The wedge:
Decomposes a heroic challenge (the Stabilization Triangle) into a limited set of monumental tasks.
Establishes a unit of action that permits quantitative discussion of cost, pace, risk.
Establishes a unit of action that facilitates quantitative comparisons and trade-offs.

27. Outline of Talk
The Wedges Model: A simple quantification of carbon mitigation as the need for seven wedges
Some specific wedges
The challenge of meeting Basic Human Needs is at most 0.2 wedges.
4. Parting thoughts.

28. Basic Human Needs and Fossil Energy
The challenge of meeting Basic Human Needs for electricity and clean cooking fuels is widely understood to be political, not technical:
Power can be brought to all villages.
The indoor air quality catastrophe related to cooking fuels in rural and urban areas can be solved with modern fuels.
The diesel fuel for village-scale engines and the LPG (propane) or DME (dimethyl ether) fuel for clean cooking can be produced from biomass, natural gas, crude oil, or coal.
The following four slides explain that meeting these needs for all humanity has a negligible effect on global carbon emissions.

29. Basic Human Needs and Carbon
People without access (billions)
Sufficiency (per capita-year)
Carbon required (GtC/yr)
Electricity
1.6
50W
0.15*
Clean cooking fuel
2.6
35 kg propane
0.07
Total
0.22†
*using global average C-intensity of power in 2002: 160 kgC/kWh
†current global carbon emissions: 7 GtC/yr
Instantly meeting Basic Human Needs for electricity and clean cooking fuel would produce only a three percent increase in global CO2 emissions. Including coal and kerosene not burned, estimates would be still less.

30. -0.15 wedges: Faster provision of electricity for 1.6 billion people
0.15 GtC/yr
Accelerated Access
3.75 GtC
Business As Usual ‘ ‘
2055 ‘
2005
2030
1.6 Billion people get access to 600 kWh/yr of electricity by 2030 in AA, but only by 2055 in BAU. Electricity is provided at the current world average carbon intensity: 160 gC/kWh. With linear ramps, AA adds 3.75 GtC of CO2 emissions to the atmosphere. One “stabilization wedge” is 25 GtC of avoided emissions, so following AA instead of BAU is wedges.

31. -0. 07 wedges: Faster provision of clean cooking fuels for 2
-0.07 wedges: Faster provision of clean cooking fuels for 2.6 billion people
0.07 GtC/yr
Accelerated Access
Business As Usual
1.75 GtC ‘ ‘
2055 ‘
2005
2030
2.6 Billion people get access to 35 kg/yr of LPG (propane) or equivalent clean cooking fuel by 2030 in AA, but only by 2055 in BAU. With linear ramps, AA adds 1.75 GtC of CO2 emissions to the atmosphere. One “stabilization wedge” is 25 GtC of avoided emissions, so following AA instead of BAU is wedges.

32. Wedges O Seven “wedges” projected path14
Billion of Tons of Carbon Emitted per Year
14 GtC/y
Basic Human Needs for cooking and electricity
Seven “wedges” O 7
Historical
emissions
7 GtC/y
Flat path
1.9 
1955
2005
2055
2105

33. Problems of Poverty, Problems of Modernity
Distinguish problems of poverty from problems of modernity.
Problems of poverty are largely a matter of political will. They are solved when governments are sufficiently motivated to give priority to equity and public health.
Problems of modernity require more than political will. Examples are the growing scarcity of low-cost hydrocarbons and the build-up of CO2. No country can solve such problems on its own. Still, there is an immense amount that every country can do.
Both kinds of problems are daunting and urgent. But they almost do not overlap.

34. Outline of Talk
The Wedges Model: A simple quantification of carbon mitigation as the need for seven wedges
Some specific wedges
The challenge of meeting Basic Human Needs is at most 0.2 wedges.
4. Parting thoughts.

35. Emission Commitments from Capital Investments
Historic emissions, all uses
power-plant lifetime CO2 commitments WEO-2004 Reference Scenario.
Lifetime in years: coal 60, gas 40, oil 20.
Policy priority: Deter investments in new long-lived high-carbon stock:
not only new power plants, but also new buildings.
Needed: “Commitment accounting.”
Credit for comparison: David Hawkins, NRDC

36. New Coal Build by Decade
221
500
670
Total:
1391 GW
Failing to develop alternatives to conventional coal means missing a huge opportunity to avoid additional carbon lock-in.
The developing world in particular is scheduled to build huge amounts of new coal capacity. If advanced technologies are ready, ways can be found to get them used but if we delay, very large amounts of conventional capacity will be built.
According to IEA, about 250 GW of new coal will be built this decade; an additional 483 GW will be built in the next decade; and over 710 additional GW will be built between
Some of this capacity can be avoided with efficiency investments and some by increasing use of renewable resources. But a substantial amount of new coal capacity is likely to be built. The question is what technology will be used.
We have missed the chance to influence technology choice for much of this decade. Failure to act now means we could miss the next decade as well.
Source: IEA,WEO 2004; Reference Scenario

37. Mitigate in developing countries now!
Some argue that developing countries should not be burdened with carbon mitigation until significant steps have been taken in industrialized countries. This formulation is seriously misguided.
Much of the world’s construction of long-lived capital stock is in developing countries. Unless energy efficiency and carbon efficiency are incorporated into new buildings and power plants now, wherever they are built, these facilities will become a liability when a price is later put on CO2 emissions.
Instead, call for “leapfrogging”: The introduction of advanced technology in developing countries first, or at least no later than in industrialized countries. The world learns faster, reducing everyone’s costs. Leapfrogging is a path to globally coordinated mitigation.
How to compensate those who move first is a separable challenge.

38. Consensus Building via Wedges?
Advocates of particular wedges agree:
It is already time to act.
It is too soon to pick “winners.”
Subsidy of early stages is often desirable.
At later stages, markets help to choose the best wedges.
The best wedges for one country may not be the best for another.
The environmental and social costs of scale-up need attention.
Can a consensus for early action be built on stabilization wedges?

39. National subsidies have elicited wedge technologies at large scale
Wedges Technology
Subsidy
CO2 transport
EOR (U.S.)
CO2 geological storage
EOR (U.S.), Sleipner (Norway)
Wind
Wind electricity (Germany, Denmark, U.K.)
Nuclear power
Nuclear power (U.S., Russia, France)
Coal-to-H2
Fertilizer (China)
Biofuels
Sugarcane ethanol (Brazil), wood waste (Sweden)
Coal-to-liquids (negative wedges)
Synfuels (South Africa)
All of the wedge technologies have already been commercialized at scale, but generally in only a few countries. Most subsidies have been motivated by energy security, not climate.
The whole world has learned from these national experiences.

40. $100/tC Form of Energy Equivalent to $100/tC
Carbon emission charges in the neighborhood of $100/tC can enable scale-up of most of the wedges. (PV is an exception.)
Form of Energy
Equivalent to $100/tC
Natural gas
$1.50/1000 scf
Crude oil
$12/barrel
Coal
$65/U.S. ton
Gasoline
25¢/gallon (ethanol subsidy: 50¢/gallon)
Electricity from coal
2.2¢/kWh (wind and nuclear subsidies: 1.8 ¢/kWh)
Electricity from natural gas
1.0¢/kWh
Today’s global energy system
$700 billion/year (2% of GWP)
Gasoline: 1 m3 = U.S. gals; 630 kgC/m3 gasoline.
Crude oil: 1 bbl = 42 U.S. gals; 730 kgC/m3 crude oil
Coal: 1 U.S. ton = 907 kg; kgC/kg coal
Natural gas: 1 Nm3 = scf; kgC/ Nm3 natural gas
Electricity from coal: GJ/metric ton coal (12,600 Btu/pound); 40% conversion efficiency
Electricity from natural gas: GJ/metric ton natural gas; kgC/kg natural gas; 50% conversion efficiency
Today’s global energy system: 7 GtC/y
NOT IN TABLE:
Hydrogen from coal: 18¢/kgH2, assuming 5.0 tC/tH2
Hydrogen from natural gas 9¢/kgH2, assuming 2.5 tC/tH2
$100/tC is approximately the EU trading price for the past six months.

41. A world transformed by deliberate attention to carbon
A world with the same total CO2 emissions in 2055 as in 2005 will also have:
Institutions for carbon management that reliably communicate the price of carbon.
If wedges of nuclear power are achieved, strong international enforcement mechanisms to control nuclear proliferation.
If wedges of CO2 capture and storage are achieved, widespread permitting of geological storage.
If wedges of renewable energy and enhanced storage in forests and soils are achieved, extensive land reclamation and rural development.
A planetary consciousness.
Not an unhappy prospect!

42. Can We Do It?
People are becoming increasingly anxious about our limited understanding of the experiments we are performing on the only Earth we have…
…and are learning that there are ways to live more cautiously.
We should anticipate a discontinuity:
What has seemed too hard becomes what simply must be done.
Precedents include abolishing child labor, addressing the needs of the disabled, and mitigating air pollution.

43. Two Messages for the World Bank audience
Meeting Basic Human Needs has a negligible impact on the climate problem
Mitigation must begin now in developing countries.