1. Tackling the Climate Problem with Existing Technologies
Stabilization Wedges
Tackling the Climate Problem with Existing Technologies
Roberta Hotinski
CLEER UAB Seminar, March 6, 2010 1

2. 2 4 8 800 = Ocean Land Biosphere (net) Fossil Fuel Burning +
billion tons go out
Ocean
Land Biosphere (net)
Fossil Fuel
Burning + 8
800
billion tons carbon
billion
tons go in
ATMOSPHERE
billion tons added every year

3. ( ) ATMOSPHERE “Doubled” CO2 1200 Today 800 Pre-Industrial 600 Glacial
Billions of tons of carbon
“Doubled” CO2
Today
Pre-Industrial
Glacial
800
1200
600
400
billions of tons carbon
ATMOSPHERE (
ppm )
(570)
(380)
(285)
(190)

4. Why Wedges?
This slide illustrates that there are a plethora of future scenarios for how emissions might grow in the future that result in very different CO2 concentrations. Line at 50 years in figure on left indicates timescale of interest for the wedges (50 rather than 100 years to make the problem seem more relevant)
Graphic courtesy of IPCC
Predicted global temperature change of °C by 2100

5. Historical Emissions
Billions of Tons Carbon Emitted per Year 16
Historical
emissions 8
1950
2000
2050
2100 5

6. Stabilization Triangle
The Stabilization Triangle
Billions of Tons Carbon Emitted per Year 16
Current path = “ramp”
Stabilization Triangle
Interim Goal
Historical
emissions 8
Flat path
1.6
1950
2000
2050
2100
Today and for the interim goal, global per-capita emissions are ≈ 1 tC/yr. 6

7. Stabilization Triangle
The Stabilization Triangle
Billions of Tons Carbon Emitted per Year
Easier CO2 target 16
Current path = “ramp”
~850 ppm
Stabilization Triangle
Interim Goal
Historical
emissions 8
Flat path
Tougher CO2 target
~500 ppm
1.6
1950
2000
2050
2100
Today and for the interim goal, global per-capita emissions are ≈ 1 tC/yr. 7

8. Stabilization Wedges
Billions of Tons Carbon Emitted per Year 16
Current path = “ramp”
16 GtC/y
Eight “wedges”
Goal: In 50 years, same
global emissions as today
Historical
emissions 8
Flat path
1.6
1950
2000
2050
2100
Today and for the interim goal, global per-capita emissions are ≈ 1 tC/yr. 8

9. What is a “Wedge”?
A “wedge” is a strategy to reduce carbon emissions that grows from zero to 1.0 GtC/yr avoided within 50 years
1 GtC/yr
Total = 25 Gigatons carbon
50 years
Cumulatively, a wedge redirects the flow of 25 GtC in its first 50 years.
A “solution” to the CO2 problem should provide at least one wedge.

10. $100/tC Form of Energy Equivalent to $100/tC Natural gas
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: 51¢/gallon)
Electricity from coal
2.2¢/kWh (wind and nuclear subsidies: 1.9 ¢/kWh)
Electricity from natural gas
1.0¢/kWh
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 was approximately the EU trading price for carbon (~$30/ton CO2) in September 2008 (Now ~$18)
A wedge is 2.5 trillion dollars ($100 billion/yr) at $100/tC.

11. Fossil Fuel-Based Strategies Renewables & Biostorage
15 Wedge Strategies in 4 Categories
Energy Efficiency
& Conservation
Fossil Fuel-Based Strategies
Stabilization
Stabilization
Triangle
Triangle
2008
2058
Renewables & Biostorage
Nuclear Power 11

12. Use the Wedges Table to compare strategies:
= Electricity Production, =Heating and Direct Fuel Use, =Transportation, = Biostorage

13. Photos courtesy of Ford Motor Co., DOE, EPA
Efficiency
Produce today’s electric capacity with double today’s efficiency
Double the fuel efficiency of the world’s cars or halve miles traveled
Average coal plant efficiency is 32% today
There are about 600 million cars today, with 2 billion projected for 2055
“E,T, H” = can be applied to electric, transport, or heating sectors, $=rough indication of cost (on a scale of $ to $$$)
38% of total U.S. carbon emissions come from residential and commercial buildings
Carbon emissions from residential and commerical are largely due to electricity consumption (68% and 77%)
>70% of all electricity in the U.S. used in buildings
Large opportunities for emissions reductions in the building sector through both efficiency/conservation and low-carbon electricity.
- 243 million cars in US (2004, Bureau of Transportation statistics)
Use best efficiency practices in all residential and commercial buildings
Replacing all the world’s incandescent bulbs with CFL’s would provide 1/4 of one wedge

14. Fuel Switching
Substitute 1400 natural gas electric plants for an equal number of coal-fired facilities
Photo by J.C. Willett (U.S. Geological Survey).
“E,H” = can be applied to electric or heating sectors, $=rough indication of cost (on a scale of $ to $$$)
Effort needed for 1 wedge:
Build 1400 GW of capacity powered by natural gas instead of coal (60% of current fossil fuel electric capacity)
Requires an amount of natural gas equal to that used for all purposes today
So a slice is 50 LNG tanker discharges/day by m3/tanker, or
one new “Alaska” 4 Bscfd.
Detailed Description: NATURAL GAS TURBINES ARE BEING DEVELOPED TO PRODUCE ELECTRICITY IN A SIMPLE, LOW COST ENVIRONMENTALLY FRIENDLY WAY. DOE'S NATIONAL ENERGY TECHNOLOGY LABORATORY (NETL) INITIATED THE ADVANCED TURBINE SYSTEMS (ATS) PROGRAM AND HAS PARTNERED WITH INDUSTRY TO PRODUCE A NEW GENERATION OF HIGH EFFICIENCY GAS TURBINES FOR CENTRAL STATION ELECTRICITY PRODUCTION, USING CLEAN BURNING NATURAL GAS.
700 1-GW baseload coal plants (5400 TWh/y) emit 1 GtC/y.
Natural gas: 1 GtC/y = 190 Bscfd
Yr 2000 electricity:
Coal : TWh/y; Natural gas: 2700 TWh/y.
A wedge requires an amount of natural gas equal to that used for all purposes today
A wedge worth of natural gas requires about 190 bscfd - U.S. currently imports about 17 bscfd

15. Carbon Capture & Storage
Implement CCS at
800 GW coal electric plants or
1600 GW natural gas electric plants or
180 coal synfuels plants or
10 times today’s capacity of hydrogen plants
“E,T, H” = can be applied to electric, transport, or heating sectors, $=rough indication of cost (on a scale of $ to $$$)
Graphic courtesy of Alberta Geological Survey
There are currently three storage projects that each inject 1 million tons of CO2 per year – by 2055 need 3500.
Requires about 100 times the amount of CO2 currently injected annually for EOR (most in the U.S.)

16. Nuclear Electricity
Triple the world’s nuclear electricity capacity by 2055
Graphic courtesy of NRC
“E” = can be applied to electric sector, $$=rough indication of cost (on a scale of $ to $$$)
Plutonium (Pu) production by 2054, if fuel cycles are unchanged: 4000 t Pu (and another 4000 t Pu if current capacity is continued).
Compare with ~ 1000 t Pu in all current spent fuel, ~ 100 t Pu in all U.S. weapons.
5 kg ~ Pu critical mass.
The rate of installation required for a wedge from electricity is equal to the global rate of nuclear expansion from
104 of world’s 435 nuclear electric plants are in the United States

17. Wind Electricity
Install 1 million 2 MW windmills to replace coal-based electricity, OR
Use 2 million windmills to produce hydrogen fuel
“E,T, H” = can be applied to electric, transport, or heating sectors, $-$$=rough indication of cost (on a scale of $ to $$$)
A wedge worth of wind electricity will require increasing current capacity by a factor of 15
Photo courtesy of DOE
Current U.S. capacity about 35,000 MW

18. Photos courtesy of DOE Photovoltaics Program
Solar Electricity
Install 20,000 square kilometers for dedicated use by 2054
Photos courtesy of DOE Photovoltaics Program
“E” = can be applied to electric sector, $$$=rough indication of cost (on a scale of $ to $$$)
A wedge of solar electricity would mean increasing current capacity 700 times
US PV potential estimated to be ~500 GW
(Navigant Consulting and Clean Power Research, Study for the Energy Foundation)

19. Biofuels Scale up current global ethanol production by 20 times
Photo courtesy of NREL
“T, H” = can be applied to transport or heating sectors, $$=rough indication of cost (on a scale of $ to $$$)
Using current practices, one wedge requires planting an area the size of India with biofuels crops
Need ~1000 billion liters ethanol per year for a wedge – U.S. currently producing ~40 billion liters/yr

20. Natural Sinks Eliminate tropical deforestation OR
Plant new forests over an area the size of the continental U.S.
Use conservation tillage on all cropland (1600 Mha)
“B” = biostorage sector, $=rough indication of cost (on a scale of $ to $$$)
Conservation tillage is currently practiced on less than 10% of global cropland
U.S. forest sequestration potential estimated at million tons C/yr
(Birdsey et al.)
Photo courtesy of NREL, SUNY Stonybrook, United Nations FAO

21. Please take a minute and choose 8 wedge strategies you feel are the most promising for reducing global emissions
(can use duplicates) 21

23. Take Home Messages
To avoid a doubling of atmospheric CO2, we need to rapidly deploy low- carbon energy technologies and/or enhance natural sinks
We already have an adequate portfolio of technologies to make large cuts in emissions
No one technology can do the whole job – a variety of strategies will be needed
Every “wedge” has associated impacts and costs 23

24. From McKibben, “Carbon’s New Math,” National Geographic, October 2007

25. From Socolow & Pacala, “A Plan to Keep Carbon in Check,” Scientific American, Sept. 200625

27. For more information contact Roberta Hotinski hotinski@princeton.edu27