Iron Fertilization, Air Capture,
and Geoengineering
Woods Hole, MA
26 September 2007
David Keith
(keith@ucalgary.ca; www.ucalgary.ca/~keith)
Director, Energy and Environmental Systems Group
Institute for Sustainable Energy, Environment and Economy
University of Calgary
1
New York Times
May 24th 1953
2
Emissions are rising faster than expected
Skeptics argued that this
“unrealistic” scenario was
included only to make the
problem look worse
This is where we need to be
heading
3
And, it’s melting quicker than models predict
Ice cover on
16 September 2007
minimum
ice cover
4
1979-2000
Human actions that
change climate
Climate
System
Climate impact
on human welfare
Human actions that
change climate
Mitigation
Climate
System
Climate impact
on human welfare
Geoengineering
Adaptation
Climate impact
on natural world
(Polar Bears)
Human actions that
change climate
Mitigation
Climate
System
Climate impact
on human welfare
Geoengineering
Adaptation
Carbon Management: Location vs Mechanism
8
Biomass Energy with Capture
9
Biomass with Capture
10
Electricity for free…
8
Biomass
with CO2 capture
… at a ~300 $/tC
carbon price
Coal
Cost of electricity (c/kWh)
Natural gas
6
Biomass
4
Cost of air capture with
current electricity prices
2
0
50
100
150
200
Carbon price ($/tC)
250
300
11
Air Capture
12
Thermodynamics of CO2 capture
Free energy of mixing:
kT ln  p 
 p0 
To get 1 bar it takes:
~ 6 kJ/mol starting at 10% CO2 in a power plant exhaust, and
~ 20 kJ/mol starting at the 380 ppm ambient atmospheric concentration
It takes ~13 kJ/mol to compress from 1 to 100 bar
C + 2 O2  CO2 394 kJ/mol
Power plants are ~35% efficient (~160 kJe/mol-C from coal)
min loss of electric output should be ~12% ((6+13)/160).
Current designs are at least twice as bad.
13
Direct Air Capture
14
A
A
15
16
17
18
Cost and energy use vs flow rate
19
Negative emissions change long-run climate policy
700
Reference
650
ppmv CO2
600
Lucky
550
500
450
Unlucky
Air cap
400
350
300
2000
Air cap
2050
2100
2150
2200
2250
Year
Keith, D. W., Ha-Duong, M. & Stolaroff, J. K. Climate strategy with CO2 capture from the air.
Climatic Change (2005).
20
Air Capture Summary
1. Three uses
• Long run negative emissions (2100?).
• Acting in a rush, AC along while we do Coal CCS (2030?)
• Low Carbon Fuels and remote EOR (2015?)
2. NaOH contactor
• ETH/Rome group using commercial data on packed towers.
• Calgary/CMU using spray tower
• Less than $50/tCO2
3. NaOH regen
• Nuclear heat
• Electrochemical
• Borates/Titenates
• No good end-to-end costing.
21
Other Methods
22
Increasing ocean alkalinity
Motivation: 2×[CO3-2] + [HCO3-]  [A]
• Mg-silicates
– Olivine (Mg2SiO4) and serpentine (Mg3Si2O5(OH)4) are the most
abundant Mg-silicates
• MgO
• CaCO3
• CaO
23
Comparisons
24
25
26
27
28