Options for Capturing Carbon Dioxide from the Air Klaus S. Lackner Columbia University May, 2008

The Challenge: Holding the Stock of CO 2 constant Constant emissions at 2010 rate 33% of 2010 rate 10% of 2010 rate 0% of 2010 rate Extension of Historic Growth Rates 560 ppm 280 ppm

Comparison With Keeling’s Data

Carbon as a Low-Cost Source of Energy H.H. Rogner, 1997 Lifting Cost Cumulative Gt of Carbon Consumed US1990$ per barrel of oil equivalent Cumulative Carbon Consumption as of1997

A Triad of Large Scale Options Solar –Cost reduction and mass-manufacture Nuclear –Cost, waste, safety and security Fossil Energy –Zero emission, carbon storage and interconvertibility Efficiency, conservation and alternative energy will help, but not solve the problem

Net Zero Carbon Economy Closing the carbon cycle fossil carbon extraction power consumption CO 2 handling oxidized carbon disposal refining energy carrier CO 2 emissions CO 2 extraction from air FOSSIL FUEL CYCLE CO 2 collection

CO 2 extraction from air Permanent & safe disposal CO 2 from concentrated sources Net Zero Carbon Economy

Mg 3 Si 2 O 5 (OH) 4 + 3CO 2 (g)  3MgCO 3 + 2SiO 2 +2H 2 O(l) +63kJ/mol CO 2 Initially Air Capture is tied to Carbon Dioxide Storage

Air Capture Takes CO 2 from the atmosphere to offset CO 2 emissions Can compensate for all and any emissions Aims at distributed, small and mobile sources Preserves access to hydrocarbon fuels

The Substitution Principle All CO 2 is equal Combustion and capture cancel out –No need to co-locate Air is a perfect transport system –Mixing times are fast, weeks to months Air is an excellent storage buffer –Annual emissions are 1% of stored CO 2

Air Capture: A Different Paradigm Leave existing infrastructure intact Retain quality transportation fuels Eliminate shipping of CO 2 Open remote sites for CO 2 disposal Enable fuel recycling with low cost electricity Separate sources from sinks in space and time

Air Capture Is it Geo-Engineering? Con –Air capture simply separates sources and sinks in space and time –Air capture matches emissions one for one –Air capture provides a source of CO 2 Pro –Air capture makes it possible to control the CO 2 level in the atmosphere Air capture directly counters an emission, it does not fight one change with another

Natural Air Extraction Ocean Uptake –30% of anthropogenic CO 2 emission Trees –Biomass absorbs 100 GtC annually –Capture cost ~ $27/ton of CO 2 –Land demand too large –Leaves are underutilized for CO 2 extraction

Air Capture: Many Options Growing biomass –Terrestrial biomass: Biofuels Carbon is delivered as bio-based fuel Combustion at a power plant with CCS leads to a net carbon reduction –Marine biomass: Ocean fertilization Carbon is never collected but some is removed from the surface carbon cycle Raising the alkalinity of the ocean –Adding base E.g. dissolving CaCO 3 into the ocean –Removing acid from ocean water Removing HCl via electro-dialysis and disposing of it through neutralization

Air Capture: Collection & Regeneration Courtesy GRT Synthetic Tree

Challenge: CO 2 in air is dilute Energetics limits options –Work done on air must be small compared to heat content of carbon 10,000 J/m 3 of air No heating, no compression, no cooling Low velocity 10m/s (60 J/m 3 ) Solution: Sorbents remove CO 2 from air flow

CO 2 1 m 3 of Air 40 moles of gas, 1.16 kg wind speed 6 m/s moles of CO 2 produced by 10,000 J of gasoline Volumes are drawn to scale CO 2 Capture from Air

Wind area that carries 22 tons of CO 2 per year Wind area that carries 10 kW of wind power 0.2 m 2 for CO 2 80 m 2 for Wind Energy How much wind? (6m/sec) 50 cents/ton of CO 2 for contacting

Air Flow Ca(OH) 2 solution CO 2 diffusion CO 2 mass transfer is limited by diffusion in air boundary layer Ca(OH) 2 as an absorbent CaCO 3 precipitate

A First Attempt Air contactor: 2Na(OH) + CO 2  Na 2 CO 3 Calciner: CaCO 3  CaO+CO 2 Ion exchanger: Na 2 CO 3 + Ca(OH) 2  2Na(OH) + CaCO 3

Process Reactions Capture Device Trona Process Limestone Precipitate Dryer Fluidized Bed Hydroxylation Reactor Membrane Device (1) (2) (3) (6) (5) (4) Membrane (1) 2NaOH + CO 2  Na 2 CO 3 + H 2 O  H o = kJ/mol (2) Na 2 CO 3 + Ca(OH) 2  2NaOH + CaCO 3  H o = 57.1 kJ/mol (3) CaCO 3  CaO + CO 2  H o = kJ/mol (4) CaO + H 2 O  Ca(OH) 2  H o = kJ/mol (6) H 2 O (l)  H 2 O (g)  H o = 41. kJ/mol (5) CH 4 + 2O 2  CO 2 + 2H 2 O  H o = kJ/mol Source: Frank Zeman CO 2 Air Depleted Air

Lime Based Air Capture Is feasible Carbon Neutral < 250 kJ/mole of CO 2

Need Better Sorbents Fast Reaction Kinetics –Limited by air side transport Low binding energy –Comparable to flue gas capture Small environmental footprint Failsafe designs Sorbents designed for flue gas scrubbing are strong enough to capture CO 2 from air

Sorbent Choices 350K 300K AirPower plant

1/  Unit Cost Cost of Contacting the Air

1/  Unit Cost Cost of CO 2 from Air

Cost of CO 2 from Air (rescaled) 1/  Unit Cost Fixed Cost

Comparison to Flue Stack Scrubbing Much larger collector Similar sorbent recovery Cost is in the sorbent recovery

Sketching out a design Compare to windmills in 1960 Cost goal –$30/ton of CO 2 –Motivated by cost of fuel, oxygen, electricity, raw materials

15 km 3 /day of air As electricity producer the tower generates 3-4MW e 15 km 3 /day of air 9,500t of CO 2 pass through the tower daily. Half of it could be collected 450 MW e NGCC plant 9,500t of CO 2 pass through the tower daily. Half of it could be collected 450 MW e NGCC plant 300m 115m Cross section 10,000 m 2 air fall velocity ~15m/s Water sprayed into the air at the top of the tower cools the air and generates a downdraft.

60m by 50m 3kg of CO 2 per second 90,000 tons per year 4,000 people or 15,000 cars Would feed EOR for 800 barrels a day. 250,000 units for worldwide CO 2 emissions

Air Extraction can compensate for CO 2 emissions anywhere Art Courtesy Stonehaven CCS, Montreal 2NaOH + CO 2  Na 2 CO 3

GRT’s approach to air capture GRT in Tucson has developed a sorbent process that is energetically efficient, always carbon positive GRT plans to provide small factory produced units Begin with the physical CO 2 market Together with Allen Wright & Gary Comer, I helped found a company to develop air capture technology. I am now a member

GRT’s Vision Small factory produced units can be packed into a standard 40 foot shipping container

The first of a kind

Collection and Regeneration Collection Natural wind carries CO 2 to collector CO 2 binds to surface on ion exchange sorbent materials Regeneration CO 2 is recovered with: ○ liquid water wash ○ or carbonate solution wash ○ or low-temperature water vapor ○ plus optional low grade heat Regenerated sorbent is reused many times over Courtesy GRT

Options for Regeneration Pressure Swing Thermal Swing Water Swing –Liquid water – wet water swing –Water vapor – humidity swing Carbonate wash is a water swing –With CO 2 transfer –Salt splitter for CO 2 recovery

Electrodialysis Bipolar membrane Cl - Na + H + OH - Cl - Na + Cl - Na + H + OH - base salt acidbase acid Bipolar membrane cationic anionic membrane anionic membrane cationic anionic membrane

Air Capture: Collection & Regeneration Courtesy GRT

GRT’s Carbon, Energy and Water Balance Production costs are negligible compared to lifetime capture Energy consumption is small –Low grade heat –Electric power –Ambient energy Water consumption can substitute for energy –Water consumption can be 5 to 15 times CO 2 collection –Water can be salty or dirty –Some fresh water can be produced Indirect emissions depend on energy sources –Worst case is still carbon positive

Four Stages of Air Capture Industrial and commercial CO 2 CO 2 capture compensating for emissions CO 2 capture for reducing CO 2 concentrations in the air CO 2 capture for fuel recycling

Hydrogen or Air Extraction? Coal,Gas Fossil Fuel Oil HydrogenGasoline Consumption Distribution CO 2 TransportAir Extraction CO 2 Disposal Cost comparisons

Carbon Capture and Storage for Carbon Neutral World CCS simplifies Carbon Accounting –Ultimate Cap is Zero –Finite amount of carbon left

Air Capture Supports Underground Injection Safety Valve –Unpredicted changes in the underground reservoir should trigger a safe release of CO 2 –Compensated for by air capture Carbon Accounting –Losses can be made up by air capture –Air capture can introduce C-14 tracking

Stabilizing CO 2 in the atmosphere CO 2 capture can exceed emissions CO 2 capture can aim for design point

Energy Source Energy Consumer H2OH2O H2OH2O O2O2 O2O2 H2H2 CO 2 H2H2 CH 2 Materially Closed Energy Cycles

C H O Fuels Oxidizer Combustion products Biomass CO Fischer Tropsch Synthesis Gas Methanol Ethanol Natural Gas Town Gas Petroleum Coal Gasoline BenzeneCarbonHydrogen CO 2 H2OH2O Oxygen Increasing Hydrogen Content Increasing Oxidation State Methane Free O 2 Free C- H

C H O Fuels Oxidizer Combustion products Biomass CO Fischer Tropsch Synthesis Gas Methanol Ethanol Natural Gas Town Gas Petroleum Coal Gasoline BenzeneCarbonHydrogen CO 2 H2OH2O Oxygen Increasing Hydrogen Content Increasing Oxidation State Methane Free O 2 Free C- H

C H O Fuels Oxidizer Combustion products Biomass CO Fischer Tropsch Synthesis Gas Methanol Ethanol Natural Gas Town Gas Petroleum Coal Gasoline BenzeneCarbonHydrogen CO 2 H2OH2O Oxygen Increasing Hydrogen Content Increasing Oxidation State Methane Free O 2 Free C- H

Private Sector Carbon Extraction Carbon Sequestration Farming, Manufacturing, Service, etc. Certified Carbon Accounting certificates certification Public Institutions and Government Carbon Board guidance Permits & Credits