CEF Spotlight

Direct Air Capture of Carbon Dioxide

By David Sandalow, Julio Friedmann, Colin McCormick and Sean McCoy

Concentrations of carbon dioxide in the atmosphere have reached their highest levels in roughly three million years. Those concentrations continue to climb, year after year. The Intergovernmental Panel on Climate Change warns of extraordinary risks unless the buildup of carbon dioxide in the atmosphere slows and then reverses in the decades ahead.

However progress is slow. In 2018, global emissions increased. Few major economies are now meeting their reduction targets under the Paris Agreement. The 24th Conference of Parties to the UN Framework Convention on Climate Change, held in Poland, just ended with helpful but incremental steps forward in fighting climate change.

Against this backdrop, strategies for removing carbon dioxide from the atmosphere – in addition to deep emissions reductions – will be needed for the world to meet its climate goals. Indeed the IPCC’s Global Warming of 1.5°C report (2018) states that 100-1000 gigatons (GT) of carbon dioxide removal will be required this century to prevent global average temperatures from climbing 1.5°C (2.7°F) above pre-industrial levels. Strategies for removing carbon dioxide from the atmosphere include afforestation, ecosystem restoration and direct air capture of carbon dioxide (DAC).

Carbon dioxide can be captured directly from air using chemicals, refrigeration or membranes. Some of these techniques date to at least the 1930s, when air separation units designed to produce oxygen produced CO2 as a byproduct. (This CO2 was often sold to the food and beverage industry.) Atmospheric CO2 scrubbers have been used in submarines since the 1940s and spaceships since the 1950s.

Today three companies are operating direct air capture of carbon dioxide (DAC) facilities. Carbon Engineering, based in British Columbia, Canada, operates a DAC facility that produces both synthetic gasoline and diesel. Climeworks has three pilot plants in operation — in Switzerland, Iceland and Italy. Global Thermostat has a demonstration plant in California and is completing a pilot plant in Alabama. Additional systems are under development around the world.

DAC has notable strengths and weaknesses. The strengths include:

  • DAC has the potential to remove very large amounts of CO2 from the atmosphere.
  • These removals could be largely permanent (where CO2 is stored geologically or mineralized).
  • Land area requirements for DAC are very small.
  • Water requirements for DAC are small. (Indeed some DAC approaches produce fresh water as a by-product.)
  • DAC can be sited in a very large number of locations.

DAC’s principal weakness is cost. Today, DAC costs range from $300-600/ton CO2, with estimates for future Nth-of-a-kind costs in the range of $60-250/ton. DAC’s high costs reflect the fact that CO2 is much more dilute in the atmosphere than flue gas. The concentration of CO2 in the atmosphere is roughly 0.04%, compared to 5% in natural gas-fired flue gas and 12% in coal-fired flue gas.

To reduce the costs of DAC, RD&D and supportive policies will be required. We recommend that governments around the world launch substantial RD&D programs on DAC. These programs should include fundamental research (e.g., on new CO2 solvents and sorbents), applied science (e.g., fabrication of low-cost air contactors) and initial scale-up. The program goals should be to accelerate the cost reduction of practical DAC designs and devices. Other climate policies – including carbon pricing – should be designed to help facilitate low-cost deployment of DAC as well.

The role of the private sector will be central. We also recommend that companies explore ways to add DAC to their emissions reduction strategies, both by deploying the technology and buying low-carbon and negative-carbon materials made with DAC-derived CO2.

The movie Apollo 13 includes several scenes that feature direct air capture. After a malfunction in the space capsule endangers the mission, NASA scientists on the ground in Houston quickly realize that the CO2 scrubber in the capsule requires modification to function. Without the scrubber, CO2 concentrations in the capsule of the spacecraft will exceed safe limits and the crew will die. A team gathers around a large worktable and dumps out a handful of gadgets and objects, the few expendable and spare parts on board the spacecraft that could be used to fashion a working air-capture device. After 75 minutes, they find a solution and coach the astronauts on how to modify their existing technology to return the CO2 levels in the air to safe levels.

The growing concentration of CO2 in the atmosphere is also an urgent threat. With resolve and determination like that showed by those who saved Apollo 13, we can meet the threat. (To quote the movie’s most famous line: “Failure is not an option.”) Large-scale carbon dioxide removal will likely be essential in the global response to climate change. Direct air capture of CO2 could be an important part of the solution.


This briefing is excerpted from a report released by the authors last week. The full report can be found at https://www.icef-forum.org/pdf2018/roadmap/ICEF2018_DAC_Roadmap_20181210.pdf










David Sandalow, Center on Global Energy Policy, Columbia University Chair, ICEF Innovation Roadmap Project





Julio Friedmann, Center on Global Energy Policy, Columbia University Distinguished Associate, Energy Futures Initiative





Colin McCormick, Walsh School of Foreign Service, Georgetown University Valence Strategic





Sean McCoy, Department of Chemical and Petroleum Engineering, University of Calgary

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