Good summary of Air Capture Geoengineering Approach

For instructors who include a section of geoengineering, a very good suggested reading on one geoengineering approach, air capture of carbon dioxide, is: Nicola Jones, Sucking it Up, 458 Nature 1094-1097 (Apr. 2009) (subscription required). Air capture involves exposing air to a sorbent of lye, which reacts with carbon dioxide to create a solution of sodium carbonate. The carbon can be extracted out of the solution thourgh the addition of lime to the mix, which results in particles of calcium carbonate being settled out. This mix can be heated in a kilm, resulting in a a pure stream of captured carbon dioxide and quicklime.

Among the key take-aways from the article:

  • To keep concentrations of carbon dioxide under 450 ppm, we need to prevent the emission of (or sequester) 650 gigatons of carbon by 2100;
  • Air capture is currently estimated to cost up to $500 per ton, an imposing cost, but which could be at least potentially be offset by sale of captured carbon dioxide to the merchant market (such as those transporting ice cream, flash-freeze meat, etc.), who pay from $130-1100 per ton of carbon;
  • One researcher has projected that a total of 650 Gt of carbon could be captured through this method by 2100, with 35,000 facilities with a total footprint of 300 square kilometers;
    • The cost of this approach, which would return concentrations of carbon dioxide to 380 ppm by 2100, would be $60 trillion, or approximately $6670 billion per year
  • Another study pegs the cost of capturing 650 Gt of carbon at $325 trillion. While this is certainly an imposing sum, it compares favorably to price estimates for stabilizing carbon dioxide concentrations at 450ppm, pegged at 1-5% of global economic output.

This article could stimulate some good discussion. Among the questions that might be asked are:

  • How does air capture compare with other geoengineering schemes in terms of potential effectiveness and negative impacts?;
  • How does the cost of air capture compare to GHG mitigation approaches? Is there any reason that it might be more politically viable than these approaches?
  • Does air capture present a “moral hazard” issue, i.e. could it divert attention or resources from mitigation? If yes, would that be problematic if the technology is viable?

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