2.14: Some take-aways


We need abundant cheap, clean energy: a carbon tax (perhaps a revenue-neutral one) would help us get there. These are probably the exact same things one would have said before thinking about carbon dioxide removal. But:

The thermodynamic minimum energy needed for direct air carbon capture is less bad than I thought it would be, but still hefty by current standards, and reaching near that minimum is hard.

  • We now have the added goal to generate a surplus of cheap clean energy for use in sucking carbon out of the atmosphere through industrial chemical facilities.
  • A carbon tax or other economic incentive seems key to driving not only increased progress in renewable energy deployments, but also to driving the economics of technologically promising large-scale direct air carbon capture schemes.

Biological solutions

Agriculture based schemes for carbon capture seem interesting to consider, through methods like improving agricultural crops by creating varieties with larger and deeper root growths, through other ways of improving soil, and through methods like physical sequestration or bioenergy with carbon capture applied to otherwise unused crop residues.

This leads to a serious biology challenge of making crop varieties with the same or better yields as we have now, but with increased root mass, and potentially with other improved properties like efficiency in their use of water or nitrogen, as pursued by ARPA-E’s ROOTS program.

For pure agricultural bio-sequestration — via increased root masses, no-till farming, and so forth — cap-ex and op-ex are both arguably essentially zero (or a marginal increase in farm equipment and inputs needed per bushel if harvested crop yield decreases), and there are no costs for transport/burial/utilization in this scheme since the crops ideally just grow like usual.

For capture of crop residues, there is a need for transport and burial, but in a context where large-scale transport is already widely used, e.g., to bring the corn and such to the grocery store near you.

Diverse scientists and engineers, like the Salk Institute plant biology team, or the teams supported by the ROOTS program, are getting into the game on fundamentals of improving plants and phytoplankton for improved carbon capture in conjunction with other improved properties.

We also need improved crops for all sorts of other reasons (including as a means of adaptation to climate change), so why not also let them sequester more carbon?

Azolla, the plant that may have caused an ice age, is inspiring here, for instance in its symbiotic relationship with a microbe to fix nitrogen directly from the air, potentially improving fertilizer-related considerations. At least one company, Pivot Bio, is looking at not-unrelated things, and the Climate Foundation is apparently looking at Azolla itself.

Company formation/activity

Some updates and further resources on this:

Musk created a Carbon Removal X Prize

Carbonplan scorecards here for negative emissions proposals

The Stripe proposals are at this repo
Overall, there seems to be growing activity in the carbon capture space right now, exemplified by YC’s entry into the space, as well as Stripe’s, by the serious startups already operating in industrial direct air capture, and by early negative emissions prototype facilities already open.


In direct air capture, electrically rather than thermally switchable CO2 binding looks super interesting.


Ocean-based technology seems under-developed relative to its potential importance. As a kid, I watched the wonderful show SeaQuest, yet most of what it dreamed of hasn’t materialized. Papers like this one on electro-geochemistry represent a remarkable hybrid technology — generating useful hydrogen fuel from renewables that are uniquely abundant in the ocean, while capturing carbon and reducing ocean acidification, all without taking up space on land. They make me question how we can be more creative in our use of the open oceans. I’m not the first to have realized this. We’ll see more ocean-based creativity when we discuss the Latham Salter proposal.