November 16, 2018
Direct air capture seems necessary, but it is often pushed aside as too expensive. A recent National Academy Study says just as much.1 It states that direct air capture has ZERO potential for creating negative emissions, simply because its cost is too high. Further down, the report points out that direct air capture apart from cost has no scaling limitations. The study is supportive of blue carbon, even though it notes that its capacity for negative emissions is miniscule, and it clearly shows that all the options it considers feasible will fall short of the negative emissions that the world will need to pull itself out of the hole it dug for itself.
So why not embark on a serious program to capture carbon dioxide from the air? If the only thing that stands between an innovative and nascent technology and a successful implementation is an economic hurdle, research, development and creation of opportunities for learning provide the best approach to lower cost and move forward. Dramatic cost reductions are not assured for a new technology, but they happen routinely. Solar energy today is at least one hundred times cheaper than at the state of development of today’s direct air capture. Wind energy also has reduced its cost to a few percent of its initial value.
Indeed, one can make the case, that direct air capture is already on its way. The National Academy Study debated old reviews, like the APS study from 20112, and the PNAS paper by House et al3. Maybe it is time to admit that even peer reviewed papers can be wrong. House et al. state that it would require a fundamental breakthrough in technology to achieve costs below $1000 per ton of CO2. This is contradicted by the facts. Carbon Engineering recently published a peer-reviewed study in Joule that looks at the very same process the APS study analyzed and sets the cost between $94 and $232/tonne of CO2.4 Climeworks, which also uses a process the APS committee and House et al. were familiar with, has real costs below $600/tonne, and is on its way to drive cost down further.
It is time to move on, state clearly that the conclusions of the House et al. paper are simply incorrect, and admit that the estimates of the 2011 APS study have to be revised downward. More encouragingly, one can state that direct air capture in spite of the nay-sayers is finding a way to get on the learning curve and is beginning to drive cost down. And it is worth noting that the improvements required to be cost-effective are far smaller than what has been required and accomplished for renewable energy technologies.
End notes and references
1National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: https://org/10.17226/25259
2Socolow, Robert, Michael Desmond, Roger Aines, Jason Blackstock, Olav Bolland, Tina Kaarsberg, Nathan Lewis et al. “Direct air capture of CO2 with chemicals.” A Technology Assessment for the APS Panel on Public Affairs (2011).
3House, Kurt Zenz, Antonio C. Baclig, Manya Ranjan, Ernst A. van Nierop, Jennifer Wilcox, and Howard J. Herzog. “Economic and energetic analysis of capturing CO2 from ambient air.” Proceedings of the National Academy of Sciences 108, no. 51 (2011): 20428-20433.
4Keith, David W., Geoffrey Holmes, David St Angelo, and Kenton Heidel. “A Process for Capturing CO2 from the Atmosphere.” Joule (2018).