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Is CDR (and DAC) an expensive waste of time? Let's not throw the baby out with the bathwater

This opinion article surfaced recently in Nature, and has been making the rounds across the internet. David Ho, a respected researcher of oceanography at the University of Hawaii, makes the case against CDR (Carbon Dioxide Removal), with a particular focus on Direct Air Capture.

 

What I like about the article:

Ho does a good job of pointing out the scale of the issue, and that DAC programs will struggle to bring down CO2 concentrations in the atmosphere. He emphasizes other forms of CDR (e.g. planting trees) that will help abate some CO2 emissions as well. He also implores us all to work towards reducing our carbon emissions as much as possible, as rapidly as possible. All good stuff.

 

Issues I had with the article:

Ho mentions only DAC as a tool for permanent CO2 removal and does not mention industrial CCS, wherein CO2 is stripped out of flue streams from industrial waste (cement factories, ethanal plants, natural gas fractionation facilities, etc.) In doing so, those who are not familiar with energy transition technologies may get the impression that CO2 storage via DAC and CO2 storage via industrial flue streams are on equal footing. They are not. Current atmospheric CO2 concentrations are approximately 420 ppm (up from 280 ppm during pre-Industrial Revolution times), and thus are highly diluted...it takes a lot of work using amine chemical treatment methods to purify the CO2 concentrations before they are suitable for permanent subsurface CO2 sequestration. In contrast, flue streams from industrial waste are typically comprised of 5-15% CO2...that is almost 120 to 360 times more concentrated than atmospheric CO2. As such, non-DAC forms of CO2 capture are much more financially lucrative...for now. The chart below shows typical cost ranges for capturing and storing CO2 from different point sources. The high concentration point sources have superior economics to those with low CO2 concentrations, Direct Air Capture in particular. Nevertheless, the Inflation Reduction Act increased 45Q tax benefits for all types of CCS, and it is possible these incentives will help DAC to become profitable one day.

Another issue I had with the article was the scales used to describe CO2 abatement needs. Ho is correct in that we are emitting CO2 at a staggering pace: 40.5 billion tonnes of anthropogenic CO2 in 2022 alone! He is also correct in his assessment that massive tree-planting operations could help reduce atmospheric concentrations of CO2 compared with current CCS/CCUS projects. Indeed, as of 2022, subsurface CO2 storage volumes are currently only about 40 million tonnes per year (Global CCS Institute, 2022), though new projects (proposed and under construction) are set to increase that amount to almost 250 million tonnes per year.

 

Image Source: Global CCS Institute

Nevertheless, that is a far cry from 40.5 billion tonnes per year. What Ho fails to mention is that we are not tasked with removing that much CO2 from the atmosphere each year. In a 2021 report, the International Energy Agency, stated that to reach net-zero emissions by 2050, the world will need to deploy CCS technologies at a large scale, with the amount of CO2 captured and stored increasing from around 40 million tonnes in 2020 to between 1.7 and 7.6 billion tonnes per year by 2050, in addition to increases in renewable energy and decreases in fossil fuel production. To be sure, these are not small amounts of CO2 that must be stored underground. But we are much closer to the target volumes required to achieve our climate goals than Ho's commentary would suggest.  The passage of the Inflation Reduction Act in 2022 set off a ripple effect that will likely result in a rapid acceleration of global CCS project proposals...more than anything our recent history has experienced. Even if massive CCS expansion plans fall short of the needed CCS goals, we will at least buy more time to mitigate against the worst impacts of climate change.

As such, I recommend we not throw the baby out with the bathwater. Yes, let's work on the emissions reduction side of the equation, but give the CCS projects a chance to be part of the solution as well. We likely won't be able to plant enough trees or wean ourselves off from oil and gas fast enough to prevent a truly unfortunate future for our planet...let's keep our minds open to all potential solutions. The stakes are too high to do otherwise.