United States climate envoy John Kerry has added his voice to the chorus of lawmakers, advocates, and scientists urging that relying too heavily on carbon removal technologies to address climate change could prove irreversibly dangerous for the planet.
These new technologies may not prevent the world from passing “tipping points”—key temperature thresholds that, once passed, could trigger a cascade of unstoppable physical effects, Kerry said, in an interview with the Guardian last week.
“According to the science, and the best scientists in the world,” we may already be at or past these tipping points, Kerry said. “That’s the danger, the irreversibility.”
Many scientists agree that carbon dioxide removal (CDR) is not a climate solution at present, and that the CDR narrative must urgently be shifted to reflect this reality.
“We must stop talking about deploying CDR as a solution today, when emissions remain high—as if it somehow replaces radical, immediate emission cuts,” wrote David T. Ho, an oceanography professor at the University of Hawai’i at Mānoa, in an opinion piece for the journal Nature.
CDR methods like direct air capture (DAC), soil carbon sequestration, and afforestation, are included in all pathways identified by the Intergovernmental Panel on Climate Change to limit average global warming to within 1.5°C to 2°C above pre-industrial levels—“because we won’t be able to eliminate carbon emissions entirely on the required time scales,” Ho said. These residual emissions will partly owe to “hard to abate” sectors like aviation and shipping, which remain large sources of greenhouse gases even in the most optimistic scenarios.
“However, businesses are springing up that promise various CDR techniques as climate solutions for today,” while others “are enthusiastically buying carbon credits—essentially, investments in planting trees, or other future CDR capacity—as part of their current decarbonization commitments.”
And governments are committing vast resources to this area: in the United States, for example, the 2022 Bipartisan Infrastructure Law devoted US$3.5 billion to developing four DAC hubs, said Ho. While he welcomed government funding for CDR, he warned that such efforts are “pointless until society has almost completely eliminated its polluting activities.”
In agreement with this line of thinking, Kerry urged governments to commit to a faster shift to renewables, along with related technologies like electric vehicles that are already available for widespread deployment, and could prevent the world from breaching the 1.5°C threshold. “Part of the challenge we face right now is [that] countries that have technologies available to them are not necessarily deploying them at the rate they should be,” Kerry said.
Ho, who has spent his career studying the natural carbon cycle and developing methods to check whether carbon drawdown techniques work, explained that emissions reductions must be prioritized because the rate at which CDR works is far outpaced by the speed and volume of human pollution. He compared CDR to a time machine that could pull the atmosphere back at a rate based on current carbon removal capabilities.
For example, each of the U.S. DAC hubs “is eventually expected to extract one million tonnes of carbon dioxide each year,” he wrote. Human activity produced 40.5 billion tonnes of CO2 in 2022. So “at that rate, for every year of operation at its full potential, each hub would take the atmosphere back in time by almost 13 minutes, but in the time it took to remove those 13 minutes of CO2, the world would have spewed another full year of CO2 into the atmosphere.”
Planting eight billion trees—roughly one per person on earth—would set the clock back just 43 hours each year, and only once the trees mature.
“The time machine analogy reveals just how futile CDR currently is,” Ho wrote. “We have to shift the narrative as a matter of urgency” because large sums of money will be directed to funding climate solutions over the next few years.
It would be “a different story” if countries were to successfully decarbonize enough in the coming 20 to 30 years, Ho noted. Cutting emissions to 10% of current levels—down to around four billion tonnes of CO2 per year—would mean each DAC facility takes us back by just over two hours instead of 13 minutes.
“At that point, it would take 4,000 facilities to reach net-zero in any given year, presuming they were fully powered by renewable energy.”
Modelling indicates it is more likely that residual emissions will land at around 18% of current levels. So CDR would still need considerable scaling to reach net-zero, but building 7,290 DAC hubs—or deploying an equivalent of other CDR technologies—could be feasible if the rate of emissions was brought down first.
“We must slow the carbon clock to a crawl before we can turn it back,” Ho concluded.
The poor quality of the debate is typified by the failure even to accurately name the key options for long-term management of carbon dioxide : e.g. – “CCS” – Carbon Capture and Sequestration – should be reserved for the options that capture atmospheric carbon and sequester it in the soil (either directly or in the form of Biochar) – while Carbon Dioxide Capture and Storage – that diverts a part of industrial CO2 outputs to voids in the geology, should logically be referred to as “CDCS.”
The fossil lobby has long conflated the two pathways under the CCS acronym since doing so helps to avoid their comparison – for instance of the inefficiency of CDCS in its having to handle over three times the tonnage of CO2 gas as actual CCS manages in the form of carbon via sustainable farming and via its use of Biochar. When aiming for gigatonnes/yr scale that difference is immense.
Similarly the comparison of the utility of the pathways is stark. With CDCS, beyond the partial storage of industrial CO2 outputs no benefits are gained, while with CCS there is in addition a highly relevant increase in crop yields and hence in Food Security due to farms’ improved soil ecology, as well as a potentially major rise in rural employment in the Native Coppice Forestry needed at scale for charcoal for Biochar production.
Moreover, the hydrocarbon offgasses from coppice charcoal production can serve as feedstock for onsite conversion to methanol, an exceptionally clean-burning green liquid fuel that can displace various fossil fuels. Until 1920 this coproduction was the standard industry practice for making methanol and it offers a current yield of over 570kg per tonne of feedstock wood [NREL], which equates to 4.53 million barrels (or 2.23 million barrels of petrol-equivalent) of green fuel per million tonnes of coppice wood.
The comparison of the two pathways demands that scientists, NGOs and serious politicians should be using distinct titles for them – for example “Carbon Dioxide Removal” [CDR] for the removal and storage of industrial point-source CO2 emissions, and “Carbon Recovery” for capturing carbon from the atmospheric CO2 stock into trees and plants and thence into productive sequestration in farm soils.
For Kerry and others to directly discourage what they call “CCS” is careless and grossly counterproductive since it also discourages the necessary and highly benign option of Carbon Recovery. The concerns about fossil-owned politicians using the adoption of CDCS as a delay on ending fossil fuel use are valid only until efficient disincentives are negotiated, such as putting a low ceiling on the percentage of national CO2e accounts at UN.FCCC that can be met by CDCS carbon credits. The fact that the costs of RE are steadily falling means that investing in fossil fuel usage plus verified carbon credits will become increasingly financially inefficient over time, thereby imposing on laggards the dire prospect of holding suddenly stranded assets.