Imagine: a switch is flipped and, in the blink of an eye, every process spewing deadly pollution into the skies is replaced with something clean and sustainable. Unfortunately, even then, Earth would still become uninhabitable because of all the carbon we’ve already dumped on it. If we are to survive as a species, all this waste must be brought back to Earth, and quickly. Proponents of direct aerial capture believe it is an essential weapon for accomplishing this task; its critics say it’s so ineffective that we’d be better off trying something else first.
Direct air capture
Simply put, direct air capture (DAC) involves removing CO2 from the atmosphere by drawing air through a mechanical or chemical filter. Air is typically drawn through a DAC system via one or more fans, while filtering is done with a solid (called a sorbent) or with a liquid (called a solvent). Once captured, heat or electricity is applied to the filter material to remove the CO2, both to reuse the filter and to prepare the CO2 from. It is this last step which is often the most energy-intensive, and therefore the most expensive, part of the process. Considering how much air will need to be purified (all of it) for this to work, the DAC needs to be as energy efficient as possible.
The most cost-effective way to achieve this is to cap the smokestacks of a carbon-intensive process, such as a fossil fuel-fired factory or power plant, to prevent more CO2 releases. But this does not reduce the excess CO2 already present in the atmosphere. That’s why some scientists and entrepreneurs are inclined to bet on open-air DAC plants to clean up the skies.
THE NOAA explains that in 1960, humanity released 11 billion tons of carbon dioxide into the air each year. Half a century later, this figure is now closer to 40 billion. This is why efforts to reduce emissions are so vital. But even if we managed to reduce all our new emissions to zero, we would already have to tackle the estimated 950 gigatons of CO2 hiding in the atmosphere. At the time of writing this article, CO2 in the atmosphere as recorded by the NOAA Global Monitoring Laboratory at Mauna Loa is 422.38 ppm. The scientific consensus is that any figure above 350 ppm would result in a catastrophic catastrophe for humanity and the state of the planet in general.
This month of June, the University of Oxford According to a published study, if we are to limit warming to just 1.5 degrees (which would be catastrophic), humanity will need to extract between seven and nine billion tons of carbon dioxide from the air every year by 2050 . COP28 Declaration supports signatory countries that support carbon capture technologies. The Intergovernmental Panel on Climate Change (IPCC) said There is no viable path to avoid climate change unless large quantities of CO2 are removed from the air. This has been the status quo for some time: in 2017, a coalition of leading scientists led by Professor Jim Hansen declared that it was imperative that humanity begin mass removal of atmospheric CO2.
What to do with all the CO2
Once the DAC has sucked the unwanted carbon out of the air, it needs to be put somewhere. One option, The British Geological Survey explains, involves easily and inexpensively converting CO2 into its supercritical form, which behaves like a flowing liquid. This liquid can then be stored underground after being injected into porous rocks, with old oil fields and coal deposits appearing as ideal locations. The oil and gas industry effectively uses this approach to increase production in existing fieldsas liquid CO2 fills the space, pushing more oil toward the extraction site. But the International Energy Agency (IEA) backgrounder on Direct Air Capture suggests that more than half of all captured CO2 atmospheric emissions will need to be sequestered.
Clearly, pulling more fossil fuels out of the ground to burn doesn’t do much for the climate, and ideally the world’s governments would simply invest in efficient carbon capture to keep us from boiling to death. Fortunately for humanity’s fixation on market solutions, recycling some of the unsequestered CO2 could become an industry in itself.
CO2 can also be transformed into synthetic fuels in traditional combustion engines. Air travel is the most obvious example, especially since the size and weight of batteries make it almost impossible to build a large electric jet. Recovered CO2 can also be used as a basis for common non-combustible products, including construction materials, chemicals and agricultural products, not to mention the fizz in our drinks.
Holocene is one of several companies seeking to turn CO2 extraction into a viable long-term business by selling carbon removal credits to large companies. His approach involves drawing air through water that has been encrusted with an amniotic acid that binds to CO2. The mixture of water and CO2 is then combined with guanidine, which transforms the CO2 into a solid that can be easily filtered, allowing the reuse of the water, amino acids. The solid CO2 is then heated to a low temperature, which separates the guanidine from the gaseous CO2, ready for use or sequester. Holocene believes that a reusable solvent (and reusable chemical treatment) combined with low-temperature heat makes its approach much more cost-effective than its competitors.
Mission Zero also seeks to develop an inexpensive way to extract large amounts of CO2 from the atmosphere. He draws air into his equipment and then applies a water-based solvent. But rather than chemically treating this mixture, electrodialysis and an ion exchange process are used to purify the liquid and extract the CO2. From there, the liquid can be reused and the CO2, again, can either be buried underground or transformed into viable products. The company says its electrochemical process is also much more expensive and energy efficient than most other companies operating in this field.
Given the commercial sensitivities involved, it is not easy to get a real idea of the cost of removing CO2 from the atmosphere using open-air DAC. Depending on where you look, the figure can be as high as $600 per ton, but a more common figure is between $300 and $400. For years, the conventional wisdom was that the DAC had to reach an agreement cost of $100 per ton in order to become economically viable.
Earlier this year, Extantia Capital, a German climate-focused venture capital firm, went dig into the source of this $100 from shibboleth and I traced it to an article from the first DAC company Carbon Engineering in 2018 when it published a paper predicting its long-term cost would fall to just $94 per ton. Suddenly, the phrase “less than $100 per ton” became the benchmark that all other DAC companies were held to. But, as Extantia’s Torben Schreiter wrote, that figure was also tied to prices in 2016 dollars, so it didn’t rise with inflation. In 2023, the World Economic Forum said the cost of Direct Air Capture needed to fall “below $200 per ton” before it would be widely adopted.
It doesn’t matter whether your objectives are environmental or industrial, we know that the volume of CO2 to be extracted from the atmosphere is significant. For this to be viable, the cost of extraction must drop significantly. A better measure would be for prices to be at or below the perpetual cost of carbon dioxide as a commodity.
“All of these DAC approaches use a bunch of energy,” said Keeton Ross, CEO of Holocene. Ross says it’s the cost of this energy that keeps the price of Direct Air Capture higher than it should be. He thinks heat-based systems (like that of the Holocene) will likely win out in the end, because heat can come from a number of affordable sources. These claims that it would be possible to reduce DAC costs were convincing enough that in September Google invested in the Holocene and committed to purchasing carbon credits from it in the future.
Dr. Nicholas Chadwick, CEO of Mission Zero, told Engadget that his company is targeting around $350 per ton by 2026, but that figure “depends on a specific electricity price.” This price, he believes, is “considerably better than that available on the raw materials market”, making it obvious for industries that rely on CO2 to start buying from Mission Zero.
Road obstacles
The obvious objection to direct air capture is that although there is a lot of carbon dioxide in the atmosphere, it only makes up a relatively small proportion of the whole. I’ve heard that the process involves panning for gold in the ocean, and that the energy costs alone will make it unfeasible at the scale needed. In 2022, the Institute of Energy Economics and Financial Analysis bluntly asserted that the process “just wouldn’t work.” Part of the objection was that it can be (and is) used for enhanced oil recovery, but also that when DAC facilities are operational, they are often much less effective at capturing CO2 than initially expected.
In 2023, an article published by the Bulletin of Atomic Scientists was outraged that the US Department of Energy had invested $600 million in such a project. Its authors said that the energy costs required to filter so much air to extract just 0.04% of its total are far higher than those of other already less expensive ways of reducing emissions, and that it does not There will be no spectacular improvement in the fields of physics and chemistry. this will make Direct Air Capture considerably more efficient. They said bluntly: “It’s just stupid to build something today that we won’t need for 50 years, if ever.” »
Chadwick said much of the criticism of the DAC focuses on its technical feasibility, which he says is the wrong point. “There are tons of industrial processes where thermodynamics are terriblelook at ammonia,” he said, “it took years and years to get the yields to where they are now. What drove these otherwise inefficient processes was “the economic imperative in the marketplace,” he said. “When someone proves that they can do [Direct Air Capture] for 200 dollars per ton, all these arguments disappear.
Both Chadwick and Ross spoke about the importance of scale in helping accelerate a still-nascent industry. In 2023, Carbon Engineering, 1PointFive and Occidental inaugurated the Stratos Factory in Texas, this project, when completed, is expected to suck 500,000 tons of CO2 from the air per year. Both, however, are optimistic that the projects currently being built will help engineers resolve these questions. There is a very long way to go before we reach the billions of tons that experts think we will need to extract to have any hope of survival.
