Rocketdoc Notes Week of May 2, 2021

Global Warming Update – CO2 Removal

This article appears in the Spring 2020 issue of Energy Futures, the magazine of the MIT Energy Initiative - Researchers at MIT have designed a new effective approach to remove CO2 from both exhaust and ambient air. This could have far-reaching implications, but beware the description is technical.

An essential component of any climate change mitigation plan is cutting carbon dioxide (CO2) emissions from human activities. Some power plants now have CO2 capture equipment that grabs CO2 out of their exhaust. But those systems are each the size of a chemical plant, cost hundreds of millions of dollars, require a lot of energy to run, and work only on exhaust streams that contain high concentrations of CO2. In short, they’re not a solution for airplanes, home heating systems, or automobiles.

To make matters worse, capturing CO2 emissions from all anthropogenic sources may not solve the climate problem. “Even if all those emitters stopped tomorrow morning, we would still have to do something about the amount of CO2 in the air if we’re going to restore preindustrial atmospheric levels at a rate relevant to humanity,” says Sahag Voskian SM ’15, PhD ’19, co-founder and chief technology officer at Verdox, Inc. And developing a technology that can capture the CO2 in the air is a particularly hard problem, in part because the CO2 occurs in such low concentrations.

The CO2 capture challenge - A key problem with CO2 capture is finding a “sorbent” that will pick up CO2 in a stream of gas and then release it so the sorbent is clean and ready for reuse and the released CO2 stream can be utilized or sent to a sequestration site for long-term storage. Research has mainly focused on sorbent materials present as small particles whose surfaces contain “active sites” that capture CO2 — a process called adsorption. When the system temperature is lowered (or pressure increased), CO2 adheres to the particle surfaces. When the temperature is raised (or pressure reduced), the CO2 is released. But achieving those temperature or pressure “swings” takes considerable energy, in part because it requires treating the whole mixture, not just the CO2-bearing sorbent.

In 2015, Voskian, then a PhD candidate in chemical engineering, and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering and co-director of the MIT Energy Initiative’s Low-Carbon Energy Center for Carbon Capture, Utilization, and Storage, began to take a closer look at the temperature- and pressure-swing approach. They wondered if they could get by with using only a renewable resource — like renewably sourced electricity — rather than heat or pressure. Using electricity to elicit the chemical reactions needed for CO2 capture and conversion had been studied for several decades, but Hatton and Voskian, show in figure 1 below, had a new idea about how to engineer a more efficient adsorption device.

Figure 1 - Sahag Voskian SM ’15, PhD ’19 (left) and Professor T. Alan Hatton have developed an electrochemical cell that can capture and release carbon dioxide with just a small change in voltage.

Their work focuses on a special class of molecules called quinones. When quinone molecules are forced to take on extra electrons — which means they’re negatively charged — they have a high chemical affinity for CO2 molecules and snag any that pass. When the extra electrons are removed from the quinone molecules, the quinone’s chemical affinity for CO2 instantly disappears, and the molecules release the captured CO2.

Others have investigated the use of quinones and an electrolyte in a variety of electrochemical devices. In most cases, the devices involve two electrodes — a negative one where the dissolved quinone is activated for CO2 capture, and a positive one where it’s deactivated for CO2 release. But moving the solution from one electrode to the other requires complex flow and pumping systems that are large and take up considerable space, limiting where the devices can be used.

As an alternative, Hatton and Voskian decided to use the quinone as a solid electrode and — by applying what Hatton calls “a small change in voltage” — vary the electrical charge of the electrode itself to activate and deactivate the quinone. In such a setup, there would be no need to pump fluids around or to raise and lower the temperature or pressure, and the CO2 would end up as an easy-to-separate attachment on the solid quinone electrode. They deemed their concept “electro-swing adsorption.”

The electro-swing cell - To put their concept into practice, the researchers designed the electrochemical cell shown in the two diagrams in Figure 2 below. To maximize exposure, they put two quinone electrodes on the outside of the cell, thereby doubling its geometric capacity for CO2 capture. To switch the quinone on and off, they needed a component that would supply electrons and then take them back. For that job, they used a single ferrocene electrode, sandwiched between the two quinone electrodes but isolated from them by electrolyte membrane separators to prevent short circuits. They connected both quinone electrodes to the ferrocene electrode using the circuit of wires at the top, with a power source along the way.

Figure 2 - Electrochemical cell operation. These diagrams show the electro-swing cell as it charges, capturing carbon dioxide in passing gases (left), and as it discharges, releasing the captured CO2 (right).

The power source creates a voltage that causes electrons to flow from the ferrocene to the quinone through the wires. The quinone is now negatively charged. When CO2-containing air or exhaust is blown past these electrodes, the quinone will capture the CO2 molecules until all the active sites on its surface are filled up. During the discharge cycle, the direction of the voltage on the cell is reversed, and electrons flow from the quinone back to the ferrocene. The quinone is no longer negatively charged, so it has no chemical affinity for CO2. The CO2 molecules are released and swept out of the system by a stream of purge gas for subsequent use or disposal. The quinone is now regenerated and ready to capture more CO2.

Two additional components are key to successful operation. First is an electrolyte, in this case a liquid salt, that moistens the cell with positive and negative ions (electrically charged particles). Since electrons only flow through the external wires, those charged ions must travel within the cell from one electrode to the other to close the circuit for continued operation.

The second special ingredient is carbon nanotubes. In the electrodes, the quinone and ferrocene are both present as coatings on the surfaces of carbon nanotubes. Nanotubes are both strong and highly conductive, so they provide good support and serve as an efficient conduit for electrons traveling into and out of the quinone and ferrocene.

To fabricate a cell, researchers first synthesize a quinone- or ferrocene-based polymer, specifically, polyanthraquinone or polyvinylferrocene. They then make an “ink” by combining the polymer with carbon nanotubes in a solvent. The polymer immediately wraps around the nanotubes, connecting with them on a fundamental level.

To make the electrode, they use a non-woven carbon fiber mat as a substrate. They dip the mat into the ink, allow it to dry slowly, and then dip it again, repeating the procedure until they’ve built up a uniform coating of the composite on the substrate. The result of the process is a porous mesh that provides a large surface area of active sites and easy pathways for CO2 molecules to move in and out.

Once the researchers have prepared the quinone and ferrocene electrodes, they assemble the electrochemical cell by laminating the pieces together in the correct order — the quinone electrode, the electrolyte separator, the ferrocene electrode, another separator, and the second quinone electrode. Finally, they moisten the assembled cell with their liquid salt electrolyte.

Experimental results - To test the behavior of their system, the researchers placed a single electrochemical cell inside a custom-made, sealed box and wired it for electricity input. They then cycled the voltage and measured the key responses and capabilities of the device. The simultaneous trends in charge density put into the cell and CO2 adsorption per mole of quinone showed that when the quinone electrode is negatively charged, the amount of CO2 adsorbed goes up. And when that charge is reversed, CO2 adsorption declines.

For experiments under more realistic conditions, the researchers also fabricated full capture units — open-ended modules in which a few cells were lined up, one beside the other, with gaps between them where CO2-containing gases could travel, passing the quinone surfaces of adjacent cells.

In both experimental systems, the researchers ran tests using inlet streams with CO2 concentrations ranging from 10 percent down to 0.6 percent. The former is typical of power plant exhaust, the latter closer to concentrations in ambient indoor air. Regardless of the concentration, the efficiency of capture was essentially constant at about 90 percent. (An efficiency of 100 percent would mean that one molecule of CO2 had been captured for every electron transferred — an outcome that Hatton calls “highly unlikely” because other parasitic processes could be going on simultaneously.) The system used about 1 gigajoule of energy per ton of CO2 captured. Other methods consume between 1 and 10 gigajoules per ton, depending on the CO2 concentration of the incoming gases. Finally, the system was exceptionally durable. Over more than 7,000 charge-discharge cycles, its CO2 capture capacity dropped by only 30 percent — a loss of capacity that can readily be overcome with further refinements in the electrode preparation, say the researchers.

The remarkable performance of their system stems from what Voskian calls the “binary nature of the affinity of quinone to CO2.” The quinone has either a high affinity or no affinity at all. “The result of that binary affinity is that our system should be equally effective at treating fossil fuel combustion flue gases and confined or ambient air,” he says.

Practical applications - The experimental results confirm that the electro-swing device should be applicable in many situations. The device is compact and flexible; it operates at room temperature and normal air pressure; and it requires no large-scale, expensive ancillary equipment — only the direct current power source. This devices’ simple design should enable “plug-and-play” installation in many processes, say the researchers.

It could, for example, be retrofitted in sealed buildings to remove CO2. In most sealed buildings, ventilation systems bring in fresh outdoor air to dilute the CO2 concentration indoors. “But making frequent air exchanges with the outside requires a lot of energy to condition the incoming air,” says Hatton. “Removing the CO2 indoors would reduce the number of exchanges needed.” The result could be large energy savings. Similarly, the system could be used in confined spaces where air exchange is impossible — for example, in submarines, spacecraft, and aircraft — to ensure that occupants aren’t breathing too much CO2.

The electro-swing system could also be teamed up with renewable sources, such as solar and wind farms, and even rooftop solar panels. Such sources sometimes generate more electricity than is needed on the power grid. Instead of shutting them off, the excess electricity could be used to run a CO2 capture plant.

The researchers have also developed a concept for using their system at power plants and other facilities that generate a continuous flow of exhaust containing CO2. At such sites, pairs of units would work in parallel. “One is emptying the pure CO2 that it captured, while the other is capturing more CO2,” explains Voskian. “And then you swap them.” A system of valves would switch the airflow to the freshly emptied unit, while a purge gas would flow through the full unit, carrying the CO2 out into a separate chamber. The captured CO2 could be chemically processed into fuels or simply compressed and sent underground for long-term disposal. If the purge gas were also CO2, the result would be a steady stream of pure CO2 that soft-drink makers could use for carbonating drinks and farmers could use for feeding plants in greenhouses. Indeed, rather than burning fossil fuels to get CO2, such users could employ an electro-swing unit to generate their own CO2 while simultaneously removing CO2 from the air.

Costs and scale-up - The researchers haven’t yet published a full technoeconomic analysis, but they project capital plus operating costs at $50 to $100 per ton of CO2 captured. That range is in line with costs using other, less-flexible carbon capture systems. Methods for fabricating the electro-swing cells are also manufacturing-friendly: The electrodes can be made using standard chemical processing methods and assembled using a roll-to-roll process similar to a printing press. And the system can be scaled up as needed. According to Voskian, it should scale linearly: “If you need 10 times more capture capacity, you just manufacture 10 times more electrodes.” Together, he and Hatton, along with Brian M. Baynes PhD ’04, have formed a company called Verdox, and they’re planning to demonstrate that ease of scale-up by developing a pilot plant within the next few years.

This research was supported by an MIT Energy Initiative (MITEI) Seed Fund grant and by Eni S.p.A. through MITEI. Sahag Voskian was an Eni-MIT Energy Fellow in 2016-17 and 2017-18.

This looks like a possible breakthrough with potential to make Carbon Capture economically viable. Verdox currently has an ARPA-E award to demonstrate the efficiency of their electro-swing process. It is still early but I will track this effort and report progress from time to time.

Carbon capture is all the rage. Can these startups make it profitable?

Here are examples of carbon capture systems in operation. The first shown in figure 1 below is the capture of CO2 from a freighters exhaust that is being turned into Methanol for chemical production.

Figure 3 - Swedish startup Liquid Wind is using captured CO2 emissions to create methanol for the shipping industry. (Courtesy of Liquid Wind)

A growing number of startups have ambitions to turn carbon dioxide emissions into cold hard cash—with the hope of charting a course to clean up emissions-heavy industries without relying on perpetual government subsidies. Capturing carbon—whether it be from the air, ocean or factory smokestacks—has amassed prominent fans who see it as a moonshot that could one day help humanity reverse course on CO2 emissions.

Elon Musk recently volunteered $100 million of his own money as part of an XPrize competition to be doled out to carbon capture startups. Bill Gates has backed Carbon Engineering, a prominent startup that scrubs CO2 directly from the atmosphere. And BP, Shell and the Norwegian government have all launched significant projects to catch and bury carbon.

But the industry has received relatively little funding from venture capital in recent years, despite startup investors' frothy backing of electric vehicles (EVs) and related technologies. This is undoubtedly because EVs are perceived as very near term and a real and growing market. Carbon capture, on the other hand, is somewhere out in the undefined future with dubious profit potential. Carbon capture needs a technology breakthrough so it can demonstrate $/mT of carbon dioxide captured competitive with current carbon taxes ($30/mT of CO2 in most of Europe

VC-backed carbon capture startups took in $336.5 million last year to set a modest record, according to PitchBook data. Much of that investment was driven by non-traditional investors—oil companies, governments, and others—who participated in nearly two-thirds of all deals. Carbon capture venture capital deals over time are shown in figure 4 below.

Figure 4 –Carbon Capture Investments versus Calendar Year

Investors have plenty of reasons to be skeptical. Carbon-capture projects often involve immense capital investment, political uncertainty, and vastly longer time horizons than typical startup efforts. And storing CO2 underground in and of itself isn't a business; it relies on subsidies or a carbon market with sufficiently high prices to function. "You can capture the carbon, but then what do you do with it?" said Andrew Chung, founder and managing partner of 1955 Capital, a VC firm that invests in sustainable technologies. "You want to be able to reuse it." Carbon Engineering and Climeworks are among the most prominent companies to attempt direct-air carbon capture at scale. The approach pulls in air using massive fans, sends it through a liquid or solid filter to remove the CO2, and typically stores the gas permanently underground. Direct-air capture could effectively allow humanity to turn back the clock on past emissions, and it has gained traction with corporations and governments in recent years. Shopify recently became one of the largest corporate buyers of the technology in a deal with Carbon Engineering to capture and store 10,000 metric tons of CO2. But such direct-air carbon capture systems remain far more expensive than natural solutions like planting trees. "There's a lot of investment going into projects that will probably never return any kind of investment," said Aniruddha Sharma, co-founder and CEO of Carbon Clean, a startup that is capturing CO2 at industrial plants. That's why several startups are targeting industrial emissions sources like steel mills and cement factories, where CO2 can be found at far higher concentrations than it exists in the atmosphere. The emissions are redirected from the factory smokestacks, and the CO2 is used to create products that either trap the gas forever or give it a second life—an approach known as carbon capture and utilization. London-based Carbon Clean recently joined forces with Liquid Wind, a Swedish startup working on renewable liquid fuel. After Carbon Clean's scrubbers have captured CO2 from an industrial chimney, Liquid Wind combines it with hydrogen to create methanol. Because it captures CO2 at the point where emissions are more plentiful, Carbon Clean aims to collect the gas for less than $30 per metric ton. That's a bargain compared to the several hundred dollars per ton that other direct-air carbon capture methods cost. For its methanol to compete with traditional fuel, Liquid Wind founder and CEO Claes Fredriksson thinks that costs will have to fall to between $20 and $30 per ton of captured CO2. The joint venture aims to provide methanol fuel to the shipping industry within three years. Shipping giant Maersk has committed to making ships that are powered by methanol and expects them to be in the water by 2023 and is in discussions with Liquid Wind to provide the fuel as shown in figure 1. Carbon Clean raised $22.7 million last summer, according to PitchBook data, and is backed by Chevron and Equinor Technology Ventures. Liquid Wind has received funding from from Siemens Energy, Uniper and its partner, Carbon Clean. Turning factory CO2 into a valuable product could make such projects viable in developing countries where hefty government subsidies aren't an option. "I don't think that the subsidies are essential," said 1955 Capital's Chung, who was a general partner at Khosla Ventures before starting his own firm. The challenge for startups, once they have a scientifically proven method, is to find industrial partners who are eager to reduce their emissions and can help to develop pilot facilities next to their factories. While at Khosla, Chung invested in LanzaTech, which is using CO2 emissions to produce goods ranging from fragrances to jet fuel. Another startup, Blue Planet, has figured out a way to make rocks out of thin air. Blue Planet's system runs air from smokestacks with high concentrations of carbon dioxide through a liquid solution that causes it to form a synthetic limestone, which can replace mined sand and gravel in concrete. The process can reduce or eliminate the carbon impact of concrete, which is a leading source of greenhouse gas. "It doesn't sound too sexy but it's a really big market," said Brent Constantz, CEO of Blue Planet. Last September, Blue Planet announced a $10 million raise and has been backed by Chevron, Leonardo DiCaprio and For Good Ventures. Its synthetic rocks have been used in concrete at San Francisco International Airport. The startup is Constantz's second serious crack at carbon capture. In 2007, he founded Calera, which took a different approach to capturing carbon in cement. That company raised $182 million dollars from investors including Vinod Khosla and Madrone Capital Partners. Constantz stepped down as CEO of Calera in 2010. He thinks the approach that Blue Planet is using will be more economically viable. Because the Bay Area company doesn't need to purify the CO2 in order to turn it into a carbonate form, the startup can sequester emissions using less energy than methods that turn CO2 into its pure liquid state. The synthetic rocks also cost less to transport since they are produced near places where people already live, rather than being mined elsewhere. Point-of-emissions capture systems will be helpful in neutralizing future emissions, but they can't remove the hundreds of gigatons of CO2 in the atmosphere that scientists say will be necessary to arrest global warming. To do so will require a level of investment that could extend into the trillions of dollars. This is where we are today. It will be next to impossible to eliminate all CO2 emissions especially from third world countries. Therefore, we need a fallback Plan B. I maintain Plan B should be to develop economically competitive Carbon Capture industries and take a hard look at increasing the Earth’s albedo to keep the temperature stable while Plan B brings the ppm CO2 in Earth’s atmosphere down. It will be expensive, but we’ve pretty well run out of low-cost options.

Climeworks - The trouble right now is the extremely high cost of pulling carbon directly out of the air. Switzerland's Climeworks operates at 14 locations presently, with large factories processing ambient air and separating out the carbon (see Figure 5), but its costs are currently somewhere in the range of US$600-1000 per ton, and its own future projections graph doesn't show this price dropping much below US$250/ton by 2035 (Figure 6).

Figure 5 – Climeworks Processing Plant in Switzerland

Figure 6 – Climeworks Projected Growth and Costs/ton

Ground-based direct air capture is expensive chiefly because it's an energy-intensive process. Taking the Climeworks process as an example, large fans are used to draw in ambient air, and carbon dioxide is captured on the surface of a filter. Then the collector is closed and heated to 80-100 °C (176-212 °F), releasing a concentrated stream of CO2. This stream is then compressed to around 70 atmospheres and sent underground for geosequestration – a separate company mixes it with water and pumps it deep underground, where it reacts with basalt rock and gradually turns into stone over a few years.

CO2 Capture using Balloons

High Hopes Company - The fans, the heating and the compression are the major costs for Climeworks, and this is where High Hopes Founder and Chief Scientist Eran Oren had what may become his world-changing idea.

With the CO2 emissions well into the billions of tons, and demand expected to be driven by carbon taxes as they ramp up across the globe, price is critical. And price is where Israeli startup High Hopes believes it has a killer proposition: starting off at around US$100/ton, the company believes it can reach US$50-60 a ton with scale – by far the cheapest direct air capture solution on the market. How? Using balloons and high altitudes.

We know carbon dioxide freezes at around -80 °C (-112 °F), it turns into dry ice, which is very easy to capture. You don't need heat, you don't need compression, you can do this with minimal energy. And there's a place where you can find ambient temperatures very close to that, with lots of wind to move air through at useful rates, and carbon everywhere: in the atmosphere, 10-15 km (33,000-50,000 ft) above sea level."

So, the idea is this: put low-energy carbon capture rigs in high-altitude balloons, send them up to heights where they can work most efficiently (just below the inversion layer, where atmospheric temperatures start to rise), fill up pressure tanks with dry ice, then bring them down to Earth. As the temperature rises, the dry ice will turn back into CO2 gas, pressurizing itself thanks to the restricted volume of the tanks, and it can be sent straight out for geosequestration.

The balloons are already commercially available – they're the same device Google was using for its now-defunct Project Loon stratospheric broadband project. According to the publications, the Project Loon balloons can carry 150-200 kilos (330-400 lb) up to 20, 20-something kilometers (65,000-plus ft). So, in relevant altitudes to carbon capture it can carry something like 300 kg (660 lb). This is a commercial product, Google buys these balloons from Raven Aerostar, an American company. So, this serves as a good reference point for what is very achievable for High Hopes. he continues. Looking ahead, they will probably want to go to larger balloons. These do exist, but they're not yet commercially available. NASA and several other entities have developed and flown balloons up to around one and a half metric tons of payload. So, this doesn't require major breakthroughs in technology, and this as more or less the upper limit of what's reasonable for low development cost.

The balloons will carry two-step carbon-capture systems. As air flows in, a simple absorption process will slightly enrich the levels of carbon dioxide. Then, using a small amount of energy, some aluminum plates are cooled down to the freezing point of CO2. Dry ice freezes out of the air and settles on these plates like snowflakes, and these snowflakes are collected into the pressure tank. A key factor is that all the water vapor at these altitudes has already frozen out to ice crystals and should not collect on the plates once they are exposed to the air. None of this is new, this is a very basic process called cryodistillation. The only thing is that when you do it at high altitude, you really don't need a lot of energy to extract carbon dioxide.

The balloons will use hydrogen, both as their lighter-than-air lift gas and as the energy storage for the carbon capture and to generate energy to run their on-board navigation systems, which leverage directional wind patterns. A balloon would need to stay aloft for between 12-24 hours in order to collect a full metric ton of CO2, at which point it would come down, land, top up its hydrogen, swap its full CO2 tank for an empty one,

A state-of-the-art stratospheric balloon running for a full day on expensive hydrogen fuel, only to come down and bring home just one ton of CO2, representing US$50-100 worth of carbon capture? How does that make for good business?

The capital expenses are definitely not low here. Namely, you need the balloons, the fuel cells, and a system to manufacture the hydrogen on-site. But these are only capital expenses, they should last many years and we can divide those over a number of loads across a period of time. As to the operational expenses, most of that is just hydrogen: you use some for energy, and when you run the numbers, even under severe assumptions, the amount of energy you need for cryodistillation comes to several tens of dollars per metric ton of CO2."

Some hydrogen will also leak, due to the natural permeability of the balloon's Mylar/BoPET material. Using lift gases is always accompanied by some leakage because the molecules are very small. But putting the numbers in the equations, a balloon of relevant size will leak several kilograms per day. At several dollars per kilogram, this is not negligible but it's probably not a deal-breaker. There are extra operational expenses on the ground. But these prices scale up very, very well. The manpower you need for one balloon is quite high, but it's virtually the same as what you'd need for ten balloons, or even a hundred.

Compare that to the ground-based factories, the cost of a hundred balloons is a fraction of the cost of a factory. Even if they start with modest 50 kg (110 lb) balloons, within five balloons they claim that they are more attractive than the factories in Switzerland. And to scale up, the factories need a huge amount of land and facilities to make a significant impact. In terms of scale, High Hopes claim this is a brilliant solution.

For large-scale implementation, the team is looking at sub-Saharan Africa, close to the equator for the optimal air conditions, close to areas with abundant geosequestration potential, and somewhere with relatively clear flight paths overhead so there's minimal impact on air traffic. Location is irrelevant to the end goal; a ton of carbon pulled from one spot on the planet will have the same impact as a ton pulled from elsewhere, so the team is free to chase the ideal situation wherever on the globe it might arise.

As to the inherent safety considerations around working with hydrogen, which can blow up in spectacular fashion: "There are many," says Oren, "and as a general guideline, we're trying to use existing tech and knowledge. The bottom line is that people should not be in close proximity to large amounts of hydrogen. Lightning is quite unlikely at cruise altitude as it is far above the clouds. It's unlikely on the ground because we're aiming for areas near the equator, that have sunshine almost year-round. Tears can definitely happen, and they are taken into account as part of our operational model, by trying to prevent them, detect them, and when needed, fix them."

High Hopes has built, flown and tested small-scale demonstrator-size balloons in the "several kilos" range. "We have proven all of our assumptions, engineering-wise," says Oren. "Not to say that we haven't learned and corrected things along the way, but I can't stress enough: cryodistillation is extremely simple. These are solved problems."

"The next step is starting to scale up, continuing development and hitting their next major milestone, which is getting to 50-100 kg (110-220 lb) per day, which they expect in around eight to ten months. The real challenge is getting to the 1-ton balloons – although that technology already exists in one form or another. They think they can hit that in two to three and a half years. And even if they fail to get there, and they stall at balloons carrying just 100 kg, they believe they will still better than any other solution that currently exists.

"Direct air capture now," Oren adds, "is at around 1,000 tons a year. Generally speaking, if it doesn't get to the millions to ten of millions of tons per year, then it's probably irrelevant in the scheme of things. So that's the minimum that we're aiming at, and in terms of energy, land use, materials, rare Earth metals and technical restraints, we can scale it up as much as needed. In terms of geosequestration, the known amount of carbon we can put in the ground, that will settle there as minerals, is enough to cover everything that's been emitted so far, and many years into the future."

Without funding limitations, High Hopes claim they could extract billions of tons of carbon from the air. The debate about the need to sequester CO2 is over. High Hopes is aiming to get into the tens or hundreds of millions of tons. They claim that even if they only make it to 100,000 tons a year, it'll be much better than all the factories and facilities in the world.

As a reality check, the numbers are as daunting here as they seem to be with any climate solution. To reach just one million tons of carbon captured per year, High Hopes would need to get 2,055 massive one-ton balloons into operation, each pulling down a full CO2 tank every 18 hours. And that's assuming year-round availability and no punctures or tears.

On the other hand, carbon taxes are popping up all over the world, and they're likely to rise over the coming decades as governments put pressure on industry to account for the future costs they're causing the public sector with every ton of CO2 they put in the air.

Sweden is already taxing certain emitters at a robust US$126 per ton, and that's already high enough to work economically with a solution like this. The rest of the world is a long way behind this figure, but everything is moving in the right direction.

In most cases, the economical choice for emitters will be to embrace new technologies and decarbonize their operations or grab their CO2 and sequester it right from the source. But where that's impossible, or too expensive, direct air carbon capture will be there to bridge the gap to zero, and we're going to want it as cheap as we can possibly get it.

We wish the High Hopes team every success in their venture and will keep tabs on progress. It is a new concept, it is inventive, but the economics are unproven. We shall see.

I hope you found this cut at new carbon capture technologies interesting. I found the Electro-swing Cell the most intriguing new technology that might make a real contribution to economic carbon sequestering, but it is still too early to make that call. I wish them all good luck and hope we have some progress to report soon.

Thanks for your attention,

Dana G Andrews

retiredrocketdoc.com