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Millions poured into XPrize effort to pull CO2 out of the sky

London’s Mission Zero Technologies has developed an energy-efficient way of capturing carbon dioxide from the atmosphere and sequestering it into the dominant rock (peridotites) of the upper part of the Earth’s mantle.

Stretching across the northern coasts of Oman and the United Arab Emirates loom the vast jagged peaks of the Al Hajar mountains. The craggy outcrops are made mostly of a rock called peridotite, which absorbs carbon dioxide from the air and turns it into solid minerals. The mountains could store trillions of tonnes of human-made CO2 emissions, but the natural carbon-mineralization process works at a glacial pace.

London startup 44.01 has found a way to speed it up. For this endeavor, 44.01 is teaming up with another London startup, Mission Zero Technologies, which has developed an energy-efficient method to capture CO2 from air. Called Project Hajar, it plans to pull 1,000 tonnes of CO2/year from air at a demonstration facility in Oman, injecting some 3–4 tonnes/day into the peridotite rocks. Mission Zero’s 120 tonne-capacity pilot plant will come online in the first half of 2023.

This ambitious, clear vision made Project Hajar one of 15 winners of a milestone US $1 million award announced by the ongoing XPrize Carbon Removal competition in late April. Funded by Elon Musk, this XPrize has the largest purse yet, $100 million, for methods to pull CO2 from air and lock it away. The 15 teams, selected from over 1,100, had to demonstrate a viable approach along with scale-up plans and cost estimates.

“We require the development of a portfolio of solutions while we take lots of shots on goal.” —Gaurav Sant, UCLA

Carbon removal is not to be confused with carbon capture at smokestacks. Pulling CO2 from air, where it’s present at a very low concentration, is far more complex and costly. Yet in an April report, the U.N. Intergovernmental Panel on Climate Change says that carbon removal will be “unavoidable” to keep the planet from crossing the life-disrupting warming threshold of 1.5 °C. The decarbonizing method is gaining popularity, with high-profile investors including Musk, Bill Gates, and Google’s parent company Alphabet pouring millions into promising solutions. The Biden Administration also recently announced a $3.5 billion program for large-scale carbon removal.

The 15 award-winning approaches include direct air capture (DAC) using chemicals, turning farm waste into charcoal and burying it, growing algae or kelp, and tweaking ocean pH to boost its natural capacity to soak up CO2. The $50 million grand prize, to be awarded in 2025, is up for grabs for any team that can prove its technique will work at a scale of at least 1,000 tonnes/year.

That immense scale, as well as what happens to the CO2, will decide whether an approach can make a dent in the world’s nearly 36 billion tonnes of annual carbon emissions, says Gaurav Sant, director of UCLA’s Institute for Carbon Management, who has two entries in the competition (SeaChange and BeyonDAC), neither of which was among the 15 milestone awardees. Any meaningful approach needs to convert the gas into something stable and not just bury it in the ground from where it could leak.

“Prizes are important because they provoke optimism,” Sant says. “We require the development of a portfolio of solutions while we take lots of shots on goal. At the same time we need to be robust and thoughtful, both about the technology development but also the eventual fate of CO2.”

Not all 15 winners make the cut with those two criteria. Five projects, for instance, rely on land-based techniques like biomass-based power generation, farming algae, planting trees, or amending soil with charcoal from waste, which limits them, says Christopher Jones, a chemical and biomolecular engineer who studies carbon capture at the Georgia Institute of Technology. These approaches are low cost at under $100 per ton of captured CO2, “but there’s only so much land change you could make to capture a significant amount,” he says. “We need to capture 10 gigatons per year for negative emissions by 2060. Land and biomass approaches only scale to a few gigatons.”

Of known carbon-removal techniques, two hold the most promise, he says, citing a recent National Academies report. One is DAC and the other is carbon mineralization. “Nothing prevents us from scaling these up to the 10 gigatons per year scale needed aside from a commitment, coordination and cooperation.”

“We thought the two things that are most important to really make a difference are cost and scale. It’s not the efficiency of the process.” —Raghubir Gupta, Sustaera

Direct air capture has already taken off, with about 20 projects already underway around the world. Most rely on large fans to suck CO2 from air using liquid or solid materials, which are not cheap, and then heating the mixture by burning natural gas to remove CO2 and regenerate the adsorbing material. The downside of DAC is high fossil-fuel energy use and cost.

Sustaera in Cary, N.C., one of six milestone winners pursuing DAC, has found a way to tackle that. Chief Technology Officer Raghubir Gupta worked for two decades on carbon capture at power plants and industrial plants. “One big thing we have that not many others have is practical experience of scaling up the technology to 1,000 tonnes/day carbon dioxide capture,” he says. “With that background when we looked at CO2 removal from air, we thought the two things that are most important to really make a difference are cost and scale. It’s not the efficiency of the process.”

Sustaera uses cheap sodium carbonate to adsorb CO2. It coats the material on a high-surface area ceramic scaffold used in catalytic converters. The high surface area increases access to the sorbent and increases CO2 adsorption rate significantly, Gupta says.

The energy advantage comes from using electricity instead of heat to separate the CO2 and regenerate the sorbent. More specifically, Sustaera uses Joule heating, in which passing an electric current through a conductor produces heat. Along with the sodium carbonate, the ceramic support contains a conducting material such as carbon nanotubes. Electricity, which can be renewable, locally heats the sorbent and triggers CO2 release. At full scale, Sustaera’s system should be able to capture over 3,000 tonnes/day of CO2 at under $100/tonne. For now, says Gupta, a 1 tonne/day facility being built at the company’s R&D site in Research Triangle Park, N.C., should be ready by the end of this year.

While Sustaera focuses on making DAC cheap, Project Hajar’s promise lies in marrying DAC with permanent carbon storage via mineralization. First, project partner Mission Zero Technologies uses solvents to capture CO2 from air blown through a tower. Then an electrochemical cell separates the CO2; the process takes a third of the energy of conventional thermal separation. “It works fully with existing materials and chemicals and off-the-shelf equipment,” says Mission Zero’s cofounder Shiladitya Ghosh. Both the cooling tower and the electrochemical cell technologies are ubiquitous around the world, “so the manufacturing systems are established and available.”

Then, startup 44.01 mixes the CO2 with water and injects it via engineered boreholes into the peridotite rocks to form carbonate minerals. “We accelerate the reaction by creating physical and chemical characteristics to catalyze it such as pressure, temperature, and alkalinity balance in the subsurface,” says the company's co-founder Karan Khimji.

Like its partner, 44.01 also uses off-the-shelf equipment from the oil and gas sector. “I find beauty in that,” Khimji says. “We’re repurposing the same resources as the oil and gas sector to reverse the problem that they have contributed to.” Renewable electricity onsite will power both carbon removal and mineralization at the eventual Oman demonstration facility. Another competitive advantage is permanence. “CO2 is eliminated from existence, it doesn’t remain in gaseous form in the subsurface.”

Canada-based Carbin Minerals is looking at mine waste to lock away CO2. Magnesium-rich pulverized rocks, or tailings, from nickel and diamond mines around the world already soak up tens of thousands of tonnes of CO2 a year, turning it into magnesium carbonate, says CTO and cofounder Peter Scheuermann. By stirring them up to increase the surface area, and tweaking the physical and chemical conditions in tailing storage facilities, the company can make this natural process five times as fast. Using car-size robots to move through the rock slurry and apply a mineral treatment that the team is developing could further double that. “Our goal is to piggyback off existing industrial sites,” he says. “The manipulation technology is all kind of drop-in.”

Canada’s Carbin Minerals is testing a technology that accelerates how which mine waste converts atmospheric carbon dioxide into mineral rock, unlocking the potential for gigaton-scale removal and permanent storage.Carbin Minerals

As nickel mining increases to meet battery electrification needs, he adds, these types of mine tailings are predicted to reach 1.4 gigatonnes. “If applied appropriately, this could provide hundreds of thousands to millions of tons per year of carbon removal,” he says, giving carbon-negative nickel for EV batteries, a “one-two punch” in the climate fight.

It’s not clear to Georgia Tech’s Jones whether injecting CO2 into rocks, as Project Hajar is doing, or using mine tailings as Carbin Minerals is doing is better. The former requires energy for capture and injection, while the latter bears an environmental cost. There are also fundamental scientific questions about how much the carbon-mineralization rate can be sped up, he says. And even though there are enough types of rocks around the world to trap billions of tons of CO2, it’s unclear how much is accessible.

For sheer scale, nothing could beat the oceans as a carbon sink, says UCLA’s Sant. Three of the XPrize milestone winners have ocean-based carbon-removal platforms. But the caveat for large-scale impact is to stabilize the CO2 in ocean water, not in a geological formation, he says. The way to do that is to enhance the ocean’s natural uptake of CO2.

Here, Planetary Technologies from Nova Scotia, Canada, might have the most interesting approach. Rising carbon levels are making the world’s oceans acidic. The company purifies mine waste to make a mild antacid to restore oceanwater pH, which should help it pull more CO2 from air while reducing damage from acidification. It says that its mine-waste purification technique also produces hydrogen for energy and metals for batteries. In this way it tackles several different issues at once: carbon removal, green hydrogen production, mine-waste cleanup, and ocean restoration.

The big winner for the XPrize Carbon Removal will be announced on Earth Day 2025. But of course, there is no one winning solution, says Jones. All carbon-removal technologies have merits and demerits and bear the risk of unintended consequences. “But we have to do something,” he says. “Because there is no silver-bullet answer, it allows us to drag our feet and do nothing. The problem is big enough that you need a dozen different technologies to contribute a little.”

This article appears in the July 2022 print issue as “X-Prize Competitors Capture Carbon.”

Prachi Patel is a freelance journalist based in Pittsburgh. She writes about energy, biotechnology, materials science, nanotechnology, and computing.

I agree that we need lower carbon in the air, but the best way to do that is to prevent it from getting there in the first place. The best way is through efficiency and thoughtful energy conservation. Musk's refusal to allow his workers to tele-commute (avoid driving) at least some of the days per week flies in the face of this.

Forests, surely, are one of the biggest and most effective ways of absorbing and storing carbon dioxiode: "Forests provide a “carbon sink” that absorbs a net 7.6 billion metric tonnes of CO2 per year." https://www.wri.org/insights/forests-absorb-twice-much-carbon-they-emit-each-year

The main problem is to reduce human destruction of them.

The weakness of carbon capture and storage is the amounts are much too small to affect the Earth's clmate. One ppm of CO2 is 7,800 million metric tons. There is no technology that can bury that amount. Musk and Gates are wasting their prize money. So are government subsidies. The climate would not miss one ppm anyhow.

Utrecht leads the world in using EVs for grid storage

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

Utrecht, a largely bicycle-propelled city of 350,000 just south of Amsterdam, has become a proving ground for the bidirectional-charging techniques that have the rapt interest of automakers, engineers, city managers, and power utilities the world over. This initiative is taking place in an environment where everyday citizens want to travel without causing emissions and are increasingly aware of the value of renewables and energy security.

“We wanted to change,” says Eelco Eerenberg, one of Utrecht's deputy mayors and alderman for development, education, and public health. And part of the change involves extending the city’s EV-charging network. “We want to predict where we need to build the next electric charging station.”

So it’s a good moment to consider where vehicle-to-grid concepts first emerged and to see in Utrecht how far they’ve come.

It’s been 25 years since University of Delaware energy and environmental expert Willett Kempton and Green Mountain College energy economist Steve Letendre outlined what they saw as a “dawning interaction between electric-drive vehicles and the electric supply system.” This duo, alongside Timothy Lipman of the University of California, Berkeley, and Alec Brooks of AC Propulsion, laid the foundation for vehicle-to-grid power.

The inverter converts alternating current to direct current when charging the vehicle and back the other way when sending power into the grid. This is good for the grid. It’s yet to be shown clearly why that’s good for the driver.

Their initial idea was that garaged vehicles would have a two-way computer-controlled connection to the electric grid, which could receive power from the vehicle as well as provide power to it. Kempton and Letendre’s 1997 paper in the journal Transportation Research describes how battery power from EVs in people’s homes would feed the grid during a utility emergency or blackout. With on-street chargers, you wouldn’t even need the house.

Bidirectional charging uses an inverter about the size of a breadbasket, located either in a dedicated charging box or onboard the car. The inverter converts alternating current to direct current when charging the vehicle and back the other way when sending power into the grid. This is good for the grid. It’s yet to be shown clearly why that’s good for the driver.

This is a vexing question. Car owners can earn some money by giving a little energy back to the grid at opportune times, or can save on their power bills, or can indirectly subsidize operation of their cars this way. But from the time Kempton and Letendre outlined the concept, potential users also feared losing money, through battery wear and tear. That is, would cycling the battery more than necessary prematurely degrade the very heart of the car? Those lingering questions made it unclear whether vehicle-to-grid technologies would ever catch on.

Market watchers have seen a parade of “just about there” moments for vehicle-to-grid technology. In the United States in 2011, the University of Delaware and the New Jersey–based utility NRG Energy signed a technology-license deal for the first commercial deployment of vehicle-to-grid technology. Their research partnership ran for four years.

In recent years, there’s been an uptick in these pilot projects across Europe and the United States, as well as in China, Japan, and South Korea. In the United Kingdom, experiments are now taking place in suburban homes, using outside wall-mounted chargers metered to give credit to vehicle owners on their utility bills in exchange for uploading battery juice during peak hours. Other trials include commercial auto fleets, a set of utility vans in Copenhagen, two electric school buses in Illinois, and five in New York.

These pilot programs have remained just that, though—pilots. None evolved into a large-scale system. That could change soon. Concerns about battery wear and tear are abating. Last year, Heta Gandhi and Andrew White of the University of Rochestermodeled vehicle-to-grid economics and found battery-degradation costs to be minimal. Gandhi and White also noted that battery capital costs have gone down markedly over time, falling from well over US $1,000 per kilowatt-hour in 2010 to about $140 in 2020.

As vehicle-to-grid technology becomes feasible, Utrecht is one of the first places to fully embrace it.

The key force behind the changes taking place in this windswept Dutch city is not a global market trend or the maturity of the engineering solutions. It’s having motivated people who are also in the right place at the right time.

One is Robin Berg, who started a company called We Drive Solar from his Utrecht home in 2016. It has evolved into a car-sharing fleet operator with 225 electric vehicles of various makes and models—mostly Renault Zoes, but also Tesla Model 3s, Hyundai Konas, and Hyundai Ioniq 5s. Drawing in partners along the way, Berg has plotted ways to bring bidirectional charging to the We Drive Solar fleet. His company now has 27 vehicles with bidirectional capabilities, with another 150 expected to be added in coming months.

In 2019, Willem-Alexander, king of the Netherlands, presided over the installation of a bidirectional charging station in Utrecht. Here the king [middle] is shown with Robin Berg [left], founder of We Drive Solar, and Jerôme Pannaud [right], Renault's general manager for Belgium, the Netherlands, and Luxembourg.Patrick van Katwijk/Getty Images

Amassing that fleet wasn’t easy. We Drive Solar’s two bidirectional Renault Zoes are prototypes, which Berg obtained by partnering with the French automaker. Production Zoes capable of bidirectional charging have yet to come out. Last April, Hyundai delivered 25 bidirectionally capable long-range Ioniq 5s to We Drive Solar. These are production cars with modified software, which Hyundai is making in small numbers. It plans to introduce the technology as standard in an upcoming model.

We Drive Solar’s 1,500 subscribers don’t have to worry about battery wear and tear—that’s the company’s problem, if it is one, and Berg doesn’t think it is. “We never go to the edges of the battery,” he says, meaning that the battery is never put into a charge state high or low enough to shorten its life materially.

We Drive Solar is not a free-flowing, pick-up-by-app-and-drop-where-you-want service. Cars have dedicated parking spots. Subscribers reserve their vehicles, pick them up and drop them off in the same place, and drive them wherever they like. On the day I visited Berg, two of his cars were headed as far as the Swiss Alps, and one was going to Norway. Berg wants his customers to view particular cars (and the associated parking spots) as theirs and to use the same vehicle regularly, gaining a sense of ownership for something they don’t own at all.

That Berg took the plunge into EV ride-sharing and, in particular, into power-networking technology like bidirectional charging, isn’t surprising. In the early 2000s, he started a local service provider called LomboXnet, installing line-of-sight Wi-Fi antennas on a church steeple and on the rooftop of one of the tallest hotels in town. When Internet traffic began to crowd his radio-based network, he rolled out fiber-optic cable.

In 2007, Berg landed a contract to install rooftop solar at a local school, with the idea to set up a microgrid. He now manages 10,000 schoolhouse rooftop panels across the city. A collection of power meters lines his hallway closet, and they monitor solar energy flowing, in part, to his company’s electric-car batteries—hence the company name, We Drive Solar.

Berg did not learn about bidirectional charging through Kempton or any of the other early champions of vehicle-to-grid technology. He heard about it because of the Fukushima nuclear-plant disaster a decade ago. He owned a Nissan Leaf at the time, and he read about how these cars supplied emergency power in the Fukushima region.

“Okay, this is interesting technology,” Berg recalls thinking. “Is there a way to scale it up here?” Nissan agreed to ship him a bidirectional charger, and Berg called Utrecht city planners, saying he wanted to install a cable for it. That led to more contacts, including at the company managing the local low-voltage grid, Stedin. After he installed his charger, Stedin engineers wanted to know why his meter sometimes ran backward. Later, Irene ten Dam at the Utrecht regional development agency got wind of his experiment and was intrigued, becoming an advocate for bidirectional charging.

Berg and the people working for the city who liked what he was doing attracted further partners, including Stedin, software developers, and a charging-station manufacturer. By 2019, Willem-Alexander, king of the Netherlands, was presiding over the installation of a bidirectional charging station in Utrecht. “With both the city and the grid operator, the great thing is, they are always looking for ways to scale up,” Berg says. They don’t just want to do a project and do a report on it, he says. They really want to get to the next step.

Those next steps are taking place at a quickening pace. Utrecht now has 800 bidirectional chargers designed and manufactured by the Dutch engineering firm NieuweWeme. The city will soon need many more.

The number of charging stations in Utrecht has risen sharply over the past decade.

“People are buying more and more electric cars,” says Eerenberg, the alderman. City officials noticed a surge in such purchases in recent years, only to hear complaints from Utrechters that they then had to go through a long application process to have a charger installed where they could use it. Eerenberg, a computer scientist by training, is still working to unwind these knots. He realizes that the city has to go faster if it is to meet the Dutch government’s mandate for all new cars to be zero-emission in eight years.

The amount of energy being used to charge EVs in Utrecht has skyrocketed in recent years.

Although similar mandates to put more zero-emission vehicles on the road in New York and California failed in the past, the pressure for vehicle electrification is higher now. And Utrecht city officials want to get ahead of demand for greener transportation solutions. This is a city that just built a central underground parking garage for 12,500 bicycles and spent years digging up a freeway that ran through the center of town, replacing it with a canal in the name of clean air and healthy urban living.

A driving force in shaping these changes is Matthijs Kok, the city’s energy-transition manager. He took me on a tour—by bicycle, naturally—of Utrecht’s new green infrastructure, pointing to some recent additions, like a stationary battery designed to store solar energy from the many panels slated for installation at a local public housing development.

This map of Utrecht shows the city’s EV-charging infrastructure. Orange dots are the locations of existing charging stations; red dots denote charging stations under development. Green dots are possible sites for future charging stations.

“This is why we all do it,” Kok says, stepping away from his propped-up bike and pointing to a brick shed that houses a 400-kilowatt transformer. These transformers are the final link in the chain that runs from the power-generating plant to high-tension wires to medium-voltage substations to low-voltage transformers to people’s kitchens.

There are thousands of these transformers in a typical city. But if too many electric cars in one area need charging, transformers like this can easily become overloaded. Bidirectional charging promises to ease such problems.

Kok works with others in city government to compile data and create maps, dividing the city into neighborhoods. Each one is annotated with data on population, types of households, vehicles, and other data. Together with a contracted data-science group, and with input from ordinary citizens, they developed a policy-driven algorithm to help pick the best locations for new charging stations. The city also included incentives for deploying bidirectional chargers in its 10-year contracts with vehicle charge-station operators. So, in these chargers went.

Experts expect bidirectional charging to work particularly well for vehicles that are part of a fleet whose movements are predictable. In such cases, an operator can readily program when to charge and discharge a car’s battery.

We Drive Solar earns credit by sending battery power from its fleet to the local grid during times of peak demand and charges the cars’ batteries back up during off-peak hours. If it does that well, drivers don’t lose any range they might need when they pick up their cars. And these daily energy trades help to keep prices down for subscribers.

Encouraging car-sharing schemes like We Drive Solar appeals to Utrecht officials because of the struggle with parking—a chronic ailment common to most growing cities. A huge construction site near the Utrecht city center will soon add 10,000 new apartments. Additional housing is welcome, but 10,000 additional cars would not be. Planners want the ratio to be more like one car for every 10 households—and the amount of dedicated public parking in the new neighborhoods will reflect that goal.

Some of the cars available from We Drive Solar, including these Hyundai Ioniq 5s, are capable of bidirectional charging.We Drive Solar

Projections for the large-scale electrification of transportation in Europe are daunting. According to a Eurelectric/Deloitte report, there could be 50 million to 70 million electric vehicles in Europe by 2030, requiring several million new charging points, bidirectional or otherwise. Power-distribution grids will need hundreds of billions of euros in investment to support these new stations .

The morning before Eerenberg sat down with me at city hall to explain Utrecht’s charge-station planning algorithm, war broke out in Ukraine. Energy prices now strain many households to the breaking point. Gasoline has reached $6 a gallon (if not more) in some places in the United States. In Germany in mid-June, the driver of a modest VW Golf had to pay about €100 (more than $100) to fill the tank. In the U.K., utility bills shot up on average by more than 50 percent on the first of April.

The war upended energy policies across the European continent and around the world, focusing people’s attention on energy independence and security, and reinforcing policies already in motion, such as the creation of emission-free zones in city centers and the replacement of conventional cars with electric ones. How best to bring about the needed changes is often unclear, but modeling can help.

Nico Brinkel, who is working on his doctorate in Wilfried van Sark’s photovoltaics-integration lab at Utrecht University, focuses his models at the local level. In his calculations, he figures that, in and around Utrecht, low-voltage grid reinforcements cost about €17,000 per transformer and about €100,000 per kilometer of replacement cable. “If we are moving to a fully electrical system, if we’re adding a lot of wind energy, a lot of solar, a lot of heat pumps, a lot of electric vehicles…,” his voice trails off. “Our grid was not designed for this.”

But the electrical infrastructure will have to keep up. One of Brinkel’s studies suggests that if a good fraction of the EV chargers are bidirectional, such costs could be spread out in a more manageable way. “Ideally, I think it would be best if all of the new chargers were bidirectional,” he says. “The extra costs are not that high.”

Berg doesn’t need convincing. He has been thinking about what bidirectional charging offers the whole of the Netherlands. He figures that 1.5 million EVs with bidirectional capabilities—in a country of 8 million cars—would balance the national grid. “You could do anything with renewable energy then,” he says.

Seeing that his country is starting with just hundreds of cars capable of bidirectional charging, 1.5 million is a big number. But one day, the Dutch might actually get there.