A daring plan to save lots of the planet turns carbon dioxide into stone


The drained, crumbling peaks of the Al Hajar Mountains are slowly decomposing like a slab of rotten meat. Refined indicators of decay are throughout. Flammable hydrogen gasoline typically bubbles from groundwater. Water from pure springs is commonly saturated with minerals. This water leaves a carpet of frosty white crystals because it flows over the bottom. Only some forms of vegetation can develop in such alien soils.

Right here, within the desert nation of Oman, east of Saudi Arabia, the mountains comprise unique minerals that don’t usually exist at Earth’s floor. They fashioned dozens of kilometers (miles) under — deeper than people have ever delved searching for oil or gold. Now uncovered to air and water on Earth’s floor, these minerals show chemically unstable.

When rain falls, it trickles into cracks within the rock, carrying gases from the air. The water and gases react with the rock to kind new, colourful minerals. These jagged veins of black, white and blue-green stone push ever deeper into the bedrock. Like sluggish however highly effective fingers, the minerals widen the cracks, prying the rock aside.

a photo of a white waterfall overflowing from a blue spring
At these alkaline springs in Oman, water emerges from the bottom saturated with dissolved calcium. The calcium rapidly reacts with CO2 within the air, forming movies of calcium carbonate (calcite) that may seem inside 24 hours. The water leaves a frosty coating of calcite crystals because it flows over the rock.D. Fox

Peter Kelemen believes that these decomposing rocks might assist people remedy an essential drawback: local weather change.

Kelemen is a geologist on the Lamont-Doherty Earth Observatory in Palisades, N.Y. The white carbonate veins, he notes, fashioned as carbon dioxide (CO2) in rainwater latched onto magnesium and calcium atoms within the rocks. In different phrases, these new minerals entice the identical gasoline that people launch after they burn fossil fuels. It’s the identical greenhouse gasoline that’s warming our planet.

These uncommon rocks are unfold throughout an space of Oman concerning the dimension of Maryland. They’re naturally petrifying 50,000 to 100,000 tons of CO2 per yr, Kelemen believes. That’s puny in comparison with the 30 billion tons of CO2 that people launch annually. However Kelemen and his colleagues imagine these rocks might sooner or later solidify as much as a billion tons of CO2 per yr. Different rock formations scattered world wide might seize one other 10 billion to twenty billion tons of CO2 annually. ”You’re one thing that might probably have an effect on the human international carbon price range,” he informed me one afternoon in Oman. 

a natural spring showing stairstep terrace pools
At these pure springs in Oman, water emerges from the bottom saturated with dissolved calcium. It rapidly reacts with CO2 within the air to kind calcium carbonate (calcite). Over lengthy intervals of time, the mineral builds up into stunning stairstep terraces, referred to as travertine.D. Fox

Kelemen and his collaborator, Juerg Matter, have been engaged on this concept for almost 20 years. Matter is a geochemist on the College of Southampton in England. After I visited them in Oman in 2018, their crew was busy drilling a number of holes into the rock. They deliberate to drag up stone from as deep as 400 meters (1,300 toes) underground. These cores would assist them higher perceive a pure course of that they hope to hurry up.

Destructive emissions

Eradicating CO2 from the air as soon as appeared outlandish. Within the final 20 years, nevertheless, it has gained momentum because the urgency of local weather change has develop into clearer.

Many scientists now imagine individuals won’t cut back releases of greenhouse gases rapidly sufficient to stop Earth from warming greater than 1.5 levels Celsius (2.7 levels Fahrenheit). It’s thought that this warming restrict would avert probably the most harmful results of local weather change. These results embody runaway sea stage rise, the lack of the Amazon rainforest and frequent catastrophic storms.

Scientists at the moment are suggesting that folks resort to a method referred to as “unfavourable emissions.” These would come with huge tasks to suck billions of tons of CO2 from the air annually. They would wish to make use of many ways, corresponding to replanting forests. Or fertilizing the ocean to spur the expansion of photosynthetic plankton. The forests and plankton would naturally pull CO2 out of the air.

A number of firms are additionally constructing “direct air seize” machines to drag CO2 from the air. The captured gasoline might then be pumped underground.

Vitality firms have pumped small quantities of CO2 into empty oil and gasoline reservoirs because the Eighties. There, the gasoline is trapped between layers of sedimentary rocks, corresponding to sandstone. But when the gasoline leaks again out, it might trigger issues, warns Gregory Nemet. He’s an vitality scientist on the College of Wisconsin–Madison. “It doesn’t take rather a lot,” he says. “If it’s one or two p.c leakage, that basically places a gap in our plans to stabilize the local weather.”

However completely different rocks, like these in Oman, might extra completely entice CO2. They comprise excessive ranges of calcium and magnesium silicates. In these minerals, calcium and magnesium atoms are sure to clusters of oxygen and silicon atoms, referred to as silica. These minerals, unusual at Earth’s floor, are plentiful in rocks very deep under floor. Scientists had suspected these minerals would react with CO2 and lock it into carbonate minerals. This concept lured Matter to get entangled. He wished to check it.

A large square grid outlined in white has piles of rock samples in each square.
These samples of mantle rock, referred to as peridotite, have been reduce from completely different components of a borehole in Oman. The white flecks present carbonate minerals, which fashioned as atoms of magnesium and calcium within the rock latched onto molecules of CO2 that had been dissolved within the groundwater.Juerg Matter/Univ. of Southampton

Down the rabbit gap

Matter had simply gotten his PhD when he took a job at Lamont-Doherty again in 2001. The campus sits in a forest close to New York Metropolis. The buildings stand above cliffs that drop 100 meters (325 toes) into the Hudson River. These chocolatey brown cliffs are made from stone often known as basalt. It fashioned from lavas that erupted thousands and thousands of years in the past from deep inside Earth.

Basalts comprise calcium and magnesium silicates. David Goldberg, the geophysicist who employed Matter, wished him to strive injecting CO2 into them.

”All people thought I’m loopy, and even silly,” for attempting this, remembers Matter. Different scientists had achieved lab experiments. Their knowledge urged carbonate minerals would take lots of of years to kind. That may be far too sluggish to assault right this moment’s climate-change menace.

However in 2004, Matter and Goldberg tried anyway. They injected water 230 meters (750 toes) down a effectively drilled into the basalt. That water contained a number of kilograms (possibly 5 kilos) of CO2.

When Matter pumped the water again out per week later, the CO2 had vanished. This gasoline types a weak acid in water. The acid dissolved among the calcium and magnesium silicates within the rocks. They reacted with the gasoline to kind carbonates. And this was occurring 300 to three,000 occasions extra rapidly than in lab checks. The crew printed its findings again in 2007.

“Pondering again, it was fairly excessive danger what we did,” says Matter. There was a giant probability that it wouldn’t work. “We simply believed in it,” he says. And, he provides, “We have been actually simply fortunate.”

Matter and several other different scientists then went on the lookout for different locations to show CO2 into stone — and on a a lot larger scale. In 2012, they acquired their probability.

an aerial photo of a geothermal plant in Iceland
This geothermal plant and Carbfix website is positioned close to Hengill Volcano in Iceland. Volcanic CO2 that emerges with the new water is injected again into the basalt, to petrify — flip to stone — the CO2 as carbonate minerals.Árni Sæberg, Carbfix

10,000 tons per yr

Iceland is an island nation within the north Atlantic Ocean. Reykjavik Vitality, there, ran a geothermal energy plant close to one of many nation’s many volcanoes. The corporate wished to get rid of CO2. Its plant generated electrical energy utilizing sizzling water gushing up from underground. Volcanoes usually spew CO2. Because the water emerged from under floor, it too launched this gasoline into the air.

However there was an apparent resolution. Iceland is made nearly totally of basalt. Injecting CO2 into that basalt ought to lock it away.

In 2012, employees drilled a gap in a grassy area close to the ability plant and injected water 400 meters (1,300 toes) into the basalt under. This water held six occasions as a lot CO2 as seltzer water does. To forestall it from fizzing violently because the gasoline escaped, the water needed to be saved beneath excessive stress. Over a number of weeks, the crew injected 71 metric tons (78 U.S. tons) of CO2 into the rock.

In the meantime, Sandra Snæbjörnsdóttir (SNY-byorns-DOT-er) pumped water from one other close by gap. She’s a geologist who was engaged on this challenge, often known as Carbfix. She discovered that the CO2 was disappearing from the injected water because it seeped by the rocks. “It occurred truly quicker than we dared to hope,” she says.

a close up photo of a rock core, showing white calcum carbonate minerals along a diagonal edge in the middle of the image
CO2 that’s injected into basalts at Carbfix in Iceland is quickly solidified into white calcium carbonate minerals, as present on this drill core.Sandra Snæbjörnsdóttir, Carbfix

Over 95 p.c of the CO2 fashioned minerals — strong rock — inside two years. The crew drilled a brand new gap and retrieved stone cores from close to the injection website. The cylinders of gray-black basalt have been splotched with white. These splotches have been the carbonate minerals fashioned by the injected CO2. These outcomes appeared in Science in 2016.

The challenge is now petrifying 10,000 tons of CO2 per yr. And Carbfix has develop into a separate firm, with plans to develop its operations.

“You’ll be able to truly stuff numerous CO2 into these rocks,” says Snæbjörnsdóttir, who now works for the brand new firm. She estimates {that a} cubic meter of basalt (a block the scale of a dishwasher) can soak up greater than 100 kilograms (220 kilos) of CO2. Basaltic rock additionally sits beneath many of the world’s seafloors. Not all of that rock is appropriate for petrifying CO2. However a few of it appears to be. Snæbjörnsdóttir predicts that Carbfix will finally strive injecting CO2 into these oceanic basalts off the coast of Iceland.

a close up view of white carbonate veins running through brown and green rock
White carbonate veins crisscross an outcrop of mantle rock in Oman.Katie Pratt, Deep Carbon Observatory/Wikimedia Commons (CC BY-SA 2.5)

Matter oversaw the preliminary Carbfix experiments. However even earlier than these first injections, he was already on the lookout for extra locations to solidify CO2.

In 2007, he and Kelemen began wanting on the rocks in Oman. These rocks come from the mantle. That’s the center layer of our planet. People have by no means instantly seen it. The mantle begins about 10 kilometers (6 miles) under the seafloor and reaches 2,900 kilometers (1,800 miles) into the Earth. The Oman rocks have been a tiny fragment of mantle that had been shoved as much as the floor. It occurred thousands and thousands of years in the past throughout a uncommon geologic upheaval.

The mantle is the supply of lava and basalts. Its rocks comprise even greater ranges of calcium and magnesium silicates than do basalts. Due to this, Matter and Kelemen believed that the Oman rocks may be capable to entice extra CO2 per cubic meter than the rocks in Iceland.

Mantle rocks on the floor of the Al Hajar Mountains are crisscrossed with white carbonate veins. Matter and Kelemen used radiocarbon relationship to indicate that a few of these veins have been lower than 5,000 years outdated. This urged these rocks hadn’t simply absorbed CO2 thousands and thousands of years in the past — they have been doing so proper now. Matter and Kelemen printed these findings in 2008.

The 2 scientists nonetheless wanted to study extra about what was occurring under the floor. So in 2017 and 2018, they and a big crew of researchers drilled a number of holes in Oman to retrieve stone cores. I spent per week with them in January 2018 as they drilled in a distant valley, Wadi Lawayni (WAH-dee Lah-WAY-nee).

a photo of a drilling site in Oman. There are mountains in the distance.
The Al Hajar Mountains in Oman are a part of an enormous slab of rock, 500 kilometers (310 miles) lengthy and 60 kilometers (37 miles) huge, which fashioned within the mantle. In 2017 and 2018, researchers drilled a number of holes. They penetrated so far as 400 meters (1,300 toes) all the way down to extract cores of rock. Scientists are learning how these rocks naturally soak up CO2 and lock it into strong carbonate minerals.Juerg Matter/Univ. of Southampton

Coloured veins and effervescent rock

On a late afternoon, a number of camels wandered previous, chewing on scraggly bushes. A diesel engine roared. And a steel drill shaft, pushed by that engine, spun a number of thousand occasions per second because it reduce into the rocks beneath our toes.

Every now and then, employees in onerous hats idled the motor to a low growl. Then they raised the drill from the outlet, indifferent a steel pipe and slid out three meters (9.8 toes) of cored rock.

The cylinders of stone have been as thick as a baseball bat. After laying them out on tables, Kelemen, Matter and several other different scientists examined them.

a large section of rock core on a table
Scientists study a piece of core that has been lifted out of a borehole in Oman. White stripes within the midground are veins of magnesium carbonate.D. Fox

The grey stone was crisscrossed with white, black, orange-yellow and blue-green minerals. These veins marked the place water and gases, seeping by cracks, had reacted with the stone.

Oxygen reacted with iron within the rock — actually “rusting” it — to create yellow and orange veins. Black, blue and inexperienced veins usually have been a mineral referred to as serpentine. It types when water reacts with silicates. And the white veins have been normally carbonate minerals — though not at all times. I watched as Elisabetta Mariani ran a fast check on a vein to establish the mineral.

Mariani is a geologist on the College of Liverpool in England. Utilizing a lighter, she held a flame in opposition to the vein for a number of seconds. Then, with a plastic bottle in hand, she squeezed a number of drops of acid onto it. The heated a part of the vein fizzed like seltzer water for a number of seconds. Because it reacted with the acid, the rock was releasing tiny bubbles of CO2.

“That is magnesite,” she stated — magnesium carbonate.

These carbonate veins have been plentiful within the prime 15 meters (50 toes) of core. They have been usually as thick as a finger. Farther down, they thinned and have become much less frequent. Under 100 meters (330 toes), there have been none.

This confirmed what Matter had lengthy suspected. “The entire CO2 is mineralized within the very shallow half,” he says. As soon as rainwater has seeped in, it could spend a few years underground. However all of its CO2 is consumed proper initially.

Matter and Kelemen now assume the speed of carbonate formation may very well be boosted — and by rather a lot. Sometime, they envision CO2 being pressurized into water at 125 occasions rainwater’s pure focus (about 6 occasions that of seltzer water). This combine would then be pumped three kilometers (nearly two miles) underground. Rocks there are near 100 °C (212 °F). The excessive warmth and stress would pace up the chemical reactions that flip CO2 to stone.

That is a few years away.

a photo of a magnesium carbonate vein in a rock core
Veins of magnesium carbonate (a mineral referred to as magnesite) usually kind alongside pure cracks within the rock. These cracks supplied pathways for groundwater to seep by the rocks. That water carries dissolved CO2 from the air. Molecules of that CO2 will pair up with atoms of magnesium within the rock to kind the strong carbonate mineral. This permits the vein to develop underground, over 1000’s of years.D. Fox

Omani checks are underway

However the first child steps are beginning. Late in 2020, an Omani firm named 44.01 was arrange. (It’s named after the common weight of a molecule of CO2.) The corporate’s aim is to entice CO2 in mantle rocks in Oman.

”We’re aiming for one gigaton,” stated Talal Hasan, shortly after 44.01 was fashioned. He’s the corporate’s founder. By “gigaton,” he means a billion tons per yr.

The primary area check was, after all, fairly small. Final September, employees injected about 240 kilograms (530 kilos) of CO2 into one of many boreholes in Wadi Lawayni. A month later, Matter pulled some water samples out of one other gap a number of meters away.

Matter continues to be analyzing that water. However he hopes to search out proof that the combination of CO2 and water is reacting with the rock. “This check is simply to reveal on a area scale that the response is quick sufficient,” he says. Later, bigger checks will see if the newly forming carbonates are prying the rock aside, as anticipated. Each Matter and Kelemen are giving the corporate scientific recommendation.

However the long-term success of their imaginative and prescient will depend upon extra than simply scientific outcomes. It’s going to additionally depend upon the selections of governments world wide.

The price of turning CO2 to stone

Firms like 44.01 and Carbfix can solely flip CO2 to stone if somebody pays them to do it.

Earlier than CO2 might be injected underground, it first needs to be captured from the air. And the tech to seize CO2 will not be low-cost. Nonetheless, Nemet predicts that the price of direct air seize will come down over time (because it has for different applied sciences, corresponding to wind energy).

Even when somebody is prepared to pay for it, turning CO2 into stone would require loads of work. Firms like Carbfix and 44.01 may take 20 years to work their manner as much as injecting gigatons of CO2 per yr. And the operations wanted to do this shall be actually large.

Kelemen estimates that trapping a billion tons of CO2 per yr in Oman may require 5,000 injection wells. These wells would wish to pump a mixed 23 cubic kilometers of water into the bottom annually. That’s equal to about one quarter the annual move of the Missouri River. As a result of Oman is a desert nation, this water must come from the ocean.

Gathering a billion tons of CO2 per yr from the air would require 1000’s of machines, every concerning the dimension of a truck. Collectively, they might devour as much as 1.3 trillion kilowatt hours of electrical energy per yr. That’s thrice the quantity of electrical energy consumed by your complete state of Texas. To keep away from gushing extra CO2 into the air, this electrical energy would wish to come back from a renewable supply — corresponding to wind or photo voltaic — not fossil fuels.

Happily, Oman will get loads of sunshine. Some 600 sq. kilometers (230 sq. miles) of photo voltaic collectors might provide the electrical energy wanted. That’s about one five-hundredth of Oman’s land space. “It’s not insurmountable,” says Ajay Gambhir. “Nevertheless it’s a little bit of a problem,” notes this vitality economist. He works at Imperial School London in England.

By 2050, individuals would wish to take away as much as 20 billion tons of CO2 from the skies annually. That may require 20 of those large operations — or lots of of smaller ones — working throughout the globe.

Gambhir views these applied sciences as an essential “insurance coverage coverage.” Perfecting them will take years. But when we get to 2040 and CO2 emissions are nonetheless excessive, then will probably be too late at that time to start out engaged on them, he says. “Doing it now’s the proper factor to do.”


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