In a first, Iceland power plant turns carbon emissions to stone

June 9, 2016
Section of rock core from the CO2 storage reservoir showing vesicular basalt with a well-defined fracture with calcium carbonate mineralization. Credit: Annette K. Mortensen.

Scientists and engineers working at a major power plant in Iceland have shown for the first time that carbon dioxide emissions can be pumped into the earth and changed chemically to a solid within months—radically faster than anyone had predicted. The finding may help address a fear that so far has plagued the idea of capturing and storing CO2 underground: that emissions could seep back into the air or even explode out. A study describing the method appears this week in the leading journal Science.

The Hellisheidi power plant is the world's largest geothermal facility; it and a companion plant provide the energy for Iceland's capital, Reykjavik, plus power for industry, by pumping up volcanically heated water to run turbines. But the process is not completely clean; it also brings up volcanic gases, including carbon dioxide and nasty-smelling hydrogen sulfide.

Under a pilot project called Carbfix, started in 2012, the plant began mixing the gases with the water pumped from below and reinjecting the solution into the volcanic basalt below. In nature, when basalt is exposed to carbon dioxide and water, a series of natural chemical reactions takes place, and the carbon precipitates out into a whitish, chalky mineral. But no one knew how fast this might happen if the process were harnessed for carbon storage. Previous studies have estimated that in most rocks, it would take hundreds or even thousands of years. In the basalt below Hellisheidi, 95 percent of the injected carbon was solidified within less than two years.

Engineers and scientists have designed a system to pump volcanic gases including carbon dioxide back into the earth, where the CO2 turns into a solid. Left to right, engineer Magnus Thor Arnarson, Lamont-Doherty Earth Observatory hydrologist Martin Stute and project leader Edda Sif Arradotir of Reykjavik Energy inspect the downgoing piping system. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory

"This means that we can pump down large amounts of CO2 and store it in a very safe way over a very short period of time," said study coauthor Martin Stute, a hydrologist at Columbia University's Lamont-Doherty Earth Observatory. "In the future, we could think of using this for power plants in places where there's a lot of basalt—and there are many such places." Basically all the world's seafloors are made of the porous, blackish rock, as are about 10 percent of continental rocks.

Scientists have been tussling for years with the idea of so-called carbon capture and sequestration; the 2014 report of the Intergovernmental Panel on Climate Change suggests that without such technology, it may not be possible to limit global warming adequately. But up to now, projects have made little progress. It has been tried at only a handful of sites, and most experiments have involved pumping pure carbon dioxide into sandstone, or deep, salty aquifers. Here, it is hoped, pressure and solid layers of caprock above would seal in the waste. But scientists have worried that any miscalculation could result in emissions making their way back up through fractures, or that natural earthquakes or tremors caused by the injection itself could rupture subterranean reservoirs. A coal-fired power plant in Saskatchewan that currently runs North America's only large-scale operation at a generating station has been plagued by technical problems—and the captured carbon dioxide is being sent to oil producers who inject it into ailing wells to pressure out more oil, which produces more carbon dioxide when burned.

In 2007 Hellisheidi's operator, Reykjavik Energy, joined with a consortium including Columbia and the universities of Copenhagen and Iceland to get rid of its CO2 emissions, along with the hydrogen sulfide, which was plaguing the area. The plant produces 40,000 tons of CO2 a year—5 percent the emissions of an equivalent coal-fired plant, but still considerable. Lab experiments showed that, unlike the sedimentary rocks that most other projects have used for injection, the local basalt contains plenty of calcium, iron and magnesium, which are needed to precipitate out carbon. Experiments showed that large amounts of water would also have to be added to make the reaction go—another departure from previous projects, which have just pumped down pure carbon dioxide.

An experimental drill core held by coauthor Sandra Snaebjornsdottir is loaded with solidified carbonate, apparently produced by the new process. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory

In a 2012-2013 pilot, the team piped 250 tons of CO2 mixed with water and hydrogen sulfide down 400 to 800 meters, then monitored the formation's chemistry through a series of wells. Fast-changing compositions of carbon isotopes in water samples, initially reported in 2014, signaled that much of the carbon had mineralized within months. The new Science paper lays out the evidence conclusively.

Edda Aradottir, who heads the project for Reykjavik Energy, initially estimated the solidification process might take 8 to 12 years—much faster than previous studies had indicated. "People said there was very little truth to that—they thought it couldn't happen that fast," she said. "Then, it happened much faster. It was a very welcome surprise." Cores drilled from the injected area show the rock is heavily laced with whitish carbonate veins, apparently produced by the process. With initial signs of success, in 2014 Reyjavik Energy started injecting carbon dioxide at the rate of 5,000 tons per year. Ongoing monitoring indicates that mineralization has kept pace, said Aradottir. This summer, the company plans to double the injection rate, she said.

Iceland's Hellisheidi geothermal power plant is the world's largest. It is cleaner than those run on fossil fuels, but still emits carbon dioxide by venting volcanic gases. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory

Sigurdur Gislason, a University of Iceland geologist and study coauthor, said geothermal companies around the world have shown interest in the technology. But, he said, its greatest promise would be with fossil-fuel-powered plants, smelters and other heavy industries that produce far more emissions. The main stumbling block beyond the needed basalt, he said, is the water required—about 25 tons for every ton of CO2. But, he said, in many places seawater could be used. A 2010 Lamont study has already outlined basaltic seafloors off U.S. coasts that could be used to take up emissions. Separation and injection of CO2 in most other projects has been estimated to cost a steep $130 or so a ton. The Hellisheidi operation has an advantage in that it largely uses the plant's existing infrastructure to reinject the solution, and doesn't bother purifying the CO2. Its cost is only $30 a ton, said Aradottir.

Air photograph of Reykjavik Energy's Hellisheidi geothermal power plant. The current emissions of the powerplant are: 40,000 tons CO2/year and 12,000 tons H2S/year. The CarbFix I pilot CO2 injection site is connected to the powerplant via a pipeline that delivered some of the CO2 and H2S gases that were injected into a basaltic storage reservoir at ~500 m depth below surface. Credit: Árni Sæberg.

Fossil-fuel plants might not be able to do it as cheaply—and they would not be able to do it at all without abundant water. Another possible hitch: a separate study out this May identified subterranean microbes that seem capable of feeding off and using them to release methane, a even more potent than carbon dioxide. That means nature could sneak in and reverse the solidification process. Such microbes were thought to exist only on the deep ocean floor, but researchers found them in a California spring. Microbiologists from the Paris Institute of Earth Physics have already started studying underground microbes at the Carbfix site to investigate how they might interact with the carbon in injection.

Recently, other companies have looked at other innovative ways to use up power plants' carbon emissions. Projects include one backed by Exxon to build fuel cells that turn CO2 to energy, and an initiative by Ford to convert emissions to solid foams to build the interiors of vehicles. In a project in Oman, a separate Lamont-Doherty group is looking into pumping emissions into a different kind of rock, peridotite, which may react even more rapidly with CO2.

Lead author Juerg Matter, an adjunct researcher at Lamont now based at the United Kingdom's University of Southampton, said, "We need to deal with rising carbon emissions. This is the ultimate permanent storage—turn them back to stone."

CarbFix I carbon dioxide injection site during wireline diamond drilling to recover 150 m rock core from the subsurface carbon dioxide storage reservoir in 2014. Credit: Dr Juerg Matter

Explore further: Could storing emissions underground be the answer?

More information: "Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions," Science,

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2.3 / 5 (4) Jun 09, 2016
So you're telling us that their geothermal isn't a sealed system?
Whydening Gyre
4.6 / 5 (12) Jun 09, 2016
Apparently not, Phil. However, they are capturing a good part of it, it appears, and sequestering it in this fortuitous manner.
I like surprises - especially good ones...:-)
2.3 / 5 (9) Jun 09, 2016
LOL I will be the first one to give you a FIVE, before all the rest of your fans arrive.
This is good news for Icelanders, but I think that the CO2 transformed into stone will eventually return as a gas, though not for a very long time, hopefully.
Whydening Gyre
4.5 / 5 (10) Jun 09, 2016
A pleasant surprise from OS....
Surely, the world must be ending tomorrow...:-)
The microbes they mention may indeed return it - sooner than we might expect, but will wait on further research for that.
I am also looking forward to the results of injecting it into peridotite.
4.4 / 5 (5) Jun 09, 2016
2.1 / 5 (15) Jun 10, 2016
What a complete waste of energy and good CO2. Millions of plants will NOT thank us for this absurdity.
4.3 / 5 (11) Jun 10, 2016
and sequestering it in this fortuitous manner.

The discovery is certainly interesting. However, I'm guessing there is a limit to the amount one can sequester at a particular spot (i.e. this is probably not an 'indefinite' solution). Certainly something to look at while the changeover is in progress or for such 'unavoidable' emissions as in the case of geothermal.

What a complete waste of energy and good CO2. Millions of plants will NOT thank us for this absurdity.

What a complete waste of oxygen you are.
4 / 5 (4) Jun 10, 2016
This certainly is interesting. But if the CO2 is precipitating out of the solution, than just like any such chemical reaction if the conditions change it can go back into solution just as fast. Also I can see that a lot more research will need to be done to figure out exactly what conditions are needed for this reaction to occur so rapidly. Is it only certain types of rock? Does the H2S somehow catalyze the reaction?

And even then the article says that only 10% of the continents are basalts. If basalts are required then most locations could not easily use this. They would have to safely transport huge quantities of CO2 to appropriate locations where facilities would have to be constructed.

Again this is an interesting finding, but far from a currently usable solution to the growing CO2 emissions.
1.6 / 5 (7) Jun 10, 2016
Any and all change has to come from human emotional characteristics. From those who are apathetic and those who have uncontrollable greed. So there will be no change's. As to warming, a massive force has been set loose. Compare to an earthquake that has already occurred and an impending tsunami is forming. Can we go back and halt the earthquake that has already occurred? If human mentality could be changed, and molten liquid thorium reactors were brought on line globally, only then could the results of warming not be stopped but rather limited in duration and perhaps limited in devastation. So you see we have always had the means to care for the planet but we lack the mental maturity. As the Jewish Zealots were acting in a suicidal manner, causing everyone else in the confines of the besieged city walls to die with them, greedy humans have the same traits, being incapable of limiting their behavior, humans are doomed by their animal brain.
Jun 10, 2016
This comment has been removed by a moderator.
3.4 / 5 (10) Jun 10, 2016
That is no lie. Some poor tree worked hard to produce the oxygen that you are breathing and it was a complete waste of effort.
2.7 / 5 (7) Jun 10, 2016
How do we stop this insanity? The plants are beginning to respond to the current, small CO2 increase and are producing more than ever and these fools and others like them, are trying to take the food from our mouths. "These people should be slapped up the side of the head!"
4.5 / 5 (8) Jun 10, 2016
How do we stop this insanity? seems you need a kindergarten level explanation, here:

Plants require CO2 - that much is true.
But plants also require water. Climate change heats the globe. Droughts become more prevalent. Droughts kill plants.
This takes vastly more "food out of our mouths" than additional plant matter due to a bit more CO2.

Also CO2 goes into solution with water (creating carbonic acid) - which causes acidification of oceans. The majority of plant matter on this planet are algae which don't do well under acidic conditions because have a calcium containing structure (which dissolves under acidic conditions). Algae are the basis of the food chain (i.e. in essence this means less fish). Which again "takes food out of our mouths"

Does that spell it out to you? Or aren't you noticing how certain foods are going up in price lately?
not rated yet Jun 10, 2016
So you're telling us that their geothermal isn't a sealed system?

That's exactly what I was thinking when I read that. I wonder how much hydrogen sulfide they bring to the surface compared to what various power plants put out. I might have to research the decisions that went into the design of Hellisheidi.
3.7 / 5 (3) Jun 11, 2016
Doesn't sound useful for other than geothermal plant applications - at a 25:1 ratio water to gas, the large water requirement will make this impractical in other applications, but perhaps seawater could come into the process for some. Our best bet is still developing the CO2 emission free generation sources we have, and expanding that range of sources.
3.7 / 5 (3) Jun 11, 2016
Delusion is a wonderful thing - "LifeBasedLogic" is a name chosen by a person who has no clue what logic is........
4.5 / 5 (2) Jun 12, 2016
The majority of plant matter on this planet are algae which don't do well under acidic conditions because have a calcium containing structure

Most algae don't grow calcium shells. You're thinking of coccolithophores.

Furthermore, these algae do adapt to varying levels of CO2
researchers Kai Lohbeck, Ulf Riebesell and Thorsten Reusch took the plankton they had bred in the lab and exposed it to concentrations of carbon dioxide up to four times that in the atmosphere. They found that it can adapt, and even maintain its shell-building, though it doesn't exactly thrive. "They do less badly," Reusch said.

Their ability to adapt and survive in the "harsh" environment took less than a year

Point being that micro-organisms evolve fast. There's probably not going to be a problem with plankton as far as climate change goes, as long as there's sunlight.
5 / 5 (2) Jun 12, 2016
Ocean acidification btw. does eventually lead to higher mineral availability because it's the carbonic acid from dissolved CO2 in rain water that weathers the rocks that provide all the calcium and other minerals in the oceans in the first place.

It's the transition from low to high acidity that upsets the balance.
3.7 / 5 (3) Jun 12, 2016
Or aren't you noticing how certain foods are going up in price lately?

Oh, and there's certainly no significant relevance to current food prices with global warming so far. There are other -far- more pressing issues with foods, such as overfishing, or the use of food crops as fuel. Couple failed harvests in artifically irrigated deserts due to droughts is hardly relevant because of the weather-vs-climate distinction, and because these areas don't actually contribute so much to the global food supply that you'd feel it in your grocery store bill.

In other words, your noise is far greater than your signal here to intimidate people with food prices.

If you're going to give "kindergarden" level explainations to climate change, please make sure they're at least plausible and relevant. It's no use lying to children or child-like adults because they'll eventually see through it and then disbelieve you even more, and all you've managed is to make another denier.
4 / 5 (4) Jun 12, 2016
And there's no point in scaring people of food shortages when half the food we produce worldwide is wasted due to logistics inefficiency anyhow.
about 4.4 billion tons of food is produced annually and roughly half of it is never eaten.
Some of it is lost to inefficient harvesting, storage and transportation, while the rest is wasted by markets or consumers.

Humanity uses about 40% of this planet's surface to farming, and half of that is totally pointless waste of effort. There is no shortage of food anywhere - there's only logistical problems, such as not having the energy to process and transport food from the field to the markets in time before it spoils.

The rest is people buying more than they want to eat and throwing it away.
5 / 5 (1) Jun 13, 2016 seems you need a kindergarten level explanation, here:

Plants require CO2 - that much ......

I don't think I can come down to your kindergarten level!

First of all, CO2 has nothing to do with climate, so it has nothing to do with heating the globe. If however, we have drought, then CO2 is even more of an asset because increased CO2 reduces the water consumption requirements of all plants, so it only improves their chances of survival. And if you payed any attention to what is happening on our planet today, you would see that sea life is flourishing even with present increased CO2.

You AGW frauds are the only real threat to the future and all our survival!
5 / 5 (1) Jun 13, 2016
Also CO2 goes into solution with water (creating carbonic acid) - ...

What gives you the right to spread this kind of heinous, disinformation and deceit? When the atmosphere starts being pumped directly into and through the oceans, so that they actually have a chance to come in contact with some of the extra CO2, in the 99.999999% of the atmosphere, that never comes in contact with the oceans, when that happens, then we might have a reason for concern. But it probably wouldn't have anything to do with CO2. This is just, irresponsible AGW, Duck Speak, fear mongering! In the age of the Dinosaurs, the atmospheric CO2 level was upwards of 2500 ppm, many times higher than today, but the whole planet thrived. There was an abundance and diversity of life on this planet that is unimaginable today, that extended to land, sea and sky and the oceans were replete and reputed to be burgeoning with life.

Mindless minions like yourself are the only real threat, to all of us!

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