Geothermal Power Plant In Iceland Demonstrates Rapid “Carbon Emissions To Stone” Process

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The Hellisheidi geothermal power plant in Iceland is the largest such facility in the world — providing much of the electricity used in the country’s capital of Reykjavik, and by nearby industrial sites.

The facility generates electricity through the pumping up of volcanically-heated water, which is used to run turbines. Despite the “renewable” nature of the electricity generated by the facility, the facility does release notable levels of carbon dioxide emissions — released volcanic gases, primarily.

"Part of the piping system that pumps emissions back underground. Left to right, engineer Magnus Thor Arnarson, Lamont-Doherty Earth Observatory hydrologist Martin Stute and project leader Edda Sif Arradotir of Reykjavik Energy."
Part of the piping system that pumps emissions back underground. Left to right, engineer Magnus Thor Arnarson, Lamont-Doherty Earth Observatory hydrologist Martin Stute and project leader Edda Sif Arradotir of Reykjavik Energy.
“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.”
“An experimental drill core held by coauthor Sandra Snaebjornsdottir is laced with solidified carbonate, apparently produced by a new process that turns carbon emissions to stone when pumped underground. (All photos: Kevin Krajick/Lamont-Doherty Earth Observatory)”

As part of the pilot project known as “Carbfix” (begun back in 2012 at the facility), those involved have been working to develop a means of storing carbon emissions at the site. Recent findings there 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.”

While the potential economic applicability (on a wider-scale) of the technique has yet to truly be determined, the findings are quite interesting. A paper describing the work was recently published in the journal Science.

“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,” commented study co-author 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.”

The geology of the project site, though, is somewhat distinct — the local basalt features high levels of calcium, iron, and magnesium — so the impressive results may not translate very widely. It should also be noted here that the results depended on the injection of substantial amounts of water — 25 tons for every ton of carbon dioxide emissions. Seawater could theoretically be used, potentially cutting costs in some regions of the world, but it wasn’t in this case owing to logistics, possibly making for higher project costs than would otherwise be the case.


Thanks to the use of infrastructure that was already in place (the project site is a geothermal power plant, after all), and the fact that the carbon dioxide emissions that were stored were never purified in the first place (and that would be a costly process), the pilot project was able to achieve costs of around $30 a ton. That’s considerably less than the estimates for most other similar projects around the world.

As noted in a recent press release: “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 head of the project for Reykjavik Energy, Edda Aradottir, noted that initial estimates were of a timespan of around 8 to 12 years for solidification of the pumped carbon emissions.

“People said there was very little truth to that — they thought it couldn’t happen that fast,” she commented. “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. This summer, the company plans to double the injection rate.”

It should be remembered here that it’s not clear yet what will happen over the mid- to long-term to the carbon that’s stored this way — this is essentially a new and relatively untested approach. Will the trapped carbon remain stable? Will microbial action lead to slow (or not so slow) release? There are a lot of unknowns here.

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James Ayre

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

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