Scientists Turn CO2 Into Solid Rock

The carbon dioxide will eventually react with the porous rock and turn into a solid, carbonate compound, but that process can take centuries, if not millennia, according to study co-authorSigurdur Gislason, research professor at the University of Iceland in Reykjavik.

Matter revealed the results of this experiment as no longer gas but essentially carbon dioxide that converted into stone. The process begins by mixing carbon dioxide with water that is injected into a well containing basalt.

There were no signs of leakage of the injected carbon dioxide, which researchers had tagged with radioactive carbon-14 isotopes.

But 95 percent of the injected mixture – which they had tagged with tracer chemicals in order to check it didn’t leak out – had became chalky white stone within two years.

“Carbon storage is a critical piece of the global initiative to reducing carbon dioxide emissions and realization of the Mission Innovation goals set out in Paris”, said Sallie Greenberg, a scientist with the Illinois State Geological Survey who has collaborated with Archer Daniels Midland on a project to store large volumes of carbon dioxide in Illinois sandstone layers. It’s one of the most common types of rock on Earth, and it naturally mineralizes carbon into its own rocky structure, where it remains stable for millions of years. Scientists said the process needs to be further studied and refined. “People knew it would work but didn’t know the timescale – whether it would be rapid enough to be useful”. Both of them joined hands and the project was kick-started. It can be replicated in many other parts of the world, and doesn’t necessary involve volcanic rocks.

For one, basalt – a rock that is abundant in Iceland – is not found everywhere. The water is then pumped deep down into basaltic rocks. The two got to talking, and the project was born. “Carbon-scrubbing power plants equip their exhausts with filters with amines that bind carbon dioxide molecules”.

While this may seem something of a paradox, as geothermal is a “clean” energy, these emissions are only five percent of what an equivalent coal-fired plant would produce. Steam emissions from the Hellisheidi geothermal powerplant are visible in the background.

So, the scientists had the infrastructure, the carbon dioxide, and an enormous quantity of basalt. On contact with the target storage rocks, at 400-800 metres under the ground, the solution quickly reacted with the surrounding basaltic rock, forming carbonate minerals. After two years, the mix had turned into stone.

They immediately scaled up the project. This year, they plan to double that. Their eventual goal is to capture and sequester all their emissions in the same way. “The capacity is, for sure, in the ground to take all the CO2, and much more, actually”, she said.

Could this, then, be an answer to global warming? It was a huge surprise to all the scientists involved in the project, and we thought, ‘Wow! He notes that, of the IPCC’s hundreds of climate models, nearly all that illustrate pathways to a brighter future talk of CCS. “In a sense, you just mimic nature”, Gislason said. “It represents the tip of the iceberg”. As many fossil fuel-heavy areas also suffer water scarcity, notes Veysey, this could be problematic. In fact, the authors suggest that even the ocean itself could be used, because salt water appears to work just as well as fresh water for these reactions, and the seafloor is littered with basalt. The research could bring in a major change in the way power plants operate.

The final hurdle is cost.

And the researchers and company are already scaling up the technology, “where up to 5,000 tonnes of carbon dioxide per year are captured and stored in a basaltic reservoir”, Matter says.

This is also a nascent technology, so costs could fall as the methods are refined. Any power plant operating above a basalt formation would make a good candidate. So the approach that is taken is going to have to vary depending on where you are.