This must be one of the smartest ways to take care of the CO2 emissions that are threatening ecosystems around the world.
Scientists in Iceland think they have found a smart way to convert CO2 emissions emissions into stone.
The researchers have reported that they pumped CO2 and water underground into volcanic rock. The reaction of carbon dioxide with the minerals in the deep basalts converted carbon dioxide into immobile, chalky solid.
“Of our 220 tonnes of injected CO2, 95% was converted to limestone in less than two years,” said lead author Juerg Matter from Southampton University, UK.
“It was a huge surprise to all the scientists involved in the project, and we thought, ‘Wow! This is really fast’,” he recalled on the BBC’s Science In Action programme.
The speed at which the process of conversion occurs is very encouraging, the team writes in Science magazine.
Fixing the carbon dioxide emissions
With the alarming increase in CO2 emissions in the atmosphere, researchers are keen to investigate “carbon capture and storage” (CCS) solutions.
Previous experiments have seen pure CO2 being injected into sandstone, or deep, salty aquifers. Scientists rely on layers of impermeable capping rocks to keep the carbon dioxide from leaking back into the atmosphere.
However, The Carbfix project on Iceland seeks to solidify the unwanted carbon in place.
Under the experiment, the scientists, working with the Hellisheidi geothermal power plant outside Reykjavik, combined the waste CO2 with water to make a slightly acidic liquid and sent it hundreds of metres down into the volcanic basalts.
The low pH water (3.2) dissolved the calcium and magnesium ions in the basalts, which then reacted with the carbon dioxide to make calcium and magnesium carbonates.
The researchers also tagged the CO2 with carbon-14, a radioactive form of the element, to check if any of the injected CO2 was leaking back to the surface or through a distant watercourse.
“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 co-author Martin Stute from Columbia University’s Lamont-Doherty Earth Observatory, US.
“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.”
Dr Matter added,
“You can find basalts on every continent and, certainly, you can find them offshore because all the oceanic crust – so below the seafloor – is all basaltic rocks. In terms of the availability of basaltic rocks to take care of CO2 emissions globally – no problem.”
Christopher Rochelle, an expert on CCS at the British Geological Survey, said.
“We need to do more field-scale tests, like this one in Iceland, to better understand the types of processes that are ongoing and how fast they work,” he told BBC News.
“Here, they injected into reactive rocks and the minerals precipitated relatively quickly and are then unable to migrate anywhere. That’s great, but the rocks under Iceland are different to those under the North Sea, for example. So the approach that is taken is going to have to vary depending on where you are. We are going to need a portfolio of techniques.”
He was not involved in the Iceland experiment.