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February 04, 2013

An economical way to convert carbon dioxide into calcium carbonate

A chance discovery that sea urchins use Nickel particles to harness carbon dioxide from the sea to grow their exoskeleton could be the key to capturing tonnes of CO2 from the atmosphere.

Experts at Newcastle University, UK, have discovered that in the presence of a Nickel catalyst, CO2 can be converted rapidly and cheaply into the harmless, solid mineral, calcium carbonate.

The process developed by the Newcastle team involves passing the waste gas directly from the chimney top, through a water column rich in Nickel nano-particles and recovering the solid calcium carbonate from the bottom. They are looking for business partners to develop their patented process.



At the moment, pilot studies for Carbon Capture and Storage (CCS) systems propose the removal of CO2 by pumping it into holes deep underground. However, this is a costly and difficult process and carries with it a long term risk of the gas leaking back out - possibly many miles away from the original downward source.

An alternative solution is to convert the CO2 into calcium or magnesium carbonate.

“One way to do this is to use an enzyme called carbonic anhydrase,” explains Gaurav Bhaduri, lead author on the paper and a PhD student in the University’s School of Chemical Engineering and Advanced Materials.

“However, the enzyme is inactive in acid conditions and since one of the products of the reaction is carbonic acid, this means the enzyme is only effective for a very short time and also makes the process very expensive.

“The beauty of a Nickel catalyst is that it carries on working regardless of the pH and because of its magnetic properties it can be re-captured and re-used time and time again. It’s also very cheap – 1,000 times cheaper than the enzyme. And the by-product – the carbonate – is useful and not damaging to the environment.

“What our discovery offers is a real opportunity for industries such as power stations and chemical processing plants to capture all their waste CO2 before it ever reaches the atmosphere and store it as a safe, stable and useful product.”

Each year, humans emit on average 33.4 billion metric tons of CO2 - around 45% of which remains in the atmosphere. Typically, a petrol-driven car will produce a ton of CO2 every 4,000 miles.

Calcium carbonate, or chalk, makes up around 4% of the Earth’s crust and acts as a carbon reservoir, estimated to be equivalent to 1.5 million billion metric tons of carbon dioxide.

It is the main component of shells of marine organisms, snails, pearls, and eggshells and is a completely stable mineral, widely used in the building industry to make cement and other materials and also in hospitals to make plaster casts.



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