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Greenhouse rock could help fight global warmi -

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Greenhouse rock could help fight global warming: study

The World Today - Friday, 7 November , 2008 12:38:00

Reporter: Ashley Hall

ELEANOR HALL: A scientific study suggests that a carbon hungry form of rock could be a key tool in
the fight against global warming.

The research by two US scientists has found that the rock - which is found mostly in the Middle
East and the Islands of the Pacific - could permanently store more than 10 per cent of the world's
annual carbon dioxide emissions.

The study by a geologist and a geochemist from Columbia University in New York will be published
next week.

Ashley Hall poke to one of the study's authors, the geologist, Peter Kelemen.

PETER KELEMEN: There is basically prior to this time, two serious contenders for methods of putting
fossil carbon dioxide back into the earth and one of them is to pump CO2 gas at high pressure into
pore space in the subsurface.

Basically for example into depleted oil reservoirs and another has been to use rocks which are rich
in magnesium or calcium. To mine them, ship them to the proximity of power plants, grind them up
very fine, heat them to a high temperature, put them in high pressure reaction vessel and react
those rocks together with the CO2 to form solid carbonate minerals and that is called mineral
carbonisation.

What we are proposing is leave the rock in the ground and put the carbon dioxide into these
particular kinds of rocks and it turns out that there are some really significant advantages to
that. The reaction that takes carbon dioxide and combines it with peridotite actually gives off
heat and so if you can get that reaction going fast enough, you can keep a volume of rock at depths
in the earth hot, just from the reaction alone.

ASHLEY HALL: So this is a supercharging of the natural process?

PETER KELEMEN: That is right.

ASHLEY HALL: Once the carbon dioxide is brought into contact with the peridotite it converts to
minerals like marble and limestone, is that right?

PETER KELEMEN: That is correct. Specifically magnesium carbonate or magnasite. Calcium carbonate or
calcite and then the mixture of the two which is called dolomite.

ASHLEY HALL: What proportion of the world's annual carbon emissions could be taken care of in this
way?

PETER KELEMEN: Best case, we would calculate that one could suck up about four billion tonnes of
carbon dioxide per cubic kilometre of rock involved per year and that is about ten per cent of the
human output of CO2 to the atmosphere each year.

ASHLEY HALL: And where is peridotite found?

PETER KELEMEN: Well, the really big deposits, the largest one in the world on the surface or near
the surface is in the Sultanate of Oman which is on the coast of the Arabian Peninsular that faces
India across the Arabian Sea and then coming after that are some big islands in the western Pacific
and the Balkans, particularly Albania which perhaps has the advantage of being within pipeline
range of some really big CO2 emitters.

But there is peridotite in mountain belts all over the world, on all the continents. I guess with
the possible exception of Antarctica.

ASHLEY HALL: How far away from having this technology in commercial use are we?

PETER KELEMEN: I'm not really sure about that. We are just kind of starting out and it is really
hard to scale that kind of thing in the laboratory so we really need to move now towards moderate
scale field tests and do with this in real rocks in real time and I am not sure when exactly that
is going to happen. Probably in the next couple of years but I am not certain.

ELEANOR HALL: Peter Kelemen is the Professor of Earth Sciences at Columbia University in New York.
He was speaking about his research to Ashley Hall.