Petrify, liquefy: new ways to bury greenhouse gas

By Alister Doyle, Environment Correspondent

OSLO (Reuters) - Turn greenhouse gases to stone? Transform them into a treacle-like liquid deep under the seabed?

The ideas may sound like far-fetched schemes from an alchemist's notebook but scientists are pursuing them as many countries prepare to bury captured greenhouse gases in coming years as part of the fight against global warming.

Analysts say the search for a suitable technology could become a $150 billion-plus market. But a big worry is that gases may leak from badly chosen underground sites, perhaps jolted open by an earthquake.

Such leaks could be deadly and would stoke climate change.

Part of the answer could be to petrify or liquefy gases like carbon dioxide -- emitted for example from power plants and factories run on coal, oil or natural gas -- if technical hurdles can be overcome and costs are not too high.

"If you can convert (the gases) to stone, and it's environmentally benign and permanent, then that's better," said Juerg Matter, a German scientist at Columbia University in New York who is working on a project in Iceland to turn carbon dioxide, the main greenhouse gas, to rock.

In theory, carbon dioxide reacts with porous basalt and turns into a mineral, but no one knows how long that takes. Matter and U.S., French and Icelandic experts plan to inject 50,000 tonnes of the gas into basalt in a test starting in 2009.

Other researchers say pumping the gas into sediments below the seabed at depths of around 3,000 meters (9,800 ft) would expose it to enough pressure to turn it into a viscous liquid, like honey or treacle.