Bothered by carbon? Drop it in the sea!

WASHINGTON: Alarmed by rising carbon emission levels globally, engineers are toying with a mind-boggling solution to the sooty by-product of development.

They have visualised an inflatable bag, capable of storing 160 million tonnes of carbon dioxide, or the equivalent of 2.2 days of the emissions responsible for the worrying phenomenon of global warming.

And this bag - 100 metres in radius and several kilometres long - will rest on the seabed, some 3,000 metres below the surface.

The idea might seem straight out of science fiction, but David Keith, one of Canada's foremost experts on carbon capture and sequestration, is giving it a serious thought.

"This idea looks nutty, but as one looks closer it seems that it might be feasible with current-day technology," said Keith, who outlined the idea Monday at the 2008 Annual Conference of the American Association for the Advancement of Science in Boston.

In a paper titled "Ocean Iron Fertilisation and Carbon Sequestration: Can the Oceans Save the Planet?", Keith says that before storage the gas must be captured from power and industrial sources, compressed to liquid, and transported through pipelines extending well beyond the ocean's continental shelves.

When the liquid carbon dioxide is pumped into the ocean, the intense pressure and cold temperatures make it negatively buoyant.

"It means the carbon dioxide wants to leak downward rather than moving up to the biosphere," Keith said.

The use of containment is necessary because carbon dioxide will tend to dissolve in the ocean, which could adversely impact marine ecosystems.

Fortunately, says Keith, the cost of containment is minimal. He and his colleagues estimate that the bags can be constructed out of existing polymers for less than four cents per tonne of carbon.

Keith, who holds the Canada Research Chair in Energy and the Environment, said the idea was first conceived by Michael Pilson of the University of Rhode Island.

However, it took off only last year when Keith confirmed its feasibility with Andrew Palmer, an ocean engineer at Cambridge University.

Keith, Palmer and another colleague then advanced the concept through a technical paper at the 26th International Conference on Offshore Mechanics and Arctic Engineering in June 2007.

Keith believes it may offer a viable solution because vast flat plains occupy huge chunks of deep-sea bottom.