Deep-sea carbon storage must be tested, says leading scientist

Scientists must start dumping carbon dioxide into the deep ocean to see whether it provides a safe way of tackling global warming, a leading expert on climate change has said. Wallace Broecker, of the Lamont-Doherty Earth Observatory at New York's Columbia University, says experiments must be carried out "promptly" and has called on environmental campaigners to drop their opposition to such schemes. Experts have said carbon dioxide stripped from the exhaust gases of power stations and dumped in deep water would stay there for hundreds of years, but there is concern about the impact on marine life.

Writing for the Guardian, Broecker says: "While we know enough to say with confidence that deep ocean disposal of CO2 is certainly feasible, unless small-scale pilot experiments are conducted, information necessary to assess the impact [on sea life] will remain obscure. It is my view that a series of experiments involving one-tonne quantities of CO2 should be conducted."

He says such injections of the gas could be made from deep-sea drill ships, and monitored to see how it dispersed and affected marine life. Otherwise, he warns, the gas could be dumped in future with no idea of the consequences. "If marine disposal proves to be economically favourable and if push comes to shove, forces ... will likely intervene and deep-sea disposal will commence without adequate testing and evaluation."

Unlike most carbon capture and storage schemes, which aim to trap the gas and pump it into underground saltwater reservoirs or empty oil and gas fields, deep-sea storage would release the carbon dioxide directly into the water. Only very deep water would be suitable as great pressures are needed to stop the gas simply leaking back to the surface. At depths greater than 3,500m, scientists think the gas would be compressed into a slush that would settle on the sea bed. That rules out shallow seas such as the North Sea, but makes the Pacific Ocean a prime candidate — particularly as underground reservoir storage sites for carbon dioxide in the Pacific region could be vulnerable to earthquakes.

Broecker says 480bn tonnes of carbon dioxide could be safely dumped directly into the waters of the deep Pacific, equivalent to the carbon pollution from about 16 years of the world's current fossil fuel use.

Worms and other organisms on the sea bed directly beneath the storage site would be killed, Broecker admits, but he says the impact would be "trivial" compared to that of the fishing industry. Other experts have said the injected carbon dioxide could damage larger marine life including fish because the gas will dissolve in the seawater and make it more acidic.

Small amounts of CO2 have been injected into deep water off the California coast but there have been no large-scale experiments to test the concept. A planned pilot scheme off Hawaii was scrapped in the late 1990s after protests from local people and environmental groups. Greenpeace remains implacably against such experiments.

Broecker says: "I am in full sympathy with those who claim that the benthic world [the lowest level of a body of water] is likely a fragile one. Hence, before we poke it with CO2, we should do our homework. Therefore, I challenge Greenpeace to relax its stand and allow pilot CO2 injections to proceed."

But Bill Hare of Greenpeace said: "The urgency of reducing emissions of CO2 has never been greater. But just as with an emergency in a heavy passenger jet, the crew should never rush in to hasty actions that will ultimately make a very bad situation a lot worse. Ocean disposal of CO2 is one such option. The position of Greenpeace and of other groups opposed to this option was based on research into the effects of ocean disposal of CO2."

(By David Adam, The Guardian, 18/06/2008)