Richard Ingham Yahoo News 1 Apr 09;
PARIS (AFP) – Scientists on Wednesday said they could ease a key doubt that clouds "clean coal" -- the dream of harnessing a fuel that is as cheap and plentiful as it is environmentally dangerous.
China, India and other countries have ramped up burning of coal this decade to power their growth and brake their dependence on expensive imported oil. By doing so, they have also cranked emissions of carbon dioxide (CO2), the heat-trapping byproduct of this dirty, low-energy fuel.
A powerful lobby has emerged, sustained by the coal industry itself, to argue that with financial help and innovation, "clean coal" lies just on the horizon.
This term refers to a basket of technologies, the biggest of which is carbon capture and storage, or CCS.
Under CCS, power stations would burn coal but siphon off the CO2 at source before pumping the unwanted gas into deep chambers underground, such as disused gas or oilfields.
The CO2 would be stored there indefinitely rather than be disgorged into the atmosphere to add to the greenhouse effect.
CCS has surged up the agenda in the past few years as the United States, Australia and other big coal producers struggle to address their greenhouse-gas emissions yet also keep using their biggest sources of indigenous energy.
But ecologists and geologists have sounded a loud word of caution: what are the guarantees that these chambers are leakproof? A breach would surrender the man-made CO2 to the air, amplifying global warming.
In a study published on Wednesday in the journal Nature, a British team give a qualified "yes" to that question.
So far, attempts to investigate the leak issue have been limited to computer simulation and a few small-scale pilot studies in the North Sea and the United States, which have only been going on for a few years.
The British scientists have taken a different tack.
They pored over chemical signatures from gas fields in North America, China and Europe that are rich in natural CO2.
"We looked at nine CO2 fields, ranging from 10,000 years to about 42 million years old, and they have all stored CO2 for this length of time without obvious leakage signs," said Stuart Gilfillan, of the Scottish Centre for Carbon Storage at the University of Edinburgh.
"Basically, if you store it in the right location, the CO2 should be contained on that sort of time scale."
What traps the CO2 is, quite simply, underground water, Gilfillan and colleagues believe.
They looked at the ratio between isotopes of carbon dioxide and isotopes of a group of so-called noble gases, including helium.
These signatures indicate that highly soluble CO2 dissolves in the groundwater -- just like sparkling mineral water -- and does not leak to the surface, said Gilfillan.
The team believe that just a small amount -- just 18 percent or less -- of the CO2 reacts with minerals in the rock to form a new carbonate shell in the chamber. This is the other theoretical way by which CO can be sequestrated.
Gilfillan said the outcome is good news for "clean coal" but not an automatic green light for it.
Any potential storage site had to be thoroughly prospected to see it was geologically sound and ensure that its groundwater did not leak to the surface, he said.
"If you're talking about an old gas field or an old oil field and you've got no evidence of [gas] leakage up to the surface or oily water coming up, then that would be a strong candidate for storage."
Another shadow hanging over CCS is the cost of stripping out the CO2 and pumping it to the nearest suitable underground chamber.
Critics say the price could be higher than switching to a mix of solar, wind, fuel cells and other renewables that would resolve the problems of fossil fuels once and for all.
Carbon capture and storage moves a step closer
Greenhouse gases can be stored safely stored under the sea for millions of years, scientists have discovered, in a major step forward in the fight against climate change.
Louise Gray, The Telegraph 1 Apr 09;
Storing carbon dioxide underground in a process known as carbon capture and storage or CCS would enable fossil fuel power stations in countries like India and China to continue operating without harming the environment.
The technology is also being considered by the British Government as a way of enabling new coal-fired power stations like Kingsnorth to continue operating while meeting ambitious climate change targets on cutting carbon emissions.
However, until now it has not been certain whether it would be safe to store the carbon dioxide underground over a long period of time without leakage occuring.
Now a study published in the journal Nature has shown that for millions of years carbon dioxide has been stored safely and naturally in underground water in gas fields saturated with the greenhouse gas.
In the first real studies into greenhouse gas storage, rather than looking at computer models, scientists examined how the carbon dioxide dissolved in nine gas fields in North America, China and Europe. These gas fields were naturally filled with carbon dioxide thousands or millions of years ago.
The international team of researchers - led by the University of Manchester - found naturally occurring carbon dioxide can be trapped in two ways. The gas can dissolve in underground water – like bottled sparkling water - or it can react with minerals in rock to form new carbonate minerals.
Dr Stuart Gilfillan, the lead researcher who completed the project at the University of Edinburgh, said the study shows greenhouse gases can be stored safely underground.
He said: "We've turned the old technique of using computer models on its head and looked at natural carbon dioxide gas fields which have trapped carbon dioxide for a very long time.
"By combining two techniques, we've been able to identify exactly where the carbon dioxide is being stored for the first time. We already know that oil and gas have been stored safely in oil and gas fields over millions of years. Our study clearly shows that the carbon dioxide has been stored naturally and safely in underground water in these fields."
Professor Chris Ballentine of the University of Manchester, the project director, said the findings will help to develop storage techniques. Although further research is needed into capturing carbon dioxide from power stations and injecting it underground.
He said: "This new approach will be essential for monitoring and tracing where carbon dioxide captured from coal-fired power stations goes when we inject it underground – this is critical for future safety verification."
Professor Barbara Sherwood Lollar, of the University of Toronto and co-author of the study, hopes the new data can be fed into future computer models to make modelling underground carbon capture and storage more accurate.
