Mon, Aug 29, 2011 - Page 6 News List

FEATURE: Scientists trying to lock carbon dioxide into rock


Sometime next month, on the steaming fringes of an Icelandic volcano, an international team of scientists will begin pumping “seltzer water” into a deep hole, producing a brew that will lock away carbon dioxide forever.

Chemically disposing of carbon dioxide, the chief greenhouse gas blamed for global warming, is a kind of 21st-century alchemy that researchers and governments have hoped for to slow or halt climate change.

The American and Icelandic designers of the “CarbFix” experiment will be capitalizing on a feature of the basalt rock underpinning 90 percent of Iceland: It is a highly reactive material that will combine its calcium with a carbon dioxide solution to form limestone — permanent, harmless limestone.

The researchers caution that their upcoming six-to-12-month test could fall short of expectations, and warn against looking for a climate “fix” from CarbFix any year soon.

In fact, one of the objectives of the project, whose main sponsors are Reykjavik’s city-owned utility and US and Icelandic universities, is to train young scientists for years of work to come.

A scientific overseer of CarbFix — the man, as it happens, who also is credited with coining the term “global warming” four decades ago — says the world’s failure to heed those early warnings, to rein in greenhouse-gas emissions from coal, gasoline and other fossil fuels, is driving scientists to drastic approaches.

“Whether we do it in the next 50 years, or the 50 years after that, we’re going to have to store carbon dioxide,” Columbia University’s Wallace Broecker said in an interview in New York.

The world is already storing some carbon dioxide. As a byproduct of Norway’s natural gas production, for example, it is being pumped into a sandstone reservoir beneath the North Sea. However, people worry that such stowed-away gas could someday escape, while carbon dioxide transformed into stone would not.

The experimental transformation will take place below the dramatic landscape of Hellisheidi, 29km southeast of Reykjavik, Iceland’s capital. On an undulating, mossy moor and surrounding volcanic hills, where the last eruption occurred 2,000 years ago, Reykjavik Energy operates a huge, five-year-old geothermal power plant, drawing on 30 wells tapping into the superheated steam below, steam laden with carbon dioxide and hydrogen sulfide.

CarbFix will first separate out those two gases, and the carbon dioxide will be piped 3km to the injection well, to combine with water pumped from elsewhere. That carbonated water — seltzer — will be injected down the well, where the pressure of the pumped water, by a depth of 500m, will completely dissolve the carbon dioxide bubbles, forming carbonic acid.

“The acid’s very corrosive, so it starts to attack the rocks,” said University of Iceland geologist Sigurdur Reynir Gislason, CarbFix’s chief scientist.

The basalt rock — ancient lava flows — is porous, up to 30 percent open space filled with water. The carbonic acid will be pushed out into those pores, and over time will react with the basalt’s calcium to form calcium carbonate, or limestone.

CarbFix’s designers, in effect, are radically speeding up the natural process called weathering, in which weak carbonic acid in rainwater transforms rock minerals over geologic time scales.

The CarbFix team, beginning work in 2007, had to overcome engineering challenges, particularly in the inventive design and operation of the gas separation plant. They have applied for US and Icelandic patents for that and for the injection well technique.

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