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Clean Coal's Great Black Hope

Germany's new clean coal "Schwarze Pumpe" plant is not clean yet ...

"The Black Pump," Germany's dreadful-sounding hope for the future — in the shape of a "clean coal" facility near Poland —may clog up sooner than expected because one phase in its process for capturing and storing carbon dioxide has, so far, failed.

It's not a technological failure. The experimental carbon-capture plant in a coal-mining region of the former East Germany has functioned largely as planned. Last autumn the "Schwarze Pumpe" facility became the first coal-fired plant in the world to burn oxyfuel, or coal dust in pure oxygen. Oxyfuel releases carbon dioxide in a nearly pure form, with water vapor, which makes it easier to capture. The facility can condense the water vapor and trap the liquid CO2, then set about trying to inject it deep underground.

This oxyfuel process is one form of "carbon capture and sequestration," which goes by the name of "clean coal" because of the cleanup phase, not because of the coal itself. It can reduce CO2 emissions from a coal plant by up to 95 percent. Advocates call CCS the only hope for reducing greenhouse gases over the next 30 or 40 years, while the world still relies heavily on coal, and the German experiment would be working just fine if residents near the Schwarze Pumpe hadn't protested.

"Renewable energy yes," one protester's sign read. "Storing CO2 underground, no."

Vattenfall, the Swedish energy giant that runs the Schwarze Pumpe plant, wanted to start burying liquefied CO2 in the spring. The idea was to truck canisters of it to a nearby saline aquifer, or an old oil field near the Polish border, and inject it into the rock. But Vattenfall still has no license to bury the gas because residents near the planned sites have protested. Britain's Guardian calls it "NUMBYism" — "not under my backyard."

Neighbors say they're afraid of what might happen if the CO2 escapes. One activist from Brunsbüttel, another German town where three future clean-coal facilities are planned, imagines a scenario rather like an African killer lake, with a cloud of deadly carbon dioxide surging up from the bottom. "If there's a leak and you have a 1- to 2-meter-high level of CO2, every animal, every human being within this zone will die," Stephan Klose told IEEE Spectrumrecently.

A "1- to 2-meter-high" cloud of CO2 is a big if. Scientists argue that the real threat from a CO2 leak is to the atmosphere, not to human life.

But long-term CO2 storage is a bit like long-term nuclear storage — no one really knows what will happen. The theory is that liquefied carbon dioxide should bind with salt rock or other minerals and remain trapped in a geological grave. A Norwegian company started sequestering CO2 this way from a natural gas plant in 1996. The saline reservoir it uses belongs to an offshore oil field called Sleipner West, and so far it holds about 11 million metric tons of the gas. The Norwegians check for leaks using sonar, and nothing so far has gone wrong.

But Sleipner West is a smallish site, and it's not clear how many large, reliable carbon reservoirs the planet has. "The long-term, chemical fate of CO2 remains to be understood," MIT physicist Ernest Moniz toldScientific American in 2007. "It's like a mortgage. It gets us out of the problem in the 21st century, spreading it out over a longer time and not breaking the budget."

CCS technology has always been seen as a stopgap, a bridge from the era of fossil fuels to the dawn of fully renewable energy. But it's an important strategy because coal, for the moment, isn't going away. China, India and Russia keep growing, never mind Europe's former Soviet (and largely coal-reliant) states. Germany, for all its environmental awareness, has too much coal in its hills to quit burning the stuff, and parts of its Communist-era infrastructure — including apartment houses in the middle of Berlin — still rely on coal for heat.

Schwarze Pumpe, by the way, is an old name for the immediate area around the oxyfuel plant, not for the plant itself. This now-industrial corner of the world was first called "The Black Pump" after a famous local tavern in the 19th century. Now, of course, it's an unfortunate name for a "clean coal" experiment; but the Vattenfall plant won't scrub that image anytime soon. Until the firm finds a place to bury its CO2, all that coal exhaust is still pouring into the sky.

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