for National Geographic News
As energy prices continue to climb, researchers are stepping up their efforts to turn black, dirty coal into a green, clean fuel of the future.
Burning coal releases greenhouse gases that have been linked to global warming. But researchers are finding ways to convert coal into a zero-emissions source of electricity.
"When you try to burn coal or convert it to something else, you've got to deal with pretty difficult mineral matter," said Gordon Couch, a technologist with the International Energy Agency's Clean Coal Centre in London.
"You've got sulfur, pyrite, quartz, silica, and all kinds of stuff in with the coal."
Researchers have made progress in limiting some of these emissions in recent years, Couch says.
"For example, about 98 percent of sulfur can now be removed from emissions," he said.
But coal combustion also produces large amounts of carbon dioxide, or CO2, the major greenhouse gas. That's why the long-term goal of clean-coal research is zero-CO2 emissions.
A key to achieving this, Couch and other researchers say, is to capture the carbon dioxide and send it underground instead of releasing it into the atmosphere.
Many technologies now being developed are trying to perfect this so-called carbon-capture technique.
"To reduce [emissions] to zero, you've got to capture the carbon and stick it in the ground," Couch said.
In March the world's largest prototype carbon-capture coal plant opened in Esbjerg, Denmark.
SOURCES AND RELATED WEB SITES