In all the presidential debates, and on the campaign trail, both Senators Barack Obama and John McCain mentioned “clean coal technology”. What is clean coal?
According to Slate.com, coal accounts for more than half of nitrogen oxide emissions and about one-quarter of sulfur dioxide pollution in the US. Coal is also a major source of the particulate matter that makes smoggy air so hard on your lungs.
The American Coalition for Clean Coal Electricity defines it as "any technology to reduce pollutants associated with the burning of coal that was not in widespread use" prior to 1990 regulations. By that definition, the group can call any newer coal-based power plant clean.
"Clean coal" also refers to coal burning power plants that capture and store the excess, preventing it from contributing to climate change.