Good Question: What exactly is clean coal?

Q: What is clean coal or clean-coal technology? Does such a thing exist and why aren't we using it all the time?

A: Environmentalists frequently scoff at the notion of clean coal. While they say there's no such animal, President-elect Barack Obama and lots of others say clean coal does exist - and they are pushing for the United States to invest potentially billions of dollars in electric power plants and potentially motor fuel refineries that reduce far less pollution than existing coal-fired generators.

Proponents such as coal producers, big electric utilities and coal states such as...