The idea of clean coal is one of the most flagrant and offensive examples of greenwashing seen yet.
The American Coalition for Clean Coal Technology is by far the most prominent offender. This article at Inhabitat outlines the true cleanliness of coal. By the Coalition’s definition “clean coal” actually means
Clean coal technology: Any technology to reduce pollutants associated with the burning of coal that was not in widespread use prior to the Clean Air Act Amendments of 1990.
However, you wouldn’t know this definition by their advertisements. This billboard seen in Pennsylvania paints a pretty different picture of coal as a “clean, green” energy source.