They noted that pollution research efforts had focused almost exclusively on "conventional" pollutants - substances that were known or suspected to be carcinogenic or immediately toxic.

But even when cleaned of conventional pollutants, environmentalists point out, coal produces far more carbon dioxide, which is thought to cause global climate change, than natural gas or oil.

He said the demonstration would cost $800 million, including work to remove conventional pollutants like soot and sulfur dioxide before carbon separation.

It is listed as a conventional pollutant in the U.S. Clean Water Act.

Municipal treatment plants are designed to control conventional pollutants: BOD and suspended solids.

POTWs discharge conventional pollutants, and are covered by secondary treatment standards and state water quality standards.

A basic list of conventional pollutants is defined in the U.S. Clean Water Act.

Engineers agree that it is easier to remove sulfur, mercury, particles and other conventional pollutants from plants that use gasification.

Wastewater from restaurants and other food service industries are often more problematic due to the prevalence of conventional pollutants such as grease, organic matter and solids.

When used in older vehicles, there would also be substantial reductions in emissions of conventional pollutants leading to better air quality.