Coal-fired plants have long been considered old technology, but were kept in play as an inexpensive source of power and as part of the need to maintain a diversified base of fuel sources by power companies. But many of these plants are finally being shuttered; why exactly is that? Is it strictly due to more stringent air quality regulations imposed by the US EPA, or the emergence of natural gas as a readily available commodity fuel in the eastern US, or perhaps a combination of these and other factors? Liberty Environmental Principal and Air Quality Expert, Gavin Biebuyck, answers these questions and more.