The United States Environmental Protection Agency proposed new rules last week which would require the installation of new technology to limit emissions of mercury from coal-fired power plants. The EPA is taking comments on the new rules for 60 days.

The rules would introduce the first national limits on mercury emissions from power plants. They have been stuck in regulatory, litigation and legislative limbo for at least 20 years, and were finally mandated by a 2009 court ruling which required the EPA to introduced new rules by March 16th and finalize them by November, 2011.

John Wellinghoff, the charman of the Federal Energy Regulatory Commission, predicted that the new rules may have the effect of shifting generation to cleaner sources of electricty such as natural gas or wind, or increase energy conservation efforts. Other analysts have suggested that 15 to 20% of the U.S. coal-fired fleet could be retired by 2015 as a result of this rule.

The EPA estimates that mercury emissions from power plants would be cut by 91%, and that emissions of arsenic, chromium, nickel and particulates would also be reduced. The estimated cost to industry is $11b per year.