The U.S. Environmental Protection Agency (EPA) on Thursday issued a final rule to address greenhouse gas (GHG) emissions from the largest stationary sources, while shielding millions of small sources of GHGs from Clean Air Act permitting requirements.

The phased-in, common-sense approach will address facilities like power plants and oil refineries that are responsible for 70 percent of the greenhouse gases from stationary sources that threaten Americans' health and welfare.

"After extensive study, debate and hundreds of thousands of public comments, EPA has set common-sense thresholds for greenhouse gases that will spark clean technology innovation and protect small businesses and farms," said EPA Administrator Lisa P. Jackson.

EPA's phased-in approach will start in January 2011, when Clean Air Act permitting requirements for GHGs will kick in for large facilities that are already obtaining Clean Air Act permits for other pollutants. Those facilities will be required to include GHGs in their permit if they increase these emissions by at least 75,000 tons per year (tpy).

In July 2011, Clean Air Act permitting requirements will expand to cover all new facilities with GHG emissions of at least 100,000 tpy and modifications at existing facilities that would increase GHG emissions by at least 75,000 tpy. These permits must demonstrate the use of best available control technologies to minimize GHG emission increases when facilities are constructed or significantly modified.

The final rule addresses a group of six greenhouse gases: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride.

EPA issued a proposed rule last October and held a 60-day public comment period. The agency received about 450,000 comments, which were carefully reviewed and considered during the development of this final rule.