Large industrial emitters of carbon dioxide—such as chemical companies, refineries, and power plants—will be required to report and reduce their greenhouse gas emissions under a final rule issued last week by EPA, using its Clean Air Act authority. The rule will roll out in phases beginning in January 2011 for large facilities obtaining or modifying Clean Air Act permits needed for other pollutants. These plants would be required to include greenhouse gas emissions in their permits if they increase these emissions by 75,000 tons per year and emit at least 100,000 tons of greenhouse gases per year. EPA estimates that each year about 900 facilities that are already covered by the act will be included in the greenhouse gas provisions, along with some 550 sources that will be required to obtain greenhouse gas permits for the first time. However, it is still to be determined what these companies will have to do to limit their CO2 emissions. EPA says that best available control technologies, or BACT, for greenhouse gas emissions will be determined on a case-by-case basis, taking into account cost and effectiveness. The requirement will be released through a guidance document that has yet to be written.