Beginning in January 2011, U.S. EPA will require air permits issued for certain new and modified stationary sources to incorporate "best available control technology," or "BACT," for greenhouse gas emissions. Given the absence of established technologies to capture or destroy such pollutants, this is a significant concern for both regulated entities and the state permit writers who must begin issuing such permits in less than three months. While EPA has yet to issue long-promised guidance on what will be considered BACT for greenhouse gases, there is an indication that the guidance may arrive shortly.

On September 17, 2010, EPA forwarded draft BACT guidance to the Office of Management and Budget for review, and publication of the guidance is expected sometime in "early to mid-fall." EPA has also indicated that it expects to issue separate technical papers on greenhouse gas BACT for seven specific industrial sectors—cement, electrical generating units, pulp and paper, nitric acid plants, iron and steel, commercial boilers, and refineries.

A hint at what might be contained in EPA's forthcoming BACT guidance may be found in a report issued on October 4, 2010 by EPA's Climate Change Work Group that includes recommendations on incorporating energy-efficient processes and technologies into the permitting framework used to set BACT on a case-by-case basis. EPA has previously suggested that energy efficiency will be a key approach to setting greenhouse gas BACT until actual control technologies are available. The Work Group's report also recommends that EPA revise the Clean Air Act's "Innovative Control Technology" waiver provisions to encourage and promote the use of new and innovative control technologies for greenhouse gases emitted by stationary sources.