Structuring Power Plant Emissions Standards Under Section 111(d) of the Clean Air Act -- Standards for Existing Plants

There are a range of questions that EPA will need to address over the coming year as it develops greenhouse gas (GHG) performance standards for existing power plants under section 111(d) of the Clean Air Act (CAA). Key questions that have received significant stakeholder attention concern the appropriate stringency of the standards and the technical basis for the standards. Separate from these questions, but essential to understanding the potential impact of the standards, are questions about the form of the standard and the compliance flexibility measures allowed either by EPA or through state compliance plans. This discussion paper provides background on the CAA requirements for the regulation of GHGs for power plants and examines the potential form of the standard for existing sources, highlighting the potential pros and cons of different approaches.