This guidance provides an illustration of reasoning that a Prevention of Significant Deterioration (PSD) permitting authority may use to support the conclusion that the best available control technology (BACT) for carbon dioxide (CO2) emissions at a bioenergy facility is the combustion of biogenic fuels by itself. As of January 2, 2011, greenhouse gases (GHG), including CO2, became a pollutant subject to regulation under the Clean Air Act (CAA). Under existing PSD program regulations and EPA interpretations of those regulations, stationary sources of air pollution that require a PSD permit to authorize construction, and that would have the potential to emit (or would increase GHG emissions by) 75,000 tons CO2 equivalent (CO2e) per year (tpy) or more or are requesting to increase GHG emissions by 75,000 tons CO2e per year (tpy) but that did not obtain such a permit prior to January 2, 2011, will need to demonstrate to the appropriate reviewing authority that the proposed facility will meet GHG emission limitations through application of BACT.