On May 22, 2013, EPA approved revisions to the Wisconsin State Implementation Plan (SIP) to modify Wisconsin's Prevention of Significant Deterioration (PSD) program for greenhouse gases (GHG). The revisions establish emission thresholds for determining which new stationary sources and modification projects become subject to Wisconsin's PSD permitting requirements for their GHG emissions. Additionally, these revisions defer, until July 21, 2014, the application of the PSD permitting requirements to biogenic carbon dioxide (CO2) emissions from bioenergy and other biogenic stationary sources in Wisconsin.

On July 20, 2011, EPA published a rule allowing states to defer the regulation of CO2 emissions from bioenergy and other biogenic sources; however to use the exemption, Wisconsin had to incorporate the requirement into the SIP. This is an important change particularly for facilities wanting to permit new or modified bioenergy projects. The revision exempts consideration of biogenic emissions from PSD review until July 21, 2014. Biogenic emissions include emissions of CO2 from a stationary source directly resulting from the combustion or decomposition of biologically based materials. During the deferral period, EPA is conducting a detailed review of biogenic CO2 emissions to determine how to account for these emissions in the future (post July 21, 2014). The final rule is effective June 21, 2013.