Revisions to Definition of Cogeneration Unit in Clean Air Interstate Rule (CAIR), CAIR Federal Implementation Plans, Clean Air Mercury Rule (CAMR); and Technical Corrections to CAIR, CAIR FIPs, CAMR, and Acid Rain Program Rules

The Clean Air Interstate Rule (CAIR), CAIR Federal Implementation Plans (FIPs), and Clean Air Mercury Rule (CAMR) each include an exemption for cogeneration units that meet certain criteria. In light of information concerning biomass-fired cogeneration units that may not qualify for the exemption due to their particular combination of fuel and technical design characteristics, EPA is changing the cogeneration unit definition in CAIR, the CAIR model cap- and-trade rules, the CAIR FIPs, CAMR, and the CAMR model cap-and-trade rule. Specifically, EPA is revising the calculation methodology for the efficiency standard in the cogeneration unit definition to exclude energy input from biomass making it more likely that units co-firing biomass will be able to meet the efficiency standard and qualify for exemption. Because this change will only affect a small number of relatively low emitting units, it will have little effect on the projected emissions reductions and the environmental benefits of these rules. If EPA finalizes the proposed CAMR Federal Plan, it intends to make the definitions in that rule conform to the CAMR model cap-and- trade rule and thus, with today's action. This action also clarifies the term "total energy input" used in the efficiency calculation and makes minor technical corrections to CAIR, the CAIR FIPs, CAMR, and the Acid Rain Program rules.