The Clean Air Interstate Rule (CAIR), CAIR Federal Implementation Plans (FIPs), and Clean Air Mercury Rule (CAMR) include an exemption for cogeneration units that meet certain criteria.  However, some biomass-fired cogeneration units may not qualify for the exemption due to their particular combination of fuel and technical design characteristics.  Thus, EPA has changed the cogeneration unit definition in CAIR, CAIR model cap-and-trade rules, CAIR FIPs, CAMR and CAMR model cap-and-trade rule.   Specifically, the calculation methodology for the efficiency standard was revised to exclude energy input from biomass, thereby making it more likely that the cogeneration unit will meet the efficiency standard and qualify for the exemption.

EPA also clarified the term "total energy input" used in the efficiency calculation, clarifying that  the parameter must be based on the lower heating value.  The lower heating value must be calculated using a prescribed formula. 

EPA has made other minor technical corrections to CAIR, CAIR FIPs, CAMR, and the Acid Rain Program rules.  These address text changes that make consistent use of terms and clarify the term "Permitting authority" and "Certificate of Representation".