Two major new Waste-To-Energy (WTE) Projects have received Air Construction Permits under the Prevention of Significant Deterioration (PSD) program during the past two years and a third is scheduled to receive its permit prior to NAWTEC 20. These new facilities are being required to operate with significantly lower emissions of nitrogen oxides (NO x ) and other major air pollutants than similar existing US facilities. This paper will explore the permitting process on these three projects and the divergent approaches being taken by the applicants to meet the stringent emission requirements imposed by the PSD permits. The Palm Beach County (Florida) Renewable Energy Facility No. 2 (PBREF No. 2) will be a three unit, 3,000 ton per day (tpd) mass burn facility which will utilize Selective Catalytic Reduction (SCR) systems similar to that used in many recent European WTE facilities for NO x control. The Fairfield (Maryland) Renewable Energy (Fairfield) and Aercibo (Puerto Rico) Renewable Energy (Aercibo) Projects are each two unit, 2,106 tpd Refuse Derived Fuel (RDF) facilities which will utilize regenerative SCR (RSCR ® ) systems. This will be the first time RSCR ® has been used in a WTE application. All three permits require achievement of a NO x emission rate of 45 parts per million by volume at 7% O 2 dry basis (ppmvd). PBREF No. 2 and Fairfield received PSD permits from delegated state programs prior to the new Greenhouse Gas (GHG) and condensable PM 2.5 permitting rules going into effect at the beginning of 2011. Aercibo is being permitted by United States Environmental Protection Agency (EPA) Region II and will reflect new GHG and condensable PM 2.5 permitting rules. This paper discusses the approach to the Best Available Control Technology (BACT) and Lowest Achievement Emission Rate (LAER) determinations and differences in final permit requirements.