The water authorities in the Netherlands all joined forces to initiate a nitrous oxide (N2O) process emissions reduction acceleration program for 4 years. The aim of the program is to get insights in the emission factors for N2O and also take mitigating actions. All the WWTP’s in the Netherlands were grouped per pre-defined principles, like size and p.e. and sludge digestion or not. The first task in the acceleration program was to analyze the N2O data collected from 21 wastewater treatment plants (WWTPs) across the Netherlands to determine baseline emissions. The calculated emission factors varied substantially and ranged from 0.002 to 0.032 kg N2O emitted/kg Influent Total Nitrogen. The effort proved invaluable for understanding the data quality, the range of emissions among the Dutch WWTPs, process conditions resulting in higher and lower N2O emissions, and lessons learned for developing a standardized approach for validating data, calculating emissions and emission factors, and dealing with data gaps. The consensus-based approach has now been developed and will be implemented on a second group of 29 sites by an expert group of Dutch researchers, consultants and technologists. The methodology will consist of data validation, calculation of EFs to derive group-specific N2O emission factors.