Add_Excretie verbetering modellen (BO-43.20-101-005, BO-43-101-044)

The calculation of the N, P, and TAN excretion according to WUM (Werkgroep Uniformering berekening Mest- en mineralencijfers: Working group for calcluation of uniform manure en mineral numbers) methodology forms the basis for all subsequent steps in the calculation of ammonia emission from animal agriculture. The WUM methodology, direct, or as part of the NH3 emission calculations has been evaluated a several times, which has resulted in a number of improvement points regarding the sustantiation of the numbers used, the transparancy of these numbers and the quantification of the accuracy of the methodology (CDM, 2012, Sutton et al., 2015, Hordijk et al., 2020a, 2020b, Zom en Kasper, 2019). The reviews of Hordijk et al., 2020a, 2020b give advice for improving the total of the ammonia calculation, where it is advised to publish the underlying scientific models and to discuss these with a group of stakeholders. In a previous project a working group has indicated a number of additional improvement points. This project is aimed at improving the WUM methodology based on these improvement points.