Mechanistic modelling of ammonia emissions for fa ening pig units associated to external storage pit

An understanding and comprehensive approach of ammonia emissions is necessary to limit the impacts on environment (acidifica on), health (human and animal) and economic aspects (N losses). Modelling can fit the issues by linking ammonia emissions to prac ces of breeders and clima c condi ons. The goal of the study was to develop a mechanis c model to simulate ammonia emissions of fa ening pig unit and the external storage of slurry. The model was developed on Vensim®, using equa ons issued from literature, and mobilizing equa ons for mass transfer coefficient determined with Computational Fluid Dynamics. The model needs input data (Figure 1) rela ve to animal profile (issued from INRAporc®), feeding strategy and feeds characteris cs, clima c data, building and storage characteris cs, as well as informa on concerning the manure management (manure removal frequency from building, use or not of an external pit cover). In accordance with these input data, the model dynamically simulates room temperature and ven la on rate, pig growth, excre ons, and all the processes of N transforma on (mineraliza on, ioniza on, vola liza on). For a baseline i nerary with conven onal gene c and classic manure management (removal of slurry at the end of the fa ening period, and no cover), the results of the model have been compared to those issued from experiments with ammonia measurements, both regarding the absolute value and the dynamic of ammonia emissions. The results generally agree and therefore posi on the model as a promising tool for the management of ammonia emissions in pig farming. However, limita ons have been also iden fied on some of the parameters, managed at this stage with an empirical approach, such as the pH modelling or the distribu on of slurry between the sla ed floor and the pre-pit.