Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?
1Swiss Federal Research Station Agroscope Reckenholz-Tänikon ART – Air Pollution and Climate, Zürich, Switzerland
2Energy research Centre of the Netherlands ECN, Petten, The Netherlands
3Institut National de la Recherche Agronomique INRA, Thiverval-Grignon, France
4Institut National de la Recherche Agronomique INRA, Agrocampus Ouest, UMR1069 SAS, Rennes, France
Abstract. The EMEP/EEA guidebook 2009 for agricultural emission inventories reports average ammonia (NH3) emission factors (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique, measurement plot size, the year of measurement, and the year of publication. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements that appeared subsequently show substantially lower EFs, and appear to indicate a need for a revision of the EF in emission inventories.