Effectiveness of mechanical separation for reducing ammonia loss from field-applied slurry: Assessment through literature review and model calculations.

To assess solid-liquid separation as a technology to reduce ammonia (NH 3) emission from storage and field application of animal slurry, it is necessary to consider a possible higher NH 3 loss from the solid fraction after application than from raw slurry, as well as losses during storage. A literature review was conducted, and a case study was developed for Denmark, including cattle slurry, pig slurry, and biogas digestate applied by trailing hose, trailing shoe, or open slot injection at five different periods of the year. Standard storage emission factors were used and emission factors after field application were estimated using the ALFAM2 model with input data for dry matter (DM), pH, total ammoniacal nitrogen (TAN), and separation efficiency all from the literature compilation. In general, a clear reduction in the emission factors after application of the liquid fraction was found relative to application of raw slurry in the literature data. Case study results provide some evidence that separation of cattle slurry or digestate, followed by storage and subsequent application by trailing hose or trailing shoe of the liquid fraction and broadcast application of the solid fraction reduces overall NH 3 loss, with a higher reduction when the solid fraction is incorporated by plowing after 4 h. This effect was not present for pig slurry. For all slurry types when the raw slurry and liquid fraction is applied by open slot injection, the overall reduction in emission due to separation is not present or even negative. • NH 3 emission following application of liquid fraction is lower than raw slurry. • NH 3 loss from solid fraction can counteract lower NH 3 emission from liquid fraction. • Lower overall NH 3 emission can be obtained with separation of cattle slurry and digestate. • No evidence that NH 3 emissions are reduced with separation of pig slurry. • Application with open slot injection eliminates effect of separation on NH 3. [ABSTRACT FROM AUTHOR]