2.3. Ammonia emissions study
Four separate collections of total faeces and urine production were carried out at 12-h intervals during collection days
1–2 and stored in sealed containers at 4 ◦C. Upon final collection, the urine and faeces were pooled and macerated together
according to the original excretion ratio. Maceration was performed in an attempt to actively simulate the conditions of a
typical manure container, which would be more dynamic due to constant disturbance through addition of fresh excreta. The
respective manure sample (2 kg) was placed in a ventilated container in a temperature-controlled room maintained at 20 ◦C.
Ammonia emissions from the manure were measured over 240 h in a laboratory scale set-up as described by O’Shea et al.
(2009a). Briefly, ammonia emitted from manure was collected in three impingers through use of a pump with a ventilation
rate calibrated at 2.5 l/min. The first two impingers contained 1mol/l nitric acid (HNO3) and the third impinger contained
distilled water. The first impinger was sampled at 48, 96, 144, 192 and 240 h and the second impinger was sampled at 96 h.
Samples were collected from all three impingers at 240 h. The concentration of ammonia-nitrogen (NH3-N) contained in
each impinger was determined by the microdiffusion technique of Conway (1957). Ammonia emissions (mg) from each
manure sample were compared between different dietary treatments using the quantity volatilised from 0 to 240 h per kg
of sample. A two kilogram duplicate sample was retained in a ventilated container for each two kilogram manure sample
used in the ammonia emission study. From the duplicate sample, an aliquot (50 g) was retained at 0 and 240 h for volatile
fatty acid (VFA) determination.