Ammonia Emission from Fattening Pig Houses in Relation to Animal Activity and Carbon Dioxide Production

Patricia de Sousa, Søren Pedersen

Abstract


Ammonia emission from animal facilities is a world-wide research focus area, because ammonia
is a nuisance for the external environment. It is therefore important to know how ammonia emissions
depend on various factors, such as animal activity and ventilation rate. The objective of this
paper is to show the impact of animal activity on the variation of the diurnal ammonia emission in
controlled environment with low variation in indoor temperature. The investigation, comprising
three trials with a total of 57 24-hour measuring periods, has been dealing with animal activity,
ventilation rate and ammonia emission. In order to show how precisely the ventilation rate can be
measured on the basis of the easier measurable carbon dioxide concentration, investigations of
the ventilation rate have been made both when measured by means of measuring fans and indirectly
on the basis of the carbon dioxide concentration. Hourly ammonia emissions, where the
ventilation rate is based on carbon dioxide concentrations, have been investigated both with standard
sinusoidal corrections for diurnal variations in carbon dioxide productions and adjusted by
measured animal activity. The investigation carried out at a conventional farm shows that the
diurnal variation in animal activity can be approximated by a sinusoidal model, where about 3/4
of the diurnal variation in activity can be explained (R2 ≈ 0.75). The investigations also show
that the ventilation rate as daily average can be approximated on the basis of measurements of the
carbon dioxide concentration in the animal house, using a carbon dioxide production in accordance
with the CIGR (2002) of 0.185 m3/h per heat producing unit (1 hpu = 1000 W in animal
total heat production). The ratio between ventilation rate on a carbon dioxide basis and measured
as 24 hour average varied from 1.02 to 1.17. On hourly basis, the relation between ventilation rate
based on carbon dioxide concentration and measured by fans, very much depends on whether
adjustments for animal activity are taken into account. Without adjustment for animal activity, the
correlation is in the worst case close to zero. When using a standard adjustment for activity, the
correlation R2 between calculated and measured ventilation rates will be 0.80 or above. The correlation
between animal activity and ammonia emission was between 0.15 and 0.56.

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