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

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 (R ≈ 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 m/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 R 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.