Odour Dispersion Models

Further information: Interessengemeinschaft Geruch igG

The second regulatory approach are model calculations of the separation distance using dispersion models. Following information has to be available: odour release (Martinec et al., 1998; Schauberger et al., 1999), a dispersion model (eg the normative Gauss model used in  Austria, Kolb, 1981), calculation of the instantaneous odour concentration (Schauberger et al., 2000b) and validation of the instantaneous odour concentration taking into account the FIDO factors of odour sensation (frequency, intensity, duration and offensiveness) and reasonableness.

Austrian Odour Dispersion Model AODM

The dynamic Austrian odour dispersion model (AODM) consists of three modules: the first calculates the odour emission of the livestock building, the second estimates mean ambient concentrations by a regulatory dispersion model. The last module transforms the mean odour concentration of the dispersion model to instantaneous values according to wind velocity and stability of the atmosphere.
The emission module is based on a steady-state balance of the sensible heat fluxes to calculate the indoor temperature and the related volume flow of the ventilation system (Schauberger et al., 2000a). The corresponding odour flow is assessed by a simple model of the odour release. The consideration of the diurnal variation of the odour emission is the most important feature of this module. Since odour is mainly released by the animals, by polluted surfaces and by the feed, the diurnal variation of the emission is assumed to be in phase with animal activity. Outdoor odour sources such as slurry tanks or feed storage facilities are not taken into account. For the model calculation presented here, a mean specific odour flow of 100 OU/s LU (Martinec et al. 1998) and a mean live mass of 60 kg per fattening pig (M = 0.12 LU) were used. The model has been described extensively in Schauberger et al. (1999a and 1999b).
The model calculations were done for a pig fattening unit of 1000 pigs with a forced ventilation. The livestock building is moderately isolated, described by the U value (Tab. 1). The assumed space per animal is 0.75 m² according to welfare guide lines. The chosen system parameters for a livestock building with these specifications, typical for middle Europe, are summarised in Table 1.
The odour concentration of the centre line of the plume is calculated by the Austrian regulatory dispersion model (ÖNorm M 9440, 1992/96; Kolb, 1981) by making use of a statistics of stability classes representative for the Austrian flatlands north of the Alps. The model has been validated internationally with generally good results (e.g. Pechinger and Petz, 1995). The regulatory model is a Gaussian plume model applied for single stack emissions and distances up to 15 km. Plume rise formulae used in the model are a combination of formulae suggested by Carson and Moses (1969) and Briggs (1975). The model uses a traditional discrete stability classification scheme with dispersion parameters developed by Reuter (1970).
The regulatory model calculates half hour mean concentrations. The sensation of odour, however, depends on the momentary odour concentration and not on a mean value over a long time of integration. The peak value is derived from the half our mean value using the relationship of Smith (1973) depending on the stability of the atmosphere. These values are only valid close to the odour source. Due to turbulent mixing, the peak-to-mean ratio is reduced with increasing distance from the source using the wind velocity and the stability of the atmosphere. This peak-to-mean ratio in equation is modified by an exponential attenuation function (Mylne and Mason, 1991) using the time of travel with the distance x and the mean wind velocity u, and the Lagrangian time scale as a measure of the stability of the atmosphere (Mylne, 1992). This approach is described by Schauberger et al. (2000b).

Schauberger, G., M. Piringer (1997a): Assessment of the protection distance to avoid annoyance by odour sensation caused by livestock husbandry by the Austrian guide line. In: Voermans J.A.M., G.J. Monteny (Eds): Ammonia and Odour Emission from Animal Production Facilities, NVTL, Rosmalen (1997)
Schauberger, G., M. Piringer (1997b): Guideline to assess the protection distance to avoid annoyance by odour sensation caused by livestock husbandry. In: Bottcher R.W., Hoff S.J. (Eds): Livestock Environment V, ASAE, St. Joseph, Michigan, 1997
Schauberger, G., M. Piringer, J. Eder, H. Fiebiger, M. Köck, R. Lazar, F. Pichler-Semmelrock, T. Quendler, M. Swoboda, G. Thiemann, J. Teufelhart (1997): Österreichische Richtlinie zur Beurteilung von Immissionen aus der Nutztierhaltung in Stallungen. Gefahrstoffe - Reinhaltung der Luft 57,10:399-408.
Schauberger, G., Piringer, M., Petz, E. 1999. Diurnal and annual variation of odour emission of animal houses: a model calculation for fattening pigs. Journal of Agricultural Engineering Research 74, 3: 251-259
Schauberger, G., Piringer, M., Petz, E. 2000a. Steady-state balance model to calculate the indoor climate of livestock buildings demonstrated for fattening pigs. International Journal of Biometeorology, in print
Schauberger, G., Piringer, M., Petz, E. 2000b: Diurnal and annual variation of the sensation distance of odour emitted by livestock buildings calculated by the Austrian odour dispersion model (AODM) Atmospheric Environment, submitted

Links to other dispersion models

Last modification: January 31, 2000 Webmaster