Alternative husbandry methods are playing an increasingly important role in terms of animal welfare. In order to ensure that odour pollution from freely ventilated "animal welfare-friendly" fattening pig houses can be adequately taken into account in odour surveys for approval procedures in Germany, the odour annoyance and respectively the hedonic odour effect was investigated in more detail starting from these types of houses.
The odour annoyance potential of three alternative fattening pig houses was investigated by creating polarity profiles according to guideline VDI 3940 part 4. It was found, that the annoyance potential of those alternative housing forms with natural ventilation and outdoor area as outdoor climate stimulus, as well as bedding (straw), is lower compared to conventional housing forms.
Kathrin Kwiatkowskia*, Dr. Ralf Botha, Dr. Kirsten Suckerb
Competing interests: The author has declared that no competing interests exist.
Academic editor: Carlos N. Diaz
Content quality: This paper has been peer-reviewed by at least two reviewers. See scientific committee here.
Citation: Kathrin Kwiatkowski, Dr. Ralf Both, Dr. Kirsten Sucker, 2021, Determination of hedonic odour effect based on polarity profiles. 9th IWA Odour& VOC/Air Emission Conference, Bilbao, Spain, www.olores.org.
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ISBN: 978-84-09-37032-0
Keyword: German Guideline on Odour in Ambient Air (GOAA), odours in ambient air (odour pollution), odour annoyance, animal species-specific weighting factor, alternative fattening pig houses.
Abstract
Alternative husbandry methods are playing an increasingly important role in terms of animal welfare. In order to ensure that odour pollution from freely ventilated "animal welfare-friendly" fattening pig houses can be adequately taken into account in odour surveys for approval procedures in Germany, the odour annoyance and respectively the hedonic odour effect was investigated in more detail starting from these types of houses.
The odour annoyance potential of three alternative fattening pig houses was investigated by creating polarity profiles according to guideline VDI 3940 part 4. It was found, that the annoyance potential of those alternative housing forms with natural ventilation and outdoor area as outdoor climate stimulus, as well as bedding (straw), is lower compared to conventional housing forms.
On the basis of these results, it seems justified to apply an animal-specific weighting factor for fattening pigs (up to a number of 500 animal places in quality-assured husbandry methods with outdoor area and bedding, which demonstrably serve animal welfare) of 0.65, according to the German Guideline on Odour in Ambient Air (GOAA). This ensures that the odour pollution caused by freely ventilated "animal welfare-friendly" fattening pig houses can be properly taken into account in odour surveys in approval procedures.
1. Introduction
Initial impressions of odours, emitted from alternative fattening pig houses, have shown that they are perceived as more pleasant than those emitted from conventional houses. In order to ensure this impression and that odour pollution from freely ventilated "animal welfare-friendly" fattening pig houses can be adequately taken into account in odour surveys for approval procedures, the odour annoyance was investigated in more detail.
Odorants in ambient air are in most cases a complex mixture of substances, which can be recorded and assessed by human noses, using special investigation methods (GOAA 2008). In Germany, the evaluation system according to the German Guideline on Odour in Ambient Air (GOAA) (2008), which is used to check whether there is a significant nuisance caused by odours from facilities, is based on the relative odour duration over one year period.
Among other things, the GOAA (2008) includes a bonus-malus system based on weighting factors for odours from poultry, fattening pigs, sows and dairy cows, where the species-specific annoyance effect in ambient air is taken into account. In addition, when determining the annoyance impact of odours from industry facilities, the GOAA (2008) enables the assessment of whether the hedonic tone of an odour is "clearly pleasant” and a bonus of 0.5 can be given.
The annoyance effect of odours from animal husbandry, such as conventional fattening pigs or cattle, was determined through surveys of residents (Sucker et al. 2006). On the basis of the results, the species-specific weighting factors according to GOAA (2008) were derived. However, conducting such surveys is not possible in the vicinity of alternative flattening pig houses because of the small number of barns and the correspondingly small number of residents.
However, to assess the annoyance potential of odour pollution from freely ventilated "animal welfare-friendly" fattening pig houses, the hedonic tone was investigated by creating polarity profiles, according to guideline VDI 3940 part 4 (2010).
This method has already been used to determine animal species-specific weighting factors, e.g. for bulls, horses, dairy cattle, sheep and goats, and thus describe the annoying potential of the respective odour quality (Stoll 2017, Stoll 2019).
As a further possible application and to illustrate the method of polarity profiles according to the guideline VDI 3940 part 4 (2010), the annoyance potential of odour pollution emitted by an industrial plant is illustrated by means of an example.
2. Materials and methods
With the help of the method of polarity profiles, it is possible to classify odours according to their hedonic tone and to characterise them as clearly pleasant, as well (VDI 3940 Blatt 4 2010). According to No. 5 of GOAA (2008), these clearly pleasant odours can then be weighted with a weighting factor of 0.5 in ambient air.
A polarity profile is an instrument utilised for the multidimensional measurement of attitudes to an object such as an odour (Eyferth, 1975). The polarity profile method has been shown to be a useful tool to quantify the various dimensions of qualities and emotions evoked when smelling an odorous substance (Dalton et al., 2008).
According to guideline VDI 3940 part 4 (2010), 29 pairs of opposite adjectives (such as pleasant - unpleasant, beautiful - ugly, depressing - uplifting or happy - displeased) are evaluated abstractly, associatively, swiftly and without premeditation on a scale of -3 to +3 by at least 10 panel members. The method consists of two working steps, whereby profiles are first created for the concepts of "fragrance" and "stench" and then for the profile of the respective facility odour on site. The polarity profiles for the concepts "fragrance" and "stench" are simply based on the imagination of a fragrance or stench and are used, among other things, for the selection of panel members.
For the evaluation, the values of the profile data are multiplied by specific hedonic factor scores and the arithmetic mean value is calculated for all profiles of every type of odour performed. The comparison of the facility odour to the representative profiles of the concepts of fragrance and stench can be also done graphically, as well, using the Pearson product-moment correlation.
The coefficient is a measure of the degree of linear correlation between two at least interval-scaled characteristics and indicates the similarity of the courses of the profiles. The coefficient can assume values between -1,00 and 1,00, where -1,00 corresponds to the maximum of negative, 1,00 to the maximum of positive and 0,00 to the lack of correlation.
To qualify the hedonic tone of a facility odour as clearly pleasant, the correlation between the profile of the facility odour and the representative fragrance and stench profiles has to be greater than 0.5 and less than -0,5. (VDI 3940 Blatt 4 2010)
In order to be able to quantitatively evaluate the position of the investigated profile, the distance of the curve to the representative fragrance and stench profile was taken into consideration.
In order to determine the absolute distance to the representative profiles, the respective mean value of the summed positive and negative deviations was calculated. The absolute distance between the odour and stench profiles is 3.60. If the determined distances are now related to the distance between the fragrance and stench profile of 3.60, the result represents the relative distance. The more pleasant an odour is rated, the smaller the distance to the representative fragrance (up to 0) and the larger to the representative stench (up to 1).
Three different kinds of alternative fattening pig houses were investigated. All are closed flattening pig houses, have a natural ventilation and an outdoor area as outdoor climate stimulus, as well as bedding (straw). Two of them are operated continuously, have a space of about 2.3 m²/animal or a partly covered run and one is using the all-in/all-out method, have a space of about 0.75 m²/animal or a full covered run.
In order to demonstrate the application of the method of polarity profiles on a facility odour, the profile of the odour of a bakery was examined (Schröder 2019).
3. Results and discussion
The method of polarity profiles was used to investigate the annoyance potential of odour pollution from the outdoor area of three alternative fattening pig houses. For this purpose, the hedonic tone was examined at a low intensity / at a greater distance from the source (far/weak) and at a strong intensity / close to the source (near/strong/clear). A total of 538 polarity profiles (264 far/low and 274 near/strong/clear) were assessed in the vicinity of the barns. It can be seen that the intensity of the odours already decreases at a short distance from the source (results not shown).
When looking at the graphs of the polarity profile for fattening pigs in alternative housing ("pig alternative"), it can be seen, that the profile is shifted towards the representative odour profile. Nevertheless, these odours are less unpleasant than the odours emitted from pigs in conventional housing ("pig conventional") (Sucker et al., 2006) (see Figure 1).
Figure 1: Classification of the polarity profile "pig alternative" in the profiles of other animal species (cattle and pigs in conventional husbandry) as well as between the representative profiles for fragrance and stench and presentation of the profile of bakery odour.
According to the guideline VDI 3940 part 4 (2010), the product-moment correlation coefficient by Pearson is calculated to determine the similarity of the polarity profile of the investigated facility odour with the representative profile for fragrance and stench.
The results, shown in Table 1, reveal that all profiles of livestock odours correlate positively with the stench profile and negatively with the fragrance profile.
Since the correlation coefficient cannot be used to describe the position of the profile between the representative profiles, but only the similarity, an evaluation based on the Pearson correlation alone is not sufficient (VDI 3940 Blatt 4 2010).
In order to be able to quantitatively evaluate the position of the profile of the fattening pigs in alternative housing, the relative distance of the profile to the representative fragrance and stench profile was considered.
The relative distance makes it possible to generate a numerical quantity value to describe the position of the profiles. The values show that the profiles of pigs in alternative husbandry are shifted towards the fragrance profile compared to conventional husbandry (see Table 1).
Table 1: Correlation and relative distance of the investigated polarity profiles to the representative profiles.
| Odour type | Correlation coefficient | Relative distance | ||
| Fragrance | Stench | Fragrance | Stench | |
| Pig alternative | -0,68 | 0,87 | 0,69 | 0,31 |
| Pig conventional | -0,67 | 0,72 | 0,79 | 0,22 |
| Cattle | -0,21 | 0,53 | 0,56 | 0,44 |
| Bakery | 0,92 | -0,72 | 0,20 | 0,80 |
This indicates that the annoyance potential of alternative forms of husbandry, with outdoor area as an outdoor climate stimulus, as well as bedding (straw), is lower compared to conventional forms of husbandry. Based on these results, a bonus in the form of a weighting factor can be granted to the alternative form of husbandry.
In order to quantify the bonus and to generate a new weighting factor for fattening pigs in alternative husbandry, the relative distance of the profiles and the already existing animal-specific weighting factors are set in relation to the new results. The animal-specific weighting factor according to Table 4 of GOAA (2008) for conventional fattening pig husbandry (up to a number of animal places of approx. 5 000 fattening pigs) is 0.75, while for cattle or dairy cows with young animals and fattening bulls is 0.5.
Table 2: New weighting factor in relation to the relative distance and weighting factors of other animals
| Odour type | Weighting factor in relation to the relative distance to the fragrance and stench profile | |
| In relation of 0,5 (cattle) | In relation of 0,75 (pig conventional) | |
| Pig alternative | 0,62 | 0,66 |
| Pig conventional | 0,70 | 0,75 |
| Cattle | 0,50 | 0,53 |
In relation to the weighting factor of 0.5 for cattle husbandry, the factor for fattening pigs in alternative husbandry is 0.62 and in relation to the weighting factor of 0.75 for conventional fattening pigs, it is 0.66 (see Table 2). Against this background, a weighting factor for alternative fattening pigs of 0.65 seems justified.
There are differences between the odours quality from animal husbandry and industry. For this reason, the requirements for assessing industrial odours are different in terms of the hedonic tone, which is taken into account by the GOAA (2008). It makes it possible to assess whether a clearly pleasant odour is emitted, when determining the annoyance potential of an odours from industry facilities. The example of the facility odour shown reveals, that the profile of the bakery odour is close to the representative odour profile and correlates with 0.92 to the fragrance and -0.72 to the stench profile (see Table 1) (Schröder 2019). This shows, that hedonic tone of the odour emitted by the bakery is clearly pleasant, and according to the GOAA (2008) it can receive a bonus of 0.5 on pollution side.
4. Conclusions
The odour annoyance potential of alternative fattening pig houses was investigated by creating polarity profiles according to guideline VDI 3940 part 4 (2010). It was found that the annoyance potential of these alternative housing forms with natural ventilation and outdoor area as outdoor climate stimulus as well as bedding (straw) is lower compared to conventional housing forms.
On the basis of the results of the three livestock facilities investigated here, it seems justified to apply an animal-specific weighting factor for fattening pigs (up to a number of animal places of 500 in quality-assured husbandry methods with outdoor area and bedding, which demonstrably serve animal welfare) of 0.65 on the pollution side according to GOAA (2008). This ensures that the odour pollution caused by freely ventilated "animal welfare-friendly" fattening pig houses can be properly taken into account in odour surveys in approval procedures.
5. References
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Eyferth, K. in: Bergler, R. (Hrsg.) 1975. Das Eindrucksdifferential. Huber Verlag, Berlin.
Schröder, T. 2019. Bericht über durchgeführte Immissionsmessungen – Messung nach VDI 3940 Blatt 4, TÜV NORD Umwetschutz GmbH & Co. KG, Essen (unpublished).
Stoll, S. 2017. Erstellung von Polaritätenprofilen für das Konzept Gesatnk und Duft für die Tierarten Mastbullen, Pferde und Milchvieh. LUBW Landesanstalt für Umwelt, Messung und Naturschutz Baden-Württemberg, Karlsruhe.
Stoll, S. 2019. Erstellung von Polaritätenprofilen für das Konzept Gesatnk und Duft für die Tierarten Ziegen und Schafe. LUBW Landesanstalt für Umwelt, Messung und Naturschutz Baden-Württemberg, Karlsruhe.
Sucker, K., Müller M. Both R. 2006. Geruchsbeurteilung in der Landwirtschaft. Bericht zu Expositions-Wirkungsbeziehungen, Geruchshäufigkeit, Intensität, Hedonik und Polaritätenprofile; Materialien 73. Landesumweltamt Nordrhein-Westfalen, Essen.
VDI 3940 Blatt 4:2010-06: Bestimmung der hedonischen Geruchswirkung – Polaritätenprofile (Determination of the hedonic odour tone; Polarity profiles; bilingual version). Beuth Verlag, Berlin.