## 3 Results and Discussion
### Technological Factors  
The impact of technological factors in the form of technological and operating processes and waste properties is observed on the basis of changes in VOC and NH\({}_{3}\) concentrations. Table 6 presents the differences between individual measurement series in the odorant  
compliance with the technological regime. The impact of the technological regime and the applied solutions has been discussed by [PERSON] et al. [23]. Impact of Air Temperature and Humidity and Technological Factors on Odour Concentration and Intensity: Analyses  
At four of the examined biogas plants (A, B, E, F) for two research series, bigger \(\mathrm{c_{od}}\) (at designated points) is accompanied by higher air temperatures (irrespective of differences between the temperatures in a range from 3 \({}^{\circ}\)C to more than 18 \({}^{\circ}\)C). The same relationships are also reported in other papers [34; 36]. In the case of B biogas plant, despite small differences between mean temperatures of individual measurement series (at a level less than 3 \({}^{\circ}\)C), such dependencies are observed at almost all measuring points. In turn, at the biogas plant in Biala Podlaska in spite of a slight variation in \(\mathrm{c_{od}}\) values (from 3 ou/m\({}^{3}\) to 11 ou/m\({}^{3}\)), the dependencies between \(\mathrm{c_{od}}\) at measurement sites and average air temperature are evidently the same. It is the air temperature that seems to have a major impact among environmental drivers on odour emission. This is particularly evident in relation to \(\mathrm{c_{od}}\) at A biogas plant. During the second measurement series, the average air temperature is lower by about 61% compared to the air temperature in the first series, and in individual points, lower \(\mathrm{c_{od}}\) values are also noted--lower by 33% (in b and g points) to 84% (in point a) as is graphically illustrated in Figure 2. This trend is not observed only at one point: point f (oxygen stabilisation). At other biogas plants, the tendency is similar, and the lower temperature is accompanied by lower \(\mathrm{c_{od}}\) values (compared in the same odour sources)--lower by 17% to 90%. This is illustrated graphically in Figures 3-7. The dependencies between \(\mathrm{c_{od}}\) and average air temperature are not so evident in Stalowa Wola. The variability of \(\mathrm{c_{od}}\) between the series of tests is probably determined more by the technological factors. This tendency is less pronounced with respect to \(\mathrm{i_{od}}\) due to the aforementioned methodology that was used. At two examined biogas plants (B and F), dependencies which mirrored the observed \(\mathrm{c_{od}}\). A temperature relationship is also observed for \(\mathrm{i_{od}}\) and air temperature; a higher \(\mathrm{i_{od}}\) is found at higher air temperatures. At other biogas plants (A, D and E), \(\mathrm{i_{od}}\) is less dependent on atmospheric and ambient conditions because it was characterised by lower variability between the measurement series. At A biogas plant, the difference between average air temperatures during the test series is too small (0.3 \({}^{\circ}\)C) to assess its effect on odour nuisance. It makes the comparison impossible. At two biogas plants (A and F), a similar impact is observed of mean air humidity on \(\mathrm{c_{od}}\) and \(\mathrm{i_{od}}\) compared to the effect presented in the literature [35; 36]--a higher \(\mathrm{c_{od}}\) and \(\mathrm{i_{od}}\) at lower air humidity. However, this relationship is observed in the case of differences in air humidity at a minimum level of about 20%. It should be noted that differences in average relative air humidity at the level of 10% to 14% (as measured respectively at C and E biogas plants) do not have a significant effect on \(\mathrm{c_{od}}\) and \(\mathrm{i_{od}}\). At two biogas plants, the differences between average air humidity during separate research series are too small to assess their effect on odour nuisance.