## 3 Results and Discussion  
### Atmospheric and Ambient Conditions  
The results of the relationship between atmospheric and environmental conditions in the identified sources of odours in the individual measurement series are shown in Table 5. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Mark of Odour**} & \multicolumn{6}{c}{**Name of Odour Source at Analysed Biogas Plants**} \\ \cline{2-9}  & **Source** & **A** & **B** & **C** & **D** & **E** & **F** \\ \hline \hline \multicolumn{9}{c}{a} & \multicolumn{6}{c}{Waste storage plant} \\ \hline \multicolumn{9}{c}{b} & \multicolumn{6}{c}{Mechanical part plant (pre-treatment)} \\ \hline \multicolumn{9}{c}{c} & \multicolumn{6}{c}{Fermentation preparation plant/field} \\ \hline \multicolumn{9}{c}{d} & \multicolumn{6}{c}{Digestate dewatering plant} & \multicolumn{1}{c}{—} & \multicolumn{1}{c}{—} \\ \hline \multicolumn{9}{c}{e} & \multicolumn{1}{c}{—} & \multicolumn{1}{c}{—} & Oxygen stabilisation plant \\ \hline \multicolumn{9}{c}{f} & \multicolumn{2}{c}{Oxygen stabilisation} & \multicolumn{1}{c}{—} & Oxygen stabilisation \\ \hline \multicolumn{9}{c}{g} & \multicolumn{6}{c}{Open biofiliter surface} \\ \hline \multicolumn{9}{c}{Notes: “—” sources do not occur on the premises of a given plant, due to the applied waste treatment technology or practiced technological regime.} \\ \end{tabular}
\end{table} 
Table 4: Odour sources identified at the examined biogas plants. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Biogas**} & \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**No. of the**} & \multicolumn{6}{c}{**Odour Sources Identified at the Examined Biogas Plants**} \\ \cline{3-10}  & & & **Research Series** & **a** & **b** & **c** & **d** & **e** & **f** & **g** \\ \hline \multirow{5}{*}{**A**} & \multirow{5}{*}{T [\({}^{\circ}\)C]} & \multirow{5}{*}{1} & 31.0 & 32.0 & 28.7 & 30.5 & — & 27.7 & 32.0 \\ \cline{3-10}  & & & & \multicolumn{6}{c}{Mean 30.3 \(\pm\) 1.8} \\ \cline{3-10}  & & & 10.9 & 11.7 & 11.4 & 11.8 & — & 13.0 & 12.6 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 11.9 \(\pm\) 0.8} \\ \cline{3-10}  & & & 53.0 & 51.0 & 52.5 & 57.5 & — & 34.3 & 31.4 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 46.6 \(\pm\) 10.9} \\ \cline{3-10}  & & & 73.4 & 73.4 & 73.4 & 73.4 & — & 65.1 & 56.3 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 69.2 \(\pm\) 7.1} \\ \hline \multirow{5}{*}{**B**} & \multirow{5}{*}{T [\({}^{\circ}\)C]} & \multirow{5}{*}{1} & 16.9 & 16.9 & 16.0 & 16.5 & — & — & 16.0 \\ \cline{3-10}  & & & & \multicolumn{6}{c}{Mean 16.5 \(\pm\) 0.5} \\ \cline{3-10}  & & & 18.9 & 13.5 & 12.4 & 14.2 & — & — & 10.2 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 13.8 \(\pm\) 3.2} \\ \cline{3-10}  & & & 48.0 & 42.5 & 48.5 & 49.0 & — & — & 55.5 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 48.7 \(\pm\) 4.6} \\ \cline{3-10}  & & & 42.6 & 39.5 & 54.4 & 63.5 & — & — & 49.1 \\ \cline{3-10}  & & & \multicolumn{6}{c}{Mean 49.8 \(\pm\) 9.6} \\ \cline{3-10}  & & & & \multicolumn{6}{c}{Mean 49.8 \(\pm\) 9.6} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Measurements of air temperature (T) and relative humidity (RH) obtained in the pilot research at six biogas plants processing municipal waste; values at individual odour sources and mean value with standard deviation. During the research at four biogas plants, two measurement series were performed with significantly different average air temperatures. Temperature variations range from 10.3 \({}^{\circ}\)C in Wolka Rokicka to 18.4 \({}^{\circ}\)C in Jarocin together with 11.1 \({}^{\circ}\)C in Stalowa Wola and 12.4 \({}^{\circ}\)C in Biaia Podlaska. At two other biogas facilities (in Tychy and Promnik), differences between average air temperatures during the implementation of two measurement series are small at: 3.0 \({}^{\circ}\)C and 0.3 \({}^{\circ}\)C, respectively.