## 3 Results and Discussion
### Uncertainty of NH\({}_{3}\) Emission Factor at Biogas Production Facility
#### 3.4.3 Comparison of the NH\({}_{3}\) Emission Factors Uncertainty  
The average emission factor of the total biogas production facilities was used to calculate the uncertainty, which was compared with the uncertainty of the emission factor employed overseas. The PDF of the NH\({}_{3}\) emission factor based on waste processing was analyzed as the Lognormal distribution. The average was 0.0046 kgNH\({}_{3}\)/ton-waste. The bottom 2.5% at the 95% confidence level was 0.0044 kgNH\({}_{3}\)/ton-waste, and the top 97.5% was 0.0049 kgNH\({}_{3}\)/ton-waste. The uncertainty range of the NH\({}_{3}\) emission factor determined using these values at the 95% confidence level was between \(-\)4.3 and +6.5% (Figure 4). \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Site**} & **Mean** & **95\% Lower** & **95\% Lower** & \multirow{2}{*}{**Probability**} & \multirow{2}{*}{**Uncertainty**} \\  & **(kgNH\({}_{3}\)/10\({}^{3}\)** & **Confidence Level** & **Confidence Level** & **(kgNH\({}_{3}\)/10\({}^{3}\)** & **Density Function** & **Range** \\  & **Nm\({}^{3}\)-Biogas** & **Nm\({}^{3}\)-Biogas** & **Nm\({}^{3}\)-Biogas** & **Nm\({}^{3}\)-Biogas** & **Nm\({}^{3}\)-Biogas** & **Nm\({}^{3}\)-Biogas** \\ \hline \multicolumn{2}{c}{A biogas production facility} & \multirow{2}{*}{0.023} & \multirow{2}{*}{0.022} & \multirow{2}{*}{0.025} & Gamma & \multirow{2}{*}{\(-\)8.3\(-\)16.7\%} \\  & & & & & distribution & \\ \hline \multicolumn{2}{c}{B biogas production facility} & \multirow{2}{*}{0.168} & \multirow{2}{*}{0.154} & \multirow{2}{*}{0.182} & Lognormal & \multirow{2}{*}{\(-\)8.3\(-\)8.3\%} \\  & & & & distribution & & \\ \hline \multicolumn{2}{c}{C biogas production facility} & \multirow{2}{*}{0.194} & \multirow{2}{*}{0.179} & \multirow{2}{*}{0.211} & Gamma & \multirow{2}{*}{\(-\)6.7\(-\)8.0\%} \\ \multicolumn{2}{c}{} & & & distribution & & \\ \hline \end{tabular}
\end{table} 
Table 8: Uncertainty of the biogas production base, NH\({}_{3}\) emission factors at biogas production facility. The PDF of the NH\({}_{3}\) emission factor based on biogas production was analyzed as the Gamma distribution. The average was 0.1514 kgNH\({}_{3}\)/10\({}^{3}\) Nm\({}^{3}\)-Biogas. The bottom 2.5% at the 95% confidence level was 0.1428 kgNH\({}_{3}\)/10\({}^{3}\) Nm\({}^{3}\)-Biogas, and the top 97.5% was 0.1609 kgNH\({}_{3}\)/10\({}^{3}\) Nm\({}^{3}\)-Biogas. The uncertainty range of the NH\({}_{3}\) emission factor determined using these values at the 95% confidence level was between \(-\)5.7\(-\)6.3% (Figure 5). In this study, NH\({}_{3}\) emission factors for biogas production facilities were not developed based on N, which is different from overseas, so it was difficult to compare the emission factors except for some studies. However, it was possible to estimate the uncertainty because EMEP/EEA provides N-based emission factors with upper and lower limits with 95% confidence intervals. Therefore, to compare the level of uncertainty, the range of emission factors in EMEP/EEA was reestablished with uncertainty values and compared (Table 9). In addition, it was  
Figure 4: Uncertainty of the waste base NH\({}_{3}\) emission factor at biogas production facility. Figure 5: Uncertainty of the biogas production base NH\({}_{3}\) emission factor at biogas production facility. difficult to compare with other countries' values because the upper and lower limits of the 95% confidence interval are not presented in the case of other countries or the US EPA. A comparison with EMEP/EEA uncertainties shows that the uncertainty of the emission factors calculated in this study is much lower than the uncertainty of the 95% confidence intervals of the emission factors presented in EMEP/EEA. According to the EMEP/EEA inventory guidebook, an emission factor with an uncertainty range of 10-30% falls under class A, indicating a high level of uncertainty. Therefore, the emission factors calculated in this study are categorized as high with low uncertainty.