## 4 Conclusions  
Ammonia (NH3) emissions from South Korea's waste sector only account for the amount generated in wastewater treatment facilities. However, other countries also consider NH3 emissions from the landfill of solid waste and biogas production. In this study, NH3 emissions from biogas production facilities and the necessity of developing emission factors were reviewed. Additionally, base unit data and related content necessary for developing the NH3 emission factor were reviewed for the biogas production facilities. The emission factors were estimated, and the uncertainty analysis was carried out. Based on the findings of this study, the following points should be considered when developing NH3 emission factors for biogas production facilities in Korea. Consideration of nitrogen-based unit when developing emission factors was found to be easier compared to overseas cases, but such statistical data is currently not available in Korea. The amount of waste processed can be identified statistically, but if two or more types of waste are processed together, the type and amount of waste must be continuously identified. Biogas production has the advantage that the unit load can be unified and activity data can be easily obtained. In this study, we developed and compared emission factors based on waste treatment and biogas production that are readily available in Korea. A total of three biogas production facilities were studied, where NH3 samples were extracted for analysis. Analysis showed that the total ammonia concentration range was between 0.04 and 7.99 ppm. The NH3 emission factor was calculated based on a two-unit \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Classification**} & \multicolumn{2}{c}{**Uncertainty Range**} \\ \hline \multirow{2}{*}{This study} & Waste base NH3 emission factor at biogas production facility & \(-\)4.80\%\(\rightarrow\)7.54\% \\ \cline{2-4}  & Biogas base NH3 emission factor at biogas production facility & \(-\)5.04\%\(\rightarrow\)6.50\% \\ \hline \multirow{4}{*}{EMEP/EEA, 2019} & 5.B.1 & \multirow{2}{*}{Compost production} & \(-\)58.3\%\(\rightarrow\)191.7\% \\ \cline{3-4}  & Compost production & Window composite garden and park waste & \(-\)92.4\%\(\rightarrow\)51.5\% \\ \cline{2-4}  & \multirow{2}{*}{5.B.2} & Biogas production & \(-\)40.7\%\(\rightarrow\)82.2\% \\ \cline{3-4}  & & Pre-storage & \(-\)44.4\%\(\rightarrow\)66.7\% \\ \cline{3-4}  & & Storage of non-separated digestate & \(-\)42.9\%\(\rightarrow\)74.8\% \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison NH3 emission factors uncertainty at biogas production facility. bases. The results showed that the emission factor based on waste were 0.005 kgNH\({}_{3}\)/ton-waste and 0.150 kgNH\({}_{3}\)/10\({}^{3}\) Nm\({}^{3}\)-Biogas. Using the developed emission factors to calculate NH\({}_{3}\) emissions results in a total of 68 tons/year of NH\({}_{3}\) emissions based on biogas production and 144 tons/year based on waste. Given that NH\({}_{3}\) emissions from the waste sector in 2019 were 22 tons/year, emissions from biogas production facilities need to be considered, which requires the development of an emission factor. The uncertainty of the emission factor was \(-\)4.80\(-\)7.54% in the case of emission factor based on waste and \(-\)5.04\(-\)6.50% in the case of emission factor based on biogas. The difference in uncertainty of the emission factor was not significant, but it was lower than the uncertainty of the overseas emission factor (maximum 191%, minimum \(-\)40.7%). Therefore, it would be better to develop and apply national emission factors. Since the unit of analysis for developing emission factors for biogas production facilities is not much different between waste disposal and biogas production in terms of uncertainty, it is recommended to develop emission factors based on biogas production, considering the advantages of consistency of statistical data and administrative aspects.