## 2 Materials and Methods
### Ammonia Emission Factor Development Considerations at Biogas Production Facility  
The emission factor of air pollutants refers to the emission of air pollutants according to unit activity data, i.e., the emission factor of air pollutants in the fuel combustion sector, refers to the emission of air pollutants per unit of fuel burned, and in the case of the production of a substance, the emission of air pollutants per unit of product production is an example.  
Based on the meaning of emission factors, there are two options for biogas production facilities. On the one hand, biogas production facilities utilize waste to produce biogas, so a waste-based emission factor can be developed. On the other hand, since biogas production facilities produce biogas, it would be possible to develop an emission factor based on the production of biogas, i.e., a material like that produced in general manufacturing. However, in other countries, NH\({}_{3}\) emission factors related to biogas production are based on ammonia nitrogen. The source units that may be considered when developing NH\({}_{3}\) emission factors for Korea biogas production facilities are shown in Table 2.  
In this study, we reviewed the units that can be considered for the development of NH\({}_{3}\) emission factors for biogas production facilities in the Korean context.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Classification** & **Unit** & **Description** \\ \hline N-base & kgNH\({}_{3}\)-N/N in & Emission factors are calculated based on \\  & feedstock & NH\({}_{3}\)-N ammonia nitrogen per unit of \\  & & raw material input \\ \hline Waste base & kgNH\({}_{3}\)/tons-waste & Calculate emission factors based on the \\  & & amount of waste (food, animal manure, \\  & sewage sludge) processed \\ \hline Biogas production base & kgNH\({}_{3}\)/10\({}^{3}\) m\({}^{3}\)-biogas & Calculated emission factor based on \\  & & biogas production. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Calculation criteria for developing NH\({}_{3}\) emission factors for Biogas production facilities.  
Figure 1: Sample Collection Schematic for Ammonia Concentration Analysis.  
First, developing emission factors with N-base has the advantage of being able to compare with emission factors related to currently developed overseas biogas production facilities, but it is difficult to reflect these characteristics because ammonia nitrogen is not currently analyzed in Korea, and the types of wastes utilized for biogas production are diverse and in some cases are mixed. In addition, it is difficult to secure continuous activity data. Therefore, it was excluded from the development of emission factors in this study.  
Secondly, the method based on the waste used for biogas production has the advantage of having activity data that can be utilized because the amount of waste disposal related to biogas production is currently collected in Korea. However, with this method, it is difficult to compare similar emission factors developed overseas, and it is a little difficult to consider such a ratio because there are various types of waste used in biogas production, and some are mixed.  
Finally, in the case of biogas production, it can be utilized as an activity data since the production is currently aggregated in Korea, and it has the advantage of being applicable regardless of the type of waste processed, but this method also has the disadvantage that it is difficult to compare with overseas values that have developed emission factors based on ammonia nitrogen.  
In this study, we calculated NH\({}_{3}\) emission factors based on waste and biogas production, a method currently applicable in Korea.