## 1 Introduction  
The fine particulate matter concentration in South Korea was 19.1 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\) in 2021, which was higher than the annual average of 5 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\) of fine particulate matter recommended by the World Health Organization (WHO) [1]. Furthermore, this value surpassed the annual average atmospheric environment standard of 15 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\) in South Korea [2]. Therefore, the effective management of fine particulate matter remains a significant area of concern.  
Fine particulate matter is significantly affected by precursor pollutants that intervene in the secondary generation. In South Korea, 72% of fine particulate matter is derived from precursors, which are known to be \(\mathrm{NO_{x}}\) ammonia (NH\({}_{3}\)), and volatile organic compounds (VOCs) [3, 4].  
In South Korea, fine particulate matter mitigation policies consider many aspects, but the management of precursor pollutants is only focused on nitrogen oxide (NO\({}_{\mathrm{x}}\))and sulfur oxides (SO\({}_{\mathrm{x}}\)) [5, 6]. In the case of NH\({}_{3}\), management through the development of national emission factors and real-time measurement is challenging. Currently, there is a significant omission of NH\({}_{3}\) emissions due to the lack of data on its activity and associated emission factors. Therefore, the management of fine particulate matter must involve safeguarding the reliability of NH\({}_{3}\) emissions and relevant inventories in addition to the well-managed precursor pollutants.  
The waste sector among NH\({}_{3}\) emissions only determines the emissions from sources related to wastewater, thereby resulting in a relatively low NH\({}_{3}\) emissions rate, compared to the total emissions. In contrast, other countries include NH\({}_{3}\) emissions from biogas production facilities and landfills in their waste sector emission assessment, which is not the case in South Korea. Regarding biogas production facilities, even in overseas countries, studies have been conducted on whether increasing biogas production or reducing NH\({}_{3}\) or the greenhouse gas CH\({}_{4}\) or related substances affects biogas production, rather than developing NH\({}_{3}\) emission factors used for national emission calculations [7; 8; 9]. However, in the case of Korea, it is difficult to estimate biogas emissions due to the lack of NH3 emission factors. Therefore, it is necessary to develop emission factors before research related to increasing biogas production.  
Overseas emissions account for the NH\({}_{3}\) emissions from biogas production facilities, which are categorized under the waste sector, into their assessment by developing the emissions factor based on nitrogen content. Since NH\({}_{3}\) emissions from biogas are missing in the Korean case, it is necessary to confirm whether it is emitted or not, and to consider whether it is possible to develop an emission factor based on nitrogen as in overseas countries, or whether other factors should be considered. In the case of biogas production facilities in Korea, most of the biogas produced is used as fuel for the facility. In addition, since biogas storage tanks are sealed, NH\({}_{3}\) generated in biogas production facilities is treated by cleaning or combustion to deodorize odors after drying facilities to produce biogas.  
Therefore, this study aims to identify NH\({}_{3}\) emissions from the post-drying process of biogas production facilities in Korea and to approach the need to develop an emission factor. In addition, the reference unit was considered as one of the factors required to develop an emission factor, and an uncertainty analysis was performed to increase the reliability of the determined emission factor.