Estimation of Greenhouse Gas Emission from Hanwoo (Korean Native Cattle) Manure Management Systems

: The agricultural sector is considered one of the major sources of greenhouse gas (GHG) emissions globally. The livestock industry as a signiﬁcant contributor, is accounting for about 18% of GHG emissions measured in carbon dioxide (CO 2 ) equivalent from agricultural practices. Depending on farming practices and climatic conditions, GHGs such as methane (CH 4 ) and nitrous oxide (N 2 O) emissions from livestock agriculture can vary signiﬁcantly. Country-speciﬁc emission factors are, therefore, needed for a precise estimation of GHG emissions and to avoid uncertainties. This study was aimed at estimating the CH 4 and N 2 O emission ﬂuxes from Hanwoo (the most famous and popular Korean native cattle) manure management systems. CH 4 and N 2 O emission ﬂuxes from litter in the Hanwoo cattle barn and composting lot were monitored and calculated for 52 weeks using the dynamic chamber method. The calculated monthly average ﬂuxes of CH 4 and N 2 O from litter in the cattle barn ranged from 0.0 to 30.0 ± 13.7 and 0.896 ± 0.557 to 2.925 ± 2.853 µ g / m 2 s, respectively during the whole measurement period. While during the composting period, the monthly average of CH 4 and N 2 O emission ﬂuxes were varied from 1.449 ± 0.783 to 86.930 ± 19.092 and 0.511 ± 0.410 to 2.629 ± 1.105 µ g / m 2 s, respectively. The calculated emission ﬂuxes of CH 4 and N 2 O from manure management systems in this study were almost 5.4 and 2.1 times, respectively higher than the values reported for the Asian, South and North American countries in the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Overall, this study initiates the process along with signiﬁes the importance of developing country-speciﬁc GHG inventories for the e ﬀ ective reduction of GHG emissions from the livestock sector in Korea.


Introduction
Climate change has been one of the most significant and widely discussed challenges during the last few decades worldwide, with extreme weather patterns, sea level rise, change in ocean currents, and melting icecaps and glaciers [1]. Global climate change caused by greenhouse gas (GHG) emissions has been constantly illustrated with balances of nutrients in the agricultural setting. The livestock industry as a major contributor, is responsible for about 18% of GHG emissions measured in carbon

Chamber Installation, Composting Facility and Data Recording
The surface area of the cattle rearing barn was 736 m 2 and as a dynamic chamber, the barn was sealed and the fans were placed in front and back of the barn for continuous airflow. Three fans were fixed at the center above the main entrance ( Figure 1). Airflow rate from the fan was measured with an air flow capture hood or balometer.
In the present study, the CH4 and N2O emissions from the composting lot was measured using a mega-dynamic chamber. The entire composting lot was covered and equipped with fans for air inflow and outflow similar to the cattle barn GHG estimation system. Figure 2 represents the schematic of the composting facility. Most farms in Korea operate static pile for composting. Hence, the composting facility was designed to simulate composting as close as in practice.

Chamber Installation, Composting Facility and Data Recording
The surface area of the cattle rearing barn was 736 m 2 and as a dynamic chamber, the barn was sealed and the fans were placed in front and back of the barn for continuous airflow. Three fans were fixed at the center above the main entrance ( Figure 1). Airflow rate from the fan was measured with an air flow capture hood or balometer.
In the present study, the CH 4 and N 2 O emissions from the composting lot was measured using a mega-dynamic chamber. The entire composting lot was covered and equipped with fans for air inflow and outflow similar to the cattle barn GHG estimation system. Figure 2 represents the schematic of the composting facility. Most farms in Korea operate static pile for composting. Hence, the composting facility was designed to simulate composting as close as in practice.
Atmosphere 2020, 11, x FOR PEER REVIEW 3 of 13 emission fluxes from the Hanwoo cattle manure management systems using the dynamic chamber method.

Research Site and Description
This research was conducted from 2 November 2018 to 1 November 2019 (365 days; 52 weeks; 93 times sampling) at the Kangwon National University Annex Farm (37°56′24.1" N and 127°46′57.0" E) located in Chuncheon, Korea. During the study, 46 Hanwoo cattle between the ages of 0 and 108 months were reared in a steel-made winch-curtain barn (1071 m 2 ). Sawdust was used as bedding with ±10 cm of thickness at the beginning. A total of 24 pens were used in this study. Each pen had one to four cattle filled in with ad libitum water supply except the pen located in the bottom left ( Figure 1, cross marked), which was used for storing the silage. The housed cattle were fed with roughage, pellets, and concentrates twice a day (09:00 and 17:00).

Chamber Installation, Composting Facility and Data Recording
The surface area of the cattle rearing barn was 736 m 2 and as a dynamic chamber, the barn was sealed and the fans were placed in front and back of the barn for continuous airflow. Three fans were fixed at the center above the main entrance ( Figure 1). Airflow rate from the fan was measured with an air flow capture hood or balometer.
In the present study, the CH4 and N2O emissions from the composting lot was measured using a mega-dynamic chamber. The entire composting lot was covered and equipped with fans for air inflow and outflow similar to the cattle barn GHG estimation system. Figure 2 represents the schematic of the composting facility. Most farms in Korea operate static pile for composting. Hence, the composting facility was designed to simulate composting as close as in practice.  Temperature data from both the cattle barn and composting facility were collected using temperature logger data (HOBO ® Pro v2 Temperature/Relative Humidity Data Logger, Onset, MA, USA), placed inside the chamber and from the Korean Meteorological Data Open Portal (www.data.kma.go.kr), respectively.

Sampling Procedure
The first and last samples from the dynamic chamber were taken on 2 November 2018, and 1 November 2019, accordingly. The samples were taken twice during the week, usually on Tuesday and Friday. On the sampling day, the gas samples were collected three times with triplicates between 9:00 to 15:00 (by 3 h interval). The first sample was taken one hour later of closing the chamber and turning on the fan. The air sample from the inlet and outlet chambers were taken using a 25 mL syringe (Jung Rim Syringe, Jung Rim Medical Industrial Co. Ltd., Seoul, Korea) through a plastic hose (outer diameter = 0.6 mm and inner diameter = 0.4 mm) connected to a pump (Oil-less Diaphragm Pump 35DNS, G&M Tech Inc., Yongin, Korea). The collected samples were stored in 8 mL vacuumed glass-vials (LK LAB KOREA 99429, LK Lab Korea, Namyangju, Korea) and sealed with butyl-rubber septa (Samwoo Kurex ® 15 mm, Samwoo Kurex, Seoul, Korea). The glass vials were vacuumed using a vacuum machine (VALUE ® TF-VE245N, Teddington-France, Villeneuve la Garenne, France) for 5 min [23]. After collection, the glass vials were properly sealed with parafilm and stored for further gas chromatography (GC) analysis ( Figure 3). Temperature data from both the cattle barn and composting facility were collected using temperature logger data (HOBO ® Pro v2 Temperature/Relative Humidity Data Logger, Onset, MA, USA), placed inside the chamber and from the Korean Meteorological Data Open Portal (www.data.kma.go.kr), respectively.

Sampling Procedure
The first and last samples from the dynamic chamber were taken on 2 November 2018, and 1 November 2019, accordingly. The samples were taken twice during the week, usually on Tuesday and Friday. On the sampling day, the gas samples were collected three times with triplicates between 9:00 to 15:00 (by 3 h interval). The first sample was taken one hour later of closing the chamber and turning on the fan. The air sample from the inlet and outlet chambers were taken using a 25 mL syringe (Jung Rim Syringe, Jung Rim Medical Industrial Co. Ltd., Seoul, Korea) through a plastic hose (outer diameter = 0.6 mm and inner diameter = 0.4 mm) connected to a pump (Oil-less Diaphragm Pump 35DNS, G&M Tech Inc., Yongin, Korea). The collected samples were stored in 8 mL vacuumed glass-vials (LK LAB KOREA 99429, LK Lab Korea, Namyangju, Korea) and sealed with butyl-rubber septa (Samwoo Kurex ® 15 mm, Samwoo Kurex, Seoul, Korea). The glass vials were vacuumed using a vacuum machine (VALUE ® TF-VE245N, Teddington-France, Villeneuve la Garenne, France) for 5 min [23]. After collection, the glass vials were properly sealed with parafilm and stored for further gas chromatography (GC) analysis ( Figure 3).

Flow Rate Measurement
To calculate the air flow rate through the chamber, the wind speed profile of the fan drawing air into the chamber was determined using an airflow capture hood or balometer (Alnor ® Electronic Balancing Tool EBT721, TSI Incorporated, Shoreview, MN, USA and AIRFLOW TM Instrument ProHood TM Capture Hood PH721, TSI Instruments Ltd., London, UK). The wind speed was recorded across the surface area of the fan giving a flow rate of 0.848 m 3 /s.

Gas Chromatography Analysis
To investigate the sources and emissions of major GHG (N2O, CH4), accurate concentration analysis was made after sample collection. Gas concentration analysis was performed using a gas chromatograph device to simultaneously analyze N2O and CH4. An electronic capture detector and a pulsed discharge detector (PDD) (VICI PDDs, Valco Instrument Co. Inc., Houston, TX, USA) were equipped in gas chromatography (iGC7200A, DS Science, Gwangju, Korea). For gas analysis, Carboxen 1000 (80/100 mesh, 1.2 m × 1/8 inch) column was used and helium gas with 99.999% purity was introduced as a carrier. Temperature set-up of injector, column, and oven were 50, 160, and 50 °C, respectively. The concentrations of N2O and CH4 standard gas used in this study were 1 ppm and 100 ppm, respectively. Before analysis of the samples, GC calibration was carried out to investigate

Flow Rate Measurement
To calculate the air flow rate through the chamber, the wind speed profile of the fan drawing air into the chamber was determined using an airflow capture hood or balometer (Alnor ® Electronic Balancing Tool EBT721, TSI Incorporated, Shoreview, MN, USA and AIRFLOW TM Instrument ProHood TM Capture Hood PH721, TSI Instruments Ltd., London, UK). The wind speed was recorded across the surface area of the fan giving a flow rate of 0.848 m 3 /s.

Gas Chromatography Analysis
To investigate the sources and emissions of major GHG (N 2 O, CH 4 ), accurate concentration analysis was made after sample collection. Gas concentration analysis was performed using a gas chromatograph device to simultaneously analyze N 2 O and CH 4 . An electronic capture detector and a pulsed discharge detector (PDD) (VICI PDDs, Valco Instrument Co. Inc., Houston, TX, USA) were equipped in gas chromatography (iGC7200A, DS Science, Gwangju, Korea). For gas analysis, Carboxen 1000 (80/100 mesh, 1.2 m × 1/8 inch) column was used and helium gas with 99.999% purity was introduced as a carrier. Temperature set-up of injector, column, and oven were 50, 160, and 50 • C, respectively. The concentrations of N 2 O and CH 4 standard gas used in this study were 1 ppm and 100 ppm, respectively. Before analysis of the samples, GC calibration was carried out to investigate the Atmosphere 2020, 11, 845 5 of 12 precision and reproducibility of the repetition during analysis and each standard gas was analyzed 20 times.

Calculation of Emission Fluxes
The samples (1 mL) were taken from the 8 mL glass-vials using a 1 mL SGE syringe (Trajan Scientific Australia Pty Ltd., Victoria, Australia) to calculate emission fluxes of CH 4 and N 2 O. Each sample was injected three times to obtain N 2 O and CH 4 average concentration. N 2 O and CH 4 fluxes were calculated using the following equations, where FR represents the air flow rate through the chamber (m 3 /s), A is the surface area of emitting materials in the chamber (m 2 ), and ∆C indicates the difference in gas densities in the air inlet and outlet of the chamber (mg/m 3 ).
where (C out − C in ) TGA is the difference in concentration measured using gas chromatography (ppm), p represents the atmospheric pressure (Pa), M indicates the molecular weight of methane or nitrous oxide (CH 4 = 16.04 (g/mol); N 2 O = 44.01 (g/mol)), T is the average temperature of the analyzed air (K), and R shows the universal gas constant (8.314 J/mol K).
To calculate the emission fluxes from litter in the barn, fluxes were measured after removing the litter from the cattle barn and later subtracted from the emission fluxes. In addition, while converting the annual GHG emissions from the Hanwoo cattle manure management systems to CO 2 equivalent, global warming potential values for the 100-year time horizon mentioned in the IPCC Fourth Assessment Report were considered [24].

Statistical Analysis
The graphs were prepared using Sigma plot (version 10, 2007) and statistical analysis was conducted using GraphPad Prism (version 8.4.2, 2020). Data obtained from the cattle barn and composting facility were analyzed with one-way analysis of variance (ANOVA). Multiple comparisons were performed using Tukey's honest significant difference (HSD) post hoc test. A p-value of <0.05 was designated to determine statistical significance. The CH 4 flux in October (29.997 ± 13.692 µg/m 2 s) were higher over the values in the other months, while very low flux was recorded in June ( Figure 4). Generally, the CH 4 flux is influenced by temperature which affects microbial activity; i.e., higher CH 4 emission with high temperature [25,26]. Studies on litter reported that temperature ranges from of 35 to 50 • C was the best for microbial activity, which can be achieved with a litter height of 20 to 30 cm [27,28]. In this study, the shallow height of the litter (10 cm) and relatively low air temperature (below 35 • C) resulted in low CH 4 flux during the summer (Figure 4). Moreover, low CH 4 flux may also be caused by events such as litter mixing (red boxes) and change of bedding materials (green and blue boxes) since such events facilitate air-supply to the litter mixture. Another possible reason for low CH 4 emission during the summer Atmosphere 2020, 11, 845 6 of 12 could be the low moisture content (approximately 12.9%) of the bedding material after replacing the litter and it requires some time to reach the optimal moisture level for CH 4 production as moisture content can influence microbial activity [29]. Furthermore, compaction of the litter by cattle hoofs may prevent increasing the temperature of litter and ultimately results in low CH 4 emission [30]. CH 4 flux from the livestock manure also depends on the amount of manure produced and the part of amount anaerobically decomposes [31]. After replacing the litter (green box in March), CH 4 flux was almost close to zero and then the flux was detected again in the middle of July. Furthermore, following litter mixing, the CH 4 flux down temporarily for a few days and the emission was abruptly increased around 9.534 ± 11.823 µg/m 2 s in August with some fluctuations. Such phenomena might be happened due to the microbial degradation of organic materials for the last three months, which affects the CH 4 flux through the acidification of organic materials [32,33].

Greenhouse Gas Emissions from Litter in the Hanwoo Cattle Barn
Time-specific CH 4 flux in a day was tended to be higher at 09:00 (  The CH4 flux in October (29.997 ± 13.692 μg/m 2 ·s) were higher over the values in the other months, while very low flux was recorded in June ( Figure 4). Generally, the CH4 flux is influenced by temperature which affects microbial activity; i.e., higher CH4 emission with high temperature [25,26]. Studies on litter reported that temperature ranges from of 35 to 50 °C was the best for microbial activity, which can be achieved with a litter height of 20 to 30 cm [27,28]. In this study, the shallow height of the litter (10 cm) and relatively low air temperature (below 35 °C) resulted in low CH4 flux during the summer (Figure 4). Moreover, low CH4 flux may also be caused by events such as litter mixing (red boxes) and change of bedding materials (green and blue boxes) since such events facilitate air-supply to the litter mixture. Another possible reason for low CH4 emission during the summer could be the low moisture content (approximately 12.9%) of the bedding material after replacing the litter and it requires some time to reach the optimal moisture level for CH4 production as moisture content can influence microbial activity [29]. Furthermore, compaction of the litter by cattle hoofs may prevent increasing the temperature of litter and ultimately results in low CH4 emission [30]. CH4 flux from the livestock manure also depends on the amount of manure produced and the part of amount anaerobically decomposes [31]. After replacing the litter (green box in March), CH4 flux was almost close to zero and then the flux was detected again in the middle of July. Furthermore, following litter mixing, the CH4 flux down temporarily for a few days and the emission was abruptly increased around 9.534 ± 11.823 μg/m 2 ·s in August with some fluctuations. Such phenomena might be happened due to the microbial degradation of organic materials for the last three months, which affects the CH4 flux through the acidification of organic materials [32,33].

Estimation of Nitrous Oxide Flux
The variation in average N2O flux from litter in the barn on the sampling days are elucidated in Figure 6. The monthly average of N2O flux was ranged from 0.896 ± 0.557 to 2.925 ± 2.853 μg/m 2 ·s

Estimation of Nitrous Oxide Flux
The variation in average N 2 O flux from litter in the barn on the sampling days are elucidated in Figure 6. The monthly average of N 2 O flux was ranged from 0.896 ± 0.557 to 2.925 ± 2.853 µg/m 2 s during the whole measurement period (November 2018 to October 2019).

Estimation of Nitrous Oxide Flux
The variation in average N2O flux from litter in the barn on the sampling days are elucidated in Figure 6. The monthly average of N2O flux was ranged from 0.896 ± 0.557 to 2.925 ± 2.853 μg/m 2 ·s during the whole measurement period (November 2018 to October 2019). N2O is well known as one of GHGs having high global warming potential with only a small amount. The highest average N2O flux was estimated in November as 2.925 ± 2.853 μg/m 2 ·s, while the lowest was in January as 0.896 ± 0.557 μg/m 2 ·s, respectively. However, the fluctuation of N2O flux was not very different as compared to CH4. The time-specific N2O flux showed the highest level of 1.263 ± 0.948 μg/m 2 ·s at 12:00 but the fluxes in the morning at 09:00 and in the afternoon at 15:00 were slightly low with 1.249 ± 1.072 and 1.211 ± 1.353 μg/m 2 ·s, respectively (Figure 7a). However, no significant difference in time-specific N2O flux was observed during the study period (p > 0.05).  The seasonal variation of N2O flux follows delineates similar trend as that of CH4 flux ( Figure  7b). The average N2O flux (1.870 ± 1.990 μg/m 2 ·s) during the fall season was significantly higher than the other seasonal fluxes (p < 0.05), which indicated that the litter management practices played an important role in N2O emission rather than the temperature. Both aerobic and anaerobic status favor N2O emission from livestock manure with bedding materials [31]. When organic nitrogen and ammonia nitrogen in urine is oxidized into hydroxylamine or nitrite under aerobic conditions, part of the N2O gas can be produced [34,35] or further N2O emission occurs when the oxidized form, nitrate, is reduced under anoxic condition by denitrifier [36]. According to the litter status, simultaneous nitrification and denitrification (SND) may occur under aerobic conditions, whereas events such as litter mixing and change of bedding materials shows influence on GHG emission The seasonal variation of N 2 O flux follows delineates similar trend as that of CH 4 flux (Figure 7b). The average N 2 O flux (1.870 ± 1.990 µg/m 2 s) during the fall season was significantly higher than the other seasonal fluxes (p < 0.05), which indicated that the litter management practices played an important role in N 2 O emission rather than the temperature. Both aerobic and anaerobic status favor N 2 O emission from livestock manure with bedding materials [31]. When organic nitrogen and ammonia nitrogen in urine is oxidized into hydroxylamine or nitrite under aerobic conditions, part of the N 2 O gas can be produced [34,35] or further N 2 O emission occurs when the oxidized form, nitrate, is reduced under anoxic condition by denitrifier [36]. According to the litter status, simultaneous nitrification and denitrification (SND) may occur under aerobic conditions, whereas events such as litter mixing and change of bedding materials shows influence on GHG emission rather than other environmental conditions.

Greenhouse Gas Emissions from Composting Lot
The livestock production and manure management systems in Korea are very different to those of other parts of the world due to regional climate and limited land resources. For example, a pasture-based livestock farm will possibly focus on land spreading for manure management, whereas in barn-based farming system manure cannot be spread in the soil directly, rather the entire manure and bedding is transferred to the composting facility. Composting is done as a manure management strategy to minimize the impact of land spread manure to the environment. The Korean government recommends that prior to land application, cattle manure should stay in the composting lot for over 6 months. Accordingly, the GHG emission from composting lot need to be estimated after measuring from the cattle barn.
Composting in general is an aerobic process. Gas emission under anaerobic condition would therefore be easily to be ignored. However, since manure contains 9-30% solids and 70-91% moisture, the inner space of solid fractions may form anaerobic conditions and favor CH 4 and N 2 O production [37]. In addition, during composting if processes such as turning the composting pile and aeration not performed properly, the GHG emissions increase further [38,39].
Most cattle farms in Korea concentrate on livestock productivity without much consideration of the environmental issues related to manure management. Hence, to reflect the actual farm practices, in this study activities like turning the composting pile or aeration was not performed during composting. The measurement was carried out right after collecting the mixture of manure and bedding materials from the cattle barn to exchange the litter. The variation in average CH 4 and N 2 O fluxes on the sampling days are shown in Figure 8. The monthly averages of CH4 and N2O fluxes ranged from 1.449 ± 0.783 to 86.930 ± 19.092 and 0.511 ± 0.410 to 2.629 ± 1.105 μg/m 2 ·s during the composting period. A different trend in CH4 emission was observed when compared to the emission from litter in the cattle barn with respect to temperature (Figure 9a). During the spring season, CH4 emission was abruptly increased till May along with gradual increment of temperature, of which emission was caused by microbial activity and showed significant difference with other monthly average fluxes (p < 0.05). For N2O, significantly higher emission was also observed in May compared to the other months (p < 0.05) (Figure 9b). Gilroyed et al. explained the detail biological mechanisms of GHG production during the composting process [40]. They showed a typical GHG emission pattern over time with respect to microbial activity, temperature profile, and oxygen (O2) concentration. High CH4 emission was observed at the beginning of composting under thermophilic temperature, while N2O emission profile showed the The monthly averages of CH 4 and N 2 O fluxes ranged from 1.449 ± 0.783 to 86.930 ± 19.092 and 0.511 ± 0.410 to 2.629 ± 1.105 µg/m 2 s during the composting period. A different trend in CH 4 emission was observed when compared to the emission from litter in the cattle barn with respect to temperature (Figure 9a). During the spring season, CH 4 emission was abruptly increased till May along with gradual increment of temperature, of which emission was caused by microbial activity and showed significant difference with other monthly average fluxes (p < 0.05). For N 2 O, significantly higher emission was also observed in May compared to the other months (p < 0.05) (Figure 9b). Gilroyed et al. explained the detail biological mechanisms of GHG production during the composting process [40]. They showed a typical GHG emission pattern over time with respect to microbial activity, temperature profile, and oxygen (O 2 ) concentration. High CH 4 emission was observed at the beginning of composting under thermophilic temperature, while N 2 O emission profile showed the opposite trend with CH 4 . This finding is in line with the results reported by Hao et al. [41]. Rapid consumption of O 2 during composting due to microbial degradation of organic compounds results in a thermophilic condition, which produces CH 4 via methanogenesis [42]. N 2 O can be emitted from the composting pile through both nitrification and denitrification processes [43,44]. In this study, the actual composting process performed in the Korean farms were considered, therefore, the majority of the N 2 O was emitted during composting through nitrification. As the time passes, the temperature of the composting pile reaches to mesophilic levels, and ultimately enables the growth of nitrifying bacteria which are responsible for N 2 O emission.
The monthly averages of CH4 and N2O fluxes ranged from 1.449 ± 0.783 to 86.930 ± 19.092 and 0.511 ± 0.410 to 2.629 ± 1.105 μg/m 2 ·s during the composting period. A different trend in CH4 emission was observed when compared to the emission from litter in the cattle barn with respect to temperature (Figure 9a). During the spring season, CH4 emission was abruptly increased till May along with gradual increment of temperature, of which emission was caused by microbial activity and showed significant difference with other monthly average fluxes (p < 0.05). For N2O, significantly higher emission was also observed in May compared to the other months (p < 0.05) (Figure 9b). Gilroyed et al. explained the detail biological mechanisms of GHG production during the composting process [40]. They showed a typical GHG emission pattern over time with respect to microbial activity, temperature profile, and oxygen (O2) concentration. High CH4 emission was observed at the beginning of composting under thermophilic temperature, while N2O emission profile showed the opposite trend with CH4. This finding is in line with the results reported by Hao et al. [41]. Rapid consumption of O2 during composting due to microbial degradation of organic compounds results in a thermophilic condition, which produces CH4 via methanogenesis [42]. N2O can be emitted from the composting pile through both nitrification and denitrification processes [43,44]. In this study, the actual composting process performed in the Korean farms were considered, therefore, the majority of the N2O was emitted during composting through nitrification. As the time passes, the temperature of the composting pile reaches to mesophilic levels, and ultimately enables the growth of nitrifying bacteria which are responsible for N2O emission.

Greenhouse Gas Emissions from Manure Management Systems
By contrast with other countries, cattle in Korea are mostly raised in the barn due to lack of pasture. The annual emissions of CH 4 and N 2 O fluxes from litter in the barn were 6.192 and 1.242 µg/m 2 s, respectively, from 46 animals in 736 m 2 of cattle barn (3.124 and 0.627 kg CH 4 and N 2 O/animal year, respectively). Furthermore, CH 4 and N 2 O fluxes from litter based on unit animal were 78.1 and 184.2 kg CO 2 eq/animal year, respectively when converted to CO 2 equivalent. On the other hand, the average CH 4 and N 2 O fluxes from the composting lot were 28.037 ± 39.848 and 1.514 ± 1.051 µg/m 2 s, respectively (2.235 and 0.098 kg CH 4 and N 2 O/animal year, respectively). After converting to CO 2 equivalent, CH 4 and N 2 O fluxes from composting lot based on unit animal were calculated as 55.9 and 28.9 kg CO 2 eq/animal year, respectively. Therefore, in total a GHG of 347.1 kg CO 2 eq/animal year was emitted from the Hanwoo cattle manure management systems.

Comparison of Greenhouse Gas Emissions with Intergovernmental Panel on Climate Change (IPCC) Guidelines
According to 2006 IPCC GL for National Greenhouse Gas Inventories [23], the Tier 1 values of manure management CH 4 emission factor for beef cattle in Asia, North America, Western Europe, and South America are 1, 1, 8, and 1 kg CH 4 /animal year, respectively. While for N 2 O, the value is 0.342 kg N 2 O/animal year, with consideration of the manure treatment facilities including liquid treatment (2.5%), solid storage (90.7%), and miscellaneous (6.8%). In this study, annual emissions of CH 4 and N 2 O emission from the Hanwoo cattle manure management systems were almost 5.4 and 2.1 times, respectively higher than the values provided by IPCC. Jo et al. reported that such variation might be attributed to the differences in feeding systems and cattle breeds as the values mentioned by IPCC values were estimated based on the studies conducted mainly in western countries [21]. Country-specific emission factors are, therefore, needed rather than using the values of the 2006 IPCC GL to develop effective and efficient GHG emission reduction strategies for the livestock industries.

Conclusions
This study was conducted to evaluate the GHG emission flux from Hanwoo cattle manure management systems using the dynamic chamber method. CH 4