Key Factors in Measuring Ammonia Emissions with Dynamic Flux Chamber in Barns

sustainability

Article Key Factors in Measuring Ammonia Emissions with Dynamic Flux Chamber in Barns

Seongmin Kang 1 , Yoonjung Hong 1, Moon Soon Im 2, Seong-Dong Kim 3 and Eui-Chan Jeon 4,*

1 Climate Change & Environment Research Center, Sejong University, Seoul 05006, Korea; [email protected] (S.K.); [email protected] (Y.H.) 2 Siheung Green Environment Center, Siheung Business Center, Siheung-Si 15073, Korea; [email protected] 3 Cooperate Course for Climate Change, Sejong University, Seoul 05006, Korea; [email protected] 4 Department of Climate and Environment, Sejong University, Seoul 05006, Korea * Correspondence: [email protected]; Tel.: +82-2-3408-4353

Received: 17 July 2020; Accepted: 3 August 2020; Published: 4 August 2020

Abstract: In this study, measurement methods for estimating the NH3 emissions in barns and the development of different emission factors were reviewed, and the factors to be considered when applying a dynamic flux chamber approach were analyzed. First, one of the factors to be considered when applying the dynamic flux chamber was determined as the stabilization time in the chamber. As a result of the experiment, it was confirmed that the concentration in the chamber stabilized after 45 min. This is considered to take longer than the stabilization time of 20 min suggested in the previous study. The second is the choice of the measurement method. This method includes real-time measurement and the indophenol method. As a result of the experiment in both methods, the ammonia flux showed a difference of about 10%, so both methods are considered to be considered. Therefore, it is judged that the methodology should be selected according to the situation, such as weather or electric power secured at the barn site. In the future, if studies on whether the stabilization time in the chamber can be changed according to seasonal factors and ambient temperature, and based on a sufficiently large sample size, the results will contribute to improving the reliability of the estimated ammonia(NH3) emissions and the development of an emissions factor for use in the livestock sector in Korea.

Keywords: PM 2.5 secondary sources; livestock; ﬂux chamber method; ammonia measurement method; ammonia ﬂux

1. Introduction

1.1. Background and Purpose The annual mean concentration of PM2.5 in Korea was 24 µg/m3 in 2018, which ranked 27th highest among the 73 countries surveyed by AirVisual. When compared with those of Organization for Economic Cooperation and Development (OECD) member countries, the PM2.5 concentration of Korea was the second highest after Chile (24.9 µg/m3), indicating the second poorest air quality among OECD member countries. This level of concentration was analyzed to be nearly twice as high as that of other major developed nations, such as the United States (9.0 µg/m3), the United Kingdom (10.8 µg/m3), Japan (12.0 µg/m3), and France (13.2 µg/m3)[1]. One of the causes of the increased concentration of PM2.5 is an increase in secondary products contributing to the generation of ﬁne dust. Substances involved in the second generation of ﬁne dust include ammonia (NH3), nitrogen oxides (NOx), sulfur oxides (SOx), and Volatiile Organic Compounds (VOCs) [2–5]. In Korea, air pollutants have been monitored and controlled through related policies

Sustainability 2020, 12, 6276; doi:10.3390/su12156276 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 6276 2 of 12 such as the “Comprehensive Air Quality Improvement Plan” and “Regulation System on the Total Amount of Air Pollutant [6–8].” However, these policies focus on controlling the amounts of NOx and SOx among those substances contributing to the second generation of fine dust, and there have been few studies related to the identification of the sources of ammonia (NH3) emissions or the application of emission factors when adequately considering the environment in Korea. NH3 emissions in Korea totaled 301,303 tons as of 2016, of which NH3 from the agricultural sector accounted for approximately 78.7%. In the agricultural sector, the NH3 emissions in the livestock sector amounted to 217,464 tons, accounting for approximately 92% of the NH3 emissions in this sector, and thus an accurate estimation and management of such emissions is important [9]. Regarding the estimation of NH3 emissions in Korea, the emission factors developed by the U.S. Environmental Protection Agency (EPA) and CO-oRdinated INformation on the Environment in the European Community-AIR (CORINAIR) in Europe have mainly been applied. In addition, there are many missing emission sources that have yet to be identified. In this regard, there is a growing need for research into the identification of such missing sources as well as the development of an NH3 emission factor properly reflecting the characteristics of the Korean environment [10,11]. In this study, an NH3 measurement method applicable to the estimation of NH3 emissions in barns and the development of different emission factors are reviewed. In addition, the factors to consider when applying the widely used dynamic flux chamber method were analyzed [12].

1.2. Review of the Ammonia Measurements Methods in Barns

Barns are one of the main sources of NH3 emissions, and large amounts of NH3 are emitted from cattle sheds, pigsties, and poultry farms. Because the generation of NH3 in a livestock field may vary depending on the type of barn and operation method applied, in addition to the type of livestock, the use of an appropriate measurement method is important [13,14]. Methods applicable to the measurement of NH3 generated in barns include a tracer gas method, flux chamber method, PMU (Portable Monitoring Unit) method, and SMDAE (Saraz Method for Determination of Ammonia Emissions), descriptions of which are listed in Table1. Among such methods, for naturally ventilated or open-type barns, tracer gas, and flux chamber methods are mainly used. In Korea, the development of an NH3 emission factor in cattle and pig breeding facilities was calculated using a dynamic flux chamber. Therefore, in this study, the dynamic flux chamber method was also investigated, and the factors to be improved when considering the previous application of this method were analyzed.

Table 1. Description of an NH3 measure method in a barn.

Measure Method Description Reference Method of measuring flow direction and flow velocity by injecting trace gas and Trace Gas method [15,16] monitoring the concentration of trace gas overtime at the measurement location. Measurement is made by continuously creating a monitoring system considering PMUs (Portable the relationship between carbon dioxide production and oxygen consumption of [17,18] monitoring unit) animals, respiratory rate (representative value), the total mass of livestock in the facility, carbon dioxide production from feces, and heat and moisture production. Using a polyurethane sponge sampler (20 cm in diameter and 2 cm in thickness), SMDAE (Saraz Method a uniform mesh composed in the opposite direction was formed in the side for Determination of [19,20] (sidewall) opening of the building, uniformly distributed sampling, and the Ammonia Emissions) sampled sponge was measured for NH3 using the Kjeldahl method. The flux chamber method is basically a method of accumulating gas discharged through the surface of a medium into space (internal chamber volume) partitioned by a researcher. There is a method to calculate the concentration change rate (dC/dt) inside the chamber over time or to calculate the concentration Flux chamber Method [21–24] value after the concentration inside the chamber reaches equilibrium. In general, chambers are often used for measuring greenhouse gases (CH4,N2O) and Ammonia for landfills, agricultural lands or cattle farms, and mainly follow the standards of standard equipment provided by EPA. Sustainability 2020, 12, x FOR PEER REVIEW 3 of 13

method to calculate the concentration change rate (dC/dt) inside the chamber over time or to calculate the concentration value after the concentration inside the chamber reaches equilibrium. In general, chambers are often used for measuring greenhouse gases (CH4, N2O) and Ammonia for landfills, agricultural lands or cattle farms, and mainly follow the standards of standard equipment Sustainability 2020, 12, 6276 3 of 12 provided by EPA.

2. Method

2.1. Research Design and Process

This study reviewed previous studies to identify factors for consideration whenwhen measuringmeasuring NHNH33 generated in a barn using a dynamic flux ﬂux chamber. Pilot experiments were conducted in a laboratory after consideringconsidering thesethese identiﬁedidentified factors factors and and improving improving on on them. them. This This study study also also examined examined factors factors to considerto consider in thein the application application of actualof actual samples, samples, and and an an overview overview of theof the related related system system is presentedis presented in Figurein Figure1. 1.

Review of previous research (review of dynamic flux chamber consider factor)

Pre-experiment for dynamic flux chamber application

(Using NH3 standard gas)

Field sampling

Calculation of ammonia flux according to field sample use

Analysis of consideration factors and improvements when applying dynamic flux chamber

Figure 1. ProcessProcess of research procedure for applying a dynamic fluxflux chamber in a barn.barn. 2.2. Analysis of Ammonia in a Dynamic Flux Chamber 2.2. Analysis of Ammonia in a Dynamic Flux Chamber There are two methods to measure the amount of NH3 when using a dynamic flux chamber: There are two methods to measure the amount of NH3 when using a dynamic flux chamber: The The first method is a measurement after sampling the NH3 using an indophenol-based method at the first method is a measurement after sampling the NH3 using an indophenol-based method at the rear rear end of the dynamic flux chamber. The second method is a measurement of the NH3 concentration end of the dynamic flux chamber. The second method is a measurement of the NH3 concentration using real-time measurement equipment at the rear end of the dynamic flux chamber. In this study, using real-time measurement equipment at the rear end of the dynamic flux chamber. In this study, to analyze the factors to consider the application of a dynamic flux chamber in a barn, both methods to analyze the factors to consider the application of a dynamic flux chamber in a barn, both methods for measuring NH3 when applying a dynamic flux chamber were used for analysis. for measuring NH3 when applying a dynamic flux chamber were used for analysis. The dynamic flux chamber was fabricated directly with reference to previous studies and the EPA method [25,26]. The size is 40.64 cm in inner diameter and 17.78 cm in height and is fabricated as an integrated type. Considering the reactivity of NH3, the inner wall of the chamber (total volume of 30 L and a surface area of 0.13 m2) is treated with Teflon. In the upper part, a K-type thermocouple is installed to measure the temperature inside the chamber. A pressure release (0.64 cm bulkhead union) made of Teflon is also installed to make the pressure inside the chamber equal to the atmospheric pressure, and 0.64 cm Teflon tubing is used where the gas flows in and out. Sustainability 2020, 12, x FOR PEER REVIEW 4 of 13

The dynamic flux chamber was fabricated directly with reference to previous studies and the EPA method [25,26]. The size is 40.64 cm in inner diameter and 17.78 cm in height and is fabricated as an integrated type. Considering the reactivity of NH3, the inner wall of the chamber (total volume of 30 L and a surface area of 0.13 m2) is treated with Teflon. In the upper part, a K-type thermocouple is installed to measure the temperature inside the chamber. A pressure release (0.64 cm bulkhead union)Sustainability made2020 of, 12 ,Teflon 6276 is also installed to make the pressure inside the chamber equal to4 ofthe 12 atmospheric pressure, and 0.64cm Teflon tubing is used where the gas flows in and out. In this study, Zero Air (Ultra-high purity air 99.99999%) was used to remove various pollutants In this study, Zero Air (Ultra-high purity air 99.99999%) was used to remove various pollutants contained in the atmosphere that could affect ammonia analysis. The experimental design was made contained in the atmosphere that could aﬀect ammonia analysis. The experimental design was made to allow Zero Air to flow into the open chamber through MFC (Mass Flow Controller) and measure to allow Zero Air to ﬂow into the open chamber through MFC (Mass Flow Controller) and measure the the gas concentration at the outlet. gas concentration at the outlet.

2.2.1.2.2.1. Ammonia Ammonia Analysis Analysis Using Using Continuous Continuous Measuring Measuring Equipment Equipment

In this study, the amount of NH3 was measured using a cavity ring-down spectrometer (CRDS), In this study, the amount of NH3 was measured using a cavity ring-down spectrometer (CRDS), allowingallowing thethe factorsfactors associated associated with with the the installation installation of continuous of continuous measurement measurement equipment equipment in a dynamic in a dynamicflux chamber flux chamber to be investigated, to be investigated, a schematic a schemati diagramc diagram of which of is which shown is inshown Figure in2 .Figure CRDS 2. uses CRDS an usesanalytical an analytical method method that quantifies that quantifies a target componenta target component by analyzing by analyzing the time untilthe time the laser-irradiateduntil the laser- irradiatedinside of theinside analysis of the analysis cell completely cell completely disappears. disappears. It is capable It is capable of a fast of a and fast continuousand continuous real-time real- timemeasurement measurement without without interference interference and is and robust is ro againstbust against changes changes in ambient in ambient temperature, temperature, pressure, pressure,or vibration. or vibration. However, However, in the case in the of acase barn, of thea barn, voltage the voltage may not may be not constant, be constant, and thus and when thus when using usingCRDS, CRDS, it is necessary it is necessary to check to check the power the power supply supply and weather and weather effects. effects.

FigureFigure 2. 2. SchematicSchematic of of the the field ﬁeld setup setup using using the the cavity cavity ring-down ring-down sp spectrometerectrometer (CRDS) (CRDS)..

2.2.2.2.2.2. Ammonia Ammonia Analysis Analysis Method Method Using Using Indophenol Indophenol

InIn an an NH NH33 analysisanalysis method method using using in indophenol,dophenol, the the amount amount of of NH NH33 isis measured measured based based on on the the absorbanceabsorbance of of indophenols indophenols produced produced from from their their reaction reaction with with NH 33 ionsions through through the the addition addition of of phenol-sodiumphenol-sodium nitroprusside nitroprusside and and pent pentacyanoacyano nitrosyl nitrosyl iron iron (III) (III) solutions solutions to to the the sample sample solution solution for for NHNH33 analysis.analysis. TheThe sampling sampling of of NH NH33 waswas conducted conducted in in accordance accordance with with Korea’s Korea’s “Air “Air Pollution Pollution Process Process Test Test Method”Method” and and the the “Odor “Odor Process Process Test Test Method” Method” [27]. [27]. A A schematic schematic diagram diagram of of the the experiment experiment is is shown shown inin Figure Figure 33.. ForFor the the measurement measurement of of NH NH3,3 and, and NH NH3 absorbing3 absorbing liquid liquid (absorption (absorption using using 50 mL50 mL of a 0.5%of a 0.5%boric boric acid acid solution) solution) was was placed placed in a in 50 a mL 50 mL volumetric volumetric flask, flask, and and 45 L45 of L gas of gas was was input input at 3at L 3/min L/min for forapproximately approximately 15 15 min min using using a mini-pump.a mini-pump. The The inhaled inhaled samplesample isis transferred to a a volumetric volumetric flask, flask, thethe total total volume volume is is 50 50 mL, mL, and and 10 10 mL mL of of this this is is tran transferredsferred to to a a test test tube. tube. To To the the sample sample solution solution for for analysis,analysis, add add 5 mL ofof aa SodiumSodium Pentacyanonitrosylferrate Pentacyanonitrosylferrate (III) (III) Dihydrate, Dihydrate, shake shake vigorously, vigorously, mix mix 5 mL 5 mLof a of sodium a sodium hypochlorite hypochlorite solution, solution, and stand and atstand room at temperature room temperature for 1 h. Additionally, for 1 h. Additionally, the absorbance the absorbanceof the solution of the was solution measured was at ameasured wavelength at a of wavelength 640 nm using of a640 spectrophotometer nm using a spectrophotometer (Shimadzu 17A, (ShimadzuKyoto, Japan). 17A, The Kyoto, experimental Japan). The method experimental using the me indophenol-basedthod using the indophenol-based approach is shown approach in Figure is2. This method has the advantage of being able to adjust to the location and field situations as flexibly as possible, but it may be difficult to obtain continuous data because the process can apply only one sample every 15 min. Sustainability 2020, 12, x FOR PEER REVIEW 5 of 13 shown in Figure 2. This method has the advantage of being able to adjust to the location and field situations as flexibly as possible, but it may be difficult to obtain continuous data because the process canSustainability apply only2020 ,one12, 6276 sample every 15 min. 5 of 12

FigureFigure 3. 3. SchematicSchematic of of the the field ﬁeld setup setup using using the the indophenol indophenol method method..

2.3.2.3. NH NH3 3FluxFlux Estimation Estimation in in a aBarn Barn

TheThe method method of of calculating the NHNH33 ﬂuxflux ofof thethe househouse waswasreferred referred to to as as the the equation equation presented presented in inEPA EPA and and is asis as shown shown in in Equation Equation (1) (1) [26 [26].].

𝑉 𝐴 𝑄 𝐹𝑙𝑢𝑥 = ×(𝐿V +AC )×𝐶Q (1) Flux𝐴= 𝑉L 𝑉 + C (1) AL × V V × where 𝐹𝑙𝑢𝑥 is NH3 flux in dimensions of mass per area per time (mg/m2/min); 𝐶 is NH3 2 concentrationwhere Flux is NHin dynamic3 flux in dimensionsflux chamber of (mg/m mass per3, convert area per ppm time to (mg mg/m/m /3min);); 𝑄 isC flowis NH rate3 concentration within the 3 3 in dynamic flux chamber3 (mg/m , convert ppm to mg/m ); Q is flow rate within the dynamic flux dynamic flux chamber (m /min); 𝐴 is surface area of the inner walls of the dynamic flux chamber 3 chamber (m /min); A2 is surface area of the inner walls of the dynamic flux chamber above the surface above the surface (mC); 𝐴 is surface area covered of the dynamic flux chamber above the surface 2 2 (m(m2);); 𝑉A L isis volume surface of area the covereddynamic of flux the chamber dynamic (m flux3); chamberand 𝐿 is abovethe loss the term surface by the (m chamber); V is volume wall per of 3 unitthe dynamicarea assumed flux chamber first order (m in); concentration and L is the loss (cm/sec) term by the chamber wall per unit area assumed first order in concentration (cm/sec). 3. Results and Discussion 3. Results and Discussion 3.1. Estimation of Stabilization Time for Dynamic Flux Chamber Application 3.1. Estimation of Stabilization Time for Dynamic Flux Chamber Application To determine the NH3 concentration using a dynamic flux chamber, it is important to first To determine the NH3 concentration using a dynamic flux chamber, it is important to first determine the stabilization time and conduct the measurements using time as a parameter. Therefore, determine the stabilization time and conduct the measurements using time as a parameter. Therefore, in this study, prior to the field application of a dynamic flux chamber, a preliminary experiment was in this study, prior to the field application of a dynamic flux chamber, a preliminary experiment conducted in the laboratory using standard NH3 gas to determine the stabilization time for the was conducted in the laboratory using standard NH3 gas to determine the stabilization time for the concentration in the chamber. concentration in the chamber. The experiment was designed to apply the same conditions as those used in the field The experiment was designed to apply the same conditions as those used in the field measurements, measurements, and 50 ppm (Rigas, Korea) of standard NH3 gas was prepared through dilution with and 50 ppm (Rigas, Korea) of standard NH3 gas was prepared through dilution with Zero Air. The target Zero Air. The target concentrations were 1 and 5 ppm. The input flow of Zero Air and the standard concentrations were 1 and 5 ppm. The input flow of Zero Air and the standard NH3 gas used for NH3 gas used for dilution are shown in Table 2. dilution are shown in Table2.

TableTable 2. 2. GasGas injection injection flow ﬂow rate rate for for stabilization stabilization time time experiment experiment..

STDSTD (Standard (Standard Gas) Gas) Zero Zero Air Air(mL (mL/min)/min) 50 ppm 50 Standard ppm Standard Gas (ml/min) Gas (mL/ min) 1 ppm1 ppm 4900 4900 100 100 5 ppm5 ppm 4500 4500 500 500

To determine the stabilization time of the NH3 concentration in an open chamber, we conducted an experiment using CRDS, an instrument for measuring the continuous NH3 concentration, rather than applying an indophenol-based method. Sustainability 2020, 12, x FOR PEER REVIEW 6 of 13

To determine the stabilization time of the NH3 concentration in an open chamber, we conducted anSustainability experiment2020, using12, 6276 CRDS, an instrument for measuring the continuous NH3 concentration, rather6 of 12 than applying an indophenol-based method.

3.1.1. Stabilization Stabilization of Ammonia Concentration in the Chamber According to Zero Air Input Prior to the stabilization experiment conducted using the standard NH sample as an input, Prior to the stabilization experiment conducted using the standard NH3 sample as an input, another experiment was conducted on the change in NH concentration in the chamber without the another experiment was conducted on the change in NH3 concentration in the chamber without the introduction of Zero Air, asas wellwell asas onon thethe changechange inin thethe chamberchamber afterafter ZeroZero AirAir injection.injection. For stabilization of the NH 3 concentrationconcentration in in the the chamber chamber before before the Zero Air input, continuous CRDS measuring equipment was used, and a mean value of 3-min was applied after the stabilization of CRDS. It was demonstrated that the NH3 concentration remained remained constant constant after after stabilization. stabilization. Stabilized ammonia concentration concentration in in the the chamber chamber before before Zero Zero Air Air was was injected injected is is shown shown in in Table Table 33,, and after stabilization, a total of 180 measurements were made for 3 min. The arithmetic mean and standard deviation were calculated using of meas measurementurement data. As As the the measurement measurement results results indicate, indicate, the average concentrationconcentration ofof NHNH33 inin thethe chamberchamber waswas 5353 ppb, ppb, with with a a minimum minimum value value of of 46 46 ppb ppb and and a amaximum maximum value value of of 61 61 ppb. ppb.

Table 3. Table 3. Ammonia concentration in chambe chamberr before Zero Air injection.injection.

MeanMean (ppb) (ppb) SD SD (Standard (Standard Deviation)Deviation) (%) (%) Min Min (ppb) (ppb) Max Max (ppb) (ppb) MeasuringMeasuring 53 8 46 61 180 53 8 46 61 180

For the stabilization of the NH 3 concentrationconcentration in in the the chamber chamber after after the the input input of of Zero Zero Air, Air, a mean value of 3-min was applied after the stabilization of the CRDS, and it was observedobserved that thethe NHNH33 concentration reached 5 ppb, demonstratingdemonstrating stabilizationstabilization(Figure (Figure 44).). ForFor thethe stabilizationstabilization timetime ofof thethe NH3 concentration inin thethe chamber,chamber, 20 20 min min after after inputting inputting Zero Zero Air, Air, the the concentration concentration was was lowered lowered and andbecame became stabilized. stabilized. Therefore, Therefore, during during application application at the at actual the actual site, whensite, when the NH the3 NHconcentration3 concentration falls fallsto 5 ppbto 5 orppb lower or lower with with Zero Zero Air as Air input, as input, the inside the inside of the of chamber the chamber can be can regarded be regarded as having as having been beenreplaced replaced with Zerowith Air, Zero and Air, it isand therefore it is therefore thought thatthought this stabilizationthat this stabilization factor needs factor to be needs considered to be consideredin actual ﬁeld in actual applications. field applications.

Figure 4. StabilizationStabilization time time of of ammonia ammonia concentration according to zero air input input..

3.1.2. Stabilization Stabilization of Ammonia Concentration in the Chamber According to Standard Gas For the experiment conducted on the stabilization of the NH concentration within the chamber For the experiment conducted on the stabilization of the NH3 concentration within the chamber according toto thethe standard standard gas gas input input based based on aon value a value of 5 ppm,of 5 ppm, a pre-determined a pre-determined ﬂow rate flow (4500 rate mL (4500/min for Zero Air, and 500 mL/min for NH at 50 ppm) was set in each MFC, and a certain amount (2 mL/min) mL/min for Zero Air, and 500 mL/min3 for NH3 at 50 ppm) was set in each MFC, and a certain amount was(2 mL/min) ﬁrst vented was withoutfirst vented passing without through passing the chamber, through and the thechamber, concentration and the was concentration then measured was using then CRDS. When the NH concentration falls below 5 ppb by the Zero Air input with reference to the measured using CRDS.3 When the NH3 concentration falls below 5 ppb by the Zero Air input with results of the previous experiment, the inside of the chamber is considered to have been replaced with Zero Air, after which the standard NH3 gas is also input through the MFC. Regarding the stabilization Sustainability 2020, 12, x FOR PEER REVIEW 7 of 13 Sustainability 2020, 12, x FOR PEER REVIEW 7 of 13 Sustainabilityreference to2020 the, 12 results, 6276 of the previous experiment, the inside of the chamber is considered to 7have of 12 beenreference replaced to the with results Zero of Air,the previous after which experiment, the standard the inside NH3 ofgas the is chamberalso input is consideredthrough the to MFC. have Regardingbeen replaced the stabilizationwith Zero Air, of the after standard which NHthe 3standard gas, the moment NH3 gas at iswhich also theinput NH through3 concentration the MFC. in oftheRegarding the chamber standard the was stabilization NH measured3 gas, the ofto moment thebe co standardnstant at which after NH the 3a gas, NHcertain the3 concentration momentincrease wasat which in thought the chamberthe toNH be3 wasconcentrationthe measuredmoment the toin beinsidethe constant chamber of the after chamber was a measured certain had increase become to be wascocompletelynstant thought after replac to a be certain theed and moment increase stabilized. the was inside The thought ofresult the to chamberof be the the measurement, moment had become the completelyshowninside of in the Figure replaced chamber 5, revealed and had stabilized. become that the completely The concentration result replac of the wased measurement, and stabilized stabilized. at shown 4.9The ppm result in Figurewithin of the5 ,approximately measurement, revealed that the concentration was stabilized at 4.9 ppm within approximately 45 min after injection of the 5 ppm 45shown min afterin Figure injection 5, revealed of the 5 that ppm the standard concentration NH3 gas. was stabilized at 4.9 ppm within approximately standard45 min after NH injection3 gas. of the 5 ppm standard NH3 gas.

Figure 5. Stabilization time of ammonia concentration in the chamber according to STD (standard Figuregas) 5 ppm. 5.5. StabilizationStabilization timetime of of ammonia ammonia concentration concentration in in the the chamber chamber according according to STD to STD (standard (standard gas) 5gas) ppm. 5 ppm. The experiment conducted on the stabilization of the NH3 concentration in the chamber accordingThe experiment experimentto the 1 ppm conducted conducted standard on gason the input stabilizationthe stabilization was conducted of the of NH thein3 concentrationthe NH same3 concentration manner in the as chamber that in ofthe the accordingchamber 5-ppm tostandardaccording the 1 ppm gas to standardtheexperiment 1 ppm gas standard after input setting was gas conducted input the pre-determ was in conducted theined same flow mannerin the rate same as (4900 that manner mL/min of the as 5-ppm thatfor Zero of standard the Air, 5-ppm and gas experiment after setting the pre-determined ﬂow rate (4900 mL/min for Zero Air, and 100 mL/min 100standard mL/min gas for experiment NH3 50 ppm) after in setting each MFC.the pre-determ As shownined in Figure flow rate 6, the (4900 measurement mL/min for results Zero Air,indicate and forthat100 NH mL/minthe3 concentration50 ppm)for NH in3 50 each wasppm) MFC. stabilized in each As shown MFC. at 1 As inppm Figureshown approximately6 in, the Figure measurement 6, 45 the min measurement after results the indicate input results of that indicate 1 ppm the concentration was stabilized at 1 ppm approximately 45 min after the input of 1 ppm standard NH gas. standardthat the concentrationNH3 gas. was stabilized at 1 ppm approximately 45 min after the input of 1 3ppm standard NH3 gas.

Figure 6. Stabilization time of ammonia concentrat concentrationion in the chamber according to STD 1 ppm.ppm. Figure 6. Stabilization time of ammonia concentration in the chamber according to STD 1 ppm. The EPA (1986)(1986) guidelinesguidelines for ammoniaammonia measurement do not mention the stabilization time in the chamber. The EPA Adviento-Borbe Adviento-Borbe(1986) guidelines et et foral. al. (2010)ammonia (2010) conducted conducted measurement a study a study do on not onammonia ammoniamention and the and greenhouse stabilization greenhouse gases time gases in in a inhousethe a chamber. house using using aAdviento-Borbe chamber, a chamber, but, but, etin al. inthe (2010) the chamber, chamber, conducted stabilization stabilization a study timeon time ammonia and and measurement measurement and greenhouse time time gaseswere were in not a covered,house using and, a in chamber, the case ofbut, Kim in et the al. (2020),chamber, (2020), the stabilizationammonia emission time and of liquid measurement fertilizer timewas measuredwere not usingcovered, a chamber, and, in the butbut case notnot of thethe Kim stabilizationstabilization et al. (2020), time.time. the ammonia In many ofemission these studies, of liquid no fertilizer stabilization was measured time was mentioned.using a chamber, The results but not of thethe literaturestabilization review, time. there In many were notof these many studies, studies no in otherstabilization countries time related was Sustainability 2020, 12, x FOR PEER REVIEW 8 of 13 Sustainability 2020, 12, 6276 8 of 12 mentioned. The results of the literature review, there were not many studies in other countries related to the stabilization time of the flux chamber, so it was only possible to compare the results with the tosame the standard stabilization in Korea. time of As the a fluxresult chamber, of comparison so it was with only the possible previous to comparestudies, it the can results be seen with that the it sametakes standardlonger than in Korea.the stabilization As a result time of comparisonof 20 min suggested with the in previous the previous studies, studies it can measured be seen that with it takesthe same longer standard than the stabilizationchamber as timeshown of 20 in min Table suggested 4. This in thedifference previous is studies measured measured by real-time with the samemeasurement standard in chamber this study, as shown whereas, in Table in the4. previous This di fference study, isdata measured were obtained by real-time at intervals measurement of about in this10 min study, using whereas, only one in the concentration previous study, band data through were obtainedthe indophenol at intervals method, of about so it 10 is min judged using as only the onedifference concentration between band the number through of the data indophenol and the numb method,er of so experiments. it is judged as In the this di study,fference it betweenwas judged the numberthat the of uncertainty data and the may number be ofless experiments. because ex Inperiments this study, itwere was judgedconducted that theusing uncertainty two standard may be lessconcentrations, because experiments the stability were of conductedmultiple data using and two data standard through concentrations, real-time measurement. the stability Therefore, of multiple it datais judged and datathat throughthe ammonia real-time concentration measurement. can be Therefore, measured it isonly judged when that there the is ammonia a stabilization concentration time of canabout be 45 measured min for field only whenmeasurement. there is a stabilization time of about 45 min for field measurement.

Table 4.4. Comparison of stabilization time for ammonia concentration.concentration.

ThisThis Study Study NIER (2006) NIER (2006)[28] [28] 45 min45 min 20 min 20 min

3.2. Calculation of NH 3 FluxFlux in in a a Field Field Sample Sample According According to the Application of a Dynamic Flux Chamber In this this study, study, cattle cattle manure manure samples samples were were collected collected from from the the field, ﬁeld, as shown as shown in Figure in Figure 7, and7, andexperiments experiments were were conducted conducted using using a dyna a dynamicmic flux ﬂuxchamber chamber in the in laboratory. the laboratory.

Figure 7. Sampling of the ﬁeldfield sample.sample.

As shown in Figure8 8,, thethe experimentexperiment waswas carriedcarried out out using using the the collected collected cattle cattle manure. manure. ForFor thethe experimental procedure, Zero Air was input before the sample was added to the chamber, and once the NHNH3 concentration was detected at 5 ppb or lower, thethe samplesample waswas added.added. In the case of the indophenol-based method,method, thethe NHNH33 experiment was conducted after placement for more than 45 min, min, as inin thethe previousprevious experimental experimental results. results. In In the the case case of of the the CRDS CRDS method, method, it was it was connected connected directly directly and theand stabilization the stabilization time time was checked.was checked.

3.2.1. NH3 Flux of CRDS in a Dynamic Flux Chamber

The concentration of NH3 was measured through an open chamber and CRDS in a laboratory using the manure collected from a cattle shed. The NH3 concentration was measured by measuring the time required for the concentration to stabilize in the chamber through the CRDS after inputting the manure sample, and it was conﬁrmed that when the ﬁeld sample was used, stabilization occurred after 45 min, as shown in Figure9, which is the same time as before. When there was no change in the NH3 concentration in the chamber for 5 min after stabilization, the value at that time was used to Sustainability 2020, 12, x FOR PEER REVIEW 9 of 13

Sustainability 2020, 12, 6276 9 of 12 calculate the ﬂux. After stabilization, a total of 300 measurements were made for 5 min. The arithmetic

Sustainabilitymean and standard2020, 12, x FOR deviation PEER REVIEW were calculated using 300 pieces of measurement data. 9 of 13

Figure 8. Ammonia flux estimation experiment using a field sample.

3.2.1. NH3 Flux of CRDS in a Dynamic Flux Chamber

The concentration of NH3 was measured through an open chamber and CRDS in a laboratory using the manure collected from a cattle shed. The NH3 concentration was measured by measuring the time required for the concentration to stabilize in the chamber through the CRDS after inputting the manure sample, and it was confirmed that when the field sample was used, stabilization occurred after 45 min, as shown in Figure 9, which is the same time as before. When there was no change in the NH3 concentration in the chamber for 5 min after stabilization, the value at that time was used to calculate the flux. After stabilization, a total of 300 measurements were made for 5 min. The arithmetic mean and standardFigure deviation 8. AmmoniaAmmonia were calculat flux ﬂux estimation ed using expe experiment 300riment pieces using of measurement a field ﬁeld sample sample. data..

3.2.1. NH3 Flux of CRDS in a Dynamic Flux Chamber

The concentration of NH3 was measured through an open chamber and CRDS in a laboratory using the manure collected from a cattle shed. The NH3 concentration was measured by measuring the time required for the concentration to stabilize in the chamber through the CRDS after inputting the manure sample, and it was confirmed that when the field sample was used, stabilization occurred after 45 min, as shown in Figure 9, which is the same time as before. When there was no change in the NH3 concentration in the chamber for 5 min after stabilization, the value at that time was used to calculate the flux. After stabilization, a total of 300 measurements were made for 5 min. The arithmetic mean and standard deviation were calculated using 300 pieces of measurement data.

Figure 9. Ammonia concentration in an open chamber according to a ﬁeldfield sample.sample.

As shown in Table5 5,, the the concentration concentration analysisanalysis resultsresults showedshowed aa meanmean ofof 6.87 6.87 ppm, ppm, aa relative relative standard deviationdeviation ofof 1%,1%, andand aa concentrationconcentration rangerange ofof 6.65–7.056.65–7.05 ppm.ppm.

Table 5. Ammonia concentration of a ﬁeldfield sample by CRDS measurement.measurement.

MeanMean (ppm) (ppm) SD SD (Standard (Standard Deviation)Deviation) (%) (%) Min Min (ppm) (ppm) Max Max (ppm) MeasuringMeasuring 6.876.87 1 6.65 6.65 7.05 7.05 300 300

3.2.2. NH3 Concentration Determined Using the Indophenol-Based Method in a Dynamic Flux ChamberFigure 9. Ammonia concentration in an open chamber according to a field sample. The collection of NH samples using the indophenol-based method was conducted after measuring As shown in Table 5,3 the concentration analysis results showed a mean of 6.87 ppm, a relative the concentration stabilization time in the chamber through the CRDS after inputting the manure standard deviation of 1%, and a concentration range of 6.65–7.05 ppm. sample. Upon stabilization of the concentration, a total of 15 L was passed through the absorbing liquid for 5 min at 3 mL/min using a pump to calculate the NH concentration value, the analysis Table 5. Ammonia concentration of a field sample by CRDS3 measurement. results of which are shown in Table6. AnMean analysis (ppm) of the NH SD 3(Standardconcentration Deviat of theion) cattle-shed (%) Min manure (ppm) sample Max using(ppm) the Measuring indophenol-based method was6.87 conducted after collecting 1 a total of three samples. 6.65 The arithmetic7.05 mean300 and standard Sustainability 2020, 12, 6276 10 of 12 deviation were calculated using three pieces of analysis data. As a result of the analysis, the mean value was 6.25 ppm, the relative standard deviation was 0.27%, and the concentration ranged from 6.24 to 6.27 ppm.

Table 6. Ammonia concentration of a ﬁeld sample by the indophenol method.

Mean (ppm) SD (Standard Deviation) (%) Min (ppm) Max (ppm) Measuring 6.25 0.27 6.24 6.27 3

3.2.3. Comparison of the CRDS and Indophenol Method The CRDS and indophenol-based methods were applied in a dynamic flux chamber to analyze the target NH3 concentration for the field sample, the results of which are shown in Table7. As a result of the analysis, the concentration analyzed using CRDS was 6.87 ppm, and the concentration analyzed using the indophenol-based method was 6.25 ppm, which is a difference of approximately 10%. As a result of calculating the NH3 flux according to the analysis method applied, the NH3 flux using the 2 CRDS method was calculated as 0.52 mg/m /min, and the NH3 flux using the indophenol-based 2 method was 0.48 mg/m /min, a difference in NH3 flux of 10%, which is the same as the difference in concentration.

Table 7. Ammonia ﬂux of a ﬁeld sample according to the analysis method.

Division CRDS Indophenol Method Concentration (ppm) 6.87 6.25 Flux (mg/m2/min) 0.53 0.48

4. Conclusions

In this study, measurement methods for estimating the NH3 emissions in barns and the development of different emission factors were reviewed, and the factors to be considered when applying a dynamic flux chamber approach were analyzed. First, one of the factors to be considered when applying the dynamic flux chamber was determined as the stabilization time in the chamber. As a result of the experiment, it was confirmed that the concentration in the chamber stabilized after 45 min. This is considered to take longer than the stabilization time of 20 min suggested in the previous study. Therefore, it is considered that this should be taken into account when measuring. The second is the choice of the measurement method. This method includes real-time measurement and the indophenol method. As a result of the experiment in both methods, the ammonia flux showed a difference of about 10%, so both methods can be considered. In the case of the Indophenol method, it has the advantage of being able to cope with the location and field situation as flexibly as possible, but it is difficult to obtain continuous data by taking one sample per 15 min, and the degree of stabilization of the concentration in the chamber cannot be checked in real-time. Real-time measurement equipment has an advantage in that data can be obtained in real-time, but in the case of livestock, the voltage may not be constant, so it has the disadvantage of taking care about factors affecting power supply and weather. Therefore, it is judged that the methodology should be selected according to the situation, such as weather or electric power secured at the barn site. About the experiment in this study, the general dynamic flux chamber experiment is mainly conducted following the EPA’s chamber manufacturing specifications, so it is judged that the difference due to volume and related flow rate will not be large. Therefore, the stabilization time of this study could be considered. However, if the size and the flow rate are different, it is considered that the related factors should be additionally considered by referring to the contents of this study. Sustainability 2020, 12, 6276 11 of 12

In addition to the results of this study, if studies such as the diﬀerence in stabilization time according to seasons and ambient temperatures and the number of samples that can be represented in the development of emission factors are conducted, it may contribute to improving the reliability of ammonia inventory in the livestock sector.

Author Contributions: All authors contributed to the research presented in this work. Their contributions are presented below. Conceptualization, E.-C.J.; Methodology and writing—original draft preparation, S.K. and, Analysis, Y.H., M.S.I.; Data curation, S.-D.K. All authors have read and agreed to the published version of the manuscript. Funding: This work is supported by Korea Ministry of Environment (MOE) and Korea Environment Corporation. Acknowledgments: This work is financially supported by Korea Ministry of Environment (MOE) as “Graduate School specialized in Climate Change”. This work was carried out with the support of “Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ01499301)” Rural Development Administration, Republic of Korea. Conflicts of Interest: The authors declare no conflict of interest.

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