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Development of ammonia mass transfer coefficient models for the atmosphere above two types of the slatted floors in a pig house using computational fluid dynamics
Rong, L. ; Aarnink, A.J.A. - \ 2019
Biosystems Engineering 183 (2019). - ISSN 1537-5110 - p. 13 - 25.
Airflow pattern - Ammonia emission - CFD - Mass transfer coefficient - Pig houses
Ammonia emissions from animal production systems are a concern due to their potential adverse effects on the environment. It is important for governments to adjust their policies to control ammonia emissions from animal production. To evaluate and quantify emission factors, process-based modelling is a cost-effective procedure, particularly due to the complex and diverse transfer chains. During the modelling process, ammonia mass transfer coefficient is one of the key parameters to be determined. However, inconsistencies are found in widely used expressions for mass transfer coefficients in ammonia volatilization models. This study used CFD simulations to derive the mass transfer coefficients above metal and concrete slatted floor in an experimental pig houses with 12 full-scale pig pens. Five ammonia mass transfer coefficient models were selected for comparison with the models derived from CFD simulations. It was noticed that the models derived from wind tunnel/flux chamber experiments usually predicted lower values of ammonia mass transfer coefficients compared to the models developed from full-scale measurements and/or numerical modelling. Care is needed to extrapolate the relationships developed under controlled laboratory conditions to the commercial barns. The results indicated also that the ammonia mass transfer coefficient relies heavily on the airflow patterns which could be affected by the ventilation systems, location of the inlet and outlets, internal partitions, floor types etc. This makes it very difficult to present a universal ammonia mass transfer coefficient model for pig houses.
A model for estimating seasonal trends of ammonia emission from cattle manure applied to grassland in the Netherlands
Huijsmans, J.F.M. ; Vermeulen, G.D. ; Hol, J.M.G. ; Goedhart, P.W. - \ 2018
Atmospheric Environment 173 (2018). - ISSN 1352-2310 - p. 231 - 238.
Ammonia emission - Application techniques - Grassland - Manure - Model - Weather
Field data on ammonia emission after liquid cattle manure (‘slurry’) application to grassland were statistically analysed to reveal the effect of manure and field characteristics and of weather conditions in eight consecutive periods after manure application. Logistic regression models, modelling the emission expressed as a percentage of the ammonia still present at the start of each period as the response variable, were developed separately for broadcast spreading, narrow band application (trailing shoe) and shallow injection. Wind speed, temperature, soil type, total ammoniacal nitrogen (TAN) content and dry matter content of the manure, application rate and grass height were selected as significant explanatory variables. Their effects differed for each application method and among periods. Temperature and wind speed were generally the most important drivers for emission. The fitted regression models were used to reveal seasonal trends in NH3 emission employing historical meteorological data for the years 1991–2014. The overall average emission was higher in early and midsummer than in early spring and late summer. This seasonal trend was most pronounced for broadcast spreading followed by narrow band application, and was almost absent for shallow injection. However, due to the large variation in weather conditions, emission on a particular day in early spring can be higher than on a particular day in summer. The analysis further revealed that, in a specific scenario and depending on the application technique, emission could be reduced with 20–30% by restricting manure application to favourable days, i.e. with weather conditions with minimal emission levels.
Assessing fresh urine puddle physics in commercial dairy cow houses
Snoek, Dennis J.W. ; Stigter, Hans ; Blaauw, Sam K. ; Groot Koerkamp, Peter W.G. ; Ogink, Nico W.M. - \ 2017
Biosystems Engineering 159 (2017). - ISSN 1537-5110 - p. 133 - 142.
Ammonia emission - Cow urine - Dairy barn - Puddle area - Puddle depth
Ammonia emission from dairy barns can be reduced by measures that improve removal of urine from floors. Information characterizing physical and chemical properties of urine puddles on floors are essential to improve mitigation measures, however information representative for practical barn conditions is scanty. The objective of this paper is to assess the area (A p ) and depth (D p ) of fresh urine puddles in commercial dairy barns, and to investigate the effect of floor type, season and manure scraping on these variables. Sixteen farms were measured in a factorial design of four Floor-Management types (FMTypes). Each farm was measured in two seasons and underwent an intense-floor-cleaning treatment (PREclean) before puddle creation for the D p measurement, which was compared with those created under normal floor conditions with on-farm manure scraping. Overall mean values were 0.83 m2 for A p and 1.0 mm for D p . For both A p and D p the variation within a farm was large but negligible between farms. FMType significantly affected both variables. The V-shaped asphalt floor resulted in larger A p (1.04 m2) and D p (1.5 mm) than those of slatted and grooved floors (mean values 0.76 m2, 0.93 mm). Our study demonstrates that the draining capacity of solid floors is a critical design issue in lowering ammonia emission. The PREclean treatment resulted in D p values that were 3 times lower than values for puddles created under normal floor conditions. We conclude that there is a considerable potential to improve draining of excreted puddles by increasing the cleaning performance of manure scrapers.
Assessing fresh urine puddle chemistry in commercial dairy cow houses
Snoek, Dennis J.W. ; Stigter, Hans ; Kupers, Geert C.C. ; Groot Koerkamp, Peter W.G. ; Ogink, Nico W.M. - \ 2017
Biosystems Engineering 159 (2017). - ISSN 1537-5110 - p. 143 - 153.
Ammonia emission - Cow urine - Dairy barn - PH - Urea concentration
Ammonia emission mainly originates from urea in urine puddles on floors in dairy cow houses. This emission process can be modelled. However, required model inputs have not been updated recently. In addition, values for the model variables pH, Urinary Urea Nitrogen concentration (UUN), and their relation with farm and feed management are unknown for commercial dairy cow houses. Moreover, their effect on ammonia emission is unknown. Therefore, the objective of this paper was to investigate the pH and UUN in livestock practice. Sixteen commercial farms were measured in a factorial design of four Floor-Management types (FMTypes). Each farm was measured in two seasons and a Diet factor was defined, based on the amount of grass in total roughage. Overall mean values were 4.27 kg m-3 for UUN, an initial pH of 8.3, both in fresh puddles, and a pH(ξ) of 9.0 for random puddles at a random time. For UUN both the variation within and between farms was large, whereas the variation for pH was small. The Diet was the only factor that resulted in a significant effect, with a 0.1 difference in pH(ξ). Compared to the reference values, both the mean UUN and pH showed smaller values. The calculated potential ammonia in kg puddle-1, however, showed a huge range and was considerably larger than the commonly used reference values in the Netherlands.
Quantification of simulated cow urine puddle areas using a thermal IR camera
Snoek, Dennis ; Hofstee, Jan Willem ; Dueren den Hollander, Arjen W. van; Vernooij, Roel E. ; Ogink, Nico W.M. ; Groot Koerkamp, Peter W.G. - \ 2017
Computers and Electronics in Agriculture 137 (2017). - ISSN 0168-1699 - p. 23 - 28.
Adaptive threshold - Ammonia emission - Cow urine - Infrared camera - Puddle area
In Europe, National Emission Ceilings (NEC) have been set to regulate the emissions of harmful gases, like ammonia (NH3). From NH3 emission models and a sensitivity analysis, it is known that one of the major variables that determines NH3 emission from dairy cow houses is the urine puddle area on the floor. However, puddle area data from cow houses is scarce. This is caused by the lack of appropriate measurement methods and the challenging measurement circumstances in the houses. In a preliminary study inside commercial dairy cow houses, an IR camera was successfully tested to distinguish a fresh urine puddle from its background to determine a puddle's area. The objective of this study was to further develop, improve and validate the IR camera method to determine the area of a warm fluid layer with a measurement uncertainty of <0.1 m2. In a laboratory set-up, 90 artificial, warm, blue puddles were created, and both an IR and a colour image of each puddle was taken within 5 s after puddle application. For the colour images, three annotators determined the ground truth puddle areas (Ap,GT). For the IR images, an adaptive IR threshold algorithm was developed, based on the mean background temperature and the standard deviation of all temperature values in an image. This IR algorithm was able to automatically determine the IR puddle area (Ap,IR) in each IR image. The agreement between the two methods was assessed. The Ap,IR underestimated the Ap,GT by 2.53% for which is compensated by the model Ap,GT=1.0253·Ap,IR. This regression model intercepted with zero and the noise was only 0.0651 m2, so the measurement uncertainty was <0.1 m2. In addition, the Ap,IR was not affected by the mean background temperature.
Reduction of ammonia emissions from dairy cattle cubicle houses via improved management - or design - bases strategies : A modeling approach
Mendes, Luciano ; Pieters, Jan G. ; Snoek, J.W. ; Ogink, N.W.M. ; Brusselman, E. ; Demeyer, P. - \ 2017
Science of the Total Environment 574 (2017). - ISSN 0048-9697 - p. 520 - 531.
Ammonia emission - reduction - cubicle houses
Given the current scarcity of empirical data on ammonia (NH3) emissions from dairy cattle under different management-
based mitigation techniques, a modeling approach to assess potentialNH3 emission reduction factors is
needed. This paper introduces a process-based model that estimates NH3 emission reduction factors for a dairy
cattle barn featuring single or multiple management-based NH3 emission mitigation techniques, as compared
to another barn, to which no mitigation measure is applied. The model accounts for the following emission mitigation
measures: (a) floor scraping, (b) floor type, (c) floor flushing with water and (d) indoor acidification of
manure. Model sensitivity analysis indicated that manure acidification was the most efficient NH3 emission reduction
technique. A fair agreement was observed between reduction factors from the model and empirical estimates
found in the literature. We propose a list of combinations of techniques that achieve the largest
reductions. In order of efficiency, they are: (a) floor scraping combined with manure acidification (reduction efficiency
44–49%); (b) solid floor combined with scraping and flushing (reduction efficiency 21–27%); (c) floor
scraping combined with flushing and (d) floor scraping alone (reduction efficiency 17–22%). The model is
Dynamic behavior of PH in fresh urine puddles of dairy cows
Snoek, D.J.W. ; Ogink, N.W.M. ; Stigter, J.D. ; Agricola, S. ; De Weijer, T.M. Van; Groot Koerkamp, P.W.G. - \ 2016
Transactions of the ASABE / American Society of Agricultural and Biological Engineers 59 (2016)5. - ISSN 2151-0032 - p. 1403 - 1411.
Ammonia emission - Cow barn - Cow urine - Fresh puddle - PH
Modern livestock farming is an important contributor to ammonia (NH3) emissions. In the Netherlands, 94% of NH3 emissions originate from agriculture, of which 34% is emitted from commercial dairy cow barns. From current mechanistic modeling, it is known that the pH of urine puddles from cows is one of the most important variables in estimating NH3 emissions. However, little pH data are available from commercial cow barns. Therefore, the objective of this study was to investigate pH values and to study their dynamic behavior in fresh, on-floor urine puddles in these barns. To do this, the pH of urine puddles was measured for 4 h per puddle, and a model was developed to describe the pH behavior. In total, 26 fresh puddles were measured from cows at three commercial dairy farms in summer and winter. At farm level, we found initial pH values of 8.1 through 8.4, which increased to 8.9 through 9.4 after 4 h. The pH difference between summer and winter was 0.3 (p <0.05), but this was not confirmed by comparisons at farm level. The pH curves of individual puddles varied substantially and could be fitted by a nonlinear regression model. This model contained correlated coefficients that were able to describe the main, known chemical processes of a urine puddle. However, no linear relationship was found between initial and final pH and thus between coefficients. On average, pH quickly increased initially, declined after 1 h, and became stable around a pH of 9.15. We conclude that a pH curve will better describe the input variable in NH3 emission modeling than the current situation of using a static pH value. Based on this study, we recommend using the mean measured pH curve as input for puddle simulation during NH3 emission modeling of dairy cow barns.
Ammonia emissions from cattle slurries applied to grassland : Should application techniques be reconsidered?
Huijsmans, J.F.M. ; Schroder, Jaap ; Mosquera, J. ; Vermeulen, G.D. ; Berge, H.F.M. Ten; Neeteson, J.J. - \ 2016
Soil Use and Management 32 (2016). - ISSN 0266-0032 - p. 109 - 116.
Ammonia emission - Application techniques - Grassland - Manure - Meadow birds - Shallow injection - Slurry - Soil quality
Ammonia is easily lost after land spreading of livestock slurries. Low-emission techniques entailing injection and trailing shoes have therefore become compulsory in the Netherlands on grassland. There is an argument that the emission of ammonia after surface application is overestimated and that the emission of various other nitrogen (N) compounds, following the prescribed low-emission techniques, is underestimated. Opponents also claim that injection in particular decreases grassland yields due to its negative effect on soil quality and biodiversity. They state that a similar reduction in ammonia emissions could be realized via low-protein dairy cow diets and slurry spreading under favourable weather conditions. This study evaluates these claims and concludes that low-emission techniques reduce the loss of ammonia effectively and increase the availability of N to grassland. There are no indications that low-emission techniques per se have negative effects on soil quality, the productivity of crops and biodiversity. It has also been demonstrated that the efficacy of proposed alternatives is limited.
Assessment of porous media instead of slatted floor for modelling the airflow and ammonia emission in the pit headspace
Yin, Shuo ; Ooster, Bert van 't; Ogink, Nico W.M. ; Groot Koerkamp, Peter W.G. - \ 2016
Computers and Electronics in Agriculture 123 (2016). - ISSN 0168-1699 - p. 163 - 175.
Ammonia emission - Computational fluid dynamics (CFD) - Modelling - Porous media - Slatted floor - Turbulence
In order to reduce the emission, proper understanding of the transportation behaviour of gaseous ammonia inside the slurry pit is required. Numerical simulation by the aid of computational fluid dynamics (CFD) technique can be used for this purpose. However, direct modelling of slatted floors is complicated and may be replaced by the porous media model (PMM) as shown in earlier studies. The objective of our study is to improve the quality of simulation results by PMM, and to assess the effects of air velocity above the slatted floor (as affected by wind), pit headspace height (as affected by amount of slurry in the pit) and sidewall height (as affected by the dairy house sidewall) on the airflow features inside the pit and ammonia emission from the pit. Three different CFD models of a slatted floor were developed to evaluate whether porous media is capable to represent a slatted floor for modelling the airflow inside and ammonia emission from the slurry pit, and to study the effect of turbulence treatment in the porous media on the modelling results: a slatted floor model (SFM) which models the slatted floor as it is, a turbulent porous media model (PMM-T) and a laminar porous media model (PMM-L). Both PMM-T and PMM-L represent the slatted floor by porous media, the PMM-T assumes turbulent airflow and the PMM-L assumes laminar airflow in the porous media. The SFM was verified for a dataset acquired from a 1:8 scale wind tunnel model of the slurry pit. Results showed that the PMM (PMM-T and PMM-L) were able to predict both the airflow features inside the slurry pit and the ammonia emission from the slurry pit if the resistance parameters and flow regime of the porous media were properly set. In comparison to the SFM, the PMM-T predicted the flow pattern better, but overestimated the turbulence intensity and the consequent emission rate. PMM-L performed better in predicting the ammonia emission rate because of the relatively accurate prediction of turbulence intensity. Simulation results also showed that the ammonia emission rate increased with a higher mean airflow velocity, a smaller headspace height and the presence of sidewalls.