Determination of the mass transfer coefficient of ammonia emissions from dairy open lots using a scale model

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  • Luyu Ding, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
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  • Qifeng Li, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
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  • Chaoyuan Wang, Department of Agricultural Structure and Bioenvironmental Engineering, China Agricultural University, Key Laboratory of Agricultural Engineering in Structure and Environment, Biogas Scientific Research Institute of the Ministry of Agriculture
  • ,
  • Guoqiang Zhang
  • Ruixiang Jiang, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
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  • Ligen Yu, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
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  • Wengang Zheng, Beijing Research Center for Information Technology in Agriculture, Beijing Research Center of Intelligent Equipment for Agriculture
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  • Ronghua Gao, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
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  • Weihong Ma, Beijing Research Center for Information Technology in Agriculture, ?Beijing Academy of Agriculture and Forestry Sciences
  • ,
  • Shirui Zhang, Beijing Research Center for Information Technology in Agriculture, Beijing Research Center of Intelligent Equipment for Agriculture
  • ,
  • Zhengxiang Shi, China Agricultural University, Biogas Scientific Research Institute of the Ministry of Agriculture

Open lots are commonly used to provide outdoor free ranging spaces for dairy cows in many countries such as China and the USA. For this type of operation, the manure characteristics, floor types and environmental conditions, which potentially affect gaseous emissions from manure, are quite different from those of indoor systems. The estimation of NH3 emissions from manure depends greatly on the mass transfer coefficient, an empirical constant determined by environmental factors in the process-based emission model. Using a scale model, this study measured ammonia emissions to be expected from dairy open lots, based on different combinations of different surface air velocities (0.6–2.2 m s−1), air temperatures (15–35 °C) and relative humidity values (20–60%). Based on the two-film theory, the overall mass transfer coefficient (KOL) of NH3 was calculated from directly measured NH3 emission rates and the ammonium nitrogen content, temperature, and pH of manure. As an indicator of the driving potential of gaseous volatilisation, the vapour pressure deficit (VPD) was estimated using air temperature and relative humidity. As the VPD and surface air velocity increased, the measured NH3 emission rates ranged from 1.35 to 19.18 mg kg−1 h−1, and the estimated KOL of NH3 from dairy open lots was within the range of 1.48 × 10−6 – 7.86 × 10−6 m s−1. Using the air velocity and VPD as variables, a non-linear empirical model was developed to estimate the KOL for NH3 emissions from manure on dairy open lots (R2 = 0.69). The normalised mean error of the model was approximately 19.4%.

OriginalsprogEngelsk
TidsskriftBiosystems Engineering
Vol/bind190
Sider (fra-til)145-156
Antal sider12
ISSN1537-5110
DOI
StatusUdgivet - 2020

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