Analysis Of Ammonia Emission Rate From Intensive Caged-layer Houses Based On In-situ Monitoring Of Gas

Ammonia gas(NH3)is an important precursor of fine particulate matter(PM2.5)and is the"driving force" of air pollution.It is also recognized as one of the most prominent harmful gases in livestock and poultry houses.Poultry has great ammonia emission potential,and is one of the important sources of ammonia emission from livestock and poultry breeding houses in our country.The number of layers in China ranks first in the world,and the NH3 emissions from layer farms account for 17%-26%of the total emissions of animal husbandry.In view of the lack of in situ automatic monitoring technology for ammonia emissions in farming environment,unclear dynamic characteristics of ammonia emissions from laying hen houses and extensive estimation methods for ammonia emissions rate,we firstly constructed a real-time in-situ dynamic monitoring method based on the Internet of things,and developed a rapid and accurate detection method equipment.Then,focusing on the small and medium-sized standardized cages as the research targets,we conducted in-situ online monitoring for 2-3 years,and obtained the data information of main environmental parameters in the shed in different seasons by the method of in situ automatic monitoring,revealing the environmental parameter characteristics and ammonia emission rule in different seasons,different periods and different spaces.Finally,through the correlation analysis between ammonia emission and key environmental factors(temperature,relative humidity,wind speed and CO2 concentration,etc.),the models of ammonia emission rate were constructed and verified for small and medium-sized laying hen houses.The main results of this study are as follows:(1)Establishment of rapid detection method for livestock and poultry breeding environment and development of multi-component in-situ online monitoring equipment.Based on the development of signal processing elements with high sensor and independent intellectual property rights,we established a rapid detection method for main pollutant inhalation chamber,and developed a broad-spectrum practical multi-component in-situ online monitoring equipment for livestock and poultry breeding environment,realizing a box-type real-time data collection of main pollutant indexes(NH3,CO2,etc.),H2S and conventional breeding environment parameters(temperature,humidity,wind speed,etc.).Inhalation detection T90 for NH3 and CO2 was less than 176 s and 45 s.and detection sensitivity was less than 0.135 ?A·ppm-1 and 4 ?A·ppm-1,respectively,realizing the automatic calibration of main pollutants online,and developed the supporting application software and deployed the internet of things system,to provide long-term stability for farms in our country environment comprehensive information technology.(2)The environmental impact factors of NH3 emission rate in the laying hen houses had obvious temporal and spatial differentiation characteristics.Firstly,the seasonal differentiation of environmental impact factors was obvious.The average temperature in summer,winter and spring/autumn of the small and medium-sized standardized cages was 27.9?,8.2? and 21.1?,respectively.The average relative humidity in the laying hen houses in summer was the highest,up to 66.9%.The average relative humidity in winter is similar to that in spring and autumn,which was 47.8%and 48.3%respectively.The average CO2 concentration in laying hen houses was the lowest in summer,only 727 ppm,while it was higher in winter and spring and autumn,with an average concentration of 2550 ppm and 2395 ppm,respectively.Ammonia concentration in hen houses was the highest in winter,with an average concentration of 36.22 ppm,followed by spring and autumn(3.27 ppm)and summer(0.72 ppm).Secondly,the spatial differentiation of environmental impact factors in the laying hen houses was obvious.The environmental parameters of the small and medium-sized standardized caged-layer houses varied from the wet curtain end to the fan end in the longitudinal direction.In summer,temperature,relative humidity,wind speed and NH3 and CO2 concentration showed an increasing trend.In winter,there was no significant difference in temperature,wind speed presented an increasing trend,relative humidity was the highest at the end of wet curtain,NH3 and CO2 concentration was the highest in the middle.There was no significant difference in the house temperature in spring and autumn,and the relative humidity showed a decreasing trend.The concentration of NH3 in the house was the highest,and the concentration of CO2 at the fan end was the highest.The results showed that the ammonia emissions of laying hen houses varied significantly in different seasons and periods.(3)Temperature,humidity,wind speed,NH3 concentration and CO2 concentration have different effects on NH3 emission rate in different seasons,and the influence degree was also different.In the whole,wind speed in summer had a direct effect on NH3 emission rate,while NH3 concentration had an indirect effect.The order of action of influencing factors was that wind speed>NH3 concentration>CO2 concentration>humidity>temperature;In winter,wind speed also had a direct effect on NH3 emission rate,but the effect of NH3 concentration was no longer significant.The order of action of influencing factors was that NH3 concentration>humidity>CO2 concentration,>wind speed>temperature;Wind speed still had a very significant direct effect on NH3 emission rate in both summer and winter,but the difference of them was that temperature had an increased effect on NH3 emission rate,and the order of effect of factors was that wind speed>NH3 concentration>humidity)? CO2 concentration>temperature.Overall,ammonia concentration and wind speed were the main factors affecting the emission rate of laying hen houses.(4)The prediction models for the ammonia emission rate in summer,winter and spring/autumn seasons were constructed,i.e.,Y=72.941 WS+34.495 CNH3-71.580(R2=0.9710,P<0.01),Y=54.233 WS+1.295 CNH3-9.504(R2=0.9920,P<0.01)and Y=1.194 CNH3+0.709(R2=0.8975,P<0.01),Y=60.888 WS+3.921 CNH3-9.565(R2=0.9440,P<0.01)and Y=58.24 WS-0.69(R2=0.7476,P<0.01),respectively.The models were also verified,and the predicted value was highly consistent with the measured value,which provided an estimation method for accurate assessment of NH3 emission from such farms.NH3 emission triggered by intensive laying hens farming has attracted extensive attention in academic circles.In this study,we designed a multi-component in-situ online monitoring equipment,we identified the key environmental impact factors of NH3 emission,and then we built the NH3 emission rate prediction model in the intensive laying hens farm.This study has important theoretical and practical significance for guiding the monitoring,evaluation and emission reduction of ammonia emissions in farms.