Characteristics And Mitigation Of NH₃ Emissions From The Combined System Of Intensive Sheep Fattening Operation And Manure Compositing Facility

With the continuous development of China’s breeding scale,the intensive livestock farms are more and more,and this leads to the number of organic fertilizer processing plants is gradually increasing,while the livestock farms and organic fertilizer processing plants become the largest agricultural source of ammonia emission.Ammonia is seriously harmful to the atmosphere environment and humans,therefore,accurately assessing the ammonia emission from livestock farms and organic fertilizer processing plants,clarifying their ammonia emission factors and timely controlling ammonia emission from agricultural sources are of great significance for reducing nitrogen deposition.In this study,an open-path laser instrument,a multifunctional gas analyzer,and an inversion gas diffusion model were combined to determine the ammonia emission characteristics of the mutton sheep farm and nearby sheep manure organic fertilizer processing plants in Tangxian County,Baoding City,Hebei Province,in the winter of 2021 and the spring,summer and autumn of 2022,respectively,clarifying their ammonia emission factors,and the potential for analyzing multiple sources of emissions using the inverse dispersion technique was verified,and then scenario analysis was used to set up ammonia emission reduction technologies for different links of livestock farms and organic fertilizer processing plants to explore their ammonia emission reduction potential.The results show that:(1)This study demonstrated that the combination of inverse dispersion technique and multi-point monitoring technology can quantify the ammonia emission rates of complex sources.Through the analysis of ammonia emission from the empty pens,occupied pens and sheep manure composting plant of sheep farm,it was found that the ammonia emission rate of the sheep pen and the empty pen were(13.91±5.41)kg·hm-2·h-1,(6.72±3.27)kg·hm-2·h-1,respectively,and the ammonia emission rate of the sheep occupied pens was 2.07 times that of the empty pens.The ammonia emission rate of the manure composting plant was(5.32±3.40)kg·hm-2·h-1,which was comparable with the ammonia emission rate of(4.84 kg·hm-2·h-1)obtained by the open-path measurement,indicating that the inverse dispersion technique can accurately discrete multi-source emission rates from animal farms.(2)The variation ranges of ammonia concentration at the boundaries of farms and manure composting plant was clarified.The near-surface ammonia concentrations of the livestock farms in winter,spring,summer,and autumn were 0.37～1.14 mg·m-3,0.28～1.02 mg·m-3,0.33～0.74 mg·m-3 and 0.30～0.84 mg·m-3,respectively.The near-surface ammonia concentrations of the organic fertilizer processing plants in winter,spring,summer and autumn were 0.45～1.08 mg·m-3,0.40～1.41 mg·m-3,0.25～0.70 mg·m-3 and 0.19～1.24 mg·m-3,respectively.(3)The ammonia emission rates of the sheep farms in different seasons were measured.It was found that the ammonia emission rates in winter,spring,summer and autumn were 0.25～0.80 g·head-1·h-1,0.27～1.38 g·head-1·h-1,0.42～1.50 g·head-1·h-1,0.29～1.09 g·head-1·h-1,respectively.The average ammonia emission rate in the daytime(8:30～18:30)was 1.49,1.62,1.26,and 1.20 times of that at night,respectively.Additionally,the ammonia emission of manure in the empty pens accounted for 37.75%of the total ammonia emissions from the sheep farm.(4)The ammonia emission rates of the manure composting plant in different seasons were measured.The ammonia emission rates of manure composting plant in winter,spring,summer and autumn were measured,which were 0.39～0.99 g·t-1·h-1,0.29～1.15 g·t-1·h-1,0.19～0.77 g·t-1·h-1,0.05～0.85 g·t-1·h-1,respectively.The average ammonia emission rate in the daytime(8:30～18:30)was 1.16,1.18,1.18,and 2.73 times that at night,respectively.(5)The ammonia nitrogen emission coefficient of sheep farms and manure composting plant was clarified.The average daily ammonia emission rate of livestock farms was 9.82 g NH3 head-1·d-1,and the ammonia emission factor was 1.52 kg NH3 head-1,the nitrogen loss in the form of ammonia volatilization accounted for 33.68%of the nitrogen excretion from the mutton sheep.The average daily ammonia emission rate of manure composting plant was 13.32 g NH3 t-1·d-1,the ammonia emission factor was 4.86 kg NH3 t-1·yr-1,which accounted for 6.64%of the total ammoniacal nitrogen.(6)The potentials of ammonia reduction in sheep farms and manure composting plant were explored.The ammonia reduction of 56.70%can be achieved by adding lignite additives to the manure in pens and adopting the low-protein diet technology for the feed.The use of biofilter or water curtain technology for the ammonia discharge port of manure composting plant can achieve efficient emission reduction by 91.20%and 90.00%,respectively.In summary,this study shows that the combination of inverse dispersion technique and multi-point monitoring method can accurately discrete the ammonia emission rates of different types of emission sources in farms,and also points out that the ammonia emission of large-scale sheep farm manure generation and compost treatment system can be greatly reduced by timely cleaning sheep manure,optimizing the dietary protein content of sheep feed,and strengthening ammonia emission reduction at the exhaust port of manure composting plant.This study provides a reliable research method and control strategy for ammonia emission and nitrogen loss control in intensive sheep farms,which has important scientific significance for the green and sustainable development of large-scale sheep farms.