Study On Greenhouse Gas And Ammonia Emission Of Cow Dung During Storage

In recent years,more and more large-scale cattle farms use mechanical separation machines to separate the solid and liquid of the manure so as to improve the utilization efficiency.However,the fractions obtained after separation will be stacked for a period of time before reuse,during which a large amount of greenhouse gases and NH₃ will be emitted.There are few reports on greenhouse gas emissions during the storage of manure after solid-liquid separation,so the study on monitoring of greenhouse gas and ammonia emissions during the storage of fractions before and after solid-liquid separation has certain implications.In this study,beef manure are the research objects.The static chamber method was used to discuss the influence of solid-liquid separation technology on gas emissions in the storage process of manure,and the influence of different factors on gas emissions in the storage process of solid manure,in order to provide technical reference for greenhouse gas and ammonia emission reduction.The results of the study are as following:1.Gas emission monitoring was conducted on the untreated manure、liquid and solid parts of untreated manure,and the gas emission measured results for 90 days showed that:the cumulative CO₂ emissions of untreated manure and liquid and solid parts after solid-liquid separation were 28.2,12.6 and 57.7 g·kg^-1,respectively,and the cumulative CH₄ emissions were 7.65,3.87 and 0.90 g·kg^-1,respectively.The cumulative emissions of N₂O and NH₃ were58.64,13.13 and 28.81mg·kg^-1,respectively,and 10.71,37.64 and 3.21mg·kg^-1,respectively.Carbon dioxide was the main greenhouse gas emitted during storage of the solid fraction（63.78%）.CH₄ was the main greenhouse gas emitted of stored untreated slurry and liquid fraction（83.06%and 87.06%,respectively）.After storage,the greenhouse emissions of untreated manure,liquid part and solid part were 257.98,124.53 and 90.43 g·kg^-1,respectively.The cumulative greenhouse gas emission of untreated manure during storage was significantly higher than that of liquid and solid manure（P<0.01）.After solid-liquid separation,sum of CO₂ emissions of the solid part and liquid part increased by 40.64%,sum of NH₃ emissions of the solid part and liquid part increased by 58.51%,sum of CH₄ and N₂O emissions of the solid part and liquid part decreased by 73%and 62%relative to untreated manure,respectively.The solid-liquid separation led to an decrease of 60%of greenhouse gas emissions to the untreated slurry.2.Tests on solid manure treatment by compaction and covering for 90 days showed:compared with the control group,compacting,covering and combinations of compacting and covering all reduced the cumulative emissions of NH₃ and CO₂ from solid manure during storage,but significantly increased the emission of methane（P<0.01）.The cumulative emission of N₂O from solid manure significantly increased by compacting during storage,But covering significantly reduced the cumulative emission of N₂O during storage.The GHG emissions of untreated solid compost,compacted compost,the untreated solid compost with covering and combinations of compacting and covering during storage were 31.90,78.35,29.95 and 81.03g·kg^-1,respectively.Covering decreased the overall greenhouse effect,but compacting increased the overall greenhouse effect during storage.3.Tests on solid manure treatment by different stacking heights for 90 days showed:the cumulative emissions of CO₂,N₂O and NH₃ for 0.5 m stack height were significantly higher than height of 0.8 m and 1.1 m,but the cumulative emissions of CH₄were extremely significantly lower than height of 0.8 m and 1.1 m（P<0.01）.As the stack height increased,the cumulative emissions of CO₂,N₂O and NH₃ decreased,while the cumulative emissions of CH₄ increased.The GHG emissions at 0.5 m,0.8 m and 1.1 m stacking height was 90.43,95.24 and 108.85 g·kg^-1,respectively.Greenhouse gas emissions were significantly reduced by reducing the stack height（P<0.05）.The accumulation height of 0.5 m has the best effect on reducing comprehensive greenhouse effect.