Investigation And Analysis And Evaluation Of Manure Treatment On Dairy Farms In Jiangsu Province

With the rapid development of large-scale dairy farms,the environmental pressure brought by a large amount of feces can not be underestimated.In addition to the possible pollution to water and soil,the greenhouse effect brought by a large number of greenhouse gas emissions also has a huge impact.At present,China proposes that carbon emissions peak before 2030 and achieve carbon neutrality by 2060.Therefore,the impact of different manure treatment modes on carbon emissions of dairy farms at present is worth further exploration.This study of 25 scale dairy farms in jiangsu province is mainly waste processing pattern research,for dairy’s impact on the environment in the process of waste treatment and its carbon footprint,and adopts the method of life cycle assessment（LCA）of two representative to evaluate waste processing pattern,Qian Zhi environmental impact assessment of different patterns,based on life cycle method of the evaluation results,Meta analysis was further used to analyze the effects of different feces treatment methods on greenhouse gas emissions.The results are as follows:（1）According to the investigation of 25 large-scale dairy farms,the main utilization mode of small and medium-sized dairy farms（1000 or less）is"dry dung cleaning-dry dung transportation-waste water storage and return to the field".Large-scale dairy farms mainly adopt two modes:"mechanical dung scraping-solid-liquid separation-solid slag composting-sewage discharge standard"and"mechanical dung scraping-solid-liquid separation-solid slag composting-anaerobic fermentation of wastewater-biogas slurry returning to field and utilization".The removal rate of COD,TN,ammonia nitrogen and TP in the effluent of anaerobic fermentation biogas digester in the second treatment mode is63%to 76%,44%to 57%,47%to 55%and 37%to 51%.The biogas slurry has a high nutrient content and is suitable for returning to the field;The standard discharge of sewage can be divided into two types:the standard treatment of the pipe or farmland irrigation water,and the removal rate of COD,TN,ammonia nitrogen and TP in the standard discharge water is basically stable above 99%,97%,98%and 98%,meet the national emission standards.（2）Taking Guangling Dairy Farm in Yangzhou and Suining Dairy Farm in Xuzhou as the research objects,LCA was used to evaluate the environmental impact of the two treatment modes of standard emission treatment and returning to the field.The greenhouse effect potential（GWP）,acidification potential（AP）and eutrophication potential（EP）of the standard emission mode for 1t dairy cow manure pollution were 124.68kg CO_2eq,0.7kg SO_2eqand 0.12kg PO_4eq^-,respectively.The greenhouse effect potential（GWP）,acidification potential（AP）and eutrophication potential（EP）of 1t dairy cow manure treated by breeding cycle mode were 84.58kg CO_2eq,0.064kg SO_2eqand 0.00162kg PO_4eq^-,respectively.The comprehensive impact of the standard treatment mode on the environment is 4.25 times that of the planting and breeding cycle mode.Using the cost-benefit analysis to evaluate the economic benefits of the two models.The total cost of the dairy farm adopting the standard emission treatment mode was CNY 3400/（year·head）,and the cushion material reuse cost was about CNY 1760/（year·head）,and the net income was CNY 1670/（year·head）.The total cost of the dairy farm adopting the biogas slurry recycling treatment mode is CNY 3026/（year·head）,and the cost saved is about CNY2400/（year·head）by recycling the cushion material.The income generated from the sale of organic fertilizer and biogas power generation is about CNY 380/（year·head）,and the net income is CNY 340/（year·head）.Both in terms of environmental sustainability and economic benefit comparison,the mode of land return utilization is more advantageous.（3）The Meta method was used to analyze the carbon footprint of static composting and anaerobic fermentation.In static composting,the CH₄emission factor was 3.81g（CH₄-C）·kg^-1TC,the CO₂emission factor was 85.64g（CO₂-C）·kg^-1TC,and the N₂O emission factor was 1.69g（N₂O-N）·kg^-1TN.After anaerobic fermentation,the CH₄emission factor was 9.79g（CH₄-C）·kg^-1TC,the CO₂emission factor was 76.75g（CO₂-C）·kg^-1TC,and the N₂O emission factor was 5.72g（N₂O-N）·kg^-1TN during storage and field return.The unit biogas yield during anaerobic fermentation was 0.245 L/g VS.In static compost,corn straw mulching is beneficial to greenhouse gas emission reduction,and in the storage process after anaerobic fermentation,wood mulching is beneficial to greenhouse gas emission reduction.In the process of anaerobic fermentation,corn straw and food residues co-digested with cow dung have better gas production capacity,and anaerobic fermentation is more likely to achieve carbon neutrality.To sum up,the fecal waste treatment modes widely used in medium and large-scale dairy farms are standard discharge and planting and breeding cycle mode,among which the planting and breeding cycle mode has better sustainability.Static composting and anaerobic fermentation are commonly used to treat feces in the mode of returning to the field,and anaerobic fermentation has better carbon emission reduction benefits.