| Ammonia(NH3)is the most important alkaline gas and reactive nitrogen compound in the atmosphere and plays a key role in the new particle formation and haze pollution.Atmospheric NH3 deposition can lead to water and soil acidification,ecosystem eutrophication and biodiversity reduction.Livestock farming is being the most important source of NH3 emissions,with pig farming accounting for about 15%of global livestock emissions.The scale of pig farming in China is large,and NH3 emissions from pig farming account for 44%of total livestock emissions.Therefore,controlling NH3 emissions from pig farming is particularly important for NH3 emission reduction from anthropogenic sources in China.Acidification of pig manure with sulfuric acid(H2SO4)is an effective method to reduce NH3 emissions.However,the use of this strong acid has drawbacks.On the other hand,China produces about 40 million tons of acidic waste sludge every year.Acid sludge is diverse,large in quantity and low in utilization,and improper disposal can also cause environmental pollution.In this study,we conducted a study on the use of acid sludge as a substitute for H2SO4 to reduce NH3 in pig farming in response to two problems:huge NH3 emissions from pig farming and difficulty in resource utilization of acid wastes.In this study,pig manure was acidified,and the effects of acidification treatment on NH3 reduction and physicochemical properties of pig manure during storage were analyzed and compared;on the basis of acidification treatment to reduce NH3 emissions,suitable ratios of wine lees and vinegar dregs were selected to acidify pig manure,and aerobic composting was carried out at the end of storage,and NH3 emissions and changes in physicochemical properties of acidified pig manure from acid dregs were further analyzed;the three obtained organic fertilizers and urea were applied to soil,and the NH3 emission and physicochemical property changes of soil after fertilization were investigated,and the acid residue was predicted to reduce NH3 emission from livestock manure in China.The main research results are as follows:(1)During pig manure storage at 25℃ for 30 days,the different acidification treatments significantly reduced the NH3 emission of pig manure.The NH3 emission reduction effect of H2SO4 was better than that of organic acids,the NH3 emission reduction effect of acid residue depended on the addition ratio,and the distiller’s grains were better than vinegar residue;Acidification significantly reduced the pH of pig manure,and the effect of acid residue on the pH of pig manure was different from H2SO4,lactic acid and acetic acid,and the lowest pH in the acid residue treatment group appeared during storage;The addition of acid residue made a large amount of organic acid exist in the pig manure,and the content of most organic acids generated and then degraded;The addition of acid residue made more total carbon(TC)and total nitrogen(TN)in pig manure to be retained,acidification increased the content of soluble phosphorus(SP)in pig manure,and the addition of organic acid and distiller’s grains will increase the amount of total soluble organic carbon(TSOC);The addition of distiller’s grains could slow down the reduction of dry matter(DM)and organic matter(OM)in pig manure and make them more stable.(2)According to the NH3 emission reduction effect,the pig manure with the addition ratio of distiller’s grains(1:3)and vinegar residue(2:3)were selected for aerobic composting.When acidified pig manure was used as compost raw material,the emission of NH3 could be further reduced by 13.3%and 27.2%respectively.The addition of distiller’s grains and vinegar residue could reduced the pH and electrical conductivity(EC)of the compost body,increased the maximum temperature during the composting process,and prolonged the duration of the high temperature period of composting,but the phenomenon of delaying the time when the compost pile enters the high temperature period appeared;The addition of distiller’s grains and vinegar residues increased the final contents of nitrogen(N),organic matter(OM)and soluble phosphorus(SP)in the pile without impact on total soluble organic carbon(TSOC)in endcompost products;Comparing the results with the agricultural industry standard "Organic Fertilizers"(NY-2022503),it was found that the addition of acid residue could not cause heavy metal leaching,and it could not affect the seed germination index of compost products,and improved the total quality of organic fertilizers.(3)The organic fertilizer obtained and urea from aerobic composting were applied to the soil.The application of organic fertilizer could reduce the emission of soil NH3,but the effect of the organic fertilizer added by acid residue was not as good as that of single pig manure organic fertilizer;Organic fertilizers decreased soil pH and increased conductivity(EC),and urea had no effect on pH and conductivity(EC);Second,the three types of organic fertilizer s increased the activities of urease,alkaline phosphatase,alkaline protease,and sucrase in the soil,and also increased the abundance of ammonia-oxidizing archaea(AOA)and ammoniaoxidizing bacteria(AOB)in the soil.(4)In 2016,the total amount of livestock and poultry manure in our country is estimated to be 23.80×1011 kg,and under the manure management scenario of this study,it was estimated that 2.51 Tg(2.51×1011 kg)of NH3 will be produced.If the livestock manure is acidified before storage,distiller’s grains and vinegar residue could reduce NH3 emissions by 0.70 and 0.98 Tg,respectively,which were equivalent to 7.0 and 9.8 times of NH3 emissions from automobile exhaust,and 2.7 and 3.8 times of household coal combustion.2.3 times and 3.3 times the combustion of indoor biomass in China. |
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