Projections of NH3 emissions from manure generated by livestock production in China to 2030 under six mitigation scenarios

City-level livestock methane emissions in China from 2010 to 2020

Livestock constitute the world's largest anthropogenic source of methane (CH4), providing high-protein food to humans but also causing notable climate risks. With rapid urbanization and increasing income levels in China, the livestock sector will face even higher emission pressures, which could jeopardize China's carbon neutrality target. To formulate targeted methane reduction measures, it is crucial to estimate historical and current emissions on fine geographical scales, considering the high spatial heterogeneity and temporal variability of livestock emissions. However, there is currently a lack of time-series data on city-level livestock methane emissions in China, despite the flourishing livestock industry and large amount of meat consumed. In this study, we constructed a city-level livestock methane emission inventory with dynamic spatial-temporal emission factors considering biological, management, and environmental factors from 2010 to 2020 in China. This inventory could serve as a basic database for related research and future methane mitigation policy formulation, given the population boom and dietary changes.

Vehicular Ammonia Emissions Significantly Contribute to Urban PM2.5 Pollution in Two Chinese Megacities

Ammonia (NH₃) plays a vital role in the formation of fine particulate matter (PM_2.5). Prior studies have primarily focused on the control of agricultural NH₃ emissions, the dominant source of anthropogenic NH₃ emissions. The air quality impact from vehicular NH₃ emissions, which could be particularly important in urban areas, has not been adequately evaluated. We developed high-resolution vehicular NH₃ emission inventories for Beijing and Shanghai based on detailed link-level traffic profiles and conducted atmospheric simulations of ambient PM_2.5 concentrations contributed by vehicular NH₃ emissions. We found that vehicular NH₃ emissions shared high proportions among total anthropogenic NH₃ emissions in the urban areas of Beijing (86%) and Shanghai (45%), where vehicular NH₃ was primarily emitted by gasoline vehicles. Local vehicular NH₃ emissions could be responsible for approximately 3% of urban PM_2.5 concentrations during wintertime, and the contributions could be much higher during polluted periods (∼3 μg m^-3). We also showed that controlling vehicular NH₃ emissions will be effective and feasible to alleviate urban PM_2.5 pollution for megacities in the near future.

Significant contributions of combustion-related NH3 and non-fossil fuel NOx to elevation of nitrogen deposition in southwestern China over past five decades

Anthropogenic nitrogen (N) emissions and deposition have been increasing over past decades. However, spatiotemporal variations of N deposition levels and major sources remain unclear in many regions, which hinders making strategies of emission mitigation and evaluating effects of elevated N deposition. By investigating moss N contents and δ¹⁵ N values in southwestern (SW) China in 1954-1964, 1970-1994, and 2005-2015, we reconstructed fluxes and source contributions of atmospheric ammonium ( NH 4 + ) and nitrate ( NO 3 - ) deposition and evaluated their historical changes. For urban and non-urban sites, averaged moss N contents did not differ between 1954-1964 and 1970-1994 (1.2%-1.3%) but increased distinctly in 2005-2015 (1.6%-2.3%), and averaged moss δ¹⁵ N values decreased from +0.4‰ to +3.3‰ in 1954-1964 to -1.9‰ to -0.7‰ in 1974-1990, and to -4.8‰ to -3.6‰ in 2005-2015. Based on quantitative estimations, N deposition levels from the 1950s to the 2000s did not change in the earlier 20 years but were elevated substantially in the later 30 years. Moreover, the elevation of NH 4 + deposition (by 12.2 kg-N/ha/year at urban sites and 4.6 kg-N/ha/year at non-urban sties) was higher than that of NO 3 - deposition (by 6.0 and 2.9 kg-N/ha/year, respectively) in the later 30 years. This caused a shifted dominance from NO 3 - to NH 4 + in N deposition. Based on isotope source apportionments, contributions of combustion-related NH₃ sources (vehicle exhausts, coal combustion, and biomass burning) to the elevation of NH 4 + deposition were two times higher than volatilization NH₃ sources (wastes and fertilizers) in the later 30 years. Meanwhile, non-fossil fuel NO_x sources (biomass burning, microbial N cycles) contributed generally more than fossil fuel NO_x sources (vehicle exhausts and coal combustion) to the elevation of NO 3 - deposition. These results revealed significant contributions of combustion-related NH₃ and non-fossil fuel NO_x emissions to the historical elevation of N deposition in SW China, which is useful for emission mitigation and ecological effect evaluation of atmospheric N loading.

Immunosuppression, oxidative stress, and apoptosis in pig kidney caused by ammonia: Application of transcriptome analysis in risk assessment of ammonia exposure

Ammonia (NH₃) is a recognized environmental contaminant around the world and has adverse effects on animal and human health. However, the mechanism of the renal toxicity of NH₃ is not well understood. Pigs are considered an ideal model for biomedical and toxicological research because of the similarity to humans in physiological and biochemical basis. Therefore, in this study, twelve pigs were selected as research objects and randomly divided into two groups, namely the control group and the NH₃ group. The formal experiment lasted 30 days. The effects of excessive NH₃ inhalation on the kidney of fattening pig were evaluated by chemical analysis, ELISA, transcriptome analysis and real-time quantitative PCR (qRT-PCR) from the renal antioxidant level, renal function, blood ammonia content and gene level. Our results showed that excessive NH₃ exposure could cause an increase in blood NH₃ content, a reduction in renal GSH-Px, SOD and GSH, as well as an increase in MDA levels and an increase in serum creatinine, urea and uric acid levels. In addition, transcriptome analysis showed that NH₃ exposure caused changes in 335 differentially expressed genes (DEGs) (including 126 up-regulated DEGs and 109 down-regulated DEGs). Some highly expressed DEGs were enriched into GO terms associated with immune function, oxidative stress, and apoptosis and were verified by qRT-PCR. The qRT-PCR results were comsistent with the transcriptome results. Our results indicated that NH₃ exposure could cause changes in renal transcriptional profiles and kidney function, and induce kidney damage in the fattening pigs through oxidative stress, immune dysfunction and apoptosis. Our present study provides novel insights into the immunotoxicity mechanism of NH₃ on kidney.

Inhibition of PI3K/Akt/mTOR pathway by ammonium chloride induced apoptosis and autophagy in MAC-T cell

Ammonia is a harmful gas with a pungent odor, participates in the regulation of a variety of apoptosis and autophagy, which in turn affects the growth and differentiation of cells. To test the regulation of NH₃ on the apoptosis and autophagy of mammary epithelial cells, we selected NH₄Cl as NH₃ donor in vitro model. MTT and CCK-8 assay kits were employed to detect cell activity. Real-time quantitative PCR and western blot methods were used to detect the abundance of inflammatory molecules, apoptosis markers, and autophagy genes. We selected TUNEL kit and the Annexin-FITC/PI method to detect apoptosis. TEM analysis was used to detect autophagic vesicles, and MDC stain evaluated the formation of autophagosome. The results indicated that NH₄Cl reduced cell viability in a concentration-dependent manner and promoted cell inflammatory response, apoptosis, and autophagy. NH₄Cl stimulation notable increased the autophagosomes number. Interestingly, we also detected that the addition of LY294002 and Rapamycin inhibited the PI3K/Akt pathway and the mTOR pathway, respectively, resulting in changes in both apoptosis and autophagy. Therefore, we draw a conclusion that NH₃ may regulate the apoptosis and autophagic response of bovine mammary epithelial cells through the PI3K/Akt/mTOR signaling pathway. Further investigations on ammonia's function in other physiological respects, will be critical to provide theoretical help for the improvement of production performance. It will be also helpful for controlling the harmful gas ammonia concentration in the livestock house to protect the health of dairy cows.

Evaluation of Short-Term Exposure Levels on Ammonia and Hydrogen Sulfide During Manure-Handling Processes at Livestock Farms

Background

Ammonia and hydrogen sulfide are harmful gases generated during aerobic/anaerobic bacterial decomposition of livestock manure. We evaluated ammonia and hydrogen sulfide concentrations generated from workplaces at livestock farms and determined environmental factors influencing the gas concentrations.

Methods

Five commercial swine farms and five poultry farms were selected for monitoring. Real-time monitors were used to measure the ammonia and hydrogen sulfide concentrations and environmental conditions during the manure-handling processes. Monitoring was conducted in the manure storage facility and composting facility. Information on the farm conditions was also collected through interview and walk-through survey.

Results

The ammonia concentrations were significantly higher at the swine composting facilities (9.5-43.2 ppm) than at other manure-handling facilities at the swine and poultry farms, and high concentrations of hydrogen sulfide were identified during the manure agitation and mixing process at the swine manure storage facilities (6.9-19.5 ppm). At the poultry manure-handling facilities, the ammonia concentration was higher during the manure-handling processes (2.6-57.9 ppm), and very low hydrogen sulfide concentrations (0-3.4 ppm) were detected. The air temperature and relative humidity, volume of the facility, duration of manure storage, and the number of animals influenced the gas concentrations.

Conclusion

A high level of hazardous gases was generated during manure handling, and some levels increased up to risk levels that can threaten workers' health and safety. Some of the farm operational factors were also found to influence the gas levels. By controlling and improving these factors, it would be possible to protect workers' safety and health from occupational risks.

Reducing Ammonia Emissions from Dairy Cattle Production via Cost-Effective Manure Management Techniques in China

This study analyzed ammonia reduction potential and related costs and benefits of several ammonia emission reduction technologies applicable for dairy production from cattle in China. Specifically, these included diet manipulation, manure acidification, manure/slurry covers, and solid manure compaction. Ammonia emissions for China were estimated using the GAINS and NUFER models, while mitigation potentials of technologies were determined from laboratory studies. Ammonia reduction potentials from dairy production in China ranged from 0.8 to 222 Gg NH₃ year^-1 for the selected technologies. Implementation costs ranged from a savings of US$15 kg^-1 NH₃ abated to an expenditure of US$45 kg^-1 NH₃ abated, while the total implementation costs varied from a savings of US$1.5 billion in 2015 to an expenditure of a similar size. The best NH₃ reduction technology was manure acidification, while the most cost-effective option was diet optimization with lower crude protein input. For most abatement options, material costs were the critical element of overall costs. The fertilizer value of manure could partly offset the implementation cost of the options tested. Furthermore, benefits due to avoided health damage, as a result of reducing NH₃ emissions, could make all abatement options (except for manure compaction) profitable on the scale of a national economy.

Emissions of ammonia and hydrogen sulfide from typical dairy barns in central China and major factors influencing the emissions

There are few studies on the concentrations and emission characteristics of ammonia (NH₃) and hydrogen sulfide (H₂S) from Chinese dairy farms. The purpose of this study was to calculate the emission rates of NH₃ and H₂S during summer and to investigate influencing factors for NH₃ and H₂S emissions from typical dairy barns in central China. Eleven dairy barns with open walls and double-slope bell tower roofs from three dairy farms were studied. Five different locations in each barn were sampled both near the floor and at 1.5 m above the floor. Concentrations of NH₃ and H₂S were measured using the Nessler’s reagent spectrophotometry method and the methylene blue spectrophotometric method, respectively. NH₃ concentrations varied between 0.58 and 4.76 mg/m³ with the average of 1.54 mg/m³, while H₂S concentrations ranged from 0.024 to 0.151 mg/m³ with the average of 0.092 mg/m³. The concentrations of NH₃ and H₂S were higher during the day than at night, and were higher near the ground than at the height of 1.5 m, and were higher in the manure area than in other areas. NH₃ and H₂S concentrations in the barns were significantly correlated with nitrogen and sulfur contents in feed and manure (P < 0.05), and with temperature inside the barns (P < 0.05). Calculated emission rates of NH₃ ranged from 13.8 to 41.3 g NH₃/(AU·d), while calculated emission rates of H₂S ranged from 0.15 to 0.46 g H₂S/(AU·d). These results will serve as a starting point for a national inventory of NH₃ and H₂S for the Chinese dairy industry.

Concentrations and emissions of particulate matter and ammonia from extensive livestock farm in South China

Atmospheric particulate matter (PM) and ammonia pollution from livestock feeding have gradually become the environmental concerns due to the spring up of livestock farms in worldwide. However, researches about the formation of atmospheric particulate matter related to ammonia are still limited. Therefore, a study to survey the total suspended particles (TSP), PM with the diameter less than 10 μm (PM₁₀), PM₄, PM_2.5, PM₁, and ammonia was conducted at four types of hog houses distinguished by its building design as well as manure handling methods in South China. Four hog houses were monitored during three fattening periods from 2016 to 2017. The emissions of NH₃ per hog house averaged 210.42 μg s^-1. The emissions of PM per hog house averaged 2.017 μg h^-1 for PM₁, 2.149 μg h^-1 for PM_2.5, 2.305 μg h^-1 for PM₄, 3.950 μg h^-1 for PM₁₀, and 9.317 μg h^-1 for TSP. The emissions of PM per hog house average 2.017 μg h^-1, 2.149 μg h^-1, 2.305 μg h^-1, 3.950 μg h^-1, and 9.317 μg h^-1, respectively for PM₁, PM_2.5, PM₄, PM₁₀, and PM₁₀. In each hog house, while the quantity of manure determined the concentration of NH₃, biological fermentation bed was able to control the ammonia volatilization compared with other three manure handling methods. The largest percentage of fine PM (< 10 μm) is produced by the manual waterless method for manure handling. When it came to the manual waterless method, largest amount of fine PM (< 10 μm) was founded to form. Among various contributions of secondary inorganic PM to PM₁, the NH₃ was a dominant factor. Based on our experiment, the absolute concentration of NH₃ was inversely proportional to the concentration of PM₁ when the background influence was removed.