Objectives Significant reactive nitrogen (Nr) pollution issues exist in the manure management process of livestock and poultry farming. To explore its long-term evolutionary trends, this study systematically evaluates, from a dynamic perspective, the impacts of socioeconomic development, the application of environmental protection technologies, changes in farming scale, and agricultural policies on the nitrogen footprint (NF) in the swine manure management process.

Methods A system dynamics model targeting the nitrogen footprint of swine manure management was constructed. Six typical ammonia reduction measures were implemented, including low-protein diets, installation of biotrickling filters outside animal housing, acidification during storage, composting additives, and improved fertilization methods (liquid fertilizer injection and solid fertilizer surface application with deep tillage). The individual and combined effects of these measures were analyzed. Furthermore, nine scenarios were considered, encompassing enhanced manure recycling rates and expanded large-scale farming, to dynamically simulate the changing characteristics of the nitrogen footprint in China’s hog farming manure management from 2000 to 2050.

Results Based on per capita Gross Domestic Product (GDP) projections for future hog slaughter volumes, it is predicted that driven by demand growth, China’s hog nitrogen excretion will reach 4.416 million tons by 2050, with a conservative estimate of the nitrogen footprint generated during manure management at 3.957 million tons. The primary sources are land application (38.6%−74.7%) and off-site storage (39.6%−54.2%) stages, with NH₃-N being the main form of loss, accounting for 56.4%. Scenario analysis indicates significant differences in the regulatory effects of various emission reduction technologies. Taking the year 2050 as an example, among the six individual measures, low-protein diets exhibit the best reduction effect, achieving a 16.3% reduction in the nitrogen footprint; followed by improved fertilization methods, with liquid fertilizer injection and solid fertilizer deep tillage achieving reductions of 7.3% and 8.1%, respectively. Manure slurry acidification, by inhibiting NH₃ emissions during storage and land application, can achieve a 7.0% reduction. Given the currently low overall manure treatment rate in China, the nitrogen reduction potential of the composting process is limited (0.08%). Implementing a combination of full-chain ammonia reduction technologies can achieve an overall reduction efficiency of 35.8%. Strengthening the coordinated application of technologies across all stages of manure management is crucial for reducing nitrogen losses in the agro-pastoral system. Increasing the manure recycling rate of large-scale farms from 80% to 90% only reduces the nitrogen footprint by an average of 0.76%, reflecting the current crude fertilization practices and potential pollution risks. If all hogs are transitioned to industrial-scale farming, the nitrogen footprint can be reduced by approximately 6.3% compared to the baseline scenario, with the main reduction contributions coming from storage (115.8%) and housing (47.3%) stages, indicating significant potential for improving the level of large-scale farming in China.

Conclusions China’s hog nitrogen excretion is expected to continue growing in the future, but the system’s nitrogen retention rate is anticipated to improve. Low-protein diets and improved fertilization methods are effective reduction measures, and a combination of full-chain technologies can achieve the maximum reduction benefits. There is still considerable room for optimization in the current large-scale farming manure management, particularly in the fertilization stage.