Regulation of modern "grass-sheep-field" agro-pastoral cycle system based on life cycle assessment

Modern circular agriculture aims to minimize the number of external outputs for less impact on the environment in the complex ecosystem and the circular economy of the industry chains. Therefore, the green development of agriculture can be achieved to promote rural revitalization in China. However, accurate data support and parameter matching are still lacking in most operation of circular agriculture. Fortunately, the life cycle assessment can serve as an effective tool to evaluate the environmental impact of the entire chains in the product systems, further improving the circulating efficiency of the systems in recent years. In this study, an empirical investigation using the life cycle assessment was performed on the modern “straw-sheep-cropland” agro-pastoral system located in the northeast of Suzhou, Jiangsu Province, China. Six types of potential environmental impacts were evaluated from the sufficient data collection and tracking survey using the data characterization, standardization, and weighted summation, including the acidification potential, global warming potential, terrestrial ecotoxicity, human toxicity, freshwater aquatic ecotoxicity, and eutrophication potential. And then the environmental service energy was compared for the emission degradation before and after the regulation. The energy was calculated to consume the pollution dilution for a safe concentration. The results showed that fertilization was an important factor in the environmental performance of the cereal cropping subsystem during the wheat- and rice-growing seasons. The types of potential environmental impacts from the feed producing and sheep raising subsystems were more than 85% of the total impacts, which were much higher than that of the cereal cropping and organic composting subsystems. The environmental impacts of human toxicity and freshwater aquatic ecotoxicity were greater in each subsystem, whereas, that of terrestrial ecotoxicity was the least. After life cycle assessment, the annual environmental service energies of air, water, and soil to realize the emission degradation were 7.42×1010, 6.03×1016, and 1.59×1012 J, respectively, according to the threshold concentration of index pollutants. Subsequently, the scales of feed producing and organic composting subsystems were adjusted in line with the matching output with the input of successive subsystems, particularly under the steady production scale of cereal cropping and sheep raising subsystems. A simulated regulation was also conducted to optimize the parameters and key technologies. It was estimated that the annual environmental service energies of air, water, and soil were reduced by 52%, 44%, and 21%, respectively, compared with the original. In conclusion, a new system was formed with excellent sustainability and replication to evaluate and regulate the modern agro-pastoral system using the life cycle assessment. The finding can provide a strong reference for the optimal regulation of modern agricultural systems in diverse regions. In the future research, the local life cycle inventory database can be constructed for the life cycle assessment