Utilization of livestock manure in Denmark and its inspiration for planting-breeding combined circular agricultural development in China

Abstract: Denmark is leading in advanced animal biowaste engineering and management in the world. The comprehensive system of livestock manure utilization in Denmark can achieve planting-breeding balance and the fertilize capacity requirement, which can not only protect the healthy development of animal husbandry, but also promote the development of cropping industry. This review summarized the present situation of animal biowaste utilization technologies, specially the technical proposal of the planting-breeding balance and technologies to reduce ammonia emissions from livestock production in Denmark. The main successful experience of scientific management concept, law and regulation system, advanced technologies and utilization pattern of Danish manure management were also analyzed. The scientific management concept of manure utilization in Denmark is life-cycle pollution control during the manure utilization. Fertilizers and animal manures must be applied in the proper seasons and methods to promote the absorption of nutrients. In areas of intensive animal production, nutrients in the manure may contribute all or a substantial proportion of the local or regional fertilizer demand and some manure nutrients may even be in excess of local demand, requiring the alternative utilization to avoid the environmental overload. The overall objective of the Danish regulations on the livestock production and management of animal manures is to achieve sustainable recycling of manures in order to reduce emissions of nutrients and pollutants to the environment. Since the 1980s, Danish incentives and regulations had reduced losses of nitrogen and enhanced the use efficient of manure nitrogen, which had substituted large amounts of mineral fertilizers. The livestock farms and farmers in Denmark must ensure the amount of nutrients calculated not to exceed the allowed limits for their crops according to Danish harmony rules for the nutrient management. Farms with a livestock herd in excess of this density must have written contracts with neighbouring stockless farms, where the manure could be applied. The advanced technologies and corresponding equipment of animal waste utilization were encouraged for the investigation and application, including the solid-liquid separation of animal slurry, the ammonia and malodorous gases abatement, nutrient leaching from application and measures for reduction, technologies and logistics for handling, the transport and distribution of animal manures. Also, the life cycle assessment methodology had been applied to compare alternative manure management technologies in Denmark. There are a lot of specialists in environmental technologies and management of animal wastes, in industry and consultancy work, the agricultural advisory service and the public service. The mature utilization pattern and strategies for the efficient recycling of manures as a means of reducing leaching and runoff loss of the nutrients were also established. Nowadays, the widely used fertilizer and plenty of animal manures have brought some negative environmental impacts while increasing crop yields in China. The intention of this article is to introduce the biological, physical and chemical processes controlling pollution from the animal production and technologies needed to manage animal wastes in Denmark. Those environmentally friendly technologies for managing animal waste efficiently and in a sustainable manner are worth learning and using for reference for planting-breeding combined circular agricultural development in China.