Abstract :
[en] Due to the well-known benefits of milk and dairy products, the rapid development of the dairy sector plays a critical role in creating livelihoods, particularly for developing countries. Simultaneously, it supplies massive employment and promotes the agricultural economic development. The increasing demand and consumption of milk and dairy products lead to the intensive development of the dairy industry, along with the enormous amount of manure and sewage generated. Accordingly, the manure and sewage management (MSM) in the dairy sector not only brings considerable challenges of environmental degradation for decision-makers, but also creates opportunities to solve energy crisis and resource depletion issue and provide additional economic and social benefits. In response to a series of policy regulations implemented at both global and national levels, a wide range of dairy MSM strategies have been developed to focus on the improved management of dairy manure and sewage. As a consequence, there is an urgent need for investigating current status of dairy MSM pathways and technologies at both global and national levels, which can benefit to explore environmentally, economically, and socially feasible MSM pathways in the dairy sector.
In this thesis, a comprehensive review and a quantitatively comparative analysis for currently available dairy MSM strategies from a global scale were firstly conducted. The results indicated that the consensus of waste-to-energy pathway could be reached to mitigate global warming, eutrophication, and ecotoxicity potential remarkably. For the detailed technologies, anaerobic mono-digestion and its integrated technologies have varying degrees of impacts on reducing global warming and eutrophication potential. However, uncertain impacts for the majority of MSM pathways and detailed technologies were revealed. It indicated that the necessity is required to perform comprehensive trade-off analyses for determining the appropriate MSM pathways towards circularity and sustainability.
Secondly, taking China as an example, current technological status and performances of typical dairy MSM technologies were systematically reviewed. These MSM technologies cover the whole management chain based on the field survey of large-scale dairy farms in China, including collection, storage, manure and sewage processing and utilization stages. The analysis results highlighted the need of exploring suitable dairy MSM pathways covering the whole management chain for the government, which should maximize recycling and utilization efficiencies of various nutrients from dairy manure and sewage.
Thirdly, in order to identify key pathways to simplify the high diversity of dairy MSM strategies in China, a quantitative typology methodology using a series of data mining techniques was employed. Based on the nationwide survey data of 306 scale dairy farms in China, the results revealed four key MSM pathways. They include low-specialized and traditional (LTM), specialized and recycled (SRM), specialized and diversified (SDM), and semi-specified and biogas project (SBM) modes. The key pathways identified benefit the informed decision-makings of developing effective policies towards the sustainable development and circular economy.
Fourthly, the characteristics of general information, bio-physical resource endowments, socio-economic characteristics, production management traits, and attitude and policy subsidies among the four pathways were explored to reveal the potential determinants which might affect the decision-making of dairy farmers’ dairy MSM selection. The statistical results showed that most of indicators in terms of resource endowments, milk productivity and quality, and costs and benefits showed a clear and consistently increasing trend among four pathways (i.e. LTM<SBM<SDM<SRM). The results indicated that resource endowment availability and intensification degree are potential factors of decision-making. Moreover, the up-scaling level of sustainability and policy evaluation from farm individual scale to a higher scale is feasible based on these pathways.
In conclusion, the results of the present thesis revealed the necessity of determining appropriate dairy MSM pathways from different scales, which is expected to have the maximum nutrient recycling and utilization from manure and sewage, together with optimally overall benefits by balancing environmental, economic, and social impacts. The mathematical modelling of policy evaluation is particularly required to consider decision-making process of individual dairy farmers and sustainable impacts induced by various technologies and practices along the whole management chain.
