| Studies and practices on circular agriculture has been currently a hot spot of agriculture research in China, and there are various models of circular agriculture in different areas at present. Therefore, how to design a reasonable and scientific assessment method for circular agriculture is significantly important to promote its development in China. Aiming at a issue that a standard and quantitative assessment method for the circular agriculture has been still lacking presently, this study introduces life cycle assessment (LCA) into the EME to construct an EME-LCA framework for the comprehensive assessment of circular agriculture in China. The main results are listed as follows:(1) This study standardizes and improves the following aspects from theory point, including the calculation of environmental service, allocation of outputs emergy and classification of resource inputs, establishing a standards and models for synthesis studies of circular agriculture. As indicated in this study, effects on soil and water resources in field derived from agriculture practices can be calculated by the balance of water and organic matter in field. At the same time, based on characteristics of circular agriculture, this study indicates that outputs that can and can not make work to the following systems are useful products and by-products, respectively. Among the useful products, the outputs derived from structure break are viewed as splicts, and the ones resulted from different physic, chemical and biological processes are viewed as co-products, which are allocated emergy based on the emergy rules 2 and 3, respectively. The emergy of by-products equals to the total emergy of original inputs of the system. Moreover, due to the "emergy emformation", the emergy of bioenergy and information should be totally allocated on new outputs, and the emergy of organic matter of recycled agricultural wastes should be allocated on new outputs. Meanwhile, the renewability factor of recycled agricultureal waste should be viewed as 100.0% in emergy evaluation. The improvements above, to some extent, resolve a fact that benefits of recycling agricultural wastes, such as manure, crop straw, can not be reflected reasonably in the traditional EME.(2) Constructing an EME-LCA framework which is applicable to evaluate the circular agriculture models. The framework constructs "4R-indices" to evaluate the reduction, reuse, recycle and regulation level, as well as "system-indices" to reflect the comprehensive performance of circular agriculture system, which can respectively assess the situation of energy consumption and emissions of circular agriculture systems. By introducting life cycle inventory database into the EME method, the framework is helpful to supplement the database of the EME. At the same time, this study "splits" the circular agriculture system, by adopting life cycle thinking into the EME, to find the key points of regulating energy-saving and emissions-reducing, and to optimize the systems. Furthermore, the approach of accounting for environmental potential impacts in the LCA is introduced into the EME to supplement the drawback of the EME which does not focus on the emissions of systems.(3) Case studies show that the comprehensive performance of circular agricultural models(CM) is better than that of non-circular models (NCM), and also show that the EME-LCA framework is applicable to the assessment of circular agriculture in China. This study analyzes a "plant - livestock - biogas" CM in Jinlong farm in Heber provience based on the EME-LCA framework. The results show that, compared to the NCM, the "reduction, reuse, recycle and regulatiton" levels of the CM in Jinlong farm increase by 10.0%-97.9%, the emergy support ratio of the CM increases by 281.2%, the potential environmental impacts index of the CM reduces by 34.5%, and the emergy sustainability index of the CM is 83.6% higher that of the NCM. Moreover, if the CM was optimized by regulating the irrigation, fertilization, the source of maize and electricity, the "reduction, reuse, recycle and regulatiton" levels of the CM in Jinlong farm would be increased by 40.2%-72.1%, the emergy support ratio of the CM would be increased by 33.4%, the potential environmental impacts index of the CM would be reduced by 17.1%, and the emergy sustainability index of the CM would be increased by 88.7%, compared to the original results.Generally, the EME-LCA framework constructed on the basis of standardization of theory is applicable to reflect the "recycling benefits" and the "energy-saving and emissions-reducing" level, providing a reference of method for the assessment of circular agriculture in China... |
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