基于能值分析评估现代农牧循环系统的构建与优化

发展现代循环农业有助于推动农业生产方式高质量转型,是实现农业可持续发展的重要路径之一。但生产经营者在构建循环农业系统的过程中,因缺乏精确的参数测算,常存在投入产出不明、循环效率偏低、整体评估缺乏等问题,导致现代循环农业系统的物能高效运转面临阻碍。以江苏省太仓市东林村的现代农牧循环系统为对象,在四维时空尺度上界定系统边界并绘制能流图,全面梳理了案例系统全年运转过程中的投入与产出项目。现代“草-羊-田”农牧循环全系统由粮食种植、饲料加工、湖羊养殖与羊粪堆肥4个亚系统构成。通过模拟亚系统逐步结合、系统循环与优化调控的演进过程,采用能值分析方法对农牧系统不同构建阶段的亚系统与全系统的能值投入产出和结构进行定量评估与对比研究。结果表明,在农牧系统产业链逐步构建直至循环生产的过程中,全系统的总能值投入随各亚系统的扩增而有明显增加,系统的物能内部流通率逐渐升高。随后,以废弃物的系统内部消纳为目标,通过强化亚系统间的耦合对现状循环进行优化调控,系统所需的总能值投入有大幅减少,且各亚系统对本地资源的利用程度有明显提升。实证研究定量评估了现代农牧循环系统构建与优化过程中的能值投入与资源利用状况,为系统的高...

Evaluation on construction and optimization of modern agro-pastoral circular system based on emergy analysis

Developing modern circular agriculture is helpful to promote the high-quality transformation of agricultural production mode in China, which is one of the important ways to realize agricultural sustainable development. However, when the agricultural production operators applied the circular agriculture model to the particular system construction, there often occurred problems such as unknown input and output, low circulation efficiency and lack of overall evaluation, which led to obstacles for the efficient operation and material-energy utilization of modern circular agriculture systems. In this study, the modern "straw-sheep-cropland" agro-pastoral circular system of Donglin Village in Jiangsu Province was selected as the research object, due to its typical representativeness in the research of modern circular agriculture. The whole system consisted of 4 subsystems as cereal cropping, feed producing, sheep raising and manure composting. On the four-dimensional spatial-temporal scale, the system boundary was defined by drawing the emergy flow diagram. Hence the input and output items of the case system were comprehensively sorted out covering the entire year operation. On this basis, aiming to simulate the gradual progress of subsystems combination, system circulation and optimal regulation, 4 development stages were set as the separate cropping and raising, the connective cropping and raising (by producing or composting), the present circular, and the optimized circular. Then, the emergy input-output and structure of subsystems along with the whole system in different stages were quantitatively evaluated and comparatively studied by emergy analysis. The results showed that the gross emergy input of the feed production subsystem was the largest among 4 subsystems at the present circular stage, as its designed production scale needed a large amount of corresponding resources such as purchased straw to be invested. Meanwhile, unit emergy value of mutton from the sheep raising subsystem was the highest due to its role of consumer in the ecosystem. During the gradual process of constructing the industrial chain of the agro-pastoral system step by step until circulating production, the gross emergy input of the whole system increased obviously with the augmentation of subsystems, so did the internal circulation rate of material-energy with the development of the system construction. Subsequently, targeted at intra-system absorption of waste, the present circular system was optimally regulated by strengthening the coupling level between subsystems. At the optimized circular stage, system required lower gross emergy input and consumed less external economic resource, which demonstrated a better low emergy consumption characteristic. And the recycling of planting and breeding waste as well as self-sustaining production within the system resulted in significant enhancement of local resources utilization degree in each subsystem. In the meantime, unit emergy values of effective products and by-products produced at this stage all increased, which was mainly on account of the higher emergy level for driving the circulating operation of the system by adding extra material, energy and information. This study quantitatively evaluated emergy input and resource utilization during the construction and optimization process of modern agro-pastoral circular system based on empirical study, which could not only provide parameter support for efficient circulating operation of the system, but also supply accurate guidance for scientific system construction and replicated model promotion of circular agriculture.