基于能值分析的无公害设施蔬菜生产系统效率和可持续性评价

Efficiency and sustainability evaluation of a pollution-free vegetable production system based on emergy analysis

发展无公害蔬菜是提高我国蔬菜品质和安全性、增强蔬菜产业竞争力的重要举措。针对蔬菜生产高投入、高产出的特点,采用能值分析方法对无公害设施蔬菜生产系统两种蔬菜栽培模式进行系统效率和可持续性评价,并与一般蔬菜生产模式进行对比。结果表明,无公害蔬菜生产模式能值利用效率、可更新比例、净能值产出率、食品安全性和可持续发展能力分别比一般蔬菜生产系统平均提高24.3%、24.9%、36.0%、98.2%和3.87倍,环境负载率平均下降64.7%,系统投入的能值货币价值平均降低20.0%。在此基础上,通过情景分析表明,如果进一步综合采用收集降雨用于棚内蔬菜灌溉、沼气发电供给蔬菜灌溉利用、通过标准化管理降低人力投入,可以使现有的无公害生产方式的能值利用效率提高3.4%—10.8%,可持续性提高1.2%—31.7%。该研究也表明,将无公害蔬菜生产纳入我国以沼气为纽带的循环农业发展模式中,实现适度的产业结合与规模化经营,能够较好的提高无公害蔬菜生产的生态经济效益和可持续发展能力。

Substantial development is needed in the production of pollution-free vegetables to ensure the quality, safety, and competitiveness of vegetables in China. In contrast to customary vegetable production, pollution-free production uses organic fertilizers and biological pesticides instead of chemical fertilizers and chemical pesticides. This mode of production improves the safety of the vegetables and reduces environmental pollution, and the government is encouraging its use throughout China. Nevertheless, there is still considerable scope for research into efficient and sustainable vegetable production. Emergy evaluation is an effective tool in analyzing the efficiency and sustainability of an ecological system, which addresses the weakness of traditional energy analysis and expresses different forms of energy using a common physical basis, namely, solar emergy. It also has the advantage of taking into consideration aspects such as natural resources, labor,and ecosystem services that are generally left uncalculated by other evaluation methods. This paper evaluated the efficiency and sustainability of a pollution-free vegetable production system based on emergy analysis, and results were compared with those of a customary vegetable production system. At the same time, the renewability factor of each input item was introduced in this study to improve analysis of the types of energy input. The emergy input structure and energy-based indices such as emergy efficiency （UEV）, renewability （R）, net emergy yield ratio （EYR）, environmental loading rate （ELR）, product safety index based-emergy （PSI）, emergy sustainability index （ESI）, and emergy-based monetary value （EmRMB） were analyzed to estimate the efficiency and sustainability of the pollution-free vegetable system, and to determine the key points affecting the ecological performance of the system. The results showed that the total energy input of the two modes of the pollution-free vegetables production system were 4.97× 1016 sej/year and 4. 12 × 1016 sej/year, respectively. Compared with the customary vegetable production system, the UEV, EYR, ~R, EPSI, and ESI values of the pollution-free vegetable production system rose on average by 24.3%, 24.9%, 36.0%, 98.2%, and 387.0%, respectively; and on average the ELR value declined by 64.7% and the EmRMB by 20.0%. At the same time, we found that that labor input and irrigation were the core factors that affected the efficiency and sustainability of the system. The scenario analysis revealed that the emergy efficiency and sustainability of the current pollution-free vegetable production system could be improved by 3.4%--10.8% and by 1.2%--31.7%, respectively, by creating an efficient system capable of adjusting to changes such as collection of rainfall to irrigate vegetables in a greenhouse, usage of electricity from a biogas project to irrigate, and reducing the labor input by applying standardized management. From an economic point of view, the reduction in purchased inputs and the higher price of pollution-free vegetables can be beneficial to the farmer. Moreover, the study demonstrates that the introduction of pollution-free vegetable production into recycling agriculture and the usage of biogas slurry as the main fertilizer have positive economic and ecological effects. Consequently, there is a considerable prospect for the development of pollution-free vegetables in China. The results also indicated that emergy evaluation is an effective method to analyze the vegetable ecological system and could provide a useful tool in the development of pollution-free vegetable production in China