| With China's vigorous implementation of the "rural revitalization strategy",the comprehensive utilization model of energy and resources has become an important link of agricultural supply-side structural reform.Due to large differences between different cases of comprehensive utilization model,there is generally a lack of reference and comparability.In order to further build a methodology system for evaluation and optimization of comprehensive utilization model,it's necessary to explore risk resistance and sustainable development capabilities of the above model through a reasonable evaluation model.The paper conducted a retrospective analysis of potential connections between EMA and LCA based on different perspectives.Based on relevant research cases,the feasibility of the coupling development of the two was demonstrated.Em-LCA evaluation model was constructed,and analyzed two cases of comprehensive utilization model.The study found that economic emergy output of scenario A accounted for 96.22%,while economic emergy output of scenario B was 62.04%,indicating that scenario B lost a large amount of emergy because of waste without of utilization,that is,the supplementary chain of scenario A effectively improved the economic performance of target system.The ELR of both scenarios is lower than 5,indicating that two scenario cases will not cause irreversible functional degradation of target system area.The EER indicator of scenario A is 57%higher than that of scenario B,indicating that integrated waste utilization system could achieve higher economic benefits.This paper also conducted a comparative analysis of the two models of EMA and Em-LCA.Taking scenario A as an example,the study found that ESI indicators of both models are higher than 1,proving that target system is on a sustainable development level.Sustainability indicators(EISD and ESI)evaluated by EMA model are both 45%higher than those of Em-LCA model.Further elaboration,this part of difference is mainly reflected by ELR indicator.That is,downstream emergy caused significant environmental load,which will reduce sustainability of target system.In addition,this paper discussed sustainability between two scenarios.Taking Em-LCA model as an example,ESI indicator of scenario A is 9%higher than that of scenario B,and its EISD indicator is 71%higher than that of scenario B,indicating that EISD could be more clearly characterizing the differences between systems,and reasonable supplementary chain is also supported.Through multi-level recycling of material and energy,emergy fixed in waste resources(such as strew and manure)could be exacted in form of high-grade resources or energy,which could improve system performance and increase its sustainability.In order to make up for shortcoming of EMA and Em-LCA model in environmental impact assessment,target system was evaluated by LCA model.The study found that environmental impact of end point of scenario A is similar to scenario B,indicating that multi-level material recycling would not increase regional environmental load.The ecosystem impact accounts for 64%of end point effects of comprehensive utilization model.Therefore,in order to reduce environmental impact and optimize regional ecological performance,optimization analysis of this part should be focused on.This paper is guided by the "3R" principle,based on proportion of various emergy streams,combined with sensitivity analysis,to identify system's key emergy streams.Sustainable performance optimization model based on donor-side perspective is provided.Based on proportion of environmental impact of each process,key processes is identified,and environmental impact optimization model based on user-side is provided.This paper analyzed impact on the five key indicators by raising or lowering five types of input emergy.Emergy flow of raw material and equipment accounts for the highest proportion and highest sensitivity.After it rises 10%,EYR decreased by 6.97%and EER decreased by 6.97%,EMA model's ELR increased by 7.45%,ESI decreased by 13.42%,and EISD decreased by 19.45%.Em-LCA model's ELR increased by 5.13%,ESI decreased by 11.51%,and EISD decreased by 17.68%.It shows that Em-LCA model has stronger anti-interference ability and more comprehensive indicator connotation.Introduction of ecological services emergy and environmental impact emergy has positive significance for natural ecosystems sustainability assessment.Based on EMA model and Em-LCA model,this paper conducted optimization analysis on donor-side perspective.Based on LCA model,optimization analysis on user-side perspective is conducted.Results show that optimization of the two perspectives have a high degree of consistency in some aspects.For example,expanding the scale of planting,adopting intercropping,and adopting technical methods to improve recycling of resources within target system,etc.It shows that from the perspective of improving system sustainability or improving environmental performance,above advices should be used as the focus of optimization.In addition,the degree of recombination between the various subsystems of comprehensive utilization model should be improved,the industrial chain should be reasonably supplemented,and material-level utilization should be realized,thus improving degree of connection between the various subsystems and making their industrial coupling closer.In short,on basis of improving the economic performance,reduce regional environmental pollution,improve sustainability performance,thus improving anti-risk ability of comprehensive utilization model.Optimal design scheme of comprehensive utilization model based on "3R" principle could provide a scientific basis for relevant systematic reviews,and could provide a new perspective for similar research. |
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