Study On Life Cycle Assessment Of Large-scale Vegetable Waste Treatment System

Vegetables produce a lot of low-value and perishable wastes in the process of production and circulation,and improper disposal will cause serious environmental pollution.Domestic projects have shown that anaerobic fermentation as the core of the treatment system has the ability to scale to solve the problem,but the existing system is generally unstable,high loss,low efficiency,poor economy and other shortcomings,system performance needs to be improved.Therefore,this paper takes the typical tail vegetable processing system that has been in operation in China as the object,firstly analyzes the operational stability,processing efficiency and processing cost of the original system through the first-hand data obtained from field inspection,and summarizes the actual problems existing in the system and countermeasures.Secondly,combined with the successful cases of the existing tail vegetable treatment technology,the original system was proposed and a new system with anaerobic-aerobic fermentation as the core process was constructed.Finally,from the perspective of the whole life cycle,the evaluation model of energy,environment and economy is built.By quantifying the material flow,energy flow and monetary flow generated by the activities in each stage of the life of the system,the influence of the two systems before and after the transformation on resource consumption,ecological environment and economy is compared and demonstrated.The results of this study will provide data support for decision planning and process transformation of tail vegetable processing industry.The main conclusions are as follows:（1）In this paper,the stability,processing efficiency and operating cost of the typical scale-processing system of Songming in Yunnan Province were analyzed by combining the field investigation information and system operation data.In terms of stability,the average daily processing capacity of the pretreatment system is 454.13 t,which only reaches 18.92%of the designed value.The average p H in the anaerobic fermenter is 6.27 and the temperature is24℃.Acidification phenomenon in the tank leads to serious instability of the anaerobic system.In terms of treatment effect,the pressing efficiency of the pretreatment system is 39.35%,which only reaches 46.29%of the design value.The average COD removal rate of wastewater treatment system after treatment is 98.71%;NH3-N removal rate of 99.71%;TN removal rate of 98.07%;TP removal rate is 98.63%.In terms of operation cost,the unit treatment cost of tail vegetable was 101.38 yuan/t,among which the transportation cost,electricity cost,pharmaceutical cost and labor cost accounted for 29.59%,27.69%,15.70%and 13.17%respectively.（2）The problems that arise during the actual operation of the system in the original system on the basis of the existing facilities to build a set o f contains pretreatment,anaerobic fermentation,solid-liquid separation,aerobic treatment,biogas power generation of the new system,and combining the existing tail food processing system success stories,industry standards and test results to design the process and main equipment selection.The total installed power of the new system is 2053.5 k W,reduced by 22.43%compared with the original system,and the total investment cost is 74,834,700 yuan,reduced by47.93%compared with the original system.（3）The evaluation model of the whole life cycle from construction to abandonment of the two systems was established,and the differences in energy consumption,environmental impact and economic cost of each ton of vegetable waste treatment between the two systems were compared.In terms of energy consumption,the input energy of the new system is 82.37 MJ,the net energy value is 106.39 MJ,and the energy efficiency ratio is 2.29.Compared with the original system,the input energy is reduced by 24.83%,the net energy value is increased by 7.79%,and the energy efficiency ratio is increased by 20.53%.The energy-saving effect and energy production efficiency are significantly improved.Environmental impacts,the new system for comprehensive environmental impact load 2.83E-13,compared with the original system by146.02%,compared with the original system can reduce consumption of fossil energy 537 MJ,The quantities of CO₂,1,4-DB,C₂H₄,SO₂ and PO₄^3-were reduced by 93.7,11.89,0.009,0.23 and 0.047 kg,respectively,which showed significant environmental benefits.In terms of economy,the total life cycle cost of the new system is-96.59 yuan,and the total cost of the original system is-20.63 yuan.Both of them can generate benefits in their life cycle.However,compared with the original system,the input cost of the new system is reduced by 28.55%to 53.93 yuan,the income is increased by 11.21%to 138.58 yuan,and the environmental cost is reduced by 141.89%to-11.94 yuan.（4）The single factor sensitivity analysis of the energy,environmental and economic evaluation results of the two systems shows that in the original system,the energy consumption index EU is the most sensitive to natural gas production,with a sensitivity coefficient of 2.11.The environmental indexes ADP（f）,EP,AP and HTP were most sensitive to the energy consumption of sewage treatment,and the sensitivity coefficients were 0.624,0.136,0.346 and0.428,respectively.POCP and GWP were most sensitive to the amount of sludge landfill,and the sensitivity coefficients were 0.414 and 0.316.Economic indicators are most sensitive to government subsidies,with a sensitivity coefficient of 2.908.In the new system,the energy consumption index EU is the most sensitive to power generation,with a sensitivity coefficient of 1.159.The environmental indexes ADP（f）,GWP,AP and HTP were the most sensitive to biogas power generation,with sensitivity coefficients of 1.757,1.888,3.186and 1.726,respectively.POCP and EP were the most sensitive to anaerobic fermentation power consumption,with sensitivity coefficients of 1.380 and0.757.Economic indicators are the most sensitive to government subsidies,with a sensitivity coefficient of 0.621.