阅读说明：本技术 一种餐厨垃圾两相厌氧处理的生命周期评价方法 (Life cycle evaluation method for two-phase anaerobic treatment of kitchen waste ) 是由 刘莉莉 闫莹 朱漫漫 谷蕤年 张益恒 唐明琪 占锐 徐丰 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种餐厨垃圾两相厌氧处理的生命周期评价方法：确定餐厨垃圾两相厌氧处理的系统边界；收集基础数据并设定功能单位,进而列出餐厨垃圾生命周期清单；对环境因子进行分类,选取环境影响类型,量化评价餐厨垃圾两相厌氧处理过程的环境影响；对每一个环境影响类型中的环境因子进行特征化、标准化计算,当量因子及基准值选取参考CML-IA中的数据；对标准化后的环境影响潜值赋予一个权重值,不同的权重值表明环境影响类型的重要程度,加权求和得出总环境影响潜值,定量评价餐厨垃圾两相厌氧处理的环境影响。本发明为餐厨垃圾的二次污染防控、资源化、减量化、无害化处理提供科学依据。(The invention discloses a life cycle evaluation method for two-phase anaerobic treatment of kitchen waste, which comprises the following steps: determining a system boundary of two-phase anaerobic treatment of the kitchen waste; collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste; classifying the environmental factors, selecting an environmental influence type, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference CML-IA by the equivalent factors and the reference value; and (3) endowing the standardized environmental influence potential value with a weight value, wherein different weight values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighting and summing, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste. The invention provides scientific basis for secondary pollution prevention, control, resource utilization, reduction and harmless treatment of the kitchen waste.)

1. A life cycle evaluation method for two-phase anaerobic treatment of kitchen waste is characterized by comprising the following steps:

firstly, determining a system boundary of two-phase anaerobic treatment of the kitchen waste;

the first step of determining the system boundary of the two-phase anaerobic treatment of the kitchen waste mainly comprises three aspects: raw material and energy input; two-phase anaerobic treatment; outputting waste water, waste gas and waste residue;

secondly, collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste;

thirdly, classifying the environmental factors, selecting an environmental influence type, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference CML-IA by the equivalent factors and the reference value;

and fourthly, endowing a weighted value to the standardized environmental influence potential value, wherein different weighted values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighted summation, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste.

2. The life cycle evaluation method of two-phase anaerobic treatment of kitchen waste according to claim 1, characterized in that in the second step, basic data is obtained, a functional unit is selected to treat 1kg of kitchen waste, and the list data of all unit processes are classified and summarized to obtain a life cycle list of two-phase anaerobic treatment of kitchen waste.

3. The life cycle evaluation method of two-phase anaerobic treatment of kitchen waste according to claim 1, characterized in that in the third step, life cycle list data is input into SimaPro9.0 software to analyze and select environmental impact types, and the contribution of key links to the environment is contrasted and analyzed, wherein positive values represent environmental burden, and negative values represent environmental benefits.

4. The method for evaluating the life cycle of two-phase anaerobic treatment of kitchen waste according to claim 3, characterized in that said environmental impact type is selected from the group consisting of metal ore, mineral, air, land occupation, non-biological depletion of non-renewable energy, non-biological depletion of fossil fuel, global warming, ozone layer depletion, human toxicity, fresh water aquatic ecotoxicity, marine aquatic ecotoxicity, land ecotoxicity, photochemical oxidation, acidification, eutrophication.

5. The life cycle evaluation method of two-phase anaerobic kitchen waste treatment according to claim 3, characterized in that in the third step, the integrity of the life cycle list calculation method is ensured, and the environmental factors existing in the upstream stage and the downstream stage of the life cycle list are quantitatively calculated.

6. The life cycle evaluation method of two-phase anaerobic treatment of kitchen waste according to claim 5, characterized in that said upstream stage mainly comprises the use and transportation stage of raw materials, energy and auxiliary materials; the downstream stages mainly include various energy recovery.

7. The life cycle evaluation method for two-phase anaerobic treatment of kitchen waste according to claim 3, characterized in that in the third step, life cycle list data includes environmental influences reflected by material, resource consumption, transportation and energy utilization, and the cumulative amount expression of the related life cycle environmental factor g is as follows:

in the formula:the accumulative amount of environmental factors g of 1kg of kitchen waste to be treated is expressed in unit kg; a is_T，iThe unit kg of the accumulated amount of the environmental factors of the raw materials, the energy sources and the auxiliary materials in the life cycle unit link i; b_i，gIs the accumulation of the environmental factors in the unit link i of the life cycle, which is reflected by the downstream process, and the unit kg.

8. The life cycle evaluation method of two-phase anaerobic kitchen waste treatment according to claim 3, characterized in that in the third step, various environmental factors after quantification are classified to obtain various environmental impact types, each environmental impact type is characterized and calculated by using an equivalent factor method to obtain a characteristic environmental impact potential value with dimensions, and for comparison between different environmental impact types, the characteristic environmental impact potential value is generally standardized to remove the dimensional influence, and the expression is as follows:

in the formula: m_(j)Is a characterized environmental impact latent value for the j environmental impact type; n is the number of environmental factors in the j environmental impact type; d_(j)iIs the equivalence coefficient of the i environmental factor in the j environmental impact type; e_iIs the discharge of the environmental factor i in units of kg in the environmental impact type j.

9. The method for evaluating life cycle of two-phase anaerobic kitchen waste treatment according to claim 1, characterized in that the life cycle of the kitchen waste treatment is evaluated by an equivalent factor CO, such as global warming₂The expression is as follows:

in the formula: GWP refers to the global warming characterization environmental impact potential in kgCO₂eq/kg; n refers to the number of greenhouse gases emitted in the life cycle; delta_iRefers to the equivalence coefficient of i greenhouse gas in the life cycle; d_GWPThe method is characterized in that the greenhouse gas emission amount is i per functional unit produced, and the unit is kg;

N_j＝M_j/S_j

in the formula: n is a radical of_jTo normalize environmental impact potentials; j represents each environmental impact type; m_jCharacterizing results for each environmental impact type; s_jThe base values are normalized for each environmental impact type in the CML-IA method.

10. The life cycle evaluation method of two-phase anaerobic treatment of kitchen waste according to claim 1, characterized in that in the fourth step, the total environmental impact load is mainly determined according to the standardized result of each environmental impact type and the weight factor of each environmental impact type in the CML-IA method; the expression is as follows:

∑WF_j＝∑W_j×N_j

in the formula: WF_jThe total environmental impact load of each environmental impact type; j represents each environmental impact type; w_jWeighting factors for different environmental impact types in the CML-IA method; n is a radical of_jThe normalized environmental impact potentials for each environmental impact type.

Technical Field

The invention belongs to the technical field of anaerobic treatment and life cycle evaluation of kitchen waste, and particularly relates to a life cycle evaluation method for two-phase anaerobic treatment of kitchen waste.

Background

With the improvement of national economy and the improvement of the living standard of people, the yield of the kitchen waste in the urban household waste is in an increasing trend. In 2015, the yield of kitchen waste in China is about 9110 ten thousand tons, the daily average yield is 25 ten thousand tons, and the actual treatment capacity of the kitchen waste does not exceed 1.4 ten thousand tons per day. The kitchen waste has the characteristics of high water content, low heat value, high organic content, easy deterioration, good biodegradability and coexistence of harmfulness and recycling. Kitchen waste is treated in time, otherwise, the kitchen waste is rotten, odor is generated, a large number of mosquitoes and flies are bred, disease propagation is caused, and the emission of pollutants is increased. Since the publication of the first technical specification, namely, the kitchen waste treatment technical specification (CJJ 18-2012), new kitchen waste treatment technologies are continuously emerging. The traditional treatment methods (landfill and incineration) are not suitable for use due to low heat value and high water content. According to the current research situation, the more treatment technologies mainly comprise anaerobic and aerobic biological treatment methods, wherein the anaerobic treatment has good economic benefit, the process is easy to control, the resource degree is high, and the technology is mature and widely adopted. The two-phase anaerobic treatment technology for the kitchen waste has the advantages of high acidification reaction speed, high methane yield, high load and the like.

Life cycle assessment software (LCA) is a comprehensive environmental management tool that includes efficient assessment of potential environmental impact from raw material acquisition to final treatment, input and output of materials, energy, and identification and quantification of corresponding environmental emissions. The life cycle evaluation of the two-phase anaerobic treatment of the kitchen waste can obtain complete environmental impact types and environmental impact potential values of different processes of each environmental impact type, quantitatively evaluate the environmental impact of the two-phase anaerobic treatment technology, and provide guidance for the optimization and improvement of the two-phase anaerobic treatment process of the kitchen waste.

Disclosure of Invention

The invention aims to provide a life cycle evaluation method for two-phase anaerobic treatment of kitchen waste, aiming at the technical problems of unclear economy and environmental effect in the two-phase anaerobic treatment process of the kitchen waste. The evaluation method provided by the invention is based on a life cycle evaluation technical framework provided by ISO140, and the process list analysis method is adopted to identify and compile the environmental factors of the life cycle of the kitchen waste, so that the resource utilization and pollutant emission in the system can be visually observed, the environmental impact of the treatment process can be quantitatively evaluated, and effective guidance suggestions are provided for improving the environmental quality and saving resources.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a life cycle evaluation method for two-phase anaerobic treatment of kitchen waste, which comprises the following steps:

firstly, determining a system boundary of two-phase anaerobic treatment of the kitchen waste;

the first step of determining the system boundary of the two-phase anaerobic treatment of the kitchen waste mainly comprises three aspects: raw material and energy input; two-phase anaerobic treatment; outputting waste water, waste gas and waste residue;

secondly, collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste;

thirdly, classifying the environmental factors, selecting an environmental influence type, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference CML-IA by the equivalent factors and the reference value;

and fourthly, endowing a weighted value to the standardized environmental influence potential value, wherein different weighted values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighted summation, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste.

And in the second step, acquiring basic data, selecting a functional unit for treating 1kg of kitchen waste, and classifying and summarizing list data of all unit processes to obtain a life cycle list of two-phase anaerobic treatment of the kitchen waste.

And in the third step, the life cycle list data is input into SimaPro9.0 software to analyze and select the environmental impact type, the contribution of key links to the environment is contrasted and analyzed, the positive value represents the environmental burden, and the negative value represents the environmental benefit.

The environmental impact type is selected from the group consisting of metal ore, minerals, air, land occupation, non-biological depletion of non-renewable energy sources, non-biological depletion of fossil fuels, global warming, ozone layer depletion, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, land ecotoxicity, photochemical oxidation, acidification, eutrophication.

And in the third step, the integrity of the life cycle list calculation method is ensured, and environmental factors existing in the upstream stage and the downstream stage of the life cycle list are quantitatively calculated.

The upstream stage mainly comprises the use and transportation stages of raw materials, energy sources and auxiliary materials; the downstream stages mainly comprise various energy recovery and utilization stages, such as a cogeneration stage.

In the third step, the life cycle list data comprises the environmental influence embodied by the material, resource consumption, transportation and energy utilization, and the cumulative quantity expression of the life cycle environmental factor g is as follows:

b_T，F，g＝∑a_T，ib_i，g

in the formula: b_T,F,gThe accumulative amount of environmental factors g of 1kg of kitchen waste to be treated is expressed in unit kg; a is_T,iThe unit kg of the accumulated amount of the environmental factors of the raw materials, the energy sources and the auxiliary materials in the life cycle unit link i; b_i,gIs the accumulation of the environmental factors in the unit link i of the life cycle, which is reflected by the downstream process, and the unit kg.

In the third step, the quantized various environmental factors are classified to obtain various environmental influence types, each environmental influence type is subjected to characteristic calculation by adopting an equivalent factor method to obtain a characteristic environmental influence latent value with dimensions, and for comparison between different environmental influence types, the characteristic environmental influence latent value is subjected to standardization treatment to remove the dimensional influence, and the expression is as follows:

in the formula: m_(j)Is a characterized environmental impact latent value for the j environmental impact type; n is the number of environmental factors in the j environmental impact type; d_(j)iIs the equivalence coefficient of the i environmental factor in the j environmental impact type; e_iIs the discharge of the environmental factor i in units of kg in the environmental impact type j.

Such as global warming, equivalent factor CO₂The expression is as follows:

in the formula: GWP refers to the global warming characterization environmental impact potential in kg CO₂eq/kg; n refers to the number of greenhouse gases emitted in the life cycle; delta_iRefers to the equivalence coefficient of the ith greenhouse gas in the life cycle; d_GWPMeans the amount of the ith greenhouse gas emission per functional unit produced, unit kg.

Nj＝Mj/Sj

In the formula: n is a radical of_jTo normalize environmental impact potentials; j represents each environmental impact type; m_jCharacterizing results for each environmental impact type; s_jThe base values are normalized for each environmental impact type in the CML-IA method.

In the fourth step, the total environmental impact load is mainly determined according to the standardized result of each environmental impact type and the weight factor of each environmental impact type in the CML-IA method; the expression is as follows:

∑WF_j＝∑W_j×N_j

in the formula: WF_jThe total environmental impact load of each environmental impact type; j represents eachA type of environmental impact; w_jWeighting factors for different environmental impact types in the CML-IA method; n is a radical of_jThe normalized environmental impact potentials for each environmental impact type.

Due to the adoption of the technical scheme, the invention has the following advantages and beneficial effects:

the invention starts from the whole treatment process of the kitchen waste two-phase anaerobic treatment technology, aims to reduce the environmental impact and the resource consumption, and carries out life cycle evaluation on the kitchen waste two-phase anaerobic treatment technology.

The life cycle evaluation method for the two-phase anaerobic treatment of the kitchen waste is an objective, comprehensive and scientific evaluation method, can quantitatively represent the environmental impact and resource consumption in the two-phase anaerobic treatment process of the kitchen waste, and provides a scientific basis for optimizing the two-phase anaerobic treatment process of the kitchen waste and preventing pollution in the treatment process of the kitchen waste.

In the life cycle evaluation, the evaluation is carried out based on literature research, field actual measurement and reference to the existing database and partial empirical data, and the final result has objectivity and comprehensiveness.

The invention establishes the boundary and the life cycle list of the kitchen waste two-phase anaerobic treatment system, evaluates the environmental impact, more objectively and detailedly analyzes the environmental impact and the energy consumption in the kitchen waste treatment process, and provides scientific basis for the secondary pollution prevention, control, resource utilization, reduction and harmless treatment of the kitchen waste.

Drawings

FIG. 1 is a schematic diagram of the kitchen garbage life cycle system in embodiment 1.

FIG. 2 is a schematic diagram of the contribution of two-phase anaerobic treatment of kitchen waste to different environmental impact types.

FIG. 3 is a flow chart of the two-phase anaerobic treatment process of the kitchen waste in the comparative example.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Example 1

A life cycle evaluation method for two-phase anaerobic treatment of kitchen waste comprises the following steps:

firstly, determining the system boundary of two-phase anaerobic treatment of the kitchen waste.

The first step of determining the system boundary of the two-phase anaerobic treatment of the kitchen waste mainly comprises three aspects: raw material and energy input; two-phase anaerobic treatment; the method is used for outputting the waste water, the waste gas and the waste residue, and specifically comprises the following steps: the kitchen waste which is classified and collected from the source is transported to a waste treatment plant in Shanghai city, and the components of the kitchen waste mainly comprise food waste, a small amount of paper, bamboo, wood, fabric, plastic and metal. The method comprises the steps of sequentially carrying out pretreatment such as sorting, magnetic separation, biomass separation and the like in a treatment plant, screening out inert garbage, metal and paper, enabling acid-producing bacteria and methanogenic bacteria to grow under the optimal environmental conditions by entering a hydrolysis acidification tank and a methanogenic tank which are connected in series, then carrying out anaerobic fermentation, and finally carrying out biogas purification and cogeneration technology to obtain electric energy and heat energy. The generated biogas residues are transported to a refuse landfill, biogas slurry enters a sewage treatment plant, and waste gas generated in the whole link is subjected to subsequent treatment. As shown in fig. 1, fig. 1 is a schematic boundary diagram of a kitchen waste life cycle system.

Secondly, collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste;

in the second step, basic data are obtained through literature research, field actual measurement and database based, and mainly comprise energy and material input, product and waste output and environmental emission. Selecting a functional unit to treat 1kg of kitchen waste, classifying and summarizing list data of all unit processes to obtain a life cycle list of two-phase anaerobic treatment of the kitchen waste, as shown in table 1:

TABLE 1 List data for two-phase anaerobic treatment (per functional unit)

Table 1 is to collect and collate data of two-phase anaerobic treatment of kitchen waste in a waste treatment plant of Shanghai city, to improve the basic data and to perform subsequent life cycle evaluation. The data format in the table is mainly acquired according to the requirements of life cycle evaluation software, and mainly comprises three major parts, namely substances, input and output of resources, influence factors discharged into the atmosphere and influence factors discharged into water. The electricity and heat are negative values indicating that the available electricity and heat are output to the outside.

Thirdly, classifying the environmental factors, selecting 11 environmental influence types, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; and performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference calculation method CML-IA for the equivalent factors and the reference values, as shown in tables 2 and 3.

Inputting life cycle list data into SimaPro9.0 software (PR Consultants bv (Netherlands) by a software manufacturer), and analyzing and evaluating 11 environmental influence types, including non-biological exhaustion of metal ores, minerals, air, land occupation, non-renewable energy sources and the like, non-biological exhaustion of fossil fuels, global warming, ozone layer consumption, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, land ecotoxicity, photochemical oxidation, acidification and eutrophication; the contribution of key links to the environment is contrasted and analyzed, and scientific basis is provided for subsequent optimization and improvement of the process; the obtained data are shown in tables 4 and 5, in which positive values indicate environmental load and negative values indicate environmental benefit.

And in the third step, the integrity of the life cycle list calculation method is ensured, and environmental factors existing in the upstream stage and the downstream stage of the life cycle list are quantitatively calculated. The upstream stage mainly comprises the use and transportation stages of raw materials, energy sources and auxiliary materials; the downstream stages mainly comprise various energy recovery and utilization stages, such as a cogeneration stage.

In the third step, the life cycle inventory data comprises the environmental influence embodied by the material, resource consumption, transportation and energy utilization, and the cumulative quantity expression of the life cycle environmental factor g is as follows:

b_T，F，g＝∑a_T，ib_i，g

in the formula: b_T,F,gThe accumulative amount of environmental factors g of 1kg of kitchen waste to be treated is expressed in unit kg; a is_T,iThe unit kg of the accumulated amount of the environmental factors of the raw materials, the energy sources and the auxiliary materials in the life cycle unit link i; b_i,gIs the accumulation of the environmental factors in the unit link i of the life cycle, which is reflected by the downstream process, and the unit kg.

In the third step, the quantized various environmental factors are classified to obtain various environmental influence types, each environmental influence type is subjected to characteristic calculation by adopting an equivalent factor method to obtain a characteristic environmental influence latent value with dimensions, and for comparison between different environmental influence types, the characteristic environmental influence latent value is subjected to standardization treatment to remove the dimensional influence, and the expression is as follows:

in the formula: m_(j)Is a characterized environmental impact latent value for the j environmental impact type; n is the number of environmental factors in the j environmental impact type; d_(j)iIs the equivalence coefficient of the i environmental factor in the j environmental impact type; e_iIs the discharge of the environmental factor i in units of kg in the environmental impact type j.

Such as global warming, equivalent factor CO₂The expression is as follows:

in the formula: GWP refers to the global warming characterization environmental impact potential in kgCO₂eq/kg; n refers to the number of greenhouse gases emitted in the life cycle; delta_iRefers to the equivalence coefficient of i greenhouse gas in the life cycle; d_GWPMeans the discharge amount of greenhouse gas per functional unit i produced, unit kg.

N_j＝M_j/S_j

In the formula: n is a radical of_jTo normalize environmental impact potentials; j represents each environmental impact type; m_jCharacterizing results for each environmental impact type; s_jThe base values are normalized for each environmental impact type in the CML-IA method.

TABLE 2 Equivalence coefficients in CML-IA calculation method

In the table, the equivalent weight coefficients: such as global warming, equivalent factor CO₂The equivalent coefficient is 1, and the equivalent coefficients of other influencing factors are compared with the equivalent coefficient to carry out corresponding conversion.

TABLE 3 normalized base values in the CML-IA calculation method

TABLE 4 normalized environmental impact potentials

TABLE 5

Tables 4 and 5 show all environmental impact types in the CML-IA calculation method, and analyze and collect the impact of five links of transportation, power input, anaerobic digestion, biogas power generation and heat production on the environment. Wherein, the potential value of the influence of the electric power input, the collection and transportation and the anaerobic digestion environment is positive, which represents the environmental burden; the potential value of the heat production of the marsh gas and the influence of the marsh gas power generation environment is negative, and the environmental benefit is represented; the sum of the environmental impact potential values of all links in each environmental impact type is a negative value, which indicates that the environmental burden is counteracted to a great extent by utilizing the biogas for power generation.

And fourthly, endowing a weighted value to the standardized environmental influence potential value, wherein different weighted values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighted summation, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste. As shown in FIG. 2, FIG. 2 is a schematic diagram of the contribution of two-phase anaerobic treatment of kitchen waste to different environmental impact types. From fig. 2, it is apparent that the contribution ratio of each link to each environmental impact type is obtained when the kitchen waste is subjected to two-phase anaerobic treatment. In the aspect of marine aquatic ecotoxicity, the contribution ratio of the methane power generation in the aspect of environmental benefit is 91.6 percent; in terms of non-biological exhaustion, the total contribution ratios of collection transportation, anaerobic digestion and power input in terms of environmental burden are respectively 0.779%, 5.11% and 7.6%.

In the fourth step, the total environmental impact load is mainly determined according to the standardized result of each environmental impact type and the weight factor of each environmental impact type in the CML-IA method; the expression is as follows:

∑WF_j＝∑W_j×N_j

in the formula: WF_jThe total environmental impact load of each environmental impact type; j represents each environmental impact type; w_jWeighting factors for different environmental impact types in the CML-IA method; n is a radical of_jThe normalized environmental impact potentials for each environmental impact type.

Example 2

A life cycle evaluation method for two-phase anaerobic treatment of kitchen waste comprises the following steps:

firstly, determining the system boundary of two-phase anaerobic treatment of the kitchen waste.

The first step of determining the system boundary of the two-phase anaerobic treatment of the kitchen waste mainly comprises three aspects: raw material and energy input; two-phase anaerobic treatment; the method is used for outputting the waste water, the waste gas and the waste residue, and specifically comprises the following steps: the research case of the kitchen waste treatment project is developed in a university city in Zhejiang province, and the kitchen waste collected by the project mainly contains food waste, a small amount of gravel, paper and other sundries. The kitchen waste is discharged into a receiving hopper, drained water enters a liquid storage tank, solids are subjected to coarse sorting, crushing and screening to prepare pulp and sand deposition, three-phase separation is carried out, and anaerobic fermentation is carried out on the treated kitchen waste. The two-phase anaerobic treatment system for the kitchen waste is divided into four links of waste collection and transportation, pretreatment and fermentation, solid-liquid separation and methane utilization. And (4) conveying biogas residues generated by solid-liquid separation to a landfill site, conveying biogas slurry to a sewage treatment plant, and performing subsequent treatment on waste gas generated in the whole process.

Secondly, collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste;

in the second step, data of each link is collected, a functional unit is selected for treating 1kg of kitchen waste, and list data of all unit processes are classified and summarized to obtain a life cycle list of two-phase anaerobic treatment of the kitchen waste, as shown in table 6:

TABLE 6 List data for two-phase anaerobic treatment (per functional unit)

The data in table 6 are mainly data in 4 links of integrating waste collection and transportation, pretreatment and fermentation, solid-liquid separation and biogas utilization, namely, data related to energy, material consumption, pollutant discharge and available energy in the processing link are collected.

Thirdly, classifying the environmental factors, selecting 6 environmental influence types, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference calculation method CML-IA for the equivalent factors and the reference values;

inputting the life cycle list data into SimaPro9.0 software (PR Consultants bv (Netherlands) by a software manufacturer) to analyze and evaluate 6 environmental impact types, including non-biological exhaustion (fossil fuel), global warming, fresh water aquatic ecotoxicity, photochemical oxidation, acidification and eutrophication; the contribution of key links to the environment is contrasted and analyzed, and scientific basis is provided for subsequent optimization and improvement of the process; the data obtained are shown in table 7, where positive values indicate environmental load and negative values indicate environmental benefit.

And in the third step, the integrity of the life cycle list calculation method is ensured, and environmental factors existing in the upstream stage and the downstream stage of the life cycle list are quantitatively calculated. The upstream stage mainly comprises the use and transportation stages of raw materials, energy sources and auxiliary materials; the downstream stages mainly comprise various energy recovery and utilization stages, such as a cogeneration stage.

In the third step, the life cycle list data comprises the environmental influence embodied by the material, resource consumption, transportation and energy utilization, and the cumulative quantity expression of the life cycle environmental factor g is as follows:

b_T，F，g＝∑a_T，ib_i，g

in the formula: b_T,F,gThe accumulative amount of environmental factors g of 1kg of kitchen waste to be treated is expressed in unit kg; a is_T,iThe unit kg of the accumulated amount of the environmental factors of the raw materials, the energy sources and the auxiliary materials in the life cycle unit link i; b_i,gIs the accumulation of the environmental factors in the unit link i of the life cycle, which is reflected by the downstream process, and the unit kg.

In the third step, the quantized various environmental factors are classified to obtain various environmental influence types, each environmental influence type is subjected to characteristic calculation by adopting an equivalent factor method to obtain a characteristic environmental influence latent value with dimensions, and for comparison between different environmental influence types, the characteristic environmental influence latent value is subjected to standardization treatment to remove the dimensional influence, and the expression is as follows:

in the formula: m_(j)Is a characterized environmental impact latent value for the j environmental impact type; n is the number of environmental factors in the j environmental impact type; d_(j)iIs the equivalence coefficient of the i environmental factor in the j environmental impact type; e_iIs the discharge of the environmental factor i in units of kg in the environmental impact type j.

Such as global warming, equivalent factor CO₂The expression is as follows:

in the formula: GWP refers to the global warming characterization environmental impact potential in kgCO₂eq/kg; n refers to the number of greenhouse gases emitted in the life cycle; delta_iRefers to the equivalence coefficient of i greenhouse gas in the life cycle; d_GWPThe unit is the discharge amount of greenhouse gas per functional unit produced, and the unit is kg.

Nj＝Mj/Sj

In the formula: n is a radical of_jTo normalize environmental impact potentials; j represents each environmental impact type; m_jCharacterizing results for each environmental impact type; s_jThe base values are normalized for each environmental impact type in the CML-IA method.

TABLE 7 normalized environmental impact potentials

The data in table 7 show that in the two-phase anaerobic treatment process of the kitchen waste, the types of environmental influences caused by the solid-liquid separation link are less, the two links of pretreatment, fermentation, collection and transportation cause a certain degree of environmental burden, and the two links of biogas power generation and biogas heat generation generate a certain degree of environmental benefits. The environmental impact potential value of the collection and transportation link is large and mainly related to the transportation distance, the type of vehicles and the emission of automobile exhaust.

And fourthly, endowing a weighted value to the standardized environmental influence potential value, wherein different weighted values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighted summation, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste.

In the fourth step, the total environmental impact load is mainly determined according to the standardized result of each environmental impact type and the weight factor of each environmental impact type in the CML-IA method; the expression is as follows:

∑WF_j＝∑W_j×N_j

in the formula: WF_jThe total environmental impact load of each environmental impact type; j represents each environmental impact type; w_jWeighting factors for different environmental impact types in the CML-IA method; n is a radical of_jThe normalized environmental impact potentials for each environmental impact type.

Example 3

A life cycle evaluation method for two-phase anaerobic treatment of kitchen waste comprises the following steps:

firstly, determining the system boundary of two-phase anaerobic treatment of the kitchen waste. The first step of determining the system boundary of the two-phase anaerobic treatment of the kitchen waste mainly comprises three aspects: raw material and energy input; two-phase anaerobic treatment; the method is used for outputting the waste water, the waste gas and the waste residue, and specifically comprises the following steps: a certain food waste recycling treatment trial point-local anaerobic equipment in Suzhou city relates to the food waste which is mainly from local restaurants, and the ingredients of the food waste mainly comprise food waste, a small amount of gravel, paper, plastics and other sundries. The unit adopts a small-scale on-site two-phase anaerobic treatment device, large impurities need to be sorted manually before the device is operated, and then the kitchen waste enters a raw material collecting tank and a sorting procedure and then enters a two-phase anaerobic fermentation tank and a biogas storage tank for finally utilizing biogas. The kitchen waste two-phase anaerobic treatment system comprises three links of pretreatment, anaerobic digestion and biogas utilization, wherein biogas residues generated in the anaerobic digestion link are transported to a waste landfill, biogas slurry is transported to a sewage treatment plant, biogas utilization is achieved through a cogeneration process, and waste gas generated in the whole treatment process is subjected to subsequent treatment.

Secondly, collecting basic data and setting a functional unit, and further listing a life cycle list of the kitchen waste;

in the second step, data are obtained through field actual measurement and reference literature, data of each link are collected, a functional unit is selected to treat 1kg of kitchen waste, list data of all unit processes are classified and summarized, and a life cycle list of two-phase anaerobic treatment of the kitchen waste is obtained, as shown in table 8:

TABLE 8 List data for two-phase anaerobic treatment (per functional unit)

In table 8, the data collection and arrangement mainly comes from three links of pretreatment, anaerobic digestion and biogas utilization, namely, the data of material consumption, energy gain and loss and environmental release in the whole life cycle of the final treatment from the acquisition of raw materials are collected.

Thirdly, classifying the environmental factors, selecting 5 environmental influence types, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment process of the kitchen waste; performing characterization and standardized calculation on the environmental factors in each environmental influence type, and selecting data in a reference calculation method CML-IA for the equivalent factors and the reference values;

inputting the life cycle list data into SimaPro9.0 software (PR Consultantsbv (Netherlands) by a software manufacturer) to analyze and evaluate 5 environmental influence types including global climate warming, human toxicity, photochemical oxidation, acidification and eutrophication; the contribution of key links to the environment is contrasted and analyzed, and scientific basis is provided for subsequent optimization and improvement of the process; the obtained data are shown in table 9, in which positive values indicate environmental load and negative values indicate environmental benefit.

And in the third step, the integrity of the life cycle list calculation method is ensured, and environmental factors existing in the upstream stage and the downstream stage of the life cycle list are quantitatively calculated. The upstream stage mainly comprises the use and transportation stages of raw materials, energy sources and auxiliary materials; the downstream stages mainly comprise various energy recovery and utilization stages, such as a cogeneration stage.

In the third step, the life cycle list data comprises the environmental influence embodied by the material, resource consumption, transportation and energy utilization, and the cumulative quantity expression of the life cycle environmental factor g is as follows:

b_T，F，g＝∑a_T，ib_i，g

in the formula: b_T,F,gThe accumulative amount of environmental factors g of 1kg of kitchen waste to be treated is expressed in unit kg; a is_T,iThe unit kg of the accumulated amount of the environmental factors of the raw materials, the energy sources and the auxiliary materials in the life cycle unit link i; b_i,gIs the accumulation of the environmental factors in the unit link i of the life cycle, which is reflected by the downstream process, and the unit kg.

In the third step, the quantized various environmental factors are classified to obtain various environmental influence types, each environmental influence type is subjected to characteristic calculation by adopting an equivalent factor method to obtain a characteristic environmental influence latent value with dimensions, and for comparison between different environmental influence types, the characteristic environmental influence latent value is subjected to standardization treatment to remove the dimensional influence, and the expression is as follows:

in the formula: m_(j)Is a characterized environmental impact latent value for the j environmental impact type; n is the number of environmental factors in the j environmental impact type; d_(j)iIs the equivalence coefficient of the i environmental factor in the j environmental impact type; e_iIs the discharge of the environmental factor i in units of kg in the environmental impact type j.

Such as global warming, equivalent factor CO₂The expression is as follows:

in the formula:GWP refers to the global warming characterization environmental impact potential in kgCO₂eq/kg; n refers to the number of greenhouse gases emitted in the life cycle; delta_iRefers to the equivalence coefficient of i greenhouse gas in the life cycle; d_GWPMeans the discharge amount of greenhouse gas per functional unit i produced, unit kg.

N_j＝M_j/S_j

In the formula: n is a radical of_jTo normalize environmental impact potentials; j represents each environmental impact type; m_jCharacterizing results for each environmental impact type; s_jThe base values are normalized for each environmental impact type in the CML-IA method.

TABLE 9 normalized environmental impact potentials

The data in table 9 show that the sum of the environmental impact potentials of all links in global warming is the largest, 6.96E-15, and the power input is the main contribution process. The potential value of the environmental impact of biogas utilization is a negative value, and the environmental impact caused by material consumption, energy consumption and pollutant discharge in the two-phase anaerobic treatment process of the kitchen waste is partially counteracted. The project does not include a collection and transportation link, so that the environmental burden caused by transportation is avoided.

And fourthly, endowing a weighted value to the standardized environmental influence potential value, wherein different weighted values indicate the importance degree of the environmental influence type, obtaining a total environmental influence potential value by weighted summation, and quantitatively evaluating the environmental influence of the two-phase anaerobic treatment of the kitchen waste.

In the fourth step, the total environmental impact load is mainly determined according to the standardized result of each environmental impact type and the weight factor of each environmental impact type in the CML-IA method; the expression is as follows:

∑WF_j＝∑W_j×N_jin the formula: WF_jThe total environmental impact load of each environmental impact type; j represents each environmental impact type; w_jWeighting factors for different environmental impact types in the CML-IA method;N_jthe normalized environmental impact potentials for each environmental impact type.

Comparative example 1

Evaluation of environmental impact in the operation stage of a certain kitchen waste treatment plant in Guangdong province comprises the following steps:

firstly, selecting an evaluation range, a grade and an evaluation standard. The construction land is a kitchen waste treatment site in a certain city of Guangdong province, and the floor area is about 33000.5m²And the daily treatment scale is 300t of kitchen waste. According to relevant regulations in the national environmental protection administration "guide rules for environmental impact evaluation technology", the evaluation ranges of this time are selected as follows: (1) surface water environment: accounting is mainly carried out aiming at the project water pollution source; (2) underground water environment: the range of 200 meters upstream to 200 meters downstream of the groundwater in the area where the project is located; (3) and (3) atmospheric environment: a circular area range of 5000m in diameter centered on the target; (4) acoustic environment: the periphery of the project area extends to an area range of 200 m; (5) ecological environment: the place where the project is located is taken as the main part.

1. Atmosphere evaluation grade and standard

Grade: according to the regulation in the environmental impact evaluation technology guide atmospheric environment, smoke dust is selected as a main pollutant, and the maximum ground concentration standard occupation rate P of the main pollutant is calculated_i：

P_i＝C_i/C_oi*100％

In the formula: p_iThe maximum ground concentration of the ith pollutant is the standard rate,%; c_iFor the maximum ground concentration of the i-th pollutant, mg/m, calculated using an estimation model³；C_oiIs the standard mg/m of the quality of the environmental air of the ith pollutant³。

TABLE 10 evaluation table for atmospheric environmental impact

Evaluating a work level	Evaluation work grading criterion
		First stage	Pmax≥80％，D10％≥5km
Second stage	Others
		Three-stage	Pmax< 10% or D10％< closest distance of contamination Source from factory boundary

The standard is as follows: the second level of standards in the ambient air quality standard (GB3095-2012) is implemented.

2. Water environment evaluation grade and standard

Grading the surface water environment: the final wastewater discharge amount of the kitchen waste treatment plant is 200-800m³And d, the quality of the sewage is simple, and the water environment influence evaluation working grade of the project is selected to be three grades according to the local standard water pollutant emission limit (DB44/26-2001) of Guangdong province.

The standard is as follows: standard of surface water environment (GB3838-2002)

Grading underground water environment: the project can cause groundwater water quality pollution during operation, the groundwater environment sensitivity degree of the project area is insensitive, and the sewage discharge amount of the project is less than or equal to 1000m³And d, simply evaluating the sewage quality by three levels.

The standard is as follows: groundwater quality standard (GB/T14848-93)

3. Noise environment evaluation grade and standard

Grade: the project refers to the execution acoustic environment quality 3-class standard, the noise increase value is below 3dB (A) during the project operation, the influence on the acoustic environment of an environment sensitive point is small, the change of the influenced population is small, and the work is carried out according to three-level evaluation.

The standard is as follows: standard for quality of sound environment (GB 3096-2008).

4. Evaluation grade and standard of ecological environment

Grade: the total occupied area of the project is 33000.5m²Less than 20km²The method is located in an ecological control line, rare animals and plants do not exist in a project area, a field is a large number of exposed earth surfaces, and the work is carried out according to three-level evaluation according to ecological influence of environmental influence evaluation technical guide (HJ 19-2011) and the regulation of ecological environment evaluation work classification.

And (3) pollutant emission standard: water pollutant emission limits (DB44/26-2001) second time period, primary standard;

emission Standard of malodorous pollutants (GB14554-93)

Three types of standards of environmental noise emission Standard of Industrial Enterprise factory (GB 12348-2008);

and secondly, carrying out engineering analysis in the operation period. And (3) collecting feasibility research data and other related technical data, sorting main raw and auxiliary materials and energy consumed in the whole process, and selecting a pollution discharge link and main pollutants according to the two-phase anaerobic treatment process flow of the kitchen waste. The kitchen waste is mainly from large hotels, restaurants and dining halls, the daily treatment capacity of a kitchen waste treatment plant is 300t/d, the treatment capacity of illegal cooking oil is 50t/d, and the yield of available resource biogas is 22000m³And d, the prepared biodiesel is 25 t/d.

TABLE 11 original and auxiliary materials and energy consumption table

According to process selection, the project adopts two-phase anaerobic digestion as a main process technology, the design of a main treatment process part is executed and conforms to the operating specification of household garbage treatment facilities (SZJG43-2012), and a process flow chart is shown in figure 3.

Kitchen garbage pretreatment system: the kitchen waste is collected and transported to a discharging hall through a collecting and transporting vehicle and is butted with a receiving hopper, the receiving hopper has a filtrate function, and the filtrate is collected; crushing and sorting the slurry to remove impurities such as glass bottles, plastic bottles and the like; the sorting device is provided with a hot water spraying device, and can wash down the grease and the slurry on the surfaces of the impurities; removing sand to remove fine inorganic impurities, performing wet-heat hydrolysis on the residual slurry to obtain solid oil and slurry, performing filter pressing on the slurry, allowing the liquid to enter a homogenizing tank, allowing the solid to enter a storage tank for subsequent filter residue treatment, and conveying the crude oil to a biodiesel factory for processing.

An anaerobic fermentation system: in the project, the anaerobic fermentation adopts a two-phase anaerobic fermentation device, and mainly utilizes medium-temperature anaerobic bacteria to ensure that hydrolytic acidification and methanation production run in two reactors. Before entering an anaerobic digestion system, the pretreated kitchen waste enters a hydrolysis acidification tank for pH adjustment, and the whole anaerobic digestion mainly utilizes microorganisms to convert organic matters into methane and CO₂Water, etc., and discharging the biogas slurry and the biogas residues.

Biogas purification and cogeneration system: the biogas in the project mainly comprises the following components: methane content 60%, CO₂Content 30% H₂S content 0.3% and inert gas about 9.7%. Because the hydrogen sulfide can corrode and damage equipment, the biogas can be subjected to desulfurization treatment, and the content of the hydrogen sulfide in the desulfurized biogas is not more than 0.02 percent by calculation and meets the emission standard. The treated methane is subjected to cogeneration to obtain recyclable electricity and heat.

Biodiesel preparation system: the biodiesel in the project is a renewable diesel fuel which can replace petroleum diesel and is prepared by using crude oil in kitchen waste as a raw material through an ester exchange process. The process adopts a two-step reaction method, namely, the acidic catalytic pre-esterification reaction is firstly carried out, and then the alkaline catalytic transesterification reaction is carried out. The design scale of the biodiesel amount as the main product of the project is 25 t/d.

A biogas residue dehydration system: the residue after anaerobic digestion has high concentration and causes secondary pollution when not being treated in time, so that solid-liquid separation is needed, the biogas slurry overflows into a biogas slurry storage tank, the dehydrated biogas residues are transported to an incineration plant or a landfill for treatment, and the collected biogas slurry enters a wastewater treatment system.

TABLE 12 Table of major pollutants production and emission during the operating period

The noise value of the equipment noise in the table is taken as the average value of the noise generated by all the equipment, and the average value of the noise generated by the equipment is 64.1dB (A) after sound insulation treatment. The garbage transport vehicle can generate larger noise, and the noise source intensity of a 5m position of a general vehicle is 80dB (A).

And thirdly, predicting and evaluating the environmental influence in the operation period. Through the analysis, the influence of the waste water, the waste gas and the waste residue generated by the kitchen waste treatment plant is subjected to environment prediction, and the bearing capacity of the environment on pollution is considered. And strictly controlling the emission of pollutants according to evaluation standards.

1. Evaluation of influence of surface water and groundwater environment

And selecting a proper water quality model to predict the water environment, wherein the project accords with the characteristics of point source pollution, and the model of a material balance method is used for predicting the environment. The waste water produced by the project is 480t/d, and the waste water is treated by a self-built waste water treatment station, reaches the primary standard of the local standard 'water pollution discharge restriction' of Guangdong province (DB44/26-2001) in the second time period, and is discharged to a river by adopting a special pipeline.

2. Evaluation of atmospheric environmental impact

Odor impact prediction:

(1) prediction and evaluation factors: predicting the possible environmental influence of the process waste gas in the production process, and selecting ammonia, hydrogen sulfide and methyl mercaptan as prediction and evaluation factors.

(2) Prediction mode: according to the environmental impact evaluation guide-atmospheric environment (HJ2.2-2008), the atmospheric environment prediction work can be omitted in the tertiary evaluation, and the result of the estimation mode is directly used as a prediction and analysis basis.

3. Odor impact evaluation-protection distance:

(1) calculation of atmospheric environmental protection distance

According to the standard calculation program of the atmospheric environment protection distance of the environmental engineering assessment center of the environmental protection department, the result of the atmospheric environment protection distance of the project area source can be calculated to be 'no super-standard point'. According to the calculation result, the sanitary protection distance of ammonia is 50m, the sanitary protection distance of hydrogen sulfide is 50m, and the sanitary protection distance of methyl mercaptan is 200 m. According to the sanitary protection distance regulation, the protection distance calculated finally is 200 m.

(2) Relative specification guard distance requirements

Regarding the kitchen waste treatment project, at present, no corresponding standard or standard provides protection distance limitation for the kitchen waste treatment project, and the protection distance requirement of a household waste landfill site can only be referred to.

4. Evaluation of influence of boiler exhaust gas:

the project boiler uses methane as fuel. According to the technical manual of three wastes treatment engineering (wastewater volume), the volume content of hydrogen sulfide in the biogas generally accounts for 0.005-0.01%. The methane in the project is subjected to desulfurization treatment before cogeneration, and pollutants generated by combustion are few, so that the methane generally cannot cause serious harm to the atmosphere.

5. Evaluation of influence of Acoustic Environment

(1) Noise prediction mode

The prediction is calculated using the formula that point sources attenuate as the propagation distance increases. Calculation mode of multi-point source sound pressure level:

Leq＝10log(∑100Li)

in the formula: leq is the total equivalent sound level of the predicted points, db (a); li is the sound level contribution of the ith sound source to the predicted point, dB (A).

(2) Evaluation criteria

The factory boundary noise executes the environmental noise emission standard of the factory boundary of industrial enterprises (GB12348-2008)3 type standard. I.e., 65dB (A) daytime and 55dB (A) nighttime.

6. Evaluation of environmental impact of solid waste

(1) Digested mud cake

The mud cake after anaerobic digestion enters a treatment field for treatment or is comprehensively utilized in other ways, and the surrounding environment is not obviously influenced.

(2) Pretreatment and sorting of resource waste

Waste metal, waste plastic and waste paper separated by garbage pretreatment belong to resource wastes, and have no influence on the surrounding environment after being recycled.

(3) Domestic garbage

After the domestic garbage is collected and treated by municipal environmental sanitation departments, the domestic garbage has no influence on the surrounding environment.

(4) Kitchen waste

The kitchen waste can be automatically treated by the biomass treatment system, and the influence on the surrounding environment is avoided.

Compared with a comparative example, the life cycle evaluation technical scheme adopted by the invention has the following advantages and beneficial effects:

(1) the life cycle evaluation focuses more on the influence of the discharged pollutants on the environment, and key influence links and pollutants can be known according to the evaluation result. And environmental impact evaluation is carried out on the kitchen waste treatment plant in the operation period, and the whole evaluation process is mainly used for restricting the emission of pollutants through standards and specifications.

(2) And 3, life cycle evaluation is carried out, data sources are provided by site real-time monitoring, documents and relevant departments, a complete basic database is adopted, and a quantitative result has certain objectivity. And the environmental impact evaluation is carried out on the kitchen waste treatment plant in the operation period, and the data source is limited.

(3) The life cycle evaluation defines the system boundary, and the key process is evaluated, so that the method has pertinence. And the environmental impact evaluation is carried out on the kitchen waste treatment plant in the operation period, the evaluation range is wide, and no key point is highlighted.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.