Carbon emission accounting and planning method for sewage treatment plant

Abstract

The invention discloses a carbon emission accounting and planning method for a sewage treatment plant, and the method comprises the steps: constructing a sewage treatment plant carbon accounting boundary theory framework based on a full life cycle theory: starting from the whole process of a sewage treatment plant planning stage, a construction stage, an operation stage, an updating stage and a dismounting stage, according to the method, the range I carbon emission, the range II carbon emission and the range III carbon emission of the five stages are comprehensively considered, a sewage treatment plant carbon emission system is coupled with a sewage treatment plant carbon absorption system, and a theoretical framework of a sewage treatment plant carbon accounting boundary is systematically constructed; performing whole-process three-range accounting on the carbon emission of the sewage treatment plant: performing systematic quantification and analysis on the carbon emission of five stages and three ranges, finding out key nodes of the carbon emission of the sewage treatment plant, and providing a reliable basis for planning design and policy suggestion of the sewage treatment plant; the method disclosed by the invention plays a positive role in promoting the development of zero-carbon sewage treatment plant construction of each sewage treatment plant.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technologies, and particularly to a carbon emission accounting and planning method for sewage treatment plants. Background Art

[0002] Climate change is a major global challenge facing the world today. With the acceleration of the industrialization process and the growth of the global population, greenhouse gas emissions have increased sharply, leading to significant changes in the global climate system. Against this background, sewage treatment, as an important part of urban infrastructure, the proportion it occupies in carbon emissions cannot be ignored. Especially in the construction of a low-carbon society, the green transformation of sewage treatment plants is particularly important.

[0003] The existing carbon emission accounting system for sewage treatment plants has significant deficiencies:

[0004] First of all, the demarcation of the accounting boundary is not clear. Most studies only focus on the operation stage of sewage treatment plants, ignoring the carbon emissions in stages such as planning, construction, renovation, and demolition. And the pre-assessment in the planning stage is extremely important for controlling the carbon emissions of the entire project. This limitation leads to the inability to comprehensively evaluate the carbon emissions of sewage treatment plants.

[0005] Secondly, the singularity and non-uniformity of the accounting method are also one of the defects of the existing system. Many studies rely on single methods such as the emission factor method or the measured method, often ignoring the carbon emission characteristics and influencing factors of sewage treatment plants at different stages. For example, the energy consumption and material production in the construction stage, the energy use and chemical consumption in the operation stage, and the waste treatment in the demolition stage are not fully considered. This practice of ignoring indirect emissions makes the accounting results lack comprehensiveness and accuracy, resulting in the difficulty of comparing and verifying the results between different studies.

[0006] Finally, the existing carbon emission system for sewage treatment plants does not predict and plan the future situation of sewage treatment plants based on the concept of a green and low-carbon benchmark plant for sewage treatment, making it difficult to truly and effectively play the substantial policy guidance role of carbon emission accounting. Summary of the Invention

[0007] To solve the problems existing in the prior art, the purpose of the present invention is to provide a carbon emission accounting and planning method for sewage treatment plants, which has a positive effect on promoting the construction of zero-carbon sewage treatment plants in each sewage treatment plant.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is: a carbon emission accounting and planning method for sewage treatment plants, including the following steps:

[0009] Step 1: Construct a theoretical framework for the carbon accounting boundary of wastewater treatment plants based on the whole-life cycle theory: Starting from the whole process of the planning, construction, operation, renovation, and demolition stages of wastewater treatment plants, comprehensively consider the Scope 1, Scope 2, and Scope 3 carbon emissions in each of the five stages. Specifically, it includes the energy consumption within the plant area, the direct Scope 1 carbon emissions generated during the wastewater treatment process, and the Scope 2 carbon emissions such as externally sourced electricity. At the same time, it also considers the Scope 3 carbon emissions brought about by upstream supply chain activities and downstream waste treatment, and couples the carbon emission system of the wastewater treatment plant with the carbon absorption system of the wastewater treatment plant to systematically construct a theoretical framework for the carbon accounting boundary of the wastewater treatment plant;

[0010] Step 2: Three-scope accounting of the whole process of carbon emissions from wastewater treatment plants: The methodological model combines on-site research and carbon emission accounting to form a set of comprehensive methodological tools. Through on-site research, this study collected first-line data at different stages of wastewater treatment plants, including but not limited to energy consumption, material use, etc., ensuring the authenticity and accuracy of the data. The application of the hybrid analysis method combines the carbon emission factor method, input-output analysis method, and carbon sink estimation method to conduct refined accounting of the carbon emissions from wastewater treatment plants, improving the accuracy and reliability of the accounting. Provide a reliable basis for the planning and design of wastewater treatment plants and policy recommendations.

[0011] As a further improvement of the present invention, in Step 1, during the planning stage, a pre-assessment of carbon emissions is carried out by analyzing key information such as the environmental impact report of the wastewater treatment plant, such as construction area, designed treatment capacity, machinery use, and number of employees, etc.; during the construction stage, calculate the construction process of various buildings, covering all activities from the extraction of raw materials to the completion acceptance of the wastewater treatment plant; during the operation stage, calculate the carbon emissions during the daily monitoring and management of the wastewater treatment process. Most wastewater treatment plants need to be renovated and updated within 15 - 30 years, so the carbon emissions in this stage can be considered based on a 30-year operation life cycle; during the renovation stage, evaluate the carbon emissions of various activities during the renovation and update of existing facilities; the demolition stage includes demolishing all facilities above the preset underground range of the original wastewater treatment plant and then restoring the site.

[0012] As a further improvement of the present invention, in Step 1, Scope 1 carbon emissions refer to the carbon emissions directly generated by the wastewater treatment plant, including the direct consumption of fossil energy and the carbon emissions generated during the wastewater treatment process; Scope 2 carbon emissions include the indirect carbon emissions generated by the electricity and thermal energy used by the wastewater treatment plant; Scope 3 carbon emissions include other indirect carbon emissions from the supply chain, transportation, and waste treatment of the wastewater treatment plant.

[0013] As a further improvement of the present invention, in Step 2, the specific calculation method for the three-scope accounting of the whole process of carbon emissions from wastewater treatment plants is as follows:

[0014] Couple the process-based full-life-cycle carbon emission accounting method, the economic input-output-based life cycle analysis method EIO-LCA, and the regional carbon absorption accounting method to construct a carbon emission and carbon sink accounting system to achieve quantitative accounting of carbon emissions at all stages and in all scopes of the sewage treatment plant. The planning stage is a pre-assessment for effective control. The actual carbon emissions of the sewage treatment plant include the latter four stages, and the calculation formula is:

[0015] E sum = E C + E O + E R + E D - E A

[0016] In the formula: E sum is the accounting result of the full-life-cycle carbon emissions of the sewage treatment plant, E C is the accounting result of the carbon emissions during the construction stage of the sewage treatment plant, E O is the accounting result of the carbon emissions during the operation stage of the sewage treatment plant, E R is the accounting result of the carbon emissions during the renovation stage of the sewage treatment plant, E D is the accounting result of the carbon emissions during the demolition stage of the sewage treatment plant, E A is the accounting result of the carbon absorption of the sewage treatment plant.

[0017] As a further improvement of the present invention, the carbon emission accounting during the construction stage of the sewage treatment plant includes the scope one carbon emission accounting E C1 , the scope two carbon emission accounting E C2 and the scope three carbon emission accounting E C3 ;

[0018] The scope one carbon emission accounting E C1 during the construction stage includes construction machinery E Ccm and material transportation E Cmt :

[0019]

[0020] In the formula: E Ccm is the total direct emissions of fossil energy consumed by the construction machinery of the sewage treatment plant during the construction stage, N Ci is the number of working days of the i-th construction machinery equipment, EF icm is the carbon emission factor of the i-th construction machinery working day;

[0021]

[0022] In the formula: E Cmt is the total direct emissions of material transportation of the sewage treatment plant during the construction stage, D Ciis the transportation distance of the i-th type of transport truck, EF imt is the emission factor of the i-th type of transport truck;

[0023] Carbon emission accounting E for Scope 2 during the construction phase C2 includes externally-supplied electricity E Cep and externally-supplied heat E Chp :

[0024]

[0025] In the formula: E Cep is the carbon dioxide equivalent emission corresponding to the electricity purchased by the sewage treatment plant during the construction phase, AD Ciep is the electricity consumption of the i-th type of temporary facility purchased during the construction process of the sewage treatment plant within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th type of electricity;

[0026]

[0027] In the formula: E Chp is the carbon dioxide equivalent emission corresponding to the heat purchased by the sewage treatment plant during the construction phase, AD Cihp is the heat consumption of the i-th type of temporary facility purchased during the construction process of the sewage treatment plant within the accounting period, EF ihp is the average carbon dioxide emission factor of the i-th type of heat;

[0028] Carbon emission accounting E for Scope 3 during the construction phase C3 includes building materials E Cbm and solid waste treatment E Csw :

[0029]

[0030] In the formula: E Cbm is the carbon dioxide emission caused by the production and processing of building materials during the construction phase of the sewage treatment plant, M Ci is the consumption of the i-th type of material used during the construction phase, EF ib is the carbon emission factor of the i-th type of material;

[0031]

[0032] In the formula: E Csw is the carbon emission from treating solid waste during the construction phase, A Ci is the amount of the i-th type of solid waste or the amount of solid waste of the i-th type of solid waste disposal method during the construction process of the sewage treatment plant, EF isw is the carbon emission generated from disposing of the i-th type of solid waste or the i-th type of solid waste disposal method.

[0033] The EIO-LCA method is used to quantify greenhouse gas emissions such as the use of building materials and chemicals to make up for truncation errors. The accounting error is small but it will be more complex. The carbon emissions of the materials used in the sewage treatment plant in each department of the production chain are as follows:

[0034] E ibm = R × x i

[0035] In the formula: E ibm is the amount of CO2 emitted in the upstream production process to meet the demand y of the sewage treatment plant i R is a determined row vector, and its elements correspond to the amount of CO2 directly emitted per unit currency of each department;

[0036] The element value R i is:

[0037]

[0038] In the formula: R i is the direct carbon emission coefficient of the i-th department, c i is the direct carbon emission of the i-th department, X i is the total output of this department;

[0039] x in the input-output model i is the total output of the products of each department in the production chain:

[0040] x i = (I - A) -1 × y i

[0041] In the formula: I is the identity matrix, A is the direct consumption coefficient matrix, y i is a column vector representing the value of the imports of each product by the sewage treatment plant, and (I - A) -1 is the Leontief inverse matrix, and i is the production department corresponding to the product under study, that is, the industrial department, the tap water department, the agricultural department, etc.

[0042] As a further improvement of the present invention, the carbon emission accounting in the operation stage of the sewage treatment plant includes the scope one carbon emission accounting E O1 in the operation stage, the scope two carbon emission accounting E O2 in the operation stage, and the scope three carbon emission accounting E O3 in the operation stage;

[0043] The scope one carbon emission accounting E O1 in the operation stage includes sewage treatment E Ost :

[0044]

[0045] Where: E Ost is the carbon emissions caused by sewage treatment, is the direct carbon dioxide equivalent caused by CH4, is the direct carbon dioxide equivalent caused by N2O;

[0046]

[0047] Where: is the direct carbon dioxide equivalent caused by CH4, V is the actual daily sewage treatment volume of the sewage treatment plant, D is the actual operating days of the sewage treatment plant, COD in is the content of COD per unit volume of sewage in the influent sewage, COD out is the content of COD per unit volume of sewage in the effluent sewage, is the CH4 emission factor, that is, the mutual relationship between CH4 emissions and COD reduction, is the global warming potential value of CH4;

[0048]

[0049] Where: is the direct carbon dioxide equivalent caused by N2O, V is the actual daily sewage treatment volume of the sewage treatment plant, D is the actual operating days of the sewage treatment plant, TN in is the content of TN per unit volume of sewage in the influent sewage, TN out is the content of TN per unit volume of sewage in the effluent sewage, is the N2O-N emission factor, that is, the mutual relationship between the global warming potential value emissions of N2O-N and TN reduction, is the global warming potential value of N2O;

[0050] Carbon emissions accounting E for Scope 2 during the operation stage O2 includes externally supplied electricity E Oep and externally supplied heat E Ohp :

[0051]

[0052] Where: E Oep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the operation stage, AD Oiep is the amount of electricity purchased by the i-th treatment unit during the operation of the sewage treatment plant within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th type of electricity;

[0053]

[0054] Where: OhpCarbon dioxide equivalent emissions corresponding to the purchased heat for the sewage treatment plant during the operation stage, AD Oihp Heat quantity purchased for the i-th treatment unit during the operation of the sewage treatment plant within the accounting period, EF ihp Average carbon dioxide emission factor for the i-th type of heat;

[0055] Scope three carbon emission accounting E during the operation stage O3 Including chemical agent use E Oms And solid waste treatment E Osw :

[0056]

[0057] In the formula: E Oms Carbon emissions from the use of chemical agents during the operation stage, M Oi Consumption of the i-th chemical agent during the operation of the sewage treatment plant, EF ims Emission factor for the i-th chemical agent;

[0058]

[0059] In the formula: E Osw Carbon emissions from the treatment of solid waste during the operation stage, A Oi Quantity of the i-th solid waste or the quantity of solid waste in the i-th solid waste disposal method during the operation of the sewage treatment plant, EF isw Carbon emissions generated from the disposal of the i-th solid waste or the i-th solid waste disposal method.

[0060] As a further improvement of the present invention, carbon emission accounting E during the update stage of the sewage treatment plant R Including scope one carbon emission accounting E during the update stage R1 、Scope two carbon emission accounting E during the update stage R2 And scope three carbon emission accounting E during the update stage R3 ;

[0061] Scope one carbon emission accounting E during the update stage R1 Including construction machinery E Rcm And material transportation E Rmt :

[0062]

[0063] In the formula: E Rcm Total direct emissions of fossil energy consumed by construction machinery in the sewage treatment plant during the update stage, N Ri Number of shifts of the i-th construction machinery and equipment used for the renovation and update of the sewage treatment plant, EF icm Carbon emission factor for the i-th construction machinery shift;

[0064]

[0065] Where: E Rmt is the total direct emissions of material transportation in the sewage treatment plant during the renovation phase, D Ri is the transportation distance of the i-th transport truck in the renovation and update of the sewage treatment plant, EF imt is the emission factor of the i-th transport truck;

[0066] Carbon emission accounting of Scope 2 during the renovation phase E R2 includes externally-supplied electricity E Rep :

[0067]

[0068] Where: E Rep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the renovation phase, AD Riep is the electricity consumption of the i-th type used during the renovation and update of the sewage treatment plant within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th type of electricity;

[0069] Carbon emission accounting of Scope 3 during the renovation phase E R3 includes building materials E Rbm and solid waste treatment E Rsw :

[0070]

[0071] Where: E Rbm is the carbon emission from the production and processing of materials or equipment used during the renovation phase, M Ri is the consumption of the i-th type of material or equipment used during the renovation phase, EF ibm is the carbon emission factor of the i-th type of material or equipment;

[0072]

[0073] Where: E Rsw is the carbon emission from the treatment of solid waste during the renovation phase, A Ri is the amount of the i-th type of solid waste or the amount of solid waste of the i-th type of solid waste disposal method during the renovation of the sewage treatment plant, EF isw is the carbon emission generated from disposing of the i-th type of solid waste or the i-th type of solid waste disposal method.

[0074] As a further improvement of the present invention, the carbon emission accounting E of the demolition phase of the sewage treatment plant D includes the carbon emission accounting E of Scope 1 in the demolition phase D1 and the carbon emission accounting E of Scope 2 in the demolition phase D2Carbon Emission Accounting for Scope Three in the Demolition Phase E D3 ;

[0075] Carbon Emission Accounting for Scope One in the Demolition Phase E D1 Construction Machinery E Dcm and Material Transportation E Dmt :

[0076]

[0077] Where: E Dcm is the total direct emissions of fossil energy consumed by construction machinery in the sewage treatment plant during the demolition phase, N Di is the number of shifts of the i-th construction machinery equipment used during the demolition process, EF icm is the carbon emission factor per shift of the i-th construction machinery;

[0078]

[0079] Where: E Dmt is the total direct emissions of material transportation in the sewage treatment plant during the demolition phase, D Di is the transportation distance of the i-th transport truck during the demolition process, ET imt is the emission factor of the i-th transport truck;

[0080] Carbon Emission Accounting for Scope Two in the Demolition Phase E D2 includes externally-supplied electricity E Dep :

[0081]

[0082] Where: E Dep is the carbon dioxide equivalent emissions corresponding to the purchased electricity of the sewage treatment plant during the demolition phase, AD Diep is the electricity consumption of the i-th equipment used by the sewage treatment plant during the demolition process within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th electricity;

[0083] Carbon Emission Accounting for Scope Three in the Demolition Phase E D3 includes building materials E Dbm and solid waste treatment E Dsw :

[0084]

[0085] Where: E Dbm is the carbon emission of the filling materials used when demolishing the sewage treatment plant, M Di is the consumption of the i-th material used during the demolition, EF ibm is the carbon emission factor of the i-th material;

[0086]

[0087] Where: E Dsw To deal with carbon emissions from solid waste during the demolition phase, A Di is the amount of solid waste of the i-th type during the dismantling of the sewage treatment plant or the amount of solid waste of the i-th solid waste disposal method, EF isw Carbon emissions generated by the disposal of the i-th type of solid waste or the i-th method of solid waste disposal.

[0088] As a further improvement of the present invention, it also includes carbon emission reduction accounting, that is, carbon sink E A :

[0089] E A =∑(P i ×EF p ×10 -3 )

[0090] Where: E A is the carbon absorption accounting result of the sewage treatment plant, Pi is the canopy area of the i-th plant planted in the sewage treatment plant or the number of the i-th plant planted, EF p It is the carbon sequestration coefficient per unit area or per unit quantity of the ith plant planted in the sewage treatment plant.

[0091] Based on the shortcomings of the current carbon emission accounting system of sewage treatment plants, the present invention proposes a carbon emission accounting framework system based on the full life cycle theory to provide theoretical support for carbon emission accounting of sewage treatment plants to solve the shortcomings of the prior art. The present invention has the following characteristics:

[0092] (1) Carbon emission accounting framework for sewage treatment plants based on the full life cycle theory. This framework comprehensively covers the entire life cycle of sewage treatment plants from planning, construction, operation, renewal to demolition. This study is closely linked to the "Beijing Pollution Reduction and Carbon Reduction Synergy and Efficiency Improvement Implementation Plan", emphasizing the pre-assessment of carbon emissions in the planning stage, so as to accurately predict and control the carbon footprint of the entire life cycle. Pre-assessment is crucial to integrating the concept of pollution reduction and carbon reduction in the early stages of the project, helping to ensure that carbon emissions are effectively controlled during the construction process and achieve both environmental and economic benefits.

[0093] (2) This invention comprehensively considers direct and indirect carbon emissions of sewage treatment plants, covering three scopes of carbon emissions. Specifically, it includes energy consumption within the plant, scope 1 carbon emissions directly generated by the sewage treatment process, and scope 2 carbon emissions such as external power. At the same time, scope 3 carbon emissions caused by upstream supply chain activities and downstream waste treatment are also considered to ensure the accuracy and effectiveness of the accounting results.

[0094] (3) The methodological model integrates on-site research, carbon emission accounting, and index system assessment to form a comprehensive accounting tool. Through on-site research, this study collected first-line data at different stages of sewage treatment plants, including but not limited to energy consumption, material use, employee commuting, etc., ensuring the authenticity and accuracy of the data. The application of the hybrid analysis method combines the carbon emission factor method, input-output analysis method, and carbon sink estimation method to conduct refined accounting of the carbon emissions of sewage treatment plants, improving the accuracy and reliability of the accounting.

[0095] (4) The present invention also designs construction plans for green and low-carbon benchmark sewage treatment plants for different scenarios, providing specific and feasible paths for the low-carbon transformation of sewage treatment plants. This design is not only forward-looking but also provides a scientific basis for policy-making and actual operation.

[0096] The implementation of the present invention has the characteristics of low cost, easy measurement, high precision, strong operability, wide scope of application, etc. By accurately identifying the key areas of carbon emissions, it can point out the specific operation and technical directions for sewage treatment plants to reduce emissions, promoting the green and low-carbon transformation of the sewage treatment industry.

[0097] The beneficial effects of the present invention are as follows:

[0098] 1. The carbon emission accounting and scenario planning method system of the present invention for sewage treatment plants starts from the concept of the whole life cycle based on processes, constructs a theoretical framework for the carbon accounting boundary of sewage treatment plants based on the whole life cycle theory, and can comprehensively account for the direct carbon emissions, upstream implicit carbon emissions, and downstream indirect carbon emissions within sewage treatment plants, fundamentally revealing the carbon emission impacts and carbon emission sources in the whole life cycle process of sewage treatment plants, which is the scientific basis for reducing carbon emissions and realizing the construction of zero-carbon sewage treatment plants.

[0099] 2. The carbon emission accounting and scenario planning method system of the present invention for sewage treatment plants can not only account for the total carbon emissions of sewage treatment plants, but also identify the key nodes of carbon emission governance through the phased and range-based accounting of the carbon emissions of sewage treatment plants, which has key guiding significance for the formulation of specific carbon emission reduction measures.

[0100] 3. The carbon emission accounting and scenario planning method system of the present invention for sewage treatment plants, based on carbon emission accounting, starts from two dimensions of infrastructure construction and construction management, provides practical planning guidance for sewage treatment plants, and effectively promotes the implementation of green and low-carbon benchmark sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 It is the system framework diagram of the embodiment of the present invention;

[0102] Figure 2This is the carbon emission accounting boundary framework diagram of the sewage treatment plant based on the whole life cycle theory in the embodiments of the present invention. Detailed implementation manners

[0103] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0104] Embodiment

[0105] A carbon emission accounting and planning method for a sewage treatment plant, comprising:

[0106] 1. The theoretical framework of the carbon accounting boundary of the sewage treatment plant based on the whole life cycle theory:

[0107] In this embodiment, starting from the whole process of the planning, construction, operation, renewal, and demolition of the sewage treatment plant, the scope one carbon emissions, scope two carbon emissions, and scope three carbon emissions in each of the five stages are comprehensively considered, and the carbon emission system of the sewage treatment plant is coupled with the carbon absorption system of the sewage treatment plant to systematically construct a theoretical framework for the carbon accounting boundary of the sewage treatment plant.

[0108] In the planning stage, pre-evaluation is carried out by analyzing key information such as the environmental impact report of the sewage treatment plant, such as the construction area, designed treatment capacity, machinery use, and number of employees. The construction stage refers to all activities from the extraction of raw materials until the completion of the entire sewage treatment plant during the construction process of various buildings. In the operation stage, the carbon emissions during the daily monitoring and management of the sewage treatment process are calculated. Most sewage treatment plants need to be renovated and updated within 15 - 30 years, so the carbon emissions in this stage can be considered based on a 30-year operation life cycle. The renewal stage evaluates the carbon emissions of various activities during the renovation and update of existing facilities. The demolition stage generally refers to the complete demolition of the facilities above the preset underground range of the original sewage treatment plant and then the restoration of the site.

[0109] The scope one carbon emissions of the sewage treatment plant refer to the carbon emissions directly generated by the sewage treatment plant, including the direct consumption of fossil energy and the carbon emissions generated during the sewage treatment process. The scope two carbon emissions involve the carbon emissions generated by energy such as electricity and heat used by the sewage treatment plant. The scope three carbon emissions cover other indirect carbon emissions such as the supply chain, transportation, and waste treatment of the sewage treatment plant. The carbon emission accounting boundary framework of the sewage treatment plant is as Figure 2 shown.

[0110] 2. The whole-process three-scope accounting of the carbon emissions of the sewage treatment plant:

[0111] After proposing a refined carbon emission accounting framework in this embodiment, for the five stages and three scopes (as Figure 1Conduct systematic quantification and analysis of the carbon emissions shown in the figure, identify the key nodes of carbon emissions in wastewater treatment plants, and provide a reliable basis for subsequent planning, design, and policy recommendations. The scope of carbon emissions accounting for wastewater treatment plants is as follows:

[0112] Table 1 Regional Division and Carbon Emissions Accounting of Wastewater Treatment Plants

[0113]

[0114] 3. Specific calculation methods for the three - scope accounting of the whole - process carbon emissions in wastewater treatment plants:

[0115] In this embodiment, the process - based full - life - cycle carbon emissions accounting method, the economic input - output - based life - cycle analysis method (EIO - LCA), and the regional carbon absorption accounting method are coupled to construct a carbon emissions and carbon sink accounting system to achieve the purpose of specifically quantifying the carbon emissions at each stage and of each category in wastewater treatment plants. The planning stage is for pre - assessment for effective control. The actual carbon emissions of wastewater treatment plants include the latter four stages, and the calculation formula is:

[0116] E sum =E C +E O +E R +E D -E A (1)

[0117] Where: E sum is the accounting result of the full - life - cycle carbon emissions of the wastewater treatment plant, kg CO 2-eq ; E C is the total amount of carbon dioxide equivalent in the construction stage of the wastewater treatment plant, kg CO 2-eq ; E O is the total amount of carbon dioxide equivalent in the operation stage, kg CO 2-eq ; E R is the total amount of carbon dioxide equivalent in the renewal stage, kg CO 2-eq ; E D is the total amount of carbon dioxide equivalent in the demolition stage, kg CO 2-eq ; E A is the total amount of carbon dioxide equivalent absorbed by the wastewater treatment plant, kg CO 2-eq .

[0118] 3.1 Carbon Emissions Accounting in the Planning Stage of Wastewater Treatment Plants (E P ):

[0119] In the preliminary planning stage and construction drawing design stage of a sewage treatment plant, there are detailed data such as building material lists and bill of quantities, which can be based on the data research and scientific estimation of existing sewage treatment plants. The assessment content covers the pre-assessment of carbon emissions during the construction stage and aspects such as technology selection, energy consumption (including electricity, heat, etc.), and carbon sink absorption capacity during the operation stage. In addition, the embodied carbon emissions of key materials (such as steel, cement, concrete, glass) obtained outside the boundary of the sewage treatment plant need to be considered. The planning stage of the sewage treatment plant is the stage with the scarcest data, so the carbon emission index method is generally used to estimate the carbon emissions in this stage.

[0120] 3.1.1 Scope 1 carbon emission accounting during the planning stage (E P1 ):

[0121] 3.1.1.1 Fossil fuels (E Pcm ):

[0122] The energy consumption of construction machinery and equipment at the construction site will generate carbon emissions, including the direct carbon emissions after fuel combustion. The basic calculation formula is as follows:

[0123]

[0124] In the formula: E Pcm is the total direct emissions of fossil energy in the sewage treatment plant during the planning process, kg CO 2-eq ; N Pi is the number of shifts of the i-th construction machinery and equipment, shifts; EF icm is the carbon emission factor per shift of the i-th construction machinery, kg CO 2-eq / shift;

[0125] 3.1.2 Scope 2 carbon emission accounting during the planning stage (E P2 ):

[0126] 3.1.2.1 Outsourced electricity (E Pep ):

[0127] In a sewage treatment plant, different effluent standards result in significant differences in the electricity consumption for reducing unit oxygen-consuming pollutants. Therefore, in the planning stage, it is recommended to select data by combining the actual situation of the sewage treatment plant and referring to sewage treatment plants with similar treatment scales and processes in the surrounding area when calculating electricity consumption. By consulting relevant literature and government websites, data from different regions in the country were obtained, and the average electricity consumption per ton of water in urban sewage treatment plants across the country was 280 kWh / km 3 . According to the different treatment scales, sewage treatment plants can be divided into four categories: small (<10,000 m 3 / day), medium (10,000 - 100,000 m 3 / day), large (100,000 - 300,000 m 3 / day) and extra-large (> 300,000 m 3 / day). Data shows that small and medium-sized sewage treatment plants account for 90.7% of the total number in the country, and the energy consumption level is closely related to the sewage treatment volume and process characteristics.

[0128] Therefore, the pre-assessment of the carbon emissions from externally-supplied electricity during the operation stage can be calculated using the electricity consumption in the table and the emission factors of local electricity production. The basic calculation is as follows:

[0129]

[0130] In the formula: E Pep is the carbon dioxide emissions caused by the externally-supplied electricity of the sewage treatment plant for pre-assessment, kg CO 2-eq ; AD Piep is the average electricity consumption per ton of sewage of the i-th type of sewage treatment plant for externally-supplied electricity, kWh / (m 3 ·d); S is the planned treatment scale of the sewage treatment plant, m 3 ; D is the number of operating days of the sewage treatment plant, d; EF iep is the carbon dioxide emission factor of the externally-supplied electricity from the i-th source, kg CO 2-eq / kWh.

[0131] 3.1.2.2 Externally-supplied heat (E Php ):

[0132]

[0133] In the formula: E Php is the carbon dioxide emissions caused by the externally-supplied heat of the sewage treatment plant for pre-assessment, kg CO 2-eq ; AD Pihp is the externally-supplied heat of the i-th source purchased by the sewage treatment plant, GJ; EF iep is the carbon dioxide emission factor of the externally-supplied electricity from the i-th source, kg CO 2-eq / GJ.

[0134] 3.1.3 Scope 3 carbon emissions accounting during the planning stage (E P3 ):

[0135] 3.1.3.1 Building materials (E Pbm ):

[0136] Estimate the carbon emissions in the material production process during the preliminary planning stage, mainly considering building materials such as concrete, steel, cement mortar, and building blocks. The total weight of the selected main building materials should be higher than 95% of the total weight of all building materials, or building materials with a weight ratio less than 0.1% should be ignored. Include carbon emissions in processes such as processing, manufacturing, packaging, and storage, that is, the process from "cradle to gate". The embodied carbon emissions in the building material production stage during the planning stage are calculated according to the formula:

[0137]

[0138] In the formula: E Pbm is the carbon emissions of building materials estimated to be used during the planning stage, kg CO 2-eq ; M Pi is the consumption of the i-th material estimated to be used during the planning stage, t; EF ibm is the carbon emission factor of the i-th material estimated to be used during the planning stage, kg CO 2-eq / t;

[0139] 3.2 Carbon emission accounting for the construction stage of the sewage treatment plant (E C ):

[0140] 3.2.1 Carbon emission accounting for Scope 1 during the construction stage (E C1 ):

[0141] 3.2.1.1 Construction machinery (E Ccm ):

[0142] During the construction process, the use of construction machinery will generate direct carbon emissions. The basic calculation formula is as follows:

[0143]

[0144] In the formula: E Ccm is the total direct emissions of fossil energy consumed by construction machinery in the sewage treatment plant during the construction stage, kgCO 2-eq ; N Ci is the number of shifts of the i-th construction machinery equipment, shifts; EF icm is the carbon emission factor per shift of the i-th construction machinery, kg CO 2-eq / shift;

[0145] 3.2.1.2 Material transportation (E Cmt ):

[0146] The main transportation method of building materials is road transportation. The transportation distance data is obtained through on-site investigations and relevant map software. The units of building materials are uniformly converted into weight units according to weight conversion, and combined with the carbon emission factor of material weight and traffic to calculate the carbon emissions caused by gasoline, etc. during the material transportation process. The basic calculation formula is as follows:

[0147]

[0148] Where: E Cmt is the total direct emissions of sewage treatment plant materials transportation during the construction stage, kg CO 2-eq ; D Ci is the transportation distance of the i-th type of transport truck, km; EF imt is the emission factor of the i-th type of transport truck, kg CO 2-eq / km;

[0149] 3.2.2 Carbon emission accounting for Scope 2 during the construction stage (E C2 ):

[0150] 3.2.2.1 Purchased electricity (E Cep ):

[0151] It mainly comes from temporary facilities, including lighting, refrigeration, heating, etc. in the office area and living area during the construction stage. This part of the calculation can be carried out according to the corresponding energy consumption and carbon emission factors. The resulting indirect carbon emissions can be calculated using the electricity consumption and the carbon emission factor of electricity production. The basic calculation is as follows:

[0152]

[0153] Where: E Cep is the carbon dioxide equivalent emissions corresponding to the purchased electricity of the sewage treatment plant during the construction stage, kgCO 2-eq ; AD Ciep is the electricity consumption purchased by the i-th type of temporary facility during the construction of the sewage treatment plant during the accounting period, kWh; EF iep is the average carbon dioxide emission factor of the i-th type of electricity, kg CO 2-eq / kWh;

[0154] 3.2.2.2 Purchased heat (E Chp ):

[0155] The formula for calculating the carbon dioxide equivalent emissions corresponding to the purchased heat of the sewage treatment plant or treatment unit is as follows:

[0156]

[0157] Where: E Chp is the carbon dioxide equivalent emissions corresponding to the purchased heat of the sewage treatment plant during the construction stage, kgCO 2-eq ; AD Cihp is the heat consumption purchased by the i-th type of temporary facility during the construction of the sewage treatment plant during the accounting period, GJ; EF ihp is the average carbon dioxide equivalent emission factor of the i-th type of heat, kg CO2-eq / GJ, the recommended value can be 110 kg CO 2-eq / GJ;

[0158] 3.2.3 Carbon emission accounting for Scope 3 during the construction phase (E C3 ):

[0159] Carbon emissions take into account the embodied carbon emissions in the upstream supply chain excluding externally sourced energy, such as the consumption of chemicals and construction raw materials, as well as the embodied emissions in downstream solid waste treatment. According to the requirements of accounting accuracy, in addition to the full life cycle carbon emission coefficient method provided in the planning phase, there is also the EIO-LCA method.

[0160] The accuracy of the results of the carbon emission factor method depends on the accuracy of the carbon emission factors. To facilitate the calculation of carbon emissions during the transportation and maintenance of building materials, this paper has collected and sorted out the carbon emission factors of building materials.

[0161] 3.2.3.1 Building materials (E Cbm ):

[0162] The main building materials required for the construction of the sewage treatment plant include steel bars, wood, cement, sand and gravel, sintered bricks, etc. Indirect carbon emissions are generated during the production in the upstream supply chain. Substituting the usage of building materials and the corresponding carbon emission factors of building materials in the table into the formula can calculate their carbon emissions:

[0163]

[0164] In the formula: E Cbm is the carbon dioxide emissions caused by the production and processing of building materials during the construction phase of the sewage treatment plant, kg CO 2-eq ; M Ci is the consumption of the i-th material during the construction phase of the sewage treatment plant, t; EF ibm is the carbon emission factor of the i-th material during the construction phase of the sewage treatment plant, kg CO 2-e / t;

[0165] 3.2.3.2 Solid waste treatment (E Csw ):

[0166] The waste generated during the construction process is not treated in the sewage treatment plant, but transported to other institutions for incineration or landfill treatment. As the carbon emissions of Scope 3, the accounting formula is as follows:

[0167]

[0168] In the formula: E Csw is the carbon emissions from the treatment of solid waste during the construction phase, kg CO 2-eq ; A Ci$W_{i}$ is the amount of the $i$-th solid waste or the amount of solid waste in the $i$-th solid waste disposal method during the construction of the sewage treatment plant, kg; EF isw is the carbon emission generated by disposing of the $i$-th solid waste or the $i$-th solid waste disposal method, kg CO 2-eq / kg;

[0169] 3.2.3.3 EIO-LCA method:

[0170] The EIO-LCA method is used to quantify the greenhouse gas emissions such as the use of building materials and chemicals to make up for the truncation error. The accounting error is small but it will be more complex. The carbon emissions of the materials used in the sewage treatment plant in each department of the production chain are:

[0171] E ibm =R×x i (12)

[0172] In the formula: E ibm is the amount of CO2 emitted in the upstream production process to meet the demand y i of the sewage treatment plant; R is a determined row vector, and its elements correspond to the amount of CO2 directly emitted per unit currency of each department;

[0173] The element value R i is:

[0174]

[0175] In the formula: R i is the direct carbon emission coefficient of the $i$-th department; c i is the direct carbon emission of the $i$-th department; X i is the total output of this department;

[0176] The x in the input-output model i is the total output of the products of each department in the production chain:

[0177] x i =(I - A) -1 ×y i (14)

[0178] In the formula: I is the identity matrix; A is the direct consumption coefficient matrix; y i is the column vector representing the value of the imports of each product by the sewage treatment plant; (I - A) -1 is the Leontief inverse matrix; i is the production department corresponding to the product under study, that is, the industrial department, the tap water department, the agricultural department, etc.

[0179] 3.3 Carbon emission accounting during the operation stage of the sewage treatment plant (E O ):

[0180] 3.3.1 Carbon emission accounting for Scope 1 during the operation phase (E O1 ):

[0181] 3.3.1.1 Wastewater treatment (E Ost ):

[0182]

[0183] Where: E Ost is the direct carbon emission of the wastewater treatment plant during the operation phase, kg CO 2-eq ; is the direct carbon dioxide equivalent caused by CH4, kg CO 2-eq ; is the direct carbon dioxide equivalent caused by N2O, kg CO 2-eq ;

[0184] (1) Carbon emission accounting for methane (E CH4 ):

[0185] During the wastewater treatment process, methane emissions will be generated due to the digestion and degradation of organic matter and endogenous respiration. The carbon emission calculation formula for CH4 is:

[0186]

[0187] Where: is the direct carbon dioxide equivalent caused by CH4, kg CO 2-eq ; V is the actual daily wastewater treatment volume of the wastewater treatment plant, L / d; D is the actual operation days of the wastewater treatment plant, d; COD in is the content of COD per unit volume of wastewater in the influent, mg / L; COD out is the content of COD per unit volume of wastewater in the effluent, mg / L; is the CH4 emission factor, that is, the mutual relationship between CH4 emissions and COD reduction, is the global warming potential of CH4,

[0188] (2) Carbon emission accounting for nitrous oxide (E N2O ):

[0189] During the wastewater treatment process, emissions will be generated due to the digestion and degradation of organic matter and endogenous respiration. The carbon emission calculation formula is:

[0190]

[0191] Where: is the direct carbon dioxide equivalent caused by N2O, kg CO 2-eq; V is the actual daily sewage treatment capacity of the sewage treatment plant, L / d; D is the actual operating days of the sewage treatment plant, d; TN in is the content of TN in the sewage per unit volume of the influent sewage, mg / L; TN out is the content of TN in the sewage per unit volume of the effluent sewage, mg / L; is the N2O-N emission factor, that is, the mutual relationship between the N2O-N emission and the TN reduction amount, is the global warming potential value of N2O,

[0192] 3.3.2 Carbon emission accounting for Scope 2 during the operation stage (E O2 ):

[0193] 3.3.2.1 Purchased electricity (E Oep ):

[0194] During the sewage treatment process, facilities such as aeration blowers, agitators, lift pumps, sand and water separators, underwater thrusters, reflux pumps, sludge scrapers, and sludge dewatering equipment consume electricity, as shown in Equation (8).

[0195] 3.3.2.2 Purchased heat (E Ohp ):

[0196] During the operation stage, a large amount of heat emissions will be generated due to the operation of equipment. The indirect carbon emissions caused by it can be calculated using the heat consumption and the heat emission factor. The basic calculation formula is shown in Equation (9).

[0197] 3.3.3 Carbon emission accounting for Scope 3 during the operation stage (E O3 ):

[0198] 3.3.3.1 Chemical agent use (E Oms ):

[0199] Emissions from material consumption are mainly disinfectants added before the sewage leaves the plant, flocculants added during sludge thickening and dewatering, etc. The accounting basis is the dosage of various chemical agents and the greenhouse gas emission factors generated by various chemical agents. The basic calculation is as follows:

[0200]

[0201] In the formula: E Oms is the carbon emission from the use of chemical agents during the operation stage, kg CO 2-eq ; M Oi is the consumption of the i-th chemical agent during the operation of the sewage treatment plant, t; EF ims is the emission factor of the i-th chemical agent, kg CO 2-eq / t;

[0202] 3.3.3.2 Solid waste treatment (EOsw )

[0203] During the operation stage, due to the generation of sludge and domestic waste, etc., the operation of machinery and kitchens generates waste. The basic calculation formula is shown in Equation (11).

[0204] 3.4 Carbon emission accounting in the renovation stage of the sewage treatment plant (E R )

[0205] 3.4.1 Scope 1 carbon emission accounting in the renovation stage (E R1 )

[0206] 3.4.1.1 Construction machinery (E Rcm )

[0207] During the renovation stage, the use of construction machinery for expansion, etc. will generate direct carbon emissions. The basic calculation formula is shown in Equation (6).

[0208] 3.4.1.2 Material transportation (E Rmt )

[0209] During the renovation stage, the transportation of raw materials such as steel bars and cement is required during the expansion process, and direct carbon emissions will be generated during the transportation process. The basic calculation formula is shown in Equation (7).

[0210] 3.4.2 Scope 2 carbon emission accounting in the renovation stage (E R2 )

[0211] 3.4.2.1 Outsourced electricity (E Rep )

[0212] A large amount of energy consumption emissions will be generated during the renovation stage. The resulting indirect carbon emissions can be calculated using the electricity consumption and the electricity emission factor. The basic calculation formula is shown in Equation (8).

[0213] 3.4.3 Scope 3 carbon emission accounting in the renovation stage (E R3 )

[0214] 3.4.3.1 Building materials (E Rbm )

[0215] The main building materials required for the renovation of the sewage treatment plant, including steel bars, wood, cement, sand and gravel, sintered bricks, etc., generate indirect carbon emissions during the production in the upstream supply chain. The calculation formula is shown in Equation (10).

[0216] 3.4.3.2 Solid waste treatment (E Rsw )

[0217] During the renovation stage, a large amount of waste will be generated due to machinery and building renovation. The basic calculation formula is shown in Equation (11).

[0218] 3.5 Carbon emission accounting in the demolition stage of the sewage treatment plant (ED )

[0219] 3.5.1 Carbon emission accounting for Scope 1 during the demolition stage (E D1 )

[0220] The carbon emissions during the demolition stage are mainly the carbon generated from the use of mechanical equipment during the demolition of the sewage treatment plant and the carbon emissions generated from the transportation of waste. For the estimation of carbon emissions during the demolition stage, the carbon emissions generated from the use of mechanical equipment and the transportation of demolished waste during the demolition process can be estimated at 90% of that during the construction stage.

[0221] 3.5.1.1 Construction machinery (E Dcm )

[0222] During the demolition stage, the use of construction machinery to demolish each facility of the sewage treatment plant will generate direct carbon emissions. The basic calculation formula is shown in Equation (6).

[0223] 3.5.1.2 Material transportation (E Dmt )

[0224] During the demolition stage, the transportation of materials such as fillers is required, and direct carbon emissions will be generated during the transportation process. The basic calculation formula is shown in Equation (7).

[0225] 3.5.2 Carbon emission accounting for Scope 2 during the demolition stage (E D2 )

[0226] 3.5.2.1 Purchased electricity (E Dep )

[0227] A large amount of energy consumption emissions will be generated during the demolition stage. The indirect carbon emissions caused by it can be calculated using the electricity consumption and the electricity emission factor. The basic calculation formula is shown in Equation (8).

[0228] 3.5.3 Carbon emission accounting for Scope 3 during the demolition stage (E D3 )

[0229] 3.5.3.1 Solid waste treatment (E Dsw )

[0230] A large amount of waste will be generated due to mechanical demolition during the demolition stage. The basic calculation formula is shown in Equation (11).

[0231] 3.6 Carbon emission reduction accounting (E A )

[0232] There are landscape projects such as trees, constructed wetlands, and stabilization ponds in the sewage treatment plant. The plants included in these projects, either individually or as an overall green environmental protection system, have a very important positive impact on carbon emission reduction in the sewage treatment plant due to their carbon sequestration effect. The carbon sink capacity of green plants has a certain relationship with plant varieties, growth cycles, growth regions, and crown area, etc. The carbon sequestration coefficients of different types of plants are shown in Table 2. The carbon sink calculation formula is:

[0233] E A =∑(P i ×EF p ×10 -3 ) (19)

[0234] Where: E A is the total fixed amount of carbon sink in the sewage treatment plant, kg CO 2-eq ; P i is the crown area of the i-th plant planted in the sewage treatment plant, m 2 or the number of the i-th plant planted, plants; EF p is the carbon sequestration coefficient of the i-th plant planted in the sewage treatment plant, g CO 2-eq / (m 2 ·d) or g CO 2-eq / (plant·d).

[0235] The carbon sequestration coefficients of different types of plants are as follows:

[0236] Table 2 Carbon sequestration coefficients of different plants

[0237]

[0238] 4. Scenario planning for a green, low-carbon benchmark sewage treatment plant:

[0239] Scenario planning for the sewage treatment plant:

[0240] Based on the research and calculation results of the Shahe Reclaimed Water Plant in Beijing, this embodiment designs three types of scenario planning for the sewage treatment plant to explore the path of building a green, low-carbon benchmark plant.

[0241] The carbon reduction paths include five basic measures: building a photovoltaic power generation system, setting up a sewage source heat pump, establishing an intelligent system, recycling treated wastewater, and increasing the planting of green plants.

[0242] Based on the above policy measures, this invention analyzes and combines the actual situation of the sewage treatment plant, and designs three different sewage treatment plant carbon emission reduction plans: a low-carbon sewage treatment plant scenario plan, a deep carbon reduction scenario plan for the sewage treatment plant, and a green, low-carbon benchmark sewage treatment plant scenario plan, in order to provide certain reference for the carbon reduction practice of other sewage treatment plants. The specific planning schemes are shown in the following table:

[0243] Table 4 Carbon Reduction Scenario Planning Scheme for Sewage Treatment Plant

[0244]

[0245] The above-described embodiments merely represent the specific implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several variations and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A carbon emission accounting and planning method for a sewage treatment plant, characterized in that It includes the following steps: Step 1: Construct a theoretical framework for the carbon accounting boundary of wastewater treatment plants based on the whole life cycle theory: Starting from the whole process of the planning, construction, operation, renewal, and demolition stages of wastewater treatment plants, comprehensively consider the Scope 1 carbon emissions, Scope 2 carbon emissions, and Scope 3 carbon emissions in each of the five stages, and couple the carbon emission system of the wastewater treatment plant with the carbon absorption system of the wastewater treatment plant to systematically construct a theoretical framework for the carbon accounting boundary of the wastewater treatment plant; Step 2: Conduct a three-scope accounting of the whole process of carbon emissions from wastewater treatment plants: Systematically quantify and analyze the carbon emissions in the five stages and three scopes, find the key nodes of carbon emissions from wastewater treatment plants, and provide a reliable basis for the planning and design of wastewater treatment plants and policy recommendations.

2. The carbon emission accounting and planning method for a sewage treatment plant according to claim 1, characterized in that, In Step 1, during the planning stage, a pre-assessment is carried out by analyzing key information such as the environmental impact report of the wastewater treatment plant, such as the construction area, designed treatment capacity, machinery use, and number of employees. During the construction stage, calculate the construction processes of various buildings, covering all activities from the extraction of raw materials to the completion acceptance of the wastewater treatment plant; during the operation stage, calculate the carbon emissions during the daily monitoring and management of the wastewater treatment process. Most wastewater treatment plants need to be renovated and updated within 15 - 30 years, so the carbon emissions in this stage can be considered based on a 30-year operation life cycle. During the renewal stage, evaluate the carbon emissions of various activities during the renovation and renewal of existing facilities; the demolition stage includes demolishing all facilities above the preset underground range of the original wastewater treatment plant and restoring the site.

3. The carbon emission accounting and planning method for a sewage treatment plant according to claim 1, wherein In Step 1, Scope 1 carbon emissions refer to the carbon emissions directly generated by the wastewater treatment plant, including the direct consumption of fossil energy and the carbon emissions generated during the wastewater treatment process; Scope 2 carbon emissions include the indirect carbon emissions generated by the electricity and heat energy used by the wastewater treatment plant; Scope 3 carbon emissions include other indirect carbon emissions from the supply chain, transportation, and waste treatment of the wastewater treatment plant.

4. The carbon emission accounting and planning method for a sewage treatment plant according to claim 1 or 2 or 3, characterized in that, In Step 2, the specific calculation methods for the three-scope accounting of the whole process of carbon emissions from wastewater treatment plants are as follows: Couple the process-based whole life cycle carbon emission accounting method, the life cycle analysis method EIO-LCA based on economic input-output, and the regional carbon absorption accounting method, and combine the construction of a carbon emission and carbon sink accounting system to achieve the purpose of specifically quantitatively accounting for the carbon emissions in each stage and each scope of the wastewater treatment plant; The planning stage is a pre-assessment for effective control. The actual carbon emissions of the wastewater treatment plant include the latter four stages, and the calculation formula is: E sum = E C + E O + E R + E D - E A Where: E sum is the carbon emission accounting result of the whole life cycle of the sewage treatment plant, E C is the carbon emission accounting result of the construction stage of the sewage treatment plant, E O is the carbon emission accounting result of the operation stage of the sewage treatment plant, E R is the carbon emission accounting result of the renewal stage of the sewage treatment plant, E D is the carbon emission accounting result of the demolition stage of the sewage treatment plant, E A is the carbon absorption accounting result of the sewage treatment plant.

5. The carbon emission accounting and planning method for a sewage treatment plant according to claim 4, characterized in that Carbon emission accounting for the construction stage of a sewage treatment plant includes Scope 1 carbon emission accounting for the construction stage E C1 Scope 2 carbon emission accounting for the construction stage E C2 and Scope 3 carbon emission accounting for the construction stage E C3 ; Carbon Emission Accounting for Scope 1 during the Construction Phase E C1 including construction machinery E Ccm and material transportation E Cmt : Where: E Ccm is the total direct emissions of fossil energy consumed by construction machinery at the sewage treatment plant during the construction phase, N Ci is the number of shifts of the i-th construction machinery and equipment, EF icm is the carbon emission factor per shift of the i-th construction machinery; Where: E Cmt is the total direct emissions of sewage treatment plant materials transportation during the construction phase, D Ci is the transportation distance of the i-th type of transport truck, EF imt is the emission factor of the i-th type of transport truck; Carbon Emission Accounting for Construction Phase, Scope II, E C2 Including externally-supplied electricity, E Cep and externally-supplied heat, E Chp : Where: E Cep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the construction stage, AD Ciep is the electricity consumption purchased for the i-th temporary facility during the accounting period in the construction process of the sewage treatment plant, EF iep is the average carbon dioxide emission factor of the i-th type of electricity; Where: EC hp为 The carbon dioxide equivalent emissions corresponding to the heat purchased by the sewage treatment plant during the construction stage, AD Cihp is the amount of heat purchased by the i-th temporary facility during the construction of the sewage treatment plant within the accounting period, EF ihp is the average carbon dioxide emission factor of the i-th type of heat; Carbon Emission Accounting for Scope 3 during the Construction Phase E C3 Including building materials E Cbm and solid waste treatment E Csw : Where: E Cbm is the carbon dioxide emissions caused by the production and processing of building materials during the construction phase of the sewage treatment plant, M Ci is the consumption of the i-th material used during the construction phase, EF ibm is the carbon emission factor of the i-th material; where: E Csw is the carbon emission for treating solid waste during the construction stage, A Ci is the amount of the i-th type of solid waste during the construction of the sewage treatment plant or the amount of solid waste of the i-th type of solid waste disposal method, EF isw is the carbon emission generated from disposing of the i-th type of solid waste or the i-th type of solid waste disposal method. The EIO-LCA method is used to quantify the greenhouse gas emissions such as the use of building materials and chemicals to make up for the truncation error. The accounting error is small but it will be more complex. The carbon emissions of the materials used by the wastewater treatment plant in each department of the production chain are: F ibm = R × x i where: E ibm is the amount of CO2 emitted in the upstream production process to meet the demand y of the sewage treatment plant i ; R is a certain row vector, and its elements correspond to the amount of CO2 directly emitted per unit currency of each department Element value R i is: Where: R i is the direct carbon emission coefficient of the i-th department, c i is the direct carbon emission of the i-th department, X i is the total output of this department; x in the input-output model i is the total output of products of each department in the production chain: x i = (I - A) -1 × y i where: I is the identity matrix, A is the direct consumption coefficient matrix, and y i is the column vector representing the value of the imports of each product by the sewage treatment plant, and (I - A) -1 is the Leontief inverse matrix, and i is the production department corresponding to the product under study, namely the industrial department, the tap water department, the agricultural department, etc.

6. The carbon emission accounting and planning method for a sewage treatment plant according to claim 4, characterized in that The carbon emission accounting during the operation stage of a sewage treatment plant includes the Scope 1 carbon emission accounting during the operation stage E O1 , the Scope 2 carbon emission accounting during the operation stage E O2 and the Scope 3 carbon emission accounting during the operation stage E O3 ; Carbon emission accounting E in the first range during the operation phase O1 Including sewage treatment E Ost : Where: E Ost is the direct carbon emissions of the sewage treatment plant during the operation stage, is the direct carbon dioxide equivalent caused by CH4, is the direct carbon dioxide equivalent caused by N2O; Wherein: is the direct carbon dioxide equivalent caused by CH4, V is the actual daily sewage treatment volume of the sewage treatment plant, D is the actual operating days of the sewage treatment plant, COD in is the content of COD per unit volume of sewage in the influent sewage, COD out is the content of COD per unit volume of sewage in the effluent sewage, is the CH4 emission factor, that is, the mutual relationship between the CH4 emission volume and the COD reduction volume, is the global warming potential value of CH4; Wherein: is the direct carbon dioxide equivalent caused by N2O, V is the actual daily sewage treatment volume of the sewage treatment plant, D is the actual operating days of the sewage treatment plant, TN in is the content of TN per unit volume of sewage in the influent sewage, TN out is the content of TN per unit volume of sewage in the effluent sewage, is the N2O-N emission factor, that is, the mutual relationship between the global warming potential emissions of N2O-N and the TN reduction amount, is the global warming potential of N2O; Carbon emission accounting E in the second range of the operation stage O2 including externally transferred electricity E Oep and externally transferred heat E Ohp : Where: E Oep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the operation stage, AD Oiep is the electricity consumption purchased by the i-th treatment unit during the operation of the sewage treatment plant within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th type of electricity; Where: E Ohp is the carbon dioxide equivalent emissions corresponding to the heat purchased by the sewage treatment plant during the operation stage, AD Oihp is the amount of heat purchased by the i-th treatment unit during the operation of the sewage treatment plant within the accounting period, EF ihp is the average carbon dioxide emission factor of the i-th type of heat; Carbon Emission Accounting E in Operating Phase Range Three O3 Including chemical agent use E Oms and solid waste treatment E Osw : Where: E Oms is the carbon emission of the chemicals used in the operation stage, M Oi is the consumption of the i-th chemical during the operation of the sewage treatment plant, EF ims is the emission factor of the i-th chemical; Where: E Osw is the carbon emission of treating solid waste during the operation stage, A Oi is the amount of the i-th type of solid waste during the operation of the sewage treatment plant or the amount of solid waste of the i-th type of solid waste disposal method, EF isw is the carbon emission generated by disposing of the i-th type of solid waste or the i-th type of solid waste disposal method.

7. The carbon emission accounting and planning method for a sewage treatment plant according to claim 4, characterized in that, Carbon Emission Accounting in the Updating Stage of Sewage Treatment Plant E R Including Scope 1 Carbon Emission Accounting in the Updating Stage E R1 Scope 2 Carbon Emission Accounting in the Updating Stage E R2 And Scope 3 Carbon Emission Accounting in the Updating Stage E R3 ; Carbon emission accounting E in the first range of the update stage R1 including construction machinery E Rcm and material transportation E Rmt : Where: E Rcm is the total direct emissions of fossil energy consumed by construction machinery during the sewage treatment plant construction in the update stage, N Ri is the number of shifts of the i-th construction machinery and equipment used in the renovation and update of the sewage treatment plant, EF icm is the carbon emission factor per shift of the i-th construction machinery; Where: E Rmt is the total direct emissions of materials transportation in the sewage treatment plant during the update phase, D Ri is the transportation distance of the i-th type of transport truck in the renovation and update of the sewage treatment plant, EF imt is the emission factor of the i-th type of transport truck; Carbon Emission Accounting E in Update Phase Range II R2 Including externally transferred electricity E Rep : Where: E Rep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the update phase, AD Riep is the electricity consumption of the i-th type used during the renovation process of the sewage treatment plant within the accounting period, EF iep is the average carbon dioxide emission factor of the i-th type of electricity; Carbon Emission Accounting E in the Third Scope of the Update Phase R3 including building materials E Rbm and solid waste treatment E Rsw : Where: E Rbm is the carbon emission of the production and processing of materials or equipment used in the update stage, M Ri is the consumption of the i-th material or equipment used in the update stage, EF ibm is the carbon emission factor of the i-th material or equipment; In the formula: E Rsw is the carbon emission of treating solid waste in the update stage, A Ri is the amount of the i-th type of solid waste or the amount of solid waste of the i-th type of solid waste disposal method during the update of the sewage treatment plant, EF isw is the carbon emission generated by disposing of the i-th type of solid waste or the i-th type of solid waste disposal method.

8. The carbon emission accounting and planning method for a sewage treatment plant according to claim 4, characterized in that, Carbon Emission Accounting during the Demolition Phase of a Sewage Treatment Plant E D Including Scope 1 Carbon Emission Accounting during the Demolition Phase E D1 Scope 2 Carbon Emission Accounting during the Demolition Phase E D2 and Scope 3 Carbon Emission Accounting during the Demolition Phase E D3 ; Carbon emission accounting for Demolition Phase Scope 1 E D1 Construction machinery E Dcm and material transportation E Dmt : Where: E Dcm is the total direct emissions of fossil energy consumed by construction machinery at the sewage treatment plant during the demolition phase, N Di is the number of shifts of the i-th construction machinery and equipment used during the demolition process, EF icm is the carbon emission factor per shift of the i-th construction machinery; Where: E Dmt is the total direct emissions of sewage treatment plant materials transportation during the demolition phase, D Di is the transportation distance of the i-th type of transport truck during the demolition process, ET imt is the emission factor of the i-th type of transport truck; Carbon Emission Accounting for Demolition Phase - Scope II E D2 Including externally sourced electricity E Dep : where: E Dep is the carbon dioxide equivalent emissions corresponding to the electricity purchased by the sewage treatment plant during the demolition phase, AD Diep is the electricity consumption of the i-th equipment used during the accounting period in the process of demolishing the sewage treatment plant, EF iep is the average carbon dioxide emission factor of the i-th type of electricity; Carbon Emission Accounting for Demolition Phase, Scope III E D3 Including building materials E Dbm and solid waste treatment E Dsw : Where: E Dbm is the carbon emission of the filling material used when demolishing the sewage treatment plant, M Di is the consumption of the i-th material used during demolition, EF ibm is the carbon emission factor of the i-th material; Where: E Dsw is the carbon emission of solid waste treatment in the demolition stage, A Di is the amount of the i-th type of solid waste in the demolition process of the sewage treatment plant or the amount of solid waste of the i-th type of solid waste disposal method, EF isw is the carbon emission generated by disposing of the i-th type of solid waste or the i-th type of solid waste disposal method.

9. The carbon emission accounting and planning method for a sewage treatment plant according to claim 4, wherein It also includes carbon emission reduction accounting, i.e., carbon sink volume E A : E A = ∑(Pi × EF p × 10 -3 ) Where: E A is the carbon absorption accounting result of the sewage treatment plant, Pi is the crown area of the i-th plant planted in the sewage treatment plant or the number of the i-th plant planted, and EF p is the carbon sequestration coefficient per unit area or per unit quantity of the i-th plant planted in the sewage treatment plant.

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