Rice field carbon footprint measuring and calculating method

Abstract

The invention discloses a rice field carbon footprint measuring and calculating method, and belongs to the technical field of agricultural environment management and carbon emission accounting. According to the measuring and calculating method, firstly, an accounting boundary is precisely defined, data are collected, and eight emission sources including rice field CH4 emission, rice field nitrogen fertilizer input N2O emission, ploughing / rice transplanting / plant protection / irrigation / mechanical harvesting energy consumption CO2 emission and CO2 emission after urea application are covered; carrying out refined measurement and calculation on each emission source based on the boundary, and uniformly converting the emission amounts of CH4, N2O and various CO2 into carbon dioxide equivalent; and finally summarizing to obtain the rice field carbon footprint total amount. According to the method, the problem of measurement and calculation deviation caused by incomplete accounting boundaries and low localization adaptability of emission factors in an existing method is solved, the comprehensiveness and accuracy of carbon footprint measurement and calculation are improved, and reliable technical support is provided for rice field low-carbon management.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of agricultural environment management and carbon emission accounting, in particular to a rice field carbon footprint calculation method. BACKGROUND

[0002] Carbon footprint refers to the total amount of carbon dioxide and other greenhouse gases directly or indirectly emitted by human activities in production and life. It is a method to estimate the impact of carbon emissions on the greenhouse effect. The rice field ecosystem is an important part of the terrestrial ecosystem, and the carbon emissions in the process of rice production are affected by many factors such as the amount of agricultural materials used and the amount of methane emitted in the rice growing period. Its carbon cycle process has a significant impact on carbon balance. In order to achieve the goal of carbon emission reduction in the field of agriculture, it is necessary to accurately quantify the carbon footprint of rice fields.

[0003] However, the existing rice field carbon footprint calculation method has significant limitations. The accounting boundary of the conventional method usually only focuses on direct emissions such as methane, while ignoring indirect carbon dioxide emissions from key farming activities such as plant protection, irrigation, and urea decomposition, resulting in a serious underestimate of the calculation results.

[0004] Therefore, there is an urgent need for a new method that can overcome the above-mentioned defects and achieve complete and accurate calculation of the carbon footprint of rice fields. SUMMARY

[0005] The purpose of the present application is to provide a rice field carbon footprint calculation method, which can fundamentally solve the distortion problem of the calculation results caused by the incomplete system boundary and the over-strong universality of the emission factor of the conventional method by constructing a complete accounting boundary covering eight emission sources and using differentiated emission factors based on localized management practices.

[0006] To achieve the above-mentioned purpose, the present application provides a rice field carbon footprint calculation method, comprising the following steps: Defining the accounting boundary, which completely covers the following eight emission sources: CH4 emission from rice field, N2O emission from rice field nitrogen fertilizer input, CO2 emission from rice field cultivation, CO2 emission from transplanting and / or base fertilizer application, CO2 emission from plant protection, CO2 emission from irrigation, CO2 emission from mechanical harvesting, and CO2 emission after urea application; Based on the accounting boundary, each emission source is calculated in detail to obtain the calculation results in the form of carbon dioxide equivalent; the calculation results include CH4 emission amount from rice field, N2O emission amount from rice field nitrogen fertilizer input, CO2 emission amount from each farming activity, and CO2 emission amount from urea decomposition; Based on the calculation results in the form of carbon dioxide equivalent, the total amount of rice field carbon footprint is obtained.

[0007] Further, the CH4 emission amount from rice field is calculated by the following method: obtain the basic data of the target region by acquiring the rice planting area, the number of days from transplanting to harvesting, the proportion of irrigation methods, and the proportion of straw returning to field of the target region; Under the accounting framework of IPCC or national greenhouse gas inventory guidelines, the differentiated rice field CH4 emission factor is determined through regional literature integration and Meta analysis; According to the basic data and the rice field CH4 emission factor, the rice field CH4 emission amount is calculated by a first formula; wherein the first formula is: The rice field CH4 emission amount is calculated in terms of carbon dioxide equivalent, with the unit of t CO2e; is the rice planting area, with the unit of ha; is the rice field CH4 emission factor, with the unit of kg CH4 ha -1 day -1 ; is the number of days from rice transplanting to harvesting, with the unit of day; is the CH4 global warming potential, with the unit of t CO2e (t CH4) -1 , and the value source is the IPCC 100-year time scale warming potential, with the value of 21.

[0008] Further, the rice field CH4 emission factor is obtained by the following method: According to regional literature integration and Meta analysis, the target water management method and the target straw management method are determined; wherein the target water management method includes winter paddy field, flooded irrigation or mid-term drying field / intermittent irrigation, and the target straw management method includes straw link or straw not returning to field; Based on the target water management method and the target straw management method, the association table of management method combination and emission factor value is queried to obtain different localized rice field CH4 emission factors; According to different localized rice field CH4 emission factors, the rice field CH4 emission factor is summed up.

[0009] Further, the N2O emission amount of rice field nitrogen fertilizer input is obtained by the following method: Activity level data including fertilizer nitrogen input, manure nitrogen input and nitrogen input of straw returning to field are obtained by combining field investigation, statistical yearbook verification and expert consultation; According to regional literature integration and Meta analysis, the N2O direct emission factor of the target region is determined; According to the activity level data and the N2O direct emission factor, the rice field N2O direct emission amount data is calculated.​ According to the data of direct emission of N2O in rice fields and the data of indirect emission of N2O caused by fertilization, the N2O emission caused by nitrogen fertilizer input in rice fields is calculated by the second formula; wherein, the data of indirect emission of N2O caused by fertilization is the sum of the indirect emission of N2O after ammonia and nitrogen oxide volatilization caused by rice field fertilization through dry and wet deposition to the ground, lakes and rivers and the indirect emission of N2O caused by nitrogen leaching and runoff of rice field fertilization.

[0010] Further, the second formula is: ; Among them, is the N2O emission of rice fields, calculated in terms of carbon dioxide equivalent, with the unit of t CO2e; is the direct emission of N2O in rice fields, with the unit of t N2O-N; is the indirect emission of N2O after ammonia and nitrogen oxide volatilization caused by rice field fertilization through dry and wet deposition to the ground, lakes and rivers, with the unit of t N2O-N; is the indirect emission of N2O caused by nitrogen leaching and runoff of rice field fertilization, with the unit of t N2O-N; is the global warming potential of N2O, with the unit of t CO2e (t N2O) -1 ; the value source is the global warming potential of IPCC 100-year time scale, with the value of 310.

[0011] Further, the direct emission of N2O in rice fields is calculated according to the third formula, and the third formula includes: ; Among them, is the nitrogen input of chemical fertilizer of crop type C, with the unit of t N; is the nitrogen input of straw returned to field of crop type C, with the unit of t N; is the nitrogen input of manure of crop type C, with the unit of t N; is the direct emission factor of N2O of crop type C, with the unit of kg N2O-N / kg N; is the coefficient for converting N2O-N into N2O.

[0012] Furthermore, the CO2 emissions from each stage of agricultural activities are the sum of the total CO2 emissions from fossil fuel consumption and the total CO2 emissions from electricity consumption; among which, the total CO2 emissions from fossil fuel consumption are the sum of the CO2 emissions from diesel consumption and gasoline consumption, and the total CO2 emissions from fossil fuel consumption are calculated using the fourth formula, which includes: ; in, This represents the total CO2 emissions from fossil fuel consumption, expressed in kg CO2. For the first i Levels of fossil fuel activity, through the first i The product of the emissions of a fossil fuel and its lower heating value is given, and the unit is GJ. For the first i The CO2 emission factor of a type of fossil fuel, expressed in t CO2 / GJ; i Fossil fuels are classified into diesel and gasoline.

[0013] Furthermore, the total CO2 emissions from electricity consumption are calculated using the fifth formula, which includes: ; in, This represents the total CO2 emissions from electricity consumption, expressed in kg CO2. Power consumption, in kWh; The emission factor for the power grid is taken as the national average of 0.5839 kg CO2 / kWh.

[0014] Furthermore, the first i The CO2 emission factor for each fossil fuel is calculated using the sixth formula, which includes: ; in, The carbon content per unit calorific value of the i-th fossil fuel is expressed in t C / GJ. The carbon oxidation rate of the i-th fossil fuel is expressed in % (%). It is the ratio of the relative molecular masses of carbon dioxide to carbon.

[0015] Furthermore, the CO2 emissions from urea decomposition are calculated using the seventh formula, which includes: ; in, This represents the CO2 emissions from the decomposition of urea, expressed in kg CO2. This refers to the amount of urea applied, expressed in kg. The CO2 emission factor of urea is fixed at 0.2 kg C / kg urea.

[0016] In summary, this application has the following advantages: 1. The application first clearly defines eight core emission sources covering methane emissions in rice fields, nitrogen fertilizer-related nitrous oxide emissions, energy consumption CO2 emissions in farming processes such as plowing, transplanting, plant protection, irrigation, and mechanical harvesting, and CO2 emissions after urea application, comprehensively covering the direct and indirect carbon emission paths in the whole life cycle of rice cultivation. Compared to the limitations of existing technologies that generally ignore key emission sources such as energy consumption in plant protection and urea decomposition, the application avoids systematic omissions in carbon footprint calculation by building a complete boundary, ensuring that the calculation results can fully and truly reflect the overall carbon emissions of the rice ecosystem.

[0017] 2. The application establishes a precise accounting system that fits the actual field: for methane emissions, based on the combination of target area irrigation methods (winter water field, flooding irrigation, mid-term drying field / intermittent irrigation) and straw return ratio, differential emission factors are determined through regional literature integration and Meta analysis; for nitrous oxide emissions, activity level data (fertilizer nitrogen, manure nitrogen, straw return nitrogen input) are accurately obtained through field research, statistical yearbook verification, and expert consultation, and emission factors are also verified and determined through localized research. The application can fully adapt to the differences in regional agricultural management practices in the calculation of key gas emissions, greatly reducing the calculation deviation caused by low local adaptation of parameters, and significantly improving the consistency of the calculation results with the actual field emissions. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the application. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 is a schematic diagram of the rice field carbon footprint calculation method proposed by the embodiments of the application; Figure 2 is a schematic diagram of the accounting boundary proposed by the embodiments of the application; Figure 3 is a flowchart of the calculation of methane emissions in rice fields proposed by the embodiments of the application; Figure 4 is a flowchart of the calculation of nitrous oxide emissions proposed by the embodiments of the application. DETAILED DESCRIPTION

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0022] like Figure 1 As shown, the method for calculating the carbon footprint of paddy fields according to an embodiment of this application includes the following steps: S101. Accurately define accounting boundaries and collect data. like Figure 2 As shown, the accounting boundary of this application includes eight major emission sources, specifically: CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption during paddy field cultivation, CO2 emissions from energy consumption during transplanting and / or basal fertilizer application, CO2 emissions from energy consumption during plant protection, CO2 emissions from energy consumption during irrigation, CO2 emissions from energy consumption during mechanical harvesting, and CO2 emissions after urea application (in the calculation process, CO2 emissions after urea application correspond to the CO2 emissions from urea decomposition). The eight emission sources in this application involve the emissions of three greenhouse gases: methane, nitrous oxide, and carbon dioxide. Among these, CO2 emissions from energy consumption during paddy field cultivation, transplanting and / or basal fertilizer application, plant protection, irrigation, and mechanical harvesting are collectively referred to as CO2 emissions from energy consumption during each agricultural activity.

[0023] For these eight emission sources and the target areas requiring accounting, the following two types of data were collected: (1) Management time data: Rice planting area in the target area was obtained from agricultural statistics, government work reports and surveys. Number of days from transplanting to harvest The proportions of different irrigation methods and the proportion of straw returned to the field are shown in Table 1.

[0024] Table 1 Classification of Irrigation Methods and Straw Return to Field

[0025] (2) Activity level data: The amount of nitrogen applied by chemical fertilizers and organic fertilizers, the amount of fuel / electricity consumed in each agricultural process (tillage, rice transplanting, plant protection, irrigation and harvesting), and the amount of urea applied were obtained through field surveys, questionnaires and statistical data.

[0026] The present application explicitly covers eight major emission sources of rice field methane, nitrogen fertilizer nitrous oxide and farmland, transplanting, etc. It includes direct and indirect greenhouse gas emissions of rice cultivation, avoids the problem of underestimating carbon footprint caused by missing boundaries in traditional methods, and further ensures the integrity of the calculation. And it classifies the management time and activity level into two categories, which not only covers key management parameters such as irrigation method and straw return ratio (detailed classification ensures the pertinence of parameters), but also obtains core data such as energy consumption and fertilizer amount through multiple channels such as statistical data and field research, providing reliable data support for accurate calculation.

[0027] S102. Determine key emission factors based on differentiation and perform refined calculation Based on the accounting boundary, each emission source is refined and calculated to obtain the calculation results in the form of carbon dioxide equivalent, including the calculation results of rice field CH4 emission, N2O emission of rice field nitrogen fertilizer input, CO2 emission of energy consumption in each agricultural link, and CO2 emission of urea decomposition. In this calculation process, there are many greenhouse gases, such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), which have different effects on global warming. In order to unify the measurement and compare the emission of different greenhouse gases, the present application introduces the concept of carbon dioxide equivalent. The emission of different greenhouse gases is converted into equivalent carbon dioxide according to its contribution to global warming. Therefore, in the present application, t CO2e represents the total amount of equivalent carbon dioxide after converting the emission of various greenhouse gases, and the unit is ton (t), e represents equivalent, which means "equivalent" or "equivalent".

[0028] Specifically: 1) As shown in Figure 3 , the amount of methane emitted by the rice field is calculated: Because the methane emission of the rice field is the net result of the decomposition of organic matter by methanogenic bacteria in the anaerobic environment and the oxidation of methanotrophs. In the calculation, the present application discards the single default emission factor, and instead determines the localized and differentiated methane emission factor that matches the target area according to the specific irrigation method proportion and straw return proportion of the target area through regional literature integration and Meta analysis. That is, the proportion of different irrigation methods and the proportion of straw return are used as key inputs, and the specific emission factor corresponding to them is obtained by querying the emission factor database established based on Meta analysis of local research literature. Then the amount of methane emission under different combinations (combination of different water management methods and straw management methods) is calculated, and the total amount of methane emission of the rice field is obtained.

[0029] The amount of methane emission in the rice field is calculated by the first formula (converted into the form of carbon dioxide equivalent).

[0030] The first formula includes: ; The amount of CH4 emission in the rice field is calculated in the form of carbon dioxide equivalent, and the unit is t CO2e (the unit of emission in this application is actually t, and the suffix CO2e indicates that it is converted into the form of carbon dioxide equivalent, which is not used as a unit, for example = 1 t CO2e, which means that 1 ton of methane in the form of carbon dioxide equivalent is emitted); The rice planting area is ha (hectare); The CH4 emission factor of the rice field is kg CH4 ha -1 day -1 , which means the amount of CH4 emitted per hectare per day); The number of days from transplanting to harvesting of rice is d (day); The global warming potential of CH4 is t CO2e (t CH4 ) -1 , and the value is taken from the global warming potential of IPCC 100-year time scale, which is 21. In this application, the global warming potential (Global Warming Potential, abbreviated as GWP) is simply a measure of the contribution of greenhouse gases to climate warming. It specifically refers to the ratio of the radiative forcing produced by 1 kilogram of greenhouse gas emitted into the atmosphere within a certain period of time (usually set to 100 years) to the impact of the same mass of carbon dioxide. Radiative forcing, as a physical quantity, reflects the disturbance of various physical and chemical processes to the global energy balance, and further affects the earth's climate. For example, the GWP of methane is 21 on a 100-year time scale, which means that the ability of an equal amount of methane to cause global warming in 100 years is 21 times that of carbon dioxide.

[0031] 2) As shown in Figure 4 , the amount of nitrous oxide emission is calculated: The different types of nitrogen input (different types of nitrogen input including chemical fertilizer nitrogen input, manure nitrogen input and nitrogen input of straw returned to field) of different agricultural lands (different agricultural lands are rice, wheat, corn and other crops) are collected as activity level data, the direct emission factor of nitrous oxide of the target region is determined according to regional literature compilation and Meta analysis, and then the direct emission amount of nitrous oxide in the rice field is calculated according to the direct emission factor of nitrous oxide and the third formula. The indirect emission amount of nitrous oxide (including the indirect emission amount of nitrous oxide after the ammonia and nitrogen oxide volatilized by the fertilization of the rice field are volatilized and then deposited to the ground, lakes and rivers by dry and wet deposition, and the indirect emission amount of nitrous oxide after the nitrogen leaching / runoff caused by the fertilization of the rice field) is calculated according to the formula of the provincial list preparation guide of the IPCC national greenhouse gas list guide, the emission factor adopts the recommended value of the IPCC, the volatilization coefficient of the manure and chemical fertilizer nitrogen input of the agricultural land is 0.2 and 0.1 respectively, and the nitrogen leaching and runoff loss coefficient of the farmland is 0.2. The total emission amount of nitrous oxide is obtained by finally summarizing the direct emission amount of nitrous oxide and the indirect emission amount of nitrous oxide. The volatilization coefficient and the loss coefficient in the present application are actually the quantization parameters for accounting the indirect emission amount of nitrous oxide, and the essence is the nitrogen loss proportion coefficient. The volatilization coefficient and the loss coefficient are used for accurately calculating the proportion of nitrogen loss through the two paths of volatilization deposition and leaching runoff after the fertilization (including manure and chemical fertilizer) of the rice field, and then accounting the indirect emission amount of nitrous oxide generated by the conversion of the lost nitrogen. For example, the volatilization coefficient of the manure nitrogen input is 0.2, that is, 20%, and the volatilized nitrogen amount of the manure = manure nitrogen input amount x 0.2. These volatilized nitrogen will diffuse to the surrounding soil, lakes and rivers through atmospheric dry and wet deposition (such as rainfall and dust fall), and further convert into nitrous oxide in the environment, and this part of the emission amount is recorded as a part of the indirect emission amount of nitrous oxide volatilization.

[0032] Specifically, the third formula is: ; Among them, is the chemical fertilizer nitrogen input amount of the crop type C, and the unit is t N (the unit of the input amount in the present application is ton, which can also be converted into kilogram, and the suffix N element indicates that the input type is nitrogen element, which is not used as a unit); is the nitrogen input amount of straw returned to field of the crop type C, and the unit is t N; is the manure nitrogen input amount of the crop type C, and the unit is t N; N2O direct emission factor for crop type C, unit: kg N2O-N / kg N (wherein, kg N2O-N refers to the mass of nitrous oxide per kilogram of nitrogen, kg N refers to the input amount of nitrogen per kilogram or the nitrogen content in the emission source, which is used in the practical application of the present application to quantify the direct N2O emission per unit of nitrogen input (kg N) in the agricultural production process of a specific crop type (such as rice, corn, etc.). For example, if 0.01 kg N2O-N / kg N means that for every 1 kg of nitrogen input, this crop type will directly emit 0.01 kg of N2O in terms of nitrogen; is the coefficient for converting N2O-N to N2O.

[0033] The evaluation of the returned straw nitrogen input in the third formula of the present application is calculated according to the yield, economic coefficient, dry weight ratio, root-shoot ratio, nitrogen content of straw / root stubble, and straw returning ratio of each crop in a certain province (if the remaining areas are to be calculated, the corresponding coefficients of the region can be replaced). The relevant calculation coefficients are shown in Table 2. The evaluation of the manure nitrogen input is calculated according to the total excretion amount of livestock and poultry, the manure nutrient returning ratio of livestock and poultry, the total excretion amount of rural population, and the nitrogen loss amount of livestock and poultry manure storage and transportation management. The total excretion amount of livestock and poultry is calculated according to the number of animals and the average annual nitrogen excretion amount of different animals. Livestock breeding is mainly classified as pigs, cattle, horses, sheep, rabbits, and poultry, and the annual excretion amount of manure nitrogen is 16 kg N / head / year, 48 kg N / head / year, 40 kg N / head / year, 12 kg N / head / year, 1.1 kg N / head / year, and 0.6 kg N / head / year, respectively, according to the provincial emission inventory of China. The number of animals is obtained from the statistical yearbook. The use of calculation coefficients in the present application is as follows: first, the total mass of straw is derived from the crop yield, then the total amount of nitrogen in the straw is calculated, and finally the actual nitrogen input is obtained by combining the straw returning ratio. For example, the fresh weight yield of crops is converted to dry weight yield by the dry weight ratio, the total straw yield is derived by the economic coefficient, and the mass of underground root system (root stubble) is calculated by the root-shoot ratio. For example, assuming that the economic yield of rice in a certain region is 1000 kg / mu, and the straw returning ratio is 70%, then the dry weight of straw + root stubble = (economic yield / economic coefficient - economic yield) x (1 + root-shoot ratio) = (1000 / 0.489 - 1000) x (1 + 0.125) ≈ 1173 kg / mu. The total nitrogen amount of straw + root stubble = dry weight x nitrogen content of straw / root stubble = 1173 x 0.00753 ≈ 8.83 kg N / mu. The returned straw nitrogen input = total nitrogen amount x straw returning ratio = 8.83 x 70% ≈ 6.18 kg N / mu.

[0034] Table 2 Calculation coefficients of crop straw returning nitrogen input

[0035] The N2O direct emission amount and the N2O indirect emission amount (including the volatilization generated and the leaching runoff generated) of the rice field obtained according to the third formula, in combination with the second formula, is calculated to obtain the N2O emission amount of the nitrogen fertilizer input of the rice field (converted into the carbon dioxide equivalent form).

[0036] The second formula is: ; is the N2O emission amount of the rice field, calculated in the carbon dioxide equivalent, in t CO2e; is the N2O direct emission amount of the rice field, in t N2O-N (N2O-N in the present application refers to the mass of nitrous oxide calculated in nitrogen, which is not used as a specific unit, but only used for indicating the kind, and the unit of the emission amount is t); is the N2O indirect emission amount of the rice field caused by the volatilization of the ammonia and the nitrogen oxide after the fertilization of the rice field, and the dry and wet deposition to the ground, lakes and rivers, in t N2O-N; is the N2O indirect emission amount of the rice field caused by the nitrogen leaching and the runoff after the fertilization of the rice field, in t N2O-N; is the N2O global warming potential, in t CO2e (t N2O) -1 ; the value source is the global warming potential of the IPCC in the time scale of 100 years, and the value is 310. Among them, (t N2O) -1 represents that each ton of N2O is in t CO2e (t N2O) -1 , which represents the ton number of the carbon dioxide equivalent corresponding to each ton of nitrous oxide, and is understood as the global warming effect of one ton of nitrous oxide in the time scale of 100 years, which is equivalent to the warming effect of 310 tons of carbon dioxide.

[0037] 3) Measure the carbon dioxide emission amount: According to the energy consumption of each agricultural link (including the carbon emission caused by the fossil energy and the electric power) and the urea application amount, in combination with the corresponding carbon dioxide emission coefficient, the emission amounts are calculated respectively, and then are added to obtain the total carbon dioxide emission amount of the target region. The target region in the present application refers to the region in which the carbon footprint of the rice field needs to be measured. Among them, the energy consumption of each agricultural link includes the carbon emission generated in the links of plowing, transplanting, fertilization, pesticide application (plant protection), irrigation and harvesting in the process of rice planting, which can be calculated according to the product of the activity level energy consumption and the corresponding emission factor.

[0038] Specifically, firstly, the carbon dioxide emission factors of different fossil fuels (divided into diesel and gasoline) in the target area are calculated using formula six. Then, the total carbon dioxide emissions from fossil fuel consumption in the target area are calculated using formula four and the carbon dioxide emission factors of different fossil fuels (divided into diesel and gasoline). Next, the total carbon dioxide emissions from electricity consumption in the target area are calculated using formula five, and the carbon dioxide emissions from urea decomposition are calculated using formula seven. The total carbon dioxide emissions of the target area are obtained by summing the total carbon dioxide emissions from fossil fuel consumption, total carbon dioxide emissions from electricity consumption, and carbon dioxide emissions from urea decomposition.

[0039] The fourth formula includes: ; in, The total CO2 emissions from fossil fuel consumption are expressed in kg CO2 (the emissions in this application include methane, nitrous oxide, and carbon dioxide, all expressed in mass; suffixes indicate the type, e.g., if the emissions in this application...). =1kg CO2, which means the total carbon dioxide emissions from fossil fuel consumption is 1 kilogram). For the first i Levels of fossil fuel activity, through the first i The value of a fossil fuel is calculated by multiplying its emissions by its lower heating value. The unit is GJ, a unit of energy; 1 GJ = 10⁻⁶. 6 kJ; For the first i The CO2 emission factor of a fossil fuel, expressed in t C / GJ, represents the mass of carbon dioxide produced after the combustion of a unit of energy from a fossil fuel. For example, when... When the ratio is 0.07t C / GJ, it means that burning 1 GJ of this fossil fuel will produce 0.07 tons of carbon dioxide. i Fossil fuels are classified into diesel and gasoline.

[0040] The fifth formula includes: ; in, This represents the total CO2 emissions from electricity consumption, expressed in kg CO2. Power consumption, in kWh; The grid emission factor is taken as the national average of 0.5839 kg CO2 / kWh, which means that for every 1 kWh of electricity consumed, the corresponding CO2 emissions generated during the grid power generation process are 0.5839 kg.

[0041] The sixth formula includes: ; wherein, is the unit heat value carbon content of the i-th fossil fuel, with the unit of t C / GJ, meaning that the mass of carbon element (tons) contained in the fossil fuel per 1 gigajoule of energy, which is an inherent property of the fuel itself; is the carbon dioxide emission factor of the i-th fossil fuel, with the unit of t CO2 / GJ, meaning that the tons of carbon dioxide generated per 1 GJ of the fuel burned; is the carbon oxidation rate of the i-th fossil fuel, with the unit of %, meaning the proportion of carbon element oxidized to carbon dioxide when the fuel is burned, which reflects the degree of sufficiency of fuel combustion; is the ratio of the relative molecular mass of carbon dioxide to carbon.

[0042] The seventh formula includes: ; wherein, is the CO2 emission of urea decomposition, with the unit of kg CO2; is the application amount of urea, with the unit of kg; is the CO2 emission factor of urea, with the fixed value of 0.2 kg C / kg urea, meaning the mass of carbon element that can be decomposed, released and converted into carbon dioxide per 1 kg of urea.

[0043] wherein, the main fossil energy used in rice planting activities and product use is classified as diesel and gasoline, and the related values are shown in Table 3.

[0044] Table 3 Unit heat value carbon content, carbon oxidation rate and average low calorific value data of fossil energy

[0045] For methane (CH4) emissions, the application discards the single default factor in the traditional mode, determines the differential emission factor based on the combination of irrigation methods (3 types) and straw returning (2 types) in the target area through regional literature integration and Meta analysis, fully considers the influence of agricultural management practices on emissions, and improves the accuracy of CH4 calculation from the source. For the emission of nitrous oxide (N2O), the emission factor is verified by local research, and the subdivision coefficient recommended by IPCC (fertilizer / manure nitrogen volatilization coefficient, nitrogen leaching / runoff loss coefficient) is used for indirect emission factor, which avoids the error caused by one-size-fits-all. And the application provides corresponding targeted calculation methods for different greenhouse gases, for example, for methane, the net effect of methane production, oxidation and transmission is considered; for nitrous oxide, two production paths of direct and indirect emissions are considered; for carbon dioxide, three sources of fossil fuel combustion, power consumption and urea decomposition are considered, thereby completely covering the eight emission sources. And each emission source corresponds to a dedicated accounting formula, and the parameters in the formula provide clear value standards or calculation methods, which can ensure the repeatability and verifiability of the calculation. In the calculation process, the concept of carbon dioxide equivalent (CO2e) of IPCC standard is introduced, CH4 (value 21) and N2O (value 310) are converted into equivalent CO2 amount through global warming potential (GWP), solving the measurement problem of the difference in warming effect of different greenhouse gases.

[0046] S103. Carbon footprint integration The total amount of carbon footprint of the paddy field in the target area is obtained by adding the results of each calculation according to step S102.

[0047] Through the above steps, the accurate and complete calculation of the carbon footprint of the paddy field at the regional scale can be realized, and accurate data support is provided for agricultural low-carbon development.

[0048] In summary, the application formulates a standardized accounting process, clearly defines the quantification formula of each emission source (such as the first formula for methane emission, the fifth formula for carbon dioxide emission of power consumption, etc.), and unifies the value specification of key parameters such as IPCC standard global warming potential (GWP), power grid emission factor, and fuel heat value, thereby reducing the operation threshold. At the same time, through the regional Meta analysis and the parameter localization mechanism supported by the field research data, the calculation method of the application can be flexibly adapted to the demand for paddy field carbon footprint calculation at the provincial, municipal, and even plot scale under different climate conditions and agricultural management modes. The calculation results can provide accurate data support for agricultural low-carbon policy making, emission reduction technology screening, and low-carbon planting mode optimization, and have high practical application value and promotion prospect.

[0049] Embodiment 1 In this embodiment, the carbon footprint of the paddy field in a certain province in 2022 is calculated, including the following steps: 1. Accounting boundary and data collection The accounting boundary is determined to be the rice fields within a certain province, and relevant data for 2022 is collected, including: Rice planting area: 1.87 million hectares.

[0050] Irrigation method proportion: flooding irrigation (60%), mid-season field drying / intermittent irrigation (40%).

[0051] Straw return proportion: full amount of return (70%), no return (30%).

[0052] Fertilizer application amount (pure nitrogen) 125,000 tons, manure nitrogen input 12,000 tons, straw return nitrogen input 8,000 tons.

[0053] Total diesel consumption in main agricultural activities: 98,000 tons.

[0054] Irrigation power consumption: 420 million kWh.

[0055] Urea application amount: 83,000 tons.

[0056] 2. Key emission factor determination Methane emission factor: Through searching 15 published research papers in the past ten years in a certain province and similar ecological regions around it, Meta analysis is conducted to determine the localized emission factors under different water and straw management combinations, for example: (1) flooding irrigation + straw return: 1.65 kg CH4 / ha / day; (2) flooding irrigation + no straw return: 1.20 kg CH4 / ha / day; (3) flooding irrigation + straw return: 0.95 kg CH4 / ha / day; (4) mid-season field drying + straw return: 0.70 kg CH4 / ha / day.

[0057] Nitrous oxide emission factor: Through local literature compilation, the direct emission factor of nitrous oxide is determined to be 0.009 kg N2O-N / kg N; Grid emission factor: Taking the national average value as 0.5839 kg CO2 / kWh.

[0058] 3. Carbon emission calculation According to the formulas of the present application, the main results are as follows: (1) Calculate the methane emission of rice fields using weighted average emission factor Flooding irrigation + straw return: 60% x 70% x 1.65 = 0.693, Flooding irrigation + no straw return: 60% x 30% x 1.20 = 0.216, Mid-season field drying + straw return: 40% x 70% x 0.95 = 0.266, Mid-season burning + straw not returned to field: 40% x 30% x 0.70 = 0.084, Weighted average = 1.259 kg CH4 / ha / day, According to the first formula to calculate the methane emissions , A 187 million mu, t 100 days, 21, then the first formula is: = 187 million mu x 1.259 kg / ha / day x 100 days x 21 x 10 -3 = 495.2 million tons of CO2e.

[0059] (2) Calculate the nitrous oxide emissions Total nitrogen input = 12.5 + 1.2 + 0.8 = 14.5 million tons of N, 0.009 t N2O-N / t N, by the third formula to calculate the direct emissions of nitrous oxide , get = 14.5 million tons of N x 0.009 t N2O-N / t N x 44 / 28 = 0.205 million tons of N2O, Consider the indirect emissions (estimated at 30% of direct emissions) ≈ 0.062 million tons of N2O, that is + = 0.062, while 310, then the total N2O emissions Through the second formula to calculate = (0.205 + 0.062) million tons of N2O x 310 GWP = 82.8 million tons of CO2e.

[0060] (3) Calculate the energy consumption of carbon dioxide emissions Through the fourth formula and the sixth formula to calculate diesel emissions: 9.8 million tons x 42.652 GJ / ton x 0.0202 tons C / GJ x 0.98 x 44 / 12 x 10 3 = 30.8 million tons of CO2, Through the fifth formula to calculate the power emissions: 4.2 billion kWh x 0.5839 kg CO2 / kWh x 10 -3 = 24.5 million tons of CO2, then, the total amount of energy consumption = 30.8 + 24.5 = 55.3 million tons of CO2; Through the seventh formula to calculate the urea application CO2 emissions = 8.3 million tons x 10 3 x 0.2 kg C / kg urea x 44 / 12 x 10 -3= 610,000 tons of CO2.

[0061] Based on the above data, the summary results are as follows: Methane emissions from paddy fields: 4,952,000 tons of CO2e; Nitrous oxide emissions from nitrogen fertilizer input: 828,000 tons of CO2e; CO2 emissions from energy consumption: 553,000 tons of CO2; CO2 emissions from urea application: 61,000 tons of CO2.

[0062] The carbon emissions of the above summary results are added together to obtain the carbon footprint of paddy fields in a province in 2022 as 639.4 million tons of CO2e.

[0063] Each of the embodiments in the specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0064] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to cover all changes and modifications falling within the scope of the embodiments of the present application.

[0065] Finally, it should be noted that in the present application, relationship terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or terminal device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or terminal device including the element.

[0066] Specific examples are applied in the present application to describe the principles and implementation modes of the present application. The above embodiment descriptions are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method for measuring the carbon footprint of a rice field, characterized by, The method comprises the following steps: defining an accounting boundary which completely covers the following eight emission sources: CH4 emission of rice field, N2O emission of nitrogen fertilizer input of rice field, CO2 emission of rice field cultivation, CO2 emission of rice transplanting and / or base fertilizer application, CO2 emission of plant protection, CO2 emission of irrigation, CO2 emission of mechanical harvesting, and CO2 emission after urea application; based on the accounting boundary, fine calculation is performed on each emission source to obtain a calculation result in the form of carbon dioxide equivalent; the calculation result comprises CH4 emission amount of rice field, N2O emission amount of nitrogen fertilizer input of rice field, CO2 emission amount of each farming link, and CO2 emission amount of urea decomposition; based on the calculation result in the form of carbon dioxide equivalent, the total amount of carbon footprint of rice field is obtained.

2. The method of claim 1, wherein, The CH4 emission amount of rice field is obtained by the following method: obtaining the basic data of the target region, including rice planting area, days from transplanting to harvesting, irrigation mode proportion, and straw returning proportion; under the accounting framework of IPCC or national greenhouse gas inventory guidelines, differentiating rice field CH4 emission factors are determined through regional literature integration and Meta analysis; the CH4 emission amount of rice field is calculated by a first formula according to the basic data and the rice field CH4 emission factors; wherein, The first formula is: ; CH4emissions from rice fields in t CO2e as carbon dioxide equivalent; Rice planting area, in ha; CH4emission factor for rice field, in kg CH4 ha -1 day -1 ; Days from transplanting to harvest for rice, in days; Global warming potential for CH4 in t CO2e (t CH4) -1 The value is derived from the IPCC 100-year time scale of the warming potential, which is 21.

3. The method of claim 2, wherein, the rice field CH4 emission factors are obtained by the following method: target water management modes and target straw management modes are determined according to regional literature integration and Meta analysis; wherein, the target water management modes include winter water field, flooding irrigation, or mid-term field drying / intermittent irrigation, and the target straw management modes include straw link or non-straw returning field; based on the target water management modes and the target straw management modes, an association table of management mode combinations and emission factor values is queried to obtain different localized rice field CH4 emission factors; the rice field CH4 emission factors are summed up according to the different localized rice field CH4 emission factors.

4. The method of claim 1, wherein, The N2O emission amount of nitrogen fertilizer input of rice field is obtained by the following method: activity level data are obtained by a combination of field investigation, statistical yearbook verification, and expert consultation, including fertilizer nitrogen input amount, manure nitrogen input amount, and nitrogen input amount of returned straw; N2O direct emission factors of the target region are determined according to regional literature integration and Meta analysis; N2O direct emission amount data of rice field are calculated according to the activity level data and the N2O direct emission factors; the N2O emission amount of nitrogen fertilizer input of rice field is calculated according to the N2O direct emission amount data of rice field, N2O indirect emission amount data caused by fertilization, and a second formula; wherein, the N2O indirect emission amount data caused by fertilization is the sum of N2O indirect emission amount after ammonia and nitrogen oxide volatilization caused by rice field fertilization through dry and wet deposition to the ground, lakes and rivers, and N2O indirect emission amount caused by nitrogen leaching and runoff of rice field fertilization.

5. The method of claim 4, wherein, The second formula is: ; N2O emissions from rice fields in t CO2e. N2O direct emission for rice field, in t N2O-N; Indirect N2O emissions from rice fields due to NH3 and NOx volatilization after dry and wet deposition to the ground, lakes and rivers, in t N2O-N; Nitrogen leaching and indirect N2O emission from rice field fertilization, in t N2O-N; Global warming potential for N2O in t CO2e (t N2O) -1 ; the value is derived from the IPCC 100-year time scale of the warming potential, which is 310.

6. The method of claim 4, wherein, The N2O direct emission amount of rice field is calculated according to a third formula, and the third formula comprises: ； wherein, Nfertilizer is the amount of fertilizer nitrogen input for crop type C, in t N; Rstraw is the nitrogen input of the straw returned to the field for crop type C, in t N; manure N input for crop type C in t N; N2O direct emission factor for crop type C in kg N2O-N / kg N; Coefficient to convert N2O-N to N2O.

7. The method of claim 1, wherein, The CO2 emission amount of each agricultural link is the sum of the total CO2 emission amount of fossil fuel consumption and the total CO2 emission amount of power consumption; wherein the total CO2 emission amount of fossil fuel consumption is the sum of the CO2 emission amount of diesel consumption and the CO2 emission amount of gasoline consumption, the total CO2 emission amount of fossil fuel consumption is calculated by a fourth formula, and the fourth formula comprises: ； wherein, is the total amount of CO2emissions from fossil fuel consumption in kg CO2; For the first i type of fossil fuel activity level, the product of the emission quantity of the first i type of fossil fuel and the low calorific value is obtained, in GJ. For the first i The CO2 emission factor of a type of fossil fuel, expressed in t CO2 / GJ; i The fossil fuel is classified into diesel and gasoline.

8. The method of claim 7, wherein, The total CO2 emission amount of power consumption is calculated by a fifth formula, and the fifth formula comprises: ； wherein, is the total CO2 emissions, in kg CO2; P is the power consumption, in kWh; The grid emission factor is taken as the national average of 0.5839 kg CO2 / kWh.

9. The method for calculating the carbon footprint of paddy fields according to claim 7, characterized in that, The first i The CO2 emission factor of the fossil fuel is calculated by a sixth formula, which comprises: ； wherein, is the carbon content per unit heat value of the i-th fossil fuel, in t C / GJ; carbon oxidation rate for the i-th fossil fuel, in %; The ratio of the relative molecular mass of carbon dioxide to carbon.

10. The method of claim 1, wherein, The CO2 emission amount of urea decomposition is calculated by a seventh formula, and the seventh formula comprises: ； wherein, is the CO2 emission from urea decomposition in kg CO2; for the application rate of urea in kg; The CO2 emission factor for urea is fixed at 0.2 kg C / kg urea.

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