A method for calculating carbon footprint of rice field

Abstract

The application discloses a rice field carbon footprint calculation method, and belongs to the technical field of agricultural environmental management and carbon emission accounting. The calculation method of the application firstly accurately defines the accounting boundary and collects data, covering eight emission sources of rice CH4 emission, rice N2O emission of nitrogen fertilizer input, CO2 emission of energy consumption of ploughing / transplanting / plant protection / irrigation / mechanical harvesting, and CO2 emission after urea input; then, based on the boundary, each emission source is finely calculated, and CH4, N2O and various CO2 emissions are uniformly converted into carbon dioxide equivalent; finally, the total amount of rice field carbon footprint is obtained. The application solves the calculation deviation problem caused by the incomplete accounting boundary and the low adaptability of local emission factors of the existing method, improves the comprehensiveness and accuracy of carbon footprint calculation, and provides reliable technical support for low-carbon management of rice fields.

Description

Technical Field

[0001] This application relates to the field of agricultural environmental management and carbon emission accounting technology, and more specifically, to a method for measuring the carbon footprint of paddy fields. Background Technology

[0002] Carbon footprint refers to the total amount of carbon dioxide and other greenhouse gases emitted directly or indirectly by humans in their production and daily lives. It is a method for estimating the impact of carbon emissions on the greenhouse effect. Paddy field ecosystems are an important component of terrestrial ecosystems. Carbon emissions during rice production are influenced by multiple factors, including the amount of agricultural inputs used and methane emissions from paddy fields during the rice growing season. The carbon cycle process in paddy fields has a significant impact on the carbon balance. To achieve carbon reduction targets in agriculture, the carbon footprint of paddy fields must be accurately quantified.

[0003] However, existing methods for measuring the carbon footprint of paddy fields have significant limitations. Conventional methods typically focus only on direct emissions such as methane, while ignoring indirect carbon dioxide emissions from key agricultural processes such as plant protection, irrigation, and urea decomposition, leading to a severe underestimation of the measured results.

[0004] Therefore, there is an urgent need for a new method that can overcome the above-mentioned shortcomings and achieve complete and accurate measurement of the carbon footprint of paddy fields. Summary of the Invention

[0005] The purpose of this application is to provide a method for measuring the carbon footprint of paddy fields. This method can fundamentally solve the problem of distorted measurement results caused by incomplete system boundaries and excessive universality of emission factors in conventional methods by constructing a complete accounting boundary covering eight emission sources and adopting differentiated emission factors based on localized management practices.

[0006] To achieve the above objectives, this application provides a method for calculating the carbon footprint of paddy fields, comprising the following steps:

[0007] Define the accounting boundary, which fully covers the following eight emission sources: CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption in paddy field cultivation, CO2 emissions from energy consumption during rice 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.

[0008] Based on the accounting boundary, a detailed calculation is performed on each emission source to obtain the calculation results in the form of carbon dioxide equivalent; the calculation results include CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption in each agricultural process, and CO2 emissions from urea decomposition.

[0009] The total carbon footprint of paddy fields is obtained based on the calculation results in the form of carbon dioxide equivalent.

[0010] Furthermore, CH4 emissions from paddy fields were calculated using the following methods:

[0011] Obtain data on rice planting area, number of days from transplanting to harvest, proportion of irrigation methods, and proportion of straw returning to the field in the target area to obtain basic data for the target area;

[0012] Within the accounting framework of the IPCC or national greenhouse gas inventory guidelines, the differentiated CH4 emission factors of paddy fields were determined through regional literature review and meta-analysis.

[0013] Based on basic data and CH4 emission factors from paddy fields, the CH4 emissions from paddy fields were calculated using the first formula; the first formula is: ;

[0014] CH4 emissions from paddy fields, calculated in carbon dioxide equivalents, in t CO2e;

[0015] This refers to the rice planting area, expressed in ha (unit: hectares).

[0016] CH4 emission factor from paddy fields, unit: kg CH4ha -1 day -1 ;

[0017] This refers to the number of days from transplanting to harvesting of rice;

[0018] This represents the global warming potential of CH4, expressed in tCO2e (tCH4). -1 The value is derived from the warming potential on the IPCC 100-year timescale, and is set to 21.

[0019] Furthermore, the CH4 emission factor from paddy fields was obtained through the following methods:

[0020] Based on the compilation of regional literature and meta-analysis, target water management methods and target straw management methods were determined. Among them, target water management methods include winter paddy fields, flooded irrigation or mid-term drying / intermittent irrigation, and target straw management methods include straw management or straw not being returned to the field.

[0021] Based on the target water management method and the target straw management method, query the correlation table between the combination of management methods and the emission factor value to obtain different localized paddy field CH4 emission factors;

[0022] The CH4 emission factor of paddy fields is obtained by summing the different localized CH4 emission factors of paddy fields.

[0023] Furthermore, the N2O emissions from nitrogen fertilizer input in paddy fields were obtained using the following methods:

[0024] Activity level data were obtained through a combination of field surveys, statistical yearbook verification, and expert consultation. The activity level data included nitrogen input of chemical fertilizers, nitrogen input of manure, and nitrogen input of straw returned to the field.

[0025] Based on regional literature review and meta-analysis, the direct N2O emission factors for the target region were determined.

[0026] Data on direct N2O emissions from paddy fields were calculated based on activity level data and N2O direct emission factors.

[0027] Based on the data on direct N2O emissions from paddy fields and indirect N2O emissions from fertilization, the N2O emissions from nitrogen fertilizer input in paddy fields are calculated using the second formula. The indirect N2O emissions from fertilization are the sum of the indirect N2O emissions from ammonia and nitrogen oxides volatilized from paddy field fertilization and subsequently deposited on the ground, in lakes, and in rivers through dry and wet deposition, and the indirect N2O emissions from nitrogen leaching and runoff caused by paddy field fertilization.

[0028] Furthermore, the second formula is:

[0029] ;

[0030] in, The N2O emissions from paddy fields are calculated in carbon dioxide equivalents, with the unit being t CO2e.

[0031] This represents the direct N2O emissions from paddy fields, expressed in tons of N2O-N.

[0032] The indirect N2O emissions from the volatilization of ammonia and nitrogen oxides caused by fertilization of paddy fields, which then settle to the ground, lakes and rivers through dry and wet deposition, are expressed in t N2O-N.

[0033] The indirect emissions of nitrogen leaching and runoff N2O caused by fertilization in paddy fields, expressed in t N2O-N;

[0034] The global warming potential of N2O is expressed in units of tCO2e (tN2O). -1 The value is derived from the warming potential over the IPCC 100-year timescale, and is set to 310.

[0035] Furthermore, the direct N2O emissions from paddy fields were calculated using the third formula, which includes:

[0036] ;

[0037] in, This represents the amount of nitrogen fertilizer input for crop type C, expressed in tons of nitrogen (tN).

[0038] The amount of nitrogen input from straw returned to the field for crop type C is expressed in tons (t) of nitrogen.

[0039] The amount of nitrogen input from manure for crop type C is expressed in tons of nitrogen (tN).

[0040] The direct N2O emission factor for crop type C is expressed in kg N2O-N / kg N.

[0041] The coefficient for converting N2O-N to N2O.

[0042] 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: ;

[0043] 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.

[0044] Furthermore, the total CO2 emissions from electricity consumption are calculated using the fifth formula, which includes: ;

[0045] 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.

[0046] Furthermore, the first i The CO2 emission factor for each fossil fuel is calculated using the sixth formula, which includes: ;

[0047] 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.

[0048] Furthermore, the CO2 emissions from urea decomposition are calculated using the seventh formula, which includes: ;

[0049] 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.

[0050] In summary, this application has the following advantages:

[0051] 1. This application, for the first time, clearly defines eight core emission sources covering methane emissions from paddy fields, nitrogen fertilizer-related nitrous oxide emissions, CO2 emissions from energy consumption in agricultural activities such as tillage / transplanting / plant protection / irrigation / mechanical harvesting, and CO2 emissions after urea application. It comprehensively encompasses the direct and indirect carbon emission pathways throughout the entire lifecycle of paddy field cultivation. Compared to existing technologies that generally neglect key emission sources such as plant protection energy consumption and urea decomposition, this application, through complete boundary construction, fundamentally avoids systematic omissions in carbon footprint calculation, ensuring that the calculation results comprehensively and accurately reflect the overall carbon emission landscape of the paddy field ecosystem.

[0052] 2. This application establishes a precise accounting system that aligns with actual field conditions: For methane emissions, differentiated emission factors are determined through regional literature review and meta-analysis, based on a combination of irrigation methods (winter paddy fields, flooded irrigation, mid-term drying / intermittent irrigation) and straw return ratios in the target area. For nitrous oxide emissions, activity level data (fertilizer nitrogen, manure nitrogen, and straw return nitrogen input) are accurately obtained through multiple channels, including field surveys, statistical yearbook verification, and expert consultation. Emission factors are also verified and determined through localized research. This application enables the calculation of key gas emissions to fully adapt to regional differences in agricultural management practices, greatly reducing calculation bias caused by low localization adaptability of parameters. The consistency between the calculation results and actual field emissions is significantly improved. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of the overall process of the rice paddy carbon footprint calculation method proposed in the embodiments of this application;

[0055] Figure 2 This is a schematic diagram of the accounting boundary proposed in the embodiments of this application;

[0056] Figure 3 This is a schematic diagram of the process for calculating methane emissions from paddy fields according to an embodiment of this application;

[0057] Figure 4 This is a schematic diagram of the process for calculating nitrous oxide emissions according to an embodiment of this application. Detailed Implementation

[0058] 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.

[0059] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0060] 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:

[0061] S101. Accurately define accounting boundaries and collect data.

[0062] like Figure 2As 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.

[0063] For these eight emission sources and the target areas requiring accounting, the following two types of data were collected:

[0064] (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.

[0065] Table 1 Classification of Irrigation Methods and Straw Return to Field

[0066]

[0067] (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.

[0068] This application explicitly covers eight major emission sources across the entire rice-growing chain, including methane from paddy fields, nitrous oxide from nitrogen fertilizers, and emissions from cultivated land and rice transplanting. It encompasses both direct and indirect greenhouse gas emissions from rice cultivation, avoiding the underestimation of carbon footprint caused by missing boundaries in traditional methods and further ensuring the completeness of the calculations. Furthermore, it specifically categorizes data into two types: management time and activity level. This includes key management parameters such as irrigation methods and straw return ratios (detailed classification ensures parameter relevance), and core data such as energy consumption and fertilizer application are obtained through multiple channels including statistical data and field surveys, providing reliable data support for accurate calculations.

[0069] S102. Determine key emission factors based on differentiation and perform refined calculations.

[0070] Based on the accounting boundaries, a refined calculation is performed on each emission source to obtain the calculation results converted into carbon dioxide equivalents, including the calculation results of CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption in various agricultural processes, and CO2 emissions from urea decomposition. In this calculation process, since there are multiple greenhouse gases, such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), their impact on global warming varies. To standardize the measurement and comparison of emissions of different greenhouse gases, this application introduces the concept of carbon dioxide equivalents. The emissions of different greenhouse gases are converted into equivalent carbon dioxide amounts according to their contribution to global warming. Therefore, in this application, tCO2e represents the total amount after converting the emissions of various greenhouse gases into equivalent carbon dioxide amounts, in tons (t), and e stands for equivalent.

[0071] Specifically:

[0072] 1) such as Figure 3 As shown, the methane emissions from paddy fields are calculated:

[0073] Since methane emissions from paddy fields are the net result of methane production from the anaerobic decomposition of organic matter by methanogenic bacteria in the soil, followed by oxidation by methanogenic bacteria, this application abandons a single default emission factor in its calculations. Instead, based on the specific irrigation methods and straw return rates in the target area, and through regional literature review and meta-analysis, it determines localized and differentiated methane emission factors that match the target area. The proportions of different irrigation methods and the proportion of straw return to the field will be collected as key inputs. Specific emission factors will be obtained by querying an emission factor database established based on a meta-analysis of local research literature. Then, the methane emissions under different combinations (combinations of different water management methods and straw management methods) were calculated separately, and the total methane emissions from paddy fields were obtained by summing them up.

[0074] The methane emissions from paddy fields (converted to carbon dioxide equivalent) were calculated using the first formula.

[0075] The first formula includes:

[0076] ;

[0077] The CH4 emissions from paddy fields are calculated in carbon dioxide equivalents, with the unit being t CO2e (the emission units in this application are actually all in tons; the suffix CO2e indicates conversion to carbon dioxide equivalents and is not used as a unit, for example...). =1tCO2e, which means that 1 ton of methane in the form of carbon dioxide was emitted.

[0078] This refers to the rice planting area, expressed in hectares (ha).

[0079] CH4 emission factor from paddy fields, unit: kg CH4ha -1 day -1 (This refers to the amount of CH4 emitted per hectare per day).

[0080] This refers to the number of days from transplanting to harvesting of rice, expressed in days (d).

[0081] This represents the global warming potential of CH4, expressed in tCO2e(tCO2e). CH4 ) -1 The value is derived from the IPCC's 100-year timescale warming potential, and is set to 21. In short, the Global Warming Potential (GWP) in this application is an indicator that measures the contribution of greenhouse gases to global warming. Specifically, it refers to the ratio of the radiative forcing effect of 1 kg of greenhouse gas emitted into the atmosphere to the effect of the same mass of carbon dioxide within a specific time period (usually set at 100 years). Radiative forcing, as a physical quantity, reflects the disturbance of various physical and chemical processes to the global energy balance, thus affecting the Earth's climate. For example, the GWP of methane is 21 on a 100-year timescale, meaning that the same amount of methane has 21 times the potential to cause global warming over 100 years compared to carbon dioxide.

[0082] 2) such as Figure 4 As shown, the emissions of nitrous oxide are calculated:

[0083] Nitrogen inputs of various types (including nitrogen inputs from chemical fertilizers, manure, and straw) were collected from different types of farmland as activity-level data. Based on regional literature review and meta-analysis, the direct nitrous oxide emission factor for the target region was determined. Then, the direct nitrous oxide emissions from paddy fields were calculated using the direct nitrous oxide emission factor and the third formula. Indirect nitrous oxide emissions (including indirect emissions from ammonia and nitrogen oxides volatilized from paddy field fertilization that settle to the ground, lakes, and rivers via dry and wet deposition, and indirect emissions from nitrogen leaching / runoff caused by paddy field fertilization) were calculated using formulas from the IPCC National Greenhouse Gas Inventory Guidelines and Provincial Inventory Compilation Guidelines. The emission factor adopted the IPCC recommended values. The volatilization coefficients for nitrogen inputs from agricultural manure and chemical fertilizers were 0.2 and 0.1, respectively, and the nitrogen leaching and runoff loss coefficients for farmland were 0.2. The total nitrous oxide emissions are obtained by summing the direct and indirect emissions. The volatilization coefficient and loss coefficient used in this application are actually quantitative parameters for calculating indirect nitrous oxide emissions, essentially nitrogen loss ratio coefficients. They are used to accurately calculate the proportion of nitrogen lost through volatilization and deposition, and leaching runoff after fertilization of paddy fields (including manure and chemical fertilizers), thereby calculating the indirect emissions of nitrous oxide generated from the conversion of lost nitrogen. For example, if the volatilization coefficient of nitrogen input from manure is 0.2, or 20%, then the amount of nitrogen volatilized from manure = the amount of nitrogen input from manure × 0.2. This volatilized nitrogen will diffuse into the surrounding soil, lakes, and rivers through atmospheric dry and wet deposition (such as rainfall and dustfall), further converting into nitrous oxide in the environment. This portion of emissions is recorded as part of the indirect nitrous oxide volatilization emissions.

[0084] Specifically, the third formula is:

[0085] ;

[0086] in, The amount of fertilizer nitrogen input for crop type C is expressed in t N (the unit of input in this application is actually tons, which can also be converted to kilograms. The N element in the suffix indicates that the type of input is nitrogen and is not used as a unit).

[0087] The amount of nitrogen input from straw returned to the field for crop type C is expressed in tons (t) of nitrogen.

[0088] The amount of nitrogen input from manure for crop type C is expressed in tons of nitrogen (tN).

[0089] This refers to the direct N2O emission factor for crop type C, expressed in kg N2O-N / kg N (where kg N2O-N refers to the mass of nitrous oxide per kilogram of nitrogen, and kg N refers to the amount of nitrogen input per kilogram or the nitrogen content in the emission source). In practical applications of this application, it is used to quantify the N2O emissions directly generated per unit of nitrogen input (kg N) during agricultural production for a specific crop type (such as rice, corn, etc.). For example, if... The value is 0.01 kg N₂O-N / kg N, meaning that for every 1 kg of nitrogen added, this crop type will directly emit 0.01 kg of N₂O (as nitrogen).

[0090] The coefficient for converting N2O-N to N2O.

[0091] The assessment of nitrogen input from straw returned to the field in the third formula of this application is based on the yield, economic coefficient, dry weight ratio, root-to-shoot ratio, straw / stubble nitrogen content, and straw return-to-field ratio of various crops in a certain province (if calculations for other regions are required, the coefficients for that region should be replaced accordingly). The relevant calculation coefficients are shown in Table 2. The assessment of nitrogen input from manure is based on the total nitrogen excretion of livestock and poultry, the proportion of nutrient return from livestock and poultry manure to the field, the total nitrogen excretion of rural population, and the nitrogen loss from the storage, transportation, and management of livestock and poultry manure. The total nitrogen excretion of livestock and poultry is calculated based on the number of various types of livestock and poultry and the average annual nitrogen excretion of different animals. Livestock and poultry farming is mainly classified into pigs, cattle, horses, sheep, rabbits, and poultry. Their annual nitrogen excretion from manure is referenced from the provincial emission inventory in my country, which are 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. The number of livestock is obtained from statistical yearbooks. The purpose of the calculation coefficients in this application is to: first, derive the total mass of straw from the crop yield; then, calculate the total nitrogen content in the straw; and finally, combine the straw return ratio to obtain the actual nitrogen input. For example, the crop fresh weight yield 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 the underground root system (stubble) is calculated by the root-to-shoot ratio. For instance, assuming the economic yield of rice in a certain area is 1000 kg / mu and the straw return ratio is 70%, then the dry weight of straw + stubble = (economic yield / economic coefficient - economic yield) × (1 + root-to-shoot ratio) = (1000 / 0.489 - 1000) × (1 + 0.125) ≈ 1173 kg / mu. The total nitrogen content of straw + stubble = dry weight × straw / stubble nitrogen content = 1173 × 0.00753 ≈ 8.83 kg N / mu. Nitrogen input from straw returned to the field = total nitrogen × straw return ratio = 8.83 × 70% ≈ 6.18 kgN / mu.

[0092] Table 2 Calculation coefficients for nitrogen input from crop straw return to the field

[0093]

[0094] Based on the direct and indirect nitrous oxide emissions from paddy fields (including those from volatilization and leaching runoff) obtained from the third formula, and combined with the second formula, the nitrous oxide emissions from nitrogen fertilizer input in paddy fields (converted to carbon dioxide equivalent) can be calculated.

[0095] The second formula is: ;

[0096] The N2O emissions from paddy fields are calculated in carbon dioxide equivalents, with the unit being t CO2e.

[0097] The amount of N2O emitted directly from paddy fields is expressed in tons (t N2O-N). (In this application, N2O-N refers to the mass of nitrous oxide as nitrogen, and is not used as a specific unit, but only to indicate the type. The unit of emission is tons.)

[0098] The indirect N2O emissions from the volatilization of ammonia and nitrogen oxides caused by fertilization of paddy fields, which then settle to the ground, lakes and rivers through dry and wet deposition, are expressed in t N2O-N.

[0099] The indirect emissions of nitrogen leaching and runoff N2O caused by fertilization in paddy fields, expressed in t N2O-N;

[0100] The global warming potential of N2O is expressed in units of tCO2e (tN2O). -1 The value is derived from the IPCC's 100-year timescale warming potential, and is set to 310. Among these, (t N2O) -1 This represents the amount of N2O produced by the reaction of tCO2e (tN2O) with each ton of N2O. -1 The value represents the amount of carbon dioxide equivalent to one ton of nitrous oxide. It can be understood as the global warming effect produced by one ton of nitrous oxide over a 100-year timescale, which is equivalent to the warming effect produced by 310 tons of carbon dioxide.

[0101] 3) Calculate carbon dioxide emissions:

[0102] Based on the energy consumption of each agricultural activity (including carbon emissions from fossil fuels and electricity) and the amount of urea applied, combined with the corresponding carbon dioxide emission coefficients, the emissions are calculated separately, and then summed to obtain the total carbon dioxide emissions for the target area. The target area in this application refers to the area where the carbon footprint of paddy fields needs to be measured. Specifically, the carbon emissions generated during rice cultivation, including tillage, transplanting, fertilization, pesticide application (plant protection), irrigation, and harvesting, can be calculated by multiplying the activity level energy consumption by the corresponding emission factor.

[0103] 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.

[0104] The fourth formula includes:

[0105] ;

[0106] 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).

[0107] 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;

[0108] 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.

[0109] iFossil fuels are classified into diesel and gasoline.

[0110] The fifth formula includes:

[0111] ;

[0112] in, This represents the total CO2 emissions from electricity consumption, expressed in kg CO2.

[0113] Power consumption, in kWh;

[0114] 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.

[0115] The sixth formula includes:

[0116] ;

[0117] in, The carbon content per unit calorific value of the i-th fossil fuel is expressed in t C / GJ, which means the mass (tons) of carbon in one gigajoules of fossil fuel. It is an inherent property of the fuel itself.

[0118] denoted as the carbon dioxide emission factor for the i-th fossil fuel, expressed in tCO2 / GJ, meaning the number of tons of carbon dioxide produced by burning 1 GJ of this fuel.

[0119] Let be the carbon oxidation rate of the i-th fossil fuel, expressed as a percentage. This represents the proportion of carbon that is oxidized to carbon dioxide during fuel combustion, reflecting the degree of completeness of fuel combustion.

[0120] It is the ratio of the relative molecular masses of carbon dioxide to carbon.

[0121] The seventh formula includes:

[0122] ;

[0123] in, This represents the CO2 emissions from the decomposition of urea, expressed in kg CO2.

[0124] This refers to the amount of urea applied, expressed in kg.

[0125] The CO2 emission factor of urea is fixed at 0.2 kg C / kg urea, which means the mass of carbon elements in 1 kg of urea that can be decomposed, released and converted into carbon dioxide.

[0126] Among them, the fossil energy mainly used in rice planting activities and product use is classified as diesel and gasoline, and the relevant values ​​are shown in Table 3.

[0127] Table 3. Data on carbon content, carbon oxidation rate, and average lower heating value of fossil fuels.

[0128]

[0129] Regarding methane (CH4) emissions, this application abandons the single default factor in traditional models. Based on a combined scenario of irrigation methods (3 types) and straw return to the field (2 types) in the target area, it determines differentiated emission factors through regional literature review and meta-analysis, fully considering the impact of agricultural management practices on emissions, thus improving the accuracy of CH4 measurement from the source. For nitrous oxide (N2O) emissions, its emission factors have been validated through localized research. Indirect emission factors adopt the IPCC-recommended detailed coefficients (nitrogen volatilization coefficient of manure / fertilizer, nitrogen leaching / runoff loss coefficient), avoiding errors caused by a one-size-fits-all approach. Furthermore, this application provides corresponding targeted measurement methods for different greenhouse gases. For example, for methane, it considers the net effects of methane production, oxidation, and transport; for nitrous oxide, it considers both direct and indirect emission pathways; and for carbon dioxide, it considers three sources: fossil fuel combustion, electricity consumption, and urea decomposition, thus comprehensively covering eight major emission sources. Furthermore, each emission source corresponds to a specific accounting formula, and the parameters in the formulas all provide clear value standards or calculation methods, which can ensure the repeatability and verifiability of the calculations. In the calculation process, the IPCC standard concept of carbon dioxide equivalent (CO2e) is introduced, and CH4 (value 21) and N2O (value 310) are uniformly converted into equivalent CO2 through the global warming potential (GWP), solving the measurement problem of the differences in the warming effects of different greenhouse gases.

[0130] S103. Carbon Footprint Integration

[0131] The total carbon footprint of the target area's paddy fields is obtained by summing the results of each calculation in step S102.

[0132] By following the steps above, we can achieve accurate and complete calculation of the carbon footprint of paddy fields at the regional scale, providing precise data support for the low-carbon development of agriculture.

[0133] In summary, this application establishes a standardized accounting process, clarifies the quantification formulas for each emission source (such as the first formula for methane emissions and the fifth formula for carbon dioxide emissions from electricity consumption), and standardizes the values ​​of key parameters such as the IPCC standard Global Warming Potential (GWP), grid emission factor, and fuel calorific value, thus lowering the operational threshold. Furthermore, through a parameter localization mechanism supported by regional meta-analysis and field survey data, the calculation method in this application can flexibly adapt to the needs of provincial, municipal, and even plot-scale paddy field carbon footprint calculations under different climatic conditions and agricultural management models. Its calculation results can provide accurate data support for the formulation of low-carbon agricultural policies, the selection of emission reduction technologies, and the optimization of low-carbon planting models, possessing extremely high practical application value and promising prospects for promotion.

[0134] Example 1

[0135] This embodiment takes a certain province as the target area in 2022 and calculates the carbon footprint of paddy fields in that area, including the following steps:

[0136] 1. Accounting Boundaries and Data Collection

[0137] The accounting boundary was determined to be paddy fields within a certain province, and relevant data for 2022 was collected, including:

[0138] Rice planting area: 1.87 million hectares.

[0139] Irrigation method ratio: flood irrigation (60%), mid-term drying / intermittent irrigation (40%).

[0140] Straw return rate: full return (70%), no return (30%).

[0141] The amount of fertilizer applied (converted to pure nitrogen) was 125,000 tons, the amount of nitrogen input from manure was 12,000 tons, and the amount of nitrogen input from straw returned to the field was 8,000 tons.

[0142] Total diesel consumption in major agricultural activities: 98,000 tons.

[0143] Irrigation electricity consumption: 420 million kilowatt-hours.

[0144] Urea application amount: 83,000 tons.

[0145] 2. Determination of key emission factors

[0146] Methane emission factors: Meta-analysis was conducted by retrieving 15 research papers published in a province and surrounding similar ecological areas in the past ten years to determine the localized emission factors under different water and straw management combinations, for example: (1) flood irrigation + straw return to the field: 1.65 kg CH4 / ha / day; (2) flood irrigation + no straw return to the field: 1.20 kg CH4 / ha / day; (3) flood irrigation + straw return to the field: 0.95 kg CH4 / ha / day; (4) mid-term field drying + straw return to the field: 0.70 kg CH4 / ha / day.

[0147] Nitrous oxide emission factor: Based on local literature review, the direct emission factor of nitrous oxide was determined to be 0.009 kgN2O-N / kg N;

[0148] Grid emission factor: The national average is taken as 0.5839 kg CO2 / kWh.

[0149] 3. Carbon Emission Calculation

[0150] The main results of calculations based on the various formulas in this application are as follows:

[0151] (1) Calculate the methane emissions from paddy fields using the weighted average emission factor.

[0152] Flood irrigation + straw return to the field: 60% × 70% × 1.65 = 0.693

[0153] Flood irrigation + straw not returned to the field: 60% × 30% × 1.20 = 0.216

[0154] Mid-term field drying + straw return to the field: 40% × 70% × 0.95 = 0.266

[0155] Mid-term field drying + no straw return to the field: 40% × 30% × 0.70 = 0.084

[0156] Weighted average =1.259 kg CH4 / ha / day

[0157] Calculate methane emissions using the first formula. , A It is 1.87 million hectares. t For 100 days, If the value is 21, then substituting it into the first formula yields:

[0158] =1.87 million hectares × 1.259 kg / ha / day × 100 days × 21 × 10 -3 =4.952 million tons of CO2e.

[0159] (2) Calculate nitrous oxide emissions

[0160] Total nitrogen input = 12.5 + 1.2 + 0.8 = 14.5 million tons of N. The direct emissions of nitrous oxide are calculated using the third formula, which gives a value of 0.009t N₂O₻N / t N. ,get =145,000 tons N × 0.009t N2O - N / t N × 44 / 28 = 2,050 tons N2O

[0161] Considering indirect emissions (estimated at 30% of direct emissions) ≈ 0.062 million tons of N2O, that is + =0.062, and at the same time If the value is 310, then the total N2O emissions are... Calculated using the second formula = (0.205 + 0.062) 10,000 tons N2O × 310 GWP = 828,000 tons CO2e.

[0162] (3) Calculate carbon dioxide emissions from energy consumption

[0163] Diesel emissions are calculated using formulas four and six: 98,000 tons × 42.652 GJ / ton × 0.0202 tons C / GJ × 0.98 × 44 / 12 × 10 3 =308,000 tons of CO2,

[0164] Electricity emissions are calculated using the fifth formula: 420 million kWh × 0.5839 kg CO2 / kWh × 10 -3 =245,000 tons of CO2, then the total energy consumption = 308,000 + 245,000 = 553,000 tons of CO2;

[0165] The CO2 emissions from urea application, calculated using the seventh formula, are: 83,000 tons × 10 3 ×0.2kg C / kg urea×44 / 12×10 -3 =61,000 tons of CO2.

[0166] Based on the above data, the summary results are as follows:

[0167] methane emissions: 4.952 million tons of CO2e;

[0168] Nitrous oxide emissions from nitrogen fertilizer input: 828,000 tons of CO2e;

[0169] Energy consumption CO2 emissions: 553,000 tons of CO2;

[0170] CO2 emissions from urea application: 61,000 tons of CO2.

[0171] The carbon emissions from the above summation results are added together to obtain the carbon footprint of rice paddies in a certain province in 2022 as 459.2 + 82.8 + 55.3 + 6.1 = 639.4 million tons of CO2e.

[0172] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0173] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0174] Finally, it should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0175] This application uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for calculating the carbon footprint of paddy fields, characterized in that, Includes the following steps: The accounting boundary is defined, and the accounting boundary fully covers the following eight emission sources: CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption in paddy field cultivation, CO2 emissions from energy consumption during rice 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. Based on the aforementioned accounting boundary, a refined calculation is performed on each emission source to obtain the calculation results in the form of carbon dioxide equivalents. The calculation results include CH4 emissions from paddy fields, N2O emissions from nitrogen fertilizer input in paddy fields, CO2 emissions from energy consumption in each agricultural process, and CO2 emissions from urea decomposition. The total carbon footprint of paddy fields is obtained based on the calculation results in the form of carbon dioxide equivalent. The CH4 emissions from the paddy fields were calculated using the following method: Data on rice planting area, number of days from transplanting to harvest, proportion of irrigation methods, and proportion of straw returning to the field in the target area are obtained to obtain the basic data of the target area. Within the accounting framework of the IPCC or national greenhouse gas inventory guidelines, differentiated CH4 emission factors from paddy fields were determined through regional literature review and meta-analysis. Based on the aforementioned basic data and the CH4 emission factor from paddy fields, the CH4 emission amount from paddy fields was calculated using the first formula; where... The first formula is: ; CH4 emissions from paddy fields, calculated in carbon dioxide equivalents, in t CO2e; A represents the rice planting area, measured in ha. CH4 emission factor from paddy fields, unit: kg CH4 ha -1 day -1 ; t represents the number of days from transplanting to harvest of rice, expressed in days. This represents the global warming potential of CH4, expressed in tCO2e (tCH4). -1 The value is derived from the warming potential on the IPCC 100-year timescale, and is set to 21.

2. The method for calculating the carbon footprint of paddy fields according to claim 1, characterized in that, The CH4 emission factor from the paddy field was obtained through the following method: Based on the compilation of regional literature and meta-analysis, target water management methods and target straw management methods were determined. Among them, target water management methods include winter paddy fields, flooded irrigation or mid-term drying / intermittent irrigation, and target straw management methods include straw management or straw not being returned to the field. Based on the target water management method and the target straw management method, query the correlation table between management method combination and emission factor value to obtain different localized paddy field CH4 emission factors; The CH4 emission factor of the paddy field is obtained by summing the different localized paddy field CH4 emission factors.

3. The method for calculating the carbon footprint of paddy fields according to claim 1, characterized in that, The N2O emissions from the nitrogen fertilizer input in the paddy field were obtained using the following method: Activity level data were obtained through a combination of field surveys, statistical yearbook verification, and expert consultation. The activity level data included nitrogen input of chemical fertilizers, nitrogen input of manure, and nitrogen input of straw returned to the field. Based on regional literature review and meta-analysis, the direct N2O emission factors for the target region were determined. Based on the activity level data and the N2O direct emission factor, calculate the N2O direct emission data from paddy fields; Based on the direct N2O emission data from paddy fields and the indirect N2O emission data from fertilization, the N2O emission from nitrogen fertilizer input in paddy fields is calculated using the second formula. The indirect N2O emission data from fertilization is the sum of the indirect N2O emissions from ammonia and nitrogen oxides volatilized from paddy field fertilization and subsequently deposited onto the ground, lakes, and rivers through dry and wet deposition, and the indirect N2O emissions from nitrogen leaching and runoff caused by paddy field fertilization.

4. The method for calculating the carbon footprint of paddy fields according to claim 3, characterized in that, The second formula is: ； The N2O emissions from paddy fields are calculated in carbon dioxide equivalents, with the unit being t CO2e. This represents the direct N2O emissions from paddy fields, expressed in tons of N2O-N. The indirect N2O emissions from the volatilization of ammonia and nitrogen oxides caused by fertilization of paddy fields, which then settle to the ground, lakes and rivers through dry and wet deposition, are expressed in t N2O-N. The indirect emissions of nitrogen leaching and runoff N2O caused by fertilization in paddy fields, expressed in t N2O-N; The global warming potential of N2O is expressed in units of tCO2e (tN2O). -1 The value is derived from the warming potential over the IPCC 100-year timescale, and is set to 310.

5. The method for calculating the carbon footprint of paddy fields according to claim 3, characterized in that, The direct N2O emissions from the paddy field are calculated using a third formula, which includes: ； where F SN，C is the amount of fertilizer nitrogen input for crop type C in t N; F CR，C Rstraw is the nitrogen input of the returned straw for crop type C, in t N; F OF，C The amount of nitrogen input from manure for crop type C is expressed in tons of nitrogen (tN). The direct N2O emission factor for crop type C is expressed in kg N2O-N / kg N. The coefficient for converting N2O-N to N2O.

6. The method for calculating the carbon footprint of paddy fields according to claim 1, characterized in that, The CO2 emissions from each agricultural activity stage are the sum of CO2 emissions from fossil fuel consumption and CO2 emissions from electricity consumption; wherein, the total CO2 emissions from fossil fuel consumption are the sum of CO2 emissions from diesel consumption and CO2 emissions from gasoline consumption, and the total CO2 emissions from fossil fuel consumption are calculated using a fourth formula, which includes: ； Among them, E 化石 This represents the total CO2 emissions from fossil fuel consumption, expressed in kg CO2. AD i The activity level of the i-th fossil fuel is obtained by multiplying the emissions of the i-th fossil fuel by its lower heating value, and the unit is GJ; EF i Let be the CO2 emission factor for the i-th fossil fuel, expressed in tCO2 / GJ. i represents the type of fossil fuel, which is divided into diesel and gasoline.

7. The method for calculating the carbon footprint of paddy fields according to claim 6, characterized in that, The total CO2 emissions from the electricity consumption are calculated using a fifth formula, which includes: AND 电 =AD 电 ×EF 电 ; Among them, E 电 This represents the total CO2 emissions from electricity consumption, expressed in kg CO2. AD 电 Power consumption, in kWh; EF 电 The emission factor for the power grid is taken as the national average of 0.5839 kg CO2 / kWh.

8. The method for calculating the carbon footprint of paddy fields according to claim 6, characterized in that, The CO2 emission factor of the i-th fossil fuel is calculated using a sixth formula, which includes: ； Among them, CC i The carbon content per unit calorific value of the i-th fossil fuel is expressed in t C / GJ. OF i 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.

9. The method for calculating the carbon footprint of paddy fields according to claim 1, characterized in that, The CO2 emissions from urea decomposition are calculated using a seventh formula, which includes: ； Among them, E Urea This represents the CO2 emissions from the decomposition of urea, expressed in kg CO2. AD Urea This refers to the amount of urea applied, expressed in kg. EF Urea The CO2 emission factor of urea is fixed at 0.2 kg C / kg urea.

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