Rice Methane Reduction
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Methane (CH4) is a potent greenhouse gas (GHG) with a 100-year global warming potential (GWP) 27.9 times that of carbon dioxide1, making it a critical focus for near-term climate mitigation. Rice cultivation is one of the largest sources of methane, responsible for approximately 8% of total human-generated methane emissions; effectively 30 million tonnes of methane per year (equivalent to 840 million tonnes of CO2e annually)2. With over 170 million hectares of rice harvested worldwide each year, the scale of this emission source—and the corresponding mitigation opportunity—is substantial.
Alternate wetting and drying (AWD) is a water management practice that introduces one or more controlled drainage events during the rice growing season, temporarily lowering the water table and allowing the soil to aerate periodically, thus interrupting the anaerobic conditions that sustain methane creation. Current research consistently demonstrates that non-continuous flooding practices reduce methane emissions by 40–50% on average, with the magnitude of reduction depending on drainage frequency, duration, soil type, organic amendment practices, and climate conditions3,4. Critically, when implemented according to established agronomic guidelines—including maintaining the field water level ≤ 15 cm below the soil surface and timing drainage to avoid moisture-sensitive crop growth stages—AWD maintains or improves rice yields while simultaneously reducing water consumption by 15–30%5,6.
This Protocol establishes the requirements and standards for quantifying, reporting, and verifying greenhouse gas emission reductions achieved through the adoption of alternative water management practices in irrigated rice cultivation. It provides a consistent framework for Projects seeking to generate high-integrity CreditsCertificates for methane emission reductions, ensuring that creditedissued reductions are real, additional, independently verified, and conservatively quantified. To that end, this Protocol describes how Projects must establish baselines, monitor water management practices, measure or estimate methane and nitrous oxide fluxes, and account for project life-cycle emissions to make a full accounting of the climate benefits. This Protocol also defines project eligibility, stratification, and emission factor determination requirements, drainage verification procedures, and uncertainty quantification.
This Protocol supports Projects at varying scales, from smallholder farmer aggregation programmes covering hundreds of hectares to large-scale irrigation district interventions. It incorporates a flexible quantification approach that balances measurement precision with practical feasibility: direct field measurement via the closed-chamber method provides the highest accuracy for Projects with dedicated measurement infrastructure, while country-specific emission factors and IPCC default values enable participation by Projects in regions where direct measurement capacity is limited. This approach is designed to be inclusive without compromising scientific rigourrigor, applying progressively larger uncertainty deductions to lower-tier quantification methods to maintain conservative creditingissuances across all project types.
Throughout this Protocol, the use of “must” indicates a requirement, whereas “should” indicates a recommendation.
This Protocol relies on and is intended to be compliant with the following standards and protocols:
Additional reference standards that inform the requirements and overall practices incorporated in this Protocol include:
Protocols and Methodologies that were assessed as part of a literature review during the development of this Protocol include:
This Protocol was developed based on the current state-of-the-art, publicly available science regarding reducing GHG’s in rice cultivation. This Protocol aims to be scientifically stringent and robust. We recognize that some requirements may exceed the status quo in the market and that there are numerous opportunities to improve the rigor of this Protocol. Key future improvements to the Protocol are outlined in Appendix B.
Additionally, this Protocol will be reviewed when there is an update to published scientific literature, government policies, or legal requirements that would affect net emissions quantification or the monitoring guidelines outlined in this Protocol, or at a minimum of every 2 years.
To qualify for creditingissuances under this Protocol, a Project must meet all of the following conditions.
This Protocol is globally applicable to rice cultivation projects on irrigated, lowland rice fields.
Project rice fields must be equipped with controlled irrigation facilities such that, in both dry and wet seasons, the Project Proponent can establish the appropriate dry and flooded conditions required by the project activity.
Rice cultivation in the project area must be predominantly characterized by irrigated, flooded fields for an extended period during the growing season. Fields whose water regimes are classified as upland, rainfed, or deep water are not eligible under this Protocol.
The baseline on-season water regime scenario must correspond to one of the following conditions:
Projects must indicate which scenario best describes the baseline conditions that reflect Business As Usual (BAU).
To be eligible for crediting, each enrolled field must provide evidence that the field was under active rice cultivation with an eligible baseline on-season water regime. Under this protocol a field is defined as the smallest unit across which management ifis homogeneous. A single credible evidence source is sufficient. At minimum, the following must be evidenced:
Acceptable forms of evidence include, but are not limited to:
Isometric retains the right to use historical remote sensing data to confirm that the baseline scenario and historical land use have been accurately described.
Where a project activity involves the introduction of a rice cultivar that has not previously been cultivated in the project region, the Project Proponent must demonstrate that the newly introduced cultivar does not necessitate material changes to existing land management practices beyond those required by the eligible project activity itself.
A Project must involve one or more of the following activities that reduce anaerobic decomposition of organic matter during rice cultivation and thereby reduce methane generation:
A drainage event is defined as a period during which the field water level falls to between 5 and 15 cm below the soil surface (or between -10 and -20 kPa if using digital water sensors) before re-flooding is initiated. Only drainages that were not present in the baseline are considered additional.
During the project period, each field must maintain the same number of rice cultivation seasons per year as was practiced during the baseline period.
All fields implementing drainage-based project activities must monitor water levels during each drainage event to evidence that the project activity has occurred and to ensure that drainage does not exceed the threshold at which yield loss and associated leakage emissions become a material risk7.
For each drainage event, the field must record the water level below the soil surface at its lowest point before re-flooding. Two measurement methods are acceptable:
Readings must be taken at the lowest point reached before re-flooding for each drainage event and recorded alongside the date, time, and unique field ID. Projects must also submit geotagged photos of the field water tube measurement at this lowest point for all drainage events for at least 5% of fields in the Reporting Period.
Documentation requirements for water level monitoring are specified in the monitoring provisions in Section 9.3 of this Protocol.
The application of soil amendments can reduce the methane potential of rice paddies in addition to water-saving irrigation practices. Biochar reduces CH4 dynamics by altering soil aeration, microbial community composition, and organic carbon dynamics11,12. Methanotrophs are a novel intervention involving the application of methane-oxidizing bacteria that enhance CH4 oxidation in the soil13. Application of methane-reducing amendments such as biochar or methanotrophs is permitted when co-deployed with eligible activities described in Section 4.2. When these amendments are applied in treated fields, quantification of the Project's methane reduction using default emission factors will under-count the effective reduction; direct measurements will be subject to the uncertainty screening in Section 8.6.2, so total CreditsCertificates issued remain conservative.
Where biochar or methanotrophic bacteria are applied as a project activity, the Project Proponent must disclose the use of such amendments when describing project activities, and must stratify the project area to distinguish areas that receive these amendments from areas that do not, as set out in the Alternative Application conditional stratification criterion in Section 7.2.
The following topics are covered briefly in this Protocol due to their inclusion in the Isometric Standard, which governs all Isometric Protocols. See in-text references to the Isometric Standard for further guidance.
For each specific Project to be evaluated under this Protocol, the Project Proponent must document project characteristics in a Project Design Document (PDD) as outlined in Section 3.2 of the Isometric Standard. The PDD will form the basis for project verification and evaluation in accordance with this Protocol, and must include consideration of processes unique to each Project, such as:
Projects must be validated and net CO₂e removalsreductions verified by an independent third party, consistent with the requirements described in this Protocol as well as in the Isometric Standard.
The VVB must adhere to these requisite components:
The threshold for Materiality, considering the totality of all omissions, errors, and mis-statements, is 5%, in accordance with the Isometric Standard.
Verifiers should also verify the documentation of uncertainty of the GHG statement as required by the Isometric Standard.
Qualitative Materiality issues may also be identified and documented, such as:
Project Validation and Verification must incorporate site visits to project facilities, namely rice paddies, in accordance with the requirements of ISO 14064-3, 6.1.4.2. This is to include, at a minimum, site visits to the project site during Validation and initial Verification. Validators should, whenever possible, observe project operations to ensure full documentation of process inputs and outputs through visual observation (see the Isometric Standard).
Additional site visits may be required if there are substantial changes to field operations over the course of the Validation period or if deemed necessary by Isometric or the Validation and Verification Bodies (VVBs). Site visit plans are to be determined according to the VVB’s internal assessment, in consultation with Isometric.
Verifiers and validators must comply with the requirements defined in the Isometric Standard. In addition, VVB teams must maintain and demonstrate expertise associated with the specific technologies of interest.
All VVBs are approved by Isometric independently and impartially based on alignment with Conflict of Interest policies, rotation of VVB policies, oversight on quality and the following requirements:
Greenhouse gas reduction or avoidance can often be a result of a multi-step process, with activities in each step managed and operated by a different operator, company, or owner. When there are multiple parties involved in the process, and to avoid double-counting of net CO₂e reductions, a single Project Proponent must be specified contractually as the sole owner of CreditsCertificates. Contracts must comply with all requirements defined in the Isometric Standard.
The Project Proponent must be able to demonstrate additionality through compliance with the Isometric Standard. The counterfactual scenarios and baselines utilized to assess additionality must be project-specific, and are described in Section 7.3 of this Protocol.
Additionality determinations must be reviewed and completed at project validation, as well as in the event that significant changes to project operating conditions, such as the following:
Rice methane reduction activities—particularly alternate wetting and drying (AWD) and dry seeding—generate co-benefits beyond greenhouse gas mitigation, such as substantial reductions in irrigation water use10,14. Such co-benefits may qualify for separate payments under agricultural conservation or water stewardship schemes15. Payments for multiple ecosystem services resulting from a single management practice is known as stacking16,17.
Projects must disclose any expected or received stacked payments made to the Project Proponent or the landowner from additional ecosystem services provided as a result of project activities at Validation and all Verifications.
Should such alternative funding streams arising from project activities make Carbon Finance no longer necessary to perform the Removal or Reduction activity, the Project will no longer be considered additional (Section 5.4) and thus will not be eligible for CreditsCertificates.
The Project Proponent must demonstrate that without Carbon Finance the project activity is not Common Practice, in accordance with the requirements defined in the Isometric Standard.
The analysis must be conducted at the state or provincial level (or equivalent second-order administrative jurisdiction) in the country where the Project is being developed. Where data is unavailable at this level, the analysis may be conducted at the national level with justification. Where the Project spans multiple jurisdictions, the analysis must be conducted separately for each, and the penetration rate threshold must be satisfied in every jurisdiction in which the Project operates. All adoption is counted regardless of whether the adopting fields are registered under a carbon crediting programme.
Evidence must be drawn from publicly available information, including but not limited to:
As defined by the Isometric Standard, the proposed project activity is considered to demonstrate Common Practice additionality where the market penetration rate is below or equal to 20% of similar activities conducted without Carbon Finance.
The uncertainty in the overall estimate of net CO2e impact as a result of the Project must be accounted for. The total net CO2e impact for a specific Reporting Period must be conservatively determined, and Projects must conduct an uncertainty analysis for the net CO₂e impact calculation in compliance with requirements outlined in the Isometric Standard.
Projects must report a list of all key variables used in the net CO2e removal calculation and their uncertainties, as well as a description of the uncertainty analysis approach, including:
The uncertainty information should at least include the minimum and maximum values of each variable that goes into the net CO2e calculation (see Section 8.2 for more details). More detailed uncertainty information should be provided if available, as outlined in the Isometric Standard.
In addition, a sensitivity analysis that demonstrates the impact of each input parameter’s uncertainty on the final CO2e uncertainty must be provided. Details of the sensitivity analysis method must be provided such that a third party can reproduce the results. Input variables may be omitted from an uncertainty analysis if they contribute to a 1% change in the net CO2e removal. For all other parameters, information about uncertainty must be specified.
In accordance with the Isometric Standard, all evidence and data related to the underlying quantification of net CO2e removal and environmental monitoring will be available to the public through Isometric’s Science Platform. That includes:
The Project Proponent can request certain information to be restricted (only available to authorized Buyers, the Registry and VVB) where it is subject to confidentiality. However, that does not apply to any numerical data produced or used as part of the quantification of net CO2e impact.
In addition, in compliance with FAIR Principles, the Project Proponent should publicly disseminate deployment data that is relevant to scientific research, such as through open data repositories.
Following the Isometric Standard, CreditsCertificates issued under this Protocol are contingent on the implementation, transparent reporting, and independent verification of comprehensive safeguards. Isometric takes a holistic approach to Environmental and Social Safeguarding (ESS). Risks associated with project activities must be weighed alongside risks of climate change to support responsible innovation.
Environmental and Social Safeguards must include, but are not limited to, the following Integrity Council for the Voluntary Carbon Market (ICVCM) Core Carbon Principles:
In accordance with the Isometric Standard, Project Proponents must demonstrate active stakeholder engagement throughout project planning and operation, ensuring that all risk mitigation strategies contribute to sustainable project outcomes. Local stakeholders may contribute an in-depth understanding of the project area and operations, and provide invaluable insights and recommendations on potential risks, necessary safeguards, and specific monitoring needs.
Projects must develop a Stakeholder Engagement Plan in accordance with the requirements outlined in the Isometric Standard. The plan and supporting documentation, including evidence of meetings or other forms of engagement, must be submitted in the PDD.
The Project Proponent or participants must demonstrate legitimate legal tenure or right of use over all lands included in the project area, in addition to demonstrating the eligible baseline conditions for each field (see Section 4.1.1). This requirement ensures that the Project Proponent or participants have the authority to implement project activities, make cultivation management decisions, and claim the resulting emission reductions. Acceptable forms of evidence and the verification process are specified in Section 9.2.1.
A field may change ownership, tenant occupancy, or management during a Reporting Period and remain eligible for crediting if:
Where any of these criteria are not met, the field forfeits the opportunity to generate CreditsCertificates for the Reporting Period during which the change occurs.
Projects must document the enrollment of each participating farmer or project participant. Required documentation and the verification process are specified in Section 9.2.2.
Ensuring that participating farmers receive a fair and transparent share of the financial benefits generated from carbon CreditsCertificates is essential to the integrity and long-term sustainability of the Project.
Projects must describe the benefit-sharing mechanism with enrolled farmers. This should include:
Projects must provide training and technical support to all participating farmers, covering field preparation, irrigation and drainage management, and water level monitoring.
The scope of this Protocol includes GHG sources, sinks and reservoirs (SSRs) associated with a Rice Methane Reduction Project.
A cradle-to-grave GHG Statement must be prepared encompassing the GHG emissions relating to the activities outlined within the system boundary.
GHG emissions and reductions associated with the Project may be direct emissions from a process, or indirect emissions from combustion of fuels, electricity generation, or other sources. Emissions must include all GHG SSRs within the system boundary, from the construction or manufacturing of each physical site and associated equipment, closure and disposal of each site and associated equipment, and operation of each process, including embodied emissions of equipment and consumables used in the Project. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to project activities.
As noted in Section 7.3, the baseline scenario assumes continuous flooding of irrigated rice paddies in the absence of any project activities, producing methane through anaerobic decomposition of organic matter.
Any emissions from sub-processes or process changes that would not have taken place without the Project must be fully considered in the system boundary. Any activity that ultimately leads to the issuance of CreditsCertificates should be included in the system boundary.
The system boundary must include all relevant GHG SSRs controlled and related to the Project, including but not limited to the SSRs set out in Table 1. If any GHG SSRs within Table 1 are deemed not appropriate to include in the system boundary, they may be excluded provided that robust justification and appropriate evidence are provided in the PDD.
Table 1 System Boundary
Activity | GHG Source, Sink or Reservoir | GHGs | Scope | Timescale |
|---|---|---|---|---|
Project Establishment | Infrastructure installation | All GHGs | Equipment and materials manufacture, transport to site and installation. To include: | Before project operations start – must be accounted for in the first Reporting Period or amortized in line with allocation rules (see Section 8.4.2) |
Project Operations | Land preparation | All GHGs | Emissions from fuel and energy consumption in: | Over each Reporting Period – must be accounted for in the relevant Reporting Period (see Section 8.4.3) |
Drainage and irrigation | All GHGs | Emissions from fuel or electricity consumption for: | ||
Direct CO2 emissions from rice paddies | CO2 | CO2 emissions from organic carbon decomposition due to aerobic exposure of soil during drying phases | ||
Direct CH₄ emissions from rice paddies | CH₄ | CH₄ emissions from soil methanogenesis under the project water management regime | ||
Direct N₂O emissions from rice paddies | N₂O | N₂O emissions from nitrogen inputs to soils under AWD conditions, due to nitrification-denitrification cycling. | ||
Fertilizer use | N₂O | Emissions related to higher nitrogen application rates than in the baseline. | ||
MRV | All GHGs | Embodied, energy and transport emissions associated with field measurements (chamber sampling, laboratory analysis), monitoring equipment, and verification site visits. | ||
Misc. | All GHGs | Any SSRs not captured by the categories above. | ||
Project End-of-life | End-of-life of project infrastructure | All GHGs | Anticipated end-of-life emissions (lifecycle Modules C1–4). To include deconstruction and disposal of water control infrastructure, monitoring equipment, and any project-installed drainage systems. | After Reporting Period – must be accounted for in the first Reporting Period or amortized in line with allocation rules (see Section 8.4.4) |
The system boundary accounts for emissions that are additional in the project scenario relative to the baseline scenario. Where an SSR exists in both the baseline and project scenarios, only the incremental change in emissions attributable to the project activity must be quantified. For example, land preparation activities that occur at the same frequency and intensity under both continuous flooding and AWD regimes do not generate additional emissions and need not be separately quantified, provided the Project Proponent demonstrates that no material change has occurred. Conversely, drainage and re-irrigation pumping represents a new or intensified activity under AWD that would not occur at the same level under continuous flooding, and the associated emissions must be fully accounted for. The Project Proponent must justify any determination that an SSR is materially unchanged between the baseline and project scenarios.
Where the Project Proponent claims an SSR is materially unchanged between the baseline and project scenarios, the following evidence must be provided in the PDD:
Miscellaneous GHG emissions are those that cannot be categorized by the GHG SSR categories provided in Table 1. The Project Proponent is responsible for identifying all sources of emissions directly or indirectly related to project activities and must report any outside of the SSR categories identified as miscellaneous emissions.
In line with the GHG Accounting Module v1.1, the Project must:
AWD practices may lead to minor losses of soil organic carbon (SOC) due to accelerated aerobic decomposition during drying phases. When fields are drained during AWD cycles, oxygen penetration enables aerobic respiration, which can proceed at substantially higher rates, as evidenced by CO₂ emission pulses observed during drainage events. However, the magnitude of this SOC loss is small, estimated at approximately 0.6-1.3% per year18, and is generally lower under Safe AWD practices compared to more severe drying regimes. Critically, any SOC loss associated with AWD is minor relative to the climate benefit achieved through methane emission reductions, given the substantially higher global warming potential of CH₄. For these reasons, this methodology acknowledges SOC loss as a potential trade-off of AWD implementation but does not require its explicit quantification as a separate line item. Instead, the effect is conservatively accounted for within the overall uncertainty discount applied to creditedissued emission reductions, ensuring that net climate benefits are not overstated.
Black carbon (BC) is a short-lived climate pollutant emitted during the incomplete combustion of biomass, including the open burning of rice straw and other crop residues. BC absorbs solar radiation and contributes to atmospheric warming, with a GWP100 estimated at 34219. This represents a substantial downward revision from earlier estimates (e.g., 900 in Bond et al., 201320), reflecting advances in the understanding of BC's atmospheric lifetime, rapid adjustments to radiative forcing, and aerosol-cloud interactions. BC emissions from biomass burning are excluded from the project boundary under this protocol.
BC's climate impact remains highly uncertain. The total effective radiative forcing of BC, inclusive of aerosol-radiation interactions, aerosol-cloud interactions, rapid adjustments, and deposition on snow and ice, is estimated at 0.11 W/m² with a range of 0.20 to 0.42 W/m²19. This range includes both warming and cooling outcomes. The GWP100 for BC has been revised downward in each successive assessment since Bond et al. (2013)20, from 900 to 65821 to 34219. The magnitude and direction of this uncertainty do not support inclusion of BC in Isometric's emission reduction accounting at this time.
Additionally, open biomass burning emits BC alongside organic carbon and sulfate aerosols, both of which exert a cooling effect by scattering incoming solar radiation. The net radiative impact of a change in burning practice depends on the ratio of warming to cooling species in the smoke, which varies with combustion conditions, moisture content, and fuel type. Rice straw burning is characterised by relatively high smoldering fractions, producing elevated organic carbon to black carbon ratios. The net aerosol radiative effect of avoided biomass burning in rice systems is therefore ambiguous and potentially close to zero22,23,24.
This exclusion is conservative. Omitting BC from the project boundary results in a lower estimate of the project's total climate benefit than would be obtained by including it, and therefore does not risk over-creditingissuance. Should future scientific assessments materially revise BC's effective radiative forcing upward, this exclusion may be revisited in subsequent protocol versions.
The Project Proponent must stratify the project area into distinct strata that are internally homogeneous with respect to the criteria defined in this section. Stratification ensures that emission factors used for baseline estimation and crediting calculations are representative of the conditions within each stratum, and that within-stratum variability does not systematically bias the quantification of emission reductions.
Each stratum must be defined by a unique combination of the mandatory criteria listed below. Additional stratification by conditional and optional criteria is required or recommended as described below. Data source guidance and stratum documentation requirements are specified in Section 9.1.1.1.
Required Stratification Criteria
All Projects must stratify by the following criteria. These criteria correspond directly to the scaling factors in the 2019 IPCC25 emission factor equation for CH4 emissions from rice cultivation:
Conditional Stratification Criteria
The following criteria must be applied as stratification parameters when the specified conditions are met. Where the conditions are not present, these criteria are not required.
Recommended Stratification Criteria
It is recommended that the Project Proponent further stratify the project area using the following criteria. Additional stratification may improve the accuracy of emission estimates by reducing within-stratum variability.
Where a project area spans multiple potential sub-categories within a stratum but monitoring data cannot distinguish between them, the most conservative parameter values must be applied (i.e., the combination of parameters that would produce the lowest net reductions). The lowest value is the most conservative, as that minimizes the potential expected emissions that may be reduced. Specifically:
Strata definitions must be reviewed at each Crediting Period renewal. If management practices or site conditions have changed such that a stratum is no longer internally homogeneous with respect to the mandatory criteria, the Project Proponent must update the stratification and document the changes.
The baseline scenario represents the business-as-usual condition, describing the expected methane flux that would occur in the absence of the Project. Under this Protocol, the baseline must correspond to one of the following conditions:
The eligibility requirements for baseline conditions are defined in Section 4.1.1.
The baseline quantification accounts for CH4 emissions from methanogenesis in soil only. Under continuously flooded conditions, rice soils remain persistently anaerobic, suppressing nitrification and limiting N2O production to limiting levels. All other GHG sources are accounted for entirely as project-side emissions, where only the additional or incremental emissions attributable to the project activity are quantified (see Section 8.4).
Leakage emissions occur when project activities cause a secondary effect leading to increased GHG emissions that occur outside the system boundary of Projects. Reductions in rice production yield as a result of the project activities would result in a reduction of the supply of rice. Changes to the supply and demand equilibrium cause other market actors to shift their activities, leading to potential land conversion. This type of leakage is known as market or “indirect” leakage because its effects cannot be isolated and measured directly. Quantifying the likelihood and potential magnitude of market leakage is complex and relies heavily on modeling and available literature.
Under the project eligibility conditions on water levels outlined in Section 4.2.1, there are negligible risks to yield impacts10,28,29. Isometric deems leakage risks to be de minimis so long as these conditions are met.
The Reporting Period, [math: RP], represents an interval of time over which reductions are calculated and reported for verification. The total net CO₂e reduction is calculated using a series of measurements for a specified Reporting Period.
GHG emission calculations must include all emissions related to the project activities that occur within the Reporting Period. This includes:
Projects must confirm the length of their Reporting Period as either a single cropping season, multiple cropping seasons, or 12 consecutive months.
Net CO₂e reduction from a Rice Methane Reduction Project for each Reporting Period, [math: RP], must be calculated conservatively so as to give high confidence that the estimated net CO₂e was reduced. The net CO₂e reduction equation is:
[math: CO_2e_{Reduction,RP} =CO_2e_{Baseline,RP}-CO_2e_{Project,RP}]
(Equation 1)
Where:
Baseline emissions are summed across all strata within the Reporting Period using the following equation:
[math: CO_2e_{Baseline,RP}= \sum\limits_g (EF_{BL,g} \times A_g \times 10^{-3} \times GWP_{CH_4})]
(Equation 2)
Where:
Emission factors must be determined for each stratum using one of the following approved methods. A project may employ different approaches for different strata, provided the requirements of each approach are met.
Method 1: Default Emission Factors
Projects may calculate methane emissions using default or country-specific parameters in combination with default scaling factors25,30 (Appendix A). Note that emissions reductions determined using this Method will be subject to an additional uncertainty deduction outlined in Section 8.6.1.
The emission factor is calculated as:
[math: EF_g = EF_c \times SF_w \times SF_p \times SF_o \times t]
(Equation 3)
Where:
The organic amendment scaling factor, [math: SF_o], is calculated as follows:
[math: SF_o = (1+\sum \limits_a ROA_a \times CFOA_a)^{0.59}]
(Equation 4)
Where:
If no organic amendments are applied, the value of [math: SF_o] is 1.
If it is not possible to delineate the application rates for mixed amendment types, [math: ROA_a] and [math: CFOA_a] must be set to the lowest value to conservatively limit the potential methane that may be reduced (see Section 7.2.1).
Method 2: Direct Measurement
Instead of using default emissions factors that represent average estimates, Project Proponents may instead wish to directly measure emissions within the Project. Direct measurements impose a higher operational cost for Projects, but provide a higher confidence in their results and thus are subject to a different uncertainty deduction (see Section 8.6.2).
When directly measuring the methane flux within a stratum, Project Proponents establish one or more measurement clusters to directly quantify CH₄ emissions. In this Protocol, a measurement cluster is defined as the collection of fields and measurement locations that are targeted at quantifying methane reductions and uncertainty on a stratum level. Each measurement cluster consists of at least three reference fields, maintained under the baseline water management regime and three paired treatment areas. Both the reference fields and paired treatment areas must be located within the same stratum and must be representative of the conditions within that stratum or conservatively set with respect to all mandatory stratification criteria (see Section 7.2).
The following requirements apply when taking direct measurements:
The seasonally integrated emission factor is calculated as the arithmetic mean of the reference field measurements collected over the growing season. The measurement methodology, equipment, calibration procedures, and data quality assurance protocols must be specified in the PDD and must follow the requirements set out in Section 9.4.
Every stratum over 10,000 ha should have at least one measurement cluster. For strata exceeding 25,000 hectares, one additional measurement cluster should be included for each additional 25,000 ha (or fraction thereof). Measurement clusters must be selected to capture the central tendency and variability of conditions within the stratum. The Project Proponent must document the rationale for cluster placement in the PDD.
Method 3: Transformed Measurement
Due to operational limitations, it may not be possible to measure CH₄ emissions in all strata within a Project. In such scenarios, Project Proponents may extrapolate their measurements to unmeasured strata with the same organic amendment instead of default emission factors (described in Method 1). Doing so may lead to uncertainty more reflective of field conditions.
This Method is only eligible for an unmeasured stratum, [math: u], that shares the same organic amendment but differs in application rate, with at least one other stratum, [math: m], that has been directly measured using Method 2. The measured baseline emission factor from the measured stratum is transformed to the unmeasured stratum using the ratio of scaling factors:
[math: EF_u = EF_m \times \frac{SF_{o,u}}{SF_{o,m}}]
(Equation 5)
Where:
When a stratum, [math: u], uses a blend of organic amendments, stratum [math: m] must correspond with the most conservative classification as described in Section 7.2.1.
[math: CO_2e_{Project,RP}] is the Project’s total GHG emissions within a Reporting Period, [math: RP]. This can be calculated as:
[math: CO_2e_{Project,RP}=CO_2e_{Rice,RP}+CO_2e_{Establishment,RP}+CO_2e_{Operations,RP}+CO_2e_{End-of-Life,RP}]
(Equation 6)
Where:
[math: CO_2e_{Rice,RP}] is presented as a distinct component from [math: CO_2e_{Operations,RP}] because it represents the primary GHG fluxes that the project activity is designed to modify, i.e., residual methane from soil methanogenesis and the associated increase in nitrous oxide emissions resulting from the change in water regime. These emissions are mechanistically distinct from operational emissions (e.g., fuel consumption for pumping, land preparation, and monitoring activities) and are quantified using emission factor approaches specific to rice paddy biogeochemistry.
[math: CO_2e_{Rice,RP}] is the total GHG emissions associated with a Reporting Period, [math: RP]. This can be calculated as:
[math: CO_2e_{Rice,RP}=CO_2e_{Rice,CH_4,RP}+CO_2e_{Rice,N_2O,RP}]
(Equation 7)
Where:
[math: CO_2e_{Rice,CH_4,RP}] is calculated as:
[math: CO_2e_{Rice,CH_4,RP}=\sum\limits_g(EF_{P,g}\times A_g \times 10^{-3} \times GWP_{CH_4})]
(Equation 8)
Where:
Project activities that transition rice fields from continuous flooding to drained conditions result in increases in nitrous oxide (N2O) emissions. Under continuous flooding, rice soils remain persistently anaerobic, suppressing nitrification and limiting N2O production. When a field transitions to AWD, periodic drainage introduces aerobic conditions during dry-down periods. During these aerobic windows, ammonium (NH4) in the soil is oxidized to nitrate (NO3−) through nitrification. When the field is subsequently re-flooded, the resulting anaerobic conditions drive denitrification of this nitrate pool, producing N2O as a by-product. This mechanism occurs regardless of whether nitrogen fertilizer application rates change, as it is driven by the shift in soil redox conditions.
Projects must calculate the difference in N2O emissions between the baseline water regime and the project water regime and deduct the total from the net emission reductions.
N2O emissions from the water regime change must be calculated as follows:
[math: CO_2e_{Rice,N_2O,RP}=\sum\limits_g(Q_{N,g,RP} \times A_g) \times EF_{AWD} \times 10^{-3} \times GWP_{N_2O}]
(Equation 9 )
Where:
Country specific N2O emission factors for rice cultivation under AWD are available for very few countries. Most Projects are therefore expected to apply IPCC default emission factors, which represent the best available data for contexts where country-specific data does not exist. Where peer-reviewed country- or region-specific data or direct field measurement capacity are available, Projects must apply the higher tier in accordance with the hierarchy set out below.
The emission factors [math: EF_{AWD}] and [math: EF_{fert}] must be selected according to the following tiered hierarchy. The Project Proponent must use the highest tier for which adequate data are available.
Tier 3: Direct Field Measurement
Where the Project has the capacity to conduct direct field measurement of N2O fluxes using closed chamber methods with gas chromatograph–electron capture detector (GC-ECD) analysis, site-specific emission factors may be derived from these measurements. Tier 3 provides the highest accuracy and is the preferred approach where feasible.
Direct measurement requires sampling throughout the rice growing season at representative locations within each stratum, covering both flooded and drained periods. Measurement protocols must follow established guidelines for chamber-based N2O flux measurement from rice paddy fields. N₂O fluxes are concentrated around hydrological transitions, with substantial pulses occurring during drainage and re-flooding events. Sampling protocols should be designed to capture these emission windows, for example, by increasing sampling frequency around drainage and re-flooding events. The measurement design, including sampling locations, frequency, and timing relative to hydrological transitions, must be documented in the PDD.
Use of Tier 3 is not mandatory. N2O fluxes are episodic and highly variable in both space and time, requiring high sampling frequency and specialist laboratory equipment that may not be available in all project contexts.
Tier 2: Country-Specific or Regional Emission Factors
Where peer-reviewed, published emission factors specific to the project country or region are available, these must be used in preference to global defaults. Country-specific factors must be derived from field studies conducted under conditions comparable to the Project, including similar climate, soil type, water management regime, and nitrogen application practices.
The derivation of Tier 2 emission factors must follow the guidance provided in Chapter 11, Section 11.2.1.133 of Volume 4 of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Tier 2 emission factors must be sourced from peer-reviewed scientific literature or from national greenhouse gas inventory reports submitted to the UNFCCC. The data sources, selection criteria, and statistical methods used to derive the emission factor must be documented in the Project Design Document.
Where adequate Tier 2 data are not available, the Project must use Tier 1 emission factors.
Tier 1: IPCC Default Emission Factors
Where neither Tier 3 nor Tier 2 data are available, the Project must use default emission factors derived from the IPCC 2019 Refinement to the 2006 Guidelines for National Greenhouse Gas Inventories (Table 11.1, Chapter 11, Volume 4)33. Due to the limited availability of country-specific N2O data for rice systems globally, most projects are expected to use Tier 1 (see Section 12.2 for reference values).
GHG emissions associated with project establishment should include all historic emissions incurred as a result of project establishment, including but not limited to the SSRs set out in Table 1. For rice methane reduction projects, this includes the manufacture, transport and installation of equipment and materials for water level tubes, bunds, drainage channels, and monitoring equipment.
Project establishment emissions occur from the point of project inception up until the first Reporting Period. Establishment emissions may be accounted for in the following ways, with the allocation method selected and justified by the Project Proponent:
GHG emissions associated with [math: CO_2e_{Operations,RP}] must include all emissions associated with operational activities, including but not limited to the SSRs set out in Table 1 (Section 7.1).
[math: CO_2e_{Operations,RP}] emissions occur over the Reporting Period for the deployment being creditedissued and are applicable to the current deployment only. [math: CO_2e_{Operations,RP}] emissions must be attributed to the Reporting Period in which they occur.
When the Project involves higher nitrogen application rates than the baseline, the additional nitrogen provides further substrate for nitrification and denitrification under drained conditions. Because this nitrogen enters a drained soil environment, it produces N2O at the full emission rate applicable to drained rice fields.
Where the nitrogen application rate in the project scenario exceeds that of the baseline, additional N2O emissions must be calculated as follows:
[math: CO_2e_{Fert,N_2O,RP}=\sum\limits_g(\Delta Q_{N,g} \times A_g)\times EF_{Fert}\times10^{-3}\times GWP_{N_2O}]
(Equation 10)
Where:
[math: CO_2e_{End-of-Life,RP}] includes all emissions associated with activities that are anticipated to occur after the Reporting Period, but are directly or indirectly related to the Reporting Period. For example, this could include end-of-life emissions for project equipment (indirectly related to all deployments).
GHG emissions associated with [math: CO_2e_{End-of-Life,RP}] may occur from the end of the Reporting Period onwards, and typically through to completion of project site deconstruction and any other end-of-life activities.
GHG emissions associated with activities that are indirectly related to all deployments may be allocated in the same ways as set out in [math: CO_2e_{Establishment,RP}].
Project Proponents must use the most representative, accurate, and plausible data that is available at the time of assessment in the GHG Statement. Activity data used to inform GHG accounting may be primary data or secondary data. Project Proponents must strive to use primary data in GHG accounting, but secondary data may be used where primary data is either not available or not practical. More details on data requirements can be found in Section 3 of the GHG Accounting Module v1.1.
Project Proponents may exclude any SSRs included in Table 1 from the final net reduction quantification if these are demonstrated to be negligible. Negligible SSRs are those that fall below a Materiality threshold based on an environmental significance of less than 1% of net CO₂e reduction in any given Reporting Period. The sum of negligible SSRs must not be equal to or more than 1% of the net reduction.
To demonstrate this, Project Proponents may utilize an economic input-output (EEIO) approach as a preliminary screening test, estimating emissions based on project financial data (e.g., CAPEX data) combined with EEIO emission factors. If this screening demonstrates that emissions are below the Materiality threshold, emissions can be excluded or can be estimated using high-level estimations if included. See Section 5.0 of the Isometric GHG Accounting Module v1.1 for more details on the approach and example libraries.
Alternatively, where financial data is unavailable, Project Proponents may use other benchmarks to estimate emissions. For example, proponents may rely on physical benchmarks from industry-standard life cycle inventory databases based on activity-level parameters relevant to sectors similar to rice cultivation.
Ancillary activities, such as supplementary research and development activities and corporate administrative activities, that are associated with a Project but are not directly or indirectly related to the issuance of CreditsCertificates can be excluded from the system boundary.
This section sets out specific requirements relating to the quantification of energy use as part of the GHG Statement. Emissions associated with energy usage result from the consumption of electricity or fuel for:
Electricity
The following calculation approach must be used to estimate emissions from the project’s electricity consumption:
[math: CO_2e_{EC,PJ,RP}=EC_{grid,RP} \times EF_{grid,RP} \times (1 + f_{TDP-losses,RP}) + (EC_{generator,RP} \times EF_{generator,RP})*10^{-3}]
(Equation 11)
Where:
Project Proponents may determine the emission intensity of the electricity grid, [math: EF_{grid,RP}], using the following hierarchy:
If the generation source is a captive fossil fuel-fired power plant, Projects should make every attempt to gather information on the emission intensity of the technology generating the electricity. Where a specific emission intensity is not available, Projects must apply a default of 1.3 kg CO2e/kWh.
Projects may determine the transmission and distribution grid losses factor, [math: f_{TD-losses,RP}], using the following hierarchy:
Fuels
Section 6 of the Energy Use Accounting Module v1.3 provides requirements on how fuel-related emissions must be calculated in a Project.
How energy-related emissions must be calculated so that they can be subtracted in the net CO2e removal calculation
This section sets out specific requirements relating to the quantification of embodied emissions as part of the GHG Statement. Embodied emissions are those related to energy use or other emissions during the manufacture of equipment and materials used in a process.
Examples of project-specific materials and equipment that must be considered as part of the embodied emission calculation include, but are not limited to:
The GHG Accounting Module v1.1 sets out the approach to be followed to account for embodied emissions, including life cycle stages to be considered (Section 4.1), and data sources and emission factors (Section 3.3).
Section 4.2 of the GHG Accounting Module v1.1 provides requirements on how transportation-related emissions must be calculated in a Project.
Uncertainty deductions are applied to account for measurement and model uncertainties in the emission reduction calculation. Additionally, uncertainty deductions are used when regional emission factors are used for quantification. The applicable deduction depends on the emission factor determination method.
When estimating emissions using Method 1 (Section 8.3.1), a default uncertainty deduction of 15% must be applied to the emission reduction. This deduction reflects the inherent uncertainty in default emission and scaling factors that have not been validated by site-specific measurements.
Projects quantifying CH₄ emissions under Method 2 or Method 3 (Section 8.3.1) must compare the measured (or transformed) emission reduction distribution against the expected emission reduction derived from IPCC Tier 2 emission factors for the relevant country.
The Tier 2 expected baseline emission factor for each stratum is calculated using Equation 3 with the values provided in Appendix A. The Tier 2 expected emission reduction is the difference between the Tier 2 baseline and project emission factors for that stratum. The Tier 2 expected reduction includes an associated uncertainty range, derived from the minimum and maximum of the 95% confidence interval of the project intervention on-season water regime scaling factors (see Appendix A).
The 40th percentile of the measured (or transformed) emission reduction distribution is compared against the Tier 2 expected reduction range to determine the creditedissues emission reduction for the stratum:
This formulation ensures that the creditedissued emission reduction is monotonically non-decreasing with respect to the measured reduction distribution, meaning a project whose measurements indicate larger reductions will never receive fewer CreditsCertificates than an otherwise identical project with smaller measured reductions. The Tier 2 upper bound serves as a floor in the above-range case, reflecting that country-level evidence supports reductions at least that large, even where the measurement uncertainty penalty would otherwise reduce the creditedissued quantity below the Tier 2 expectation.
Example Uncertainty Range Calculation
A Project in India is implementing multiple drainage (AWD) on fields that were previously continuously flooded in the baseline. The fields have a pre-season water regime that was non-flooded for << 180 days, apply 5 tons/ha of straw on-season as an organic amendment, and the cultivation period is 120 days. The uncertainty screening calculation would be as follows:
[math: SF_o = (1 + 5 × 1.00)^{0.59} = 2.878]
[math: EF_{Baseline} = 0.85 \times 1.00 \times 1.00 \times 2.878 \times 120 = 293.6\ \text{kg CH₄/ha}]
[math: EF_{ProjectLowerBound} = 0.85 \times 0.72 \times 1.00 \times 2.878 \times 120 = 211.4\ \text{kg CH₄/ha}]
[math: EF_{ProjectUpperBound} = 0.85 \times 0.41 \times 1.00 \times 2.878 \times 120 = 120.4\ \text{kg CH₄/ha}]
Table 2. Example expected range of methane reduction used for screening direct measurements to determine the uncertainty deductions.
Bound | SFw | EFBaseline | EFProject | ΔEF | ΔEF |
|---|---|---|---|---|---|
Lowest Expected Reduction | 0.72 | 293.6 | 211.4 | 82.2 | 2.293 |
Highest Expected Reduction | 0.41 | 293.6 | 120.4 | 173.2 | 4.832 |
This section establishes monitoring and documentation requirements necessary to ensure the accuracy, completeness, and credibility of rice methane reduction projects.
Requirements are grouped based the following:
Requirements are further organised into two categories:
Requirements are grounded in the following principles:
Validation Requirements
Projects must provide the geographic boundary of the project area, including GPS coordinates or geospatial boundary files for all project fields.
[/R-6RYC-0]Projects must describe the baseline cultivation practices for each stratum, covering water regime, organic amendments, fertiliser type and rate, and rice varieties.
[/R-TDT1-0]Acceptable evidence includes:
Projects must describe the planned project activity, including the target water management regime, the expected drainage schedule, and whether any other methane mitigation amendments are used.
[/R-E2NP-0]Projects must confirm that the project fields are irrigated with controlled irrigation and drainage facilities.
[/R-1QHB-0]For each enrolled field, Projects must demonstrate baseline eligibility evidence per Section 4.1.1, including:
[/R-NCD0-0]Where the project activity involves the introduction of a rice cultivar that has not previously been cultivated in the project region, the Project Proponent must demonstrate in the PDD that the newly introduced cultivar does not necessitate material changes to existing land management practices beyond those required by the eligible project activity itself (see Section 4.1.2).
[/R-918N-0]Verification Requirements
For each Reporting Period, the following must be reported per field or per stratum:
The Project Proponent must document, for each enrolled field, that the number of rice cultivation seasons per year maintained during the project period is the same as that practised during the baseline period.
The Project Proponent must stratify the project area per the criteria defined in Section 7.2. Each Reporting Period, project fields must be assigned to a stratum. Stratification may change between seasons to accommodate changes in organic amendment application. This section sets out the documentation requirements for stratification, the data sources used to assign values to each criterion, and the deliverables required for each stratum.
Validation Requirements
For each stratum, the PDD must include:
Data source requirements differ by criterion type:
Stratum-level verification at each Reporting Period is addressed in Section 9.5.
When quantifying methane emissions with direct measurements, the following requirements apply:
Validation Requirements
Conditional: When using direct measurements, Projects must describe how their field samples are selected. Each measurement cluster must contain at least three reference fields for baseline measurements and at least three for project measurements.
[/R-GAZZ-0]Verification Requirements
At Verification, Projects must provide:
Validation Requirements
For each enrolled field, Projects must provide one or more of the following forms of evidence:
Isometric may cross-reference official land registry records with satellite imagery and GIS data, where available.
Verification Requirements
Projects must confirm whether any changes in field ownership, tenancy, or management control occurred during the Reporting Period. Where a change occurred, projects must demonstrate for each affected field that the four conditions in Section 6.2.1.1 are met:
Validation Requirements
For each participant at enrollment, Projects must provide:
Verification Requirements
Projects must provide an updated participant register for each Reporting Period, identifying additions and removals relative to the prior period.
Validation Requirements
The Project Proponent must describe the training program for farmers participating in the project, covering AWD principles and drainage scheduling, water level observation procedures, fertilizer management, and record-keeping obligations.
[/R-B9JY-0]Training must be documented through attendance registers, training materials, and photographic evidence.
[/G-NH2R-0]Projects must describe the benefit-sharing mechanism with enrolled farmers. This should include:
Verification Requirements
Training records must be updated each Reporting Period with evidence of training any newly enrolled farmers.
As part of ensuring compliance and for quantification of emissions reduction, farmers must submit logbooks or digital records documenting:
Water level monitoring is required for fields implementing drainage-based project activities (see Section 4.2.1). This section sets out the validation and verification deliverables for monitoring methods, recording procedures, and field records. The eligibility threshold (15 cm below the soil surface, or -20 kPa for fields monitored by digital sensor measuring soil water potential) and the exemption mechanism (national agronomist approval) are specified in Section 4.2.1.
Validation Requirements
The Project Proponent must describe the water level observation method, including placement, observation frequency, and data-capture format. Acceptable methods include: perforated observation tubes (field water tubes) installed at designated monitoring points within each field, or automated water level sensors with data logging capability.
[/R-YYEK-0]Verification Requirements
Projects must submit water level records for each monitored field or monitoring point, including:
At least 5% of fields must have a geotagged photo of the water level measurement at the point of re-flooding for each drainage event.
Validation Requirements
Projects must describe the intended quantification method per Section 8.3.1.
[/R-16RW-0]Conditional: When quantifying methane emissions withusing direct measurements, Projects must describe the closed-chamber measurement protocol, which must comply with the following minimum standards:
Gas analysis must use methods capable of detecting CH₄ and N₂O (where applicable) at concentrations relevant to field flux measurements, with demonstrated precision and accuracy traceable to certified reference standards. Suitable methods include, but are not limited to, gas chromatography (e.g., FID for CH₄, ECD for N₂O) and laser-based absorption spectroscopy (e.g., CRDS, OA-ICOS).
[/R-DHX7-0]Verification Requirements
When applicable, field measurements must be conducted at least every two weeks to sufficiently capture changes over a season. For each measurement campaign, the following must be reported:
Emission factors derived from field measurements must be accompanied by uncertainty estimates (standard error, 95% confidence intervals).
To ensure consistency and accuracy, the following reconciliation checks must be performed at each verification:
Discrepancies exceeding 5% in area or emission factor assignment must require corrective action and justification before creditsCertificates can be issued.
Isometric would like to thank the following external contributors to this protocol:
All emission factors and scaling factors are those developed by Wang et al. (2018)30 using 1,089 field measurements and used in the IPCC 2019 Refinement25.
Project proponents may substitute alternative emission factors or scaling factors where these are derived from peer-reviewed (or equally rigorous) publications, provided they are applicable to the project's region, climate, and management conditions, and approved in consultation with Isometric.
Baseline emission factors (EF) for continuously flooded fields with no organic amendment and a pre-season water regime that was non-flooded for << 180 days before cultivation for use in Equation 3. EFs and confidence interval are reported in kg CH₄ ha⁻¹ day⁻¹.
Table A1. Country-Specific Baseline Emission Factors
Country | EF (kg CH₄ ha⁻¹ d⁻¹) |
|---|---|
Bangladesh | 0.97 |
Brazil | 1.62 |
China | 1.30 |
Italy | 1.66 |
India | 0.85 |
Indonesia | 1.18 |
Japan | 1.06 |
Philippines | 0.60 |
South Korea | 1.83 |
Spain | 1.13 |
Uruguay | 0.80 |
USA | 0.65 |
Vietnam | 1.13 |
For countries not listed, the global EF of 1.19 kg CH₄ ha⁻¹ d⁻¹ may be used.
Scaling factors are relative to continuously flooded conditions (= 1.00). Multiply the baseline EF by [math: SF_w] in Equation 3 to adjust for the water regime during the crop growing season. The upper and lower CI values are used in for determining the expected range as part of the Tier 2 screening for uncertainty (see Section 8.6.2).
Table A2. Scaling Factors for Water Regime During Growing Season ([math: SF_w])
On-Season Water Regime | SFw | Lower 95% CI | Upper 95% CI |
|---|---|---|---|
Continuously flooded | 1.00 | 0.73 | 1.27 |
Single drainage | 0.71 | 0.53 | 0.94 |
Multiple drainage (AWD) | 0.55 | 0.41 | 0.72 |
Mean CH₄ fluxes and relative emission factors by pre-season water regime. Relative flux is expressed in relation to << 180 of non-flooded conditions before cultivation (= 1.00). Figure A1 provides a visual description of the eligble categories of pre-season water regimes.
[Image: ipcc_table_5_13_simple]
Figure A1. Diagram of pre-season water conditions adapted from Table 5.13 in the 2019 IPCC Refinement25.
Table A4. Pre-Season Water Regime Conversion Factors (SFp)
Pre-Season Water Regime* | SFp |
|---|---|
Non-flooded, pre-season (< 180 dry days before cultivation) | 1.00 |
Non-flooded, pre-season (> 180 dry days before cultivation) | 0.89 |
Non-flooded, pre-season (> 365 dry days before cultivation) | 0.59 |
Flooded, pre-season (> 30 flooded days before cultivation) | 2.41 |
*Detailed definitions of pre-season water regime conditions may be found in Wang et al. (2018)30.
Mean CH₄ fluxes and relative emission factors by organic amendment type. Relative flux is expressed relative to straw applied on-season (= 1.00). The upper and lower CI values are used in for determining the expected range as part of the Tier 2 screening for uncertainty (see Section 8.6.2).
Table A3. Relative Emission Factors by Organic Amendment Type
Organic Amendment Type | CFOAa |
|---|---|
Straw, on-season (< 30 days before cultivation) | 1.00 |
Straw, off-season (> 30 days before cultivation) | 0.19 |
Green manure | 0.45 |
Compost | 0.17 |
Farmyard manure | 0.21 |
The 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories provides a Tier 1 methodology for estimating nitrous oxide (N₂O) emissions from managed cropland soils, relying on default emission factors applied to various nitrogen inputs.
The emission factor for the water regime change (EFAWD) is derived from the difference between the IPCC disaggregated EF1FR values for continuously flooded rice fields and rice fields with single or multiple drainage.
Parameter | Value | Source |
|---|---|---|
EF1FR for continuous flooding | 0.003 kg N₂O-N/kg N | IPCC 2019, Table 11.133 |
EF1FR for single and multiple drainage | 0.005 kg N₂O-N/kg N | IPCC 2019, Table 11.133 |
Difference (drainage minus continuous flooding) | 0.002 kg N₂O-N/kg N | Derived |
Conversion from N2O-N to N2O | 44/28 | Molecular weight ratio |
EFAWD | 0.00314 kg N₂O/kg N | Derived from IPCC 201933 |
This factor must be applied to the total nitrogen input in the project scenario for all fields switching from continuous flooding to AWD, regardless of whether nitrogen application rates change.
Where the project scenario involves nitrogen application rates exceeding those of the baseline, the emission factor for the additional nitrogen ([math: EF_{Fert}]) is the full IPCC EF1FR for drained rice fields, converted from N2O-N to N2O.
Parameter | Value | Source |
|---|---|---|
EF1FR for single and multiple drainage | 0.005 kg N₂O-N/kg N | IPCC 2019, Table 11.133 |
Conversion from N2O-N to N2O | 44/28 | Molecular weight ratio |
EFfert | 0.00786 kg N₂O/kg N | Derived from IPCC 201933 |
EFFert is higher than EFAWD because it represents the full N2O emission rate under drained conditions for nitrogen that was not present in the baseline scenario, rather than the incremental difference between water regimes. This factor must be applied only to the incremental nitrogen (project N-input minus baseline N-input, where positive).
This Protocol was developed based on the current state of the art, publicly available science regarding rice methane reduction. This Protocol will be updated in future versions as the science underlying alternative rice agricultural techniques evolves and the overall body of knowledge and data across all processes is increased.
The following topics present future areas for expansion of this Protocol:
This Protocol will be reviewed when there is an update to published scientific literature, government policies, or legal requirements that would affect net emissions quantification or the monitoring guidelines outlined in this Protocol, or at a minimum of every 2 years.
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