Eligibility criteria
Project Developers shall demonstrate that they meet all eligibility criteria outlined in the Rainbow Standard Rules, and described below with a specific focus on ERW.
Eligibility criteria that do not require specific methodology instructions are not described here. These include:
Measurability
Real
Technology readiness level
Minimum impact
The Substitution and Targets Alignment criteria have no specific requirements and are omitted because projects under this methodology are only eligible for removal RCCs rather than avoidance RCCs.
Additionality
To demonstrate additionality, Project Developers shall perform regulatory surplus analysis, plus either investment or barrier analysis, using the Rainbow Additionality Template.
Regulatory surplus analysis shall demonstrate that there are no regulations that require or mandate project activities (for removal and avoidance activities).
Investment analysis may be used to prove that revenue from carbon finance is necessary to make the project investment a financially viable and interesting option. The investment may cover:
The creation and launching of new sites
Expansion of capacity of existing activities
Expansion by installing new processes
Business plans shall be provided as initial proof for investment analysis. During verification, audited financial statements shall be used to demonstrate that the initial estimates from the business plan were reasonable, and that carbon finance was used as initially described for the expected investment.
For launching brand new sites, additionality can be simply demonstrated if the business plan shows that carbon finance is expected to make up at least 80% of the company’s revenue, as detailed in the Rainbow Additionality Template.
Note that for investments in expansion, only the additional carbon reductions enabled by the expansion shall be eligible for Rainbow Carbon Credits.
Barrier analysis may be used to prove that the project faces financial, institutional, or technological barriers to ongoing operations that can only be overcome using carbon finance. Examples include but are not limited to:
Financial barrier: financial analysis demonstrating that the project is not financially viable, evidenced by net cash being lower than the working capital requirements, or proof that the project is not meeting the projected financial targets in the business plans and loan documents, and that carbon finance would make it financially viable.
Institutional barrier: description of new regulation that the project must make costly changes to comply with, financial analysis showing that the project cannot fund the changes on their own, and carbon finance is necessary to make it viable.
For any type of barrier analysis, audited financial statements must be provided as proof. These documents should either demonstrate the financial status to prove financial barriers, or show that the project could not independently fund solutions to overcome institutional or technological barriers.
Permanence
The permanence horizon for ERW projects certified under this methodology is 1000+ years. This is based on well-known geochemistry concepts indicating that DIC is stable in oceans and other waterways for thousands of years, and will eventually precipitate out into new stable carbonate minerals.
Several parameters measured in the Site characterization and monitoring section are used to understand the expected pathways of weathering products and their permanence, such as the expected final reservoir of DIC.
Project Developers shall:
define the timeline of the expected reactions and subsequent transport of aqueous ions to ocean storage, and
list carbon release risk scenarios for precipitated and dissolved carbon, and discuss how they are accounted for in GHG quantification and measurements.
Risk of reversal
Project Developers shall fill in the Methodology Risk evaluation template at the link below to evaluate the risk of carbon storage reversal, based on social, economic, natural, and delivery risks.
Project Developers shall assign a likelihood and severity score to each risk, and provide an explanation of their choices. The Rainbow Certification team shall evaluate the assessment and may recommend changes to the assigned scores.
The Project Developer, Rainbow Certification team, or the third-party auditor may suggest additional risks to be considered for a specific project.
Each reversal risk with a high or very risk score is subject to:
risk mitigation plan, developed by the Project Developer, that details the long-term strategies and investments for preventing, monitoring, reporting and compensating carbon removal reversal, OR
additional contributions to the buffer pool, at a rate of 3% of verified removal Rainbow Carbon Credits for each high or very high risk
No double counting
Project developers shall sign the Rainbow MRV & Registry Terms & Conditions, committing to follow the requirements outlined in the Rainbow Standard Rules, including not double using or double issuing RCCs.
Project Developers shall prove that the owner of land where rock is spread will not also issue carbon credits. This shall be proven using signed contracts.
Co-benefits
Project developers shall prove that their project provides at least 2 co-benefits from the UN Sustainable Development Goals (SDGs) framework (and no more than 4).
Common co-benefits under this methodology are detailed in the table below. Project Developers may suggest and prove other co-benefits not mentioned here.
SDG 13 on Climate Action by default is not considered a co-benefit here, since it is implicitly accounted for in the issuance of carbon credits. If the project delivers climate benefits that are not accounted for in the GHG reduction quantifications, then they may be considered as co-benefits.
Table 1 Common co-benefits that projects under this methodology may provide are detailed, including types of proof that can be used to justify each co-benefit.
SDG 12: Responsible Consumption and Production
ERW may reduce the need for agricultural lime, promoting more sustainable and resource-efficient agricultural inputs.
SDG 12: Responsible Consumption and Production
ERW may support more productive food systems by increasing crop yields through improved soil health and nutrient availability.
SDG 13: Climate Action
ERW may contribute to further climate mitigation not covered in removal RCCs by increasing soil organic carbon stocks, enhancing long-term carbon sequestration alongside CO₂ drawdown.
SDG 9: Industry, Innovation and Infrastructure
ERW projects may drive innovation through research, monitoring, and experimentation beyond methodological requirements, fostering transparent data sharing and advancing novel carbon dioxide removal solutions.
SDG 6: Clean water and sanitation
ERW protects and restores aquatic ecosystems by reducing acidity and adding bicarbonate which helps with acid buffering. This notably helps mitigate ocean acidification.
Environmental & social do no harm
Project Developers shall prove that the project does not contribute to substantial environmental and social harms.
Project Developers shall fill in the Rainbow Enhanced Rock Weathering Risk Evaluation, to evaluate the identified risks of ERW. The identified risks include:
Loss of soil organic carbon (SOC) in the near field zone (NFZ).
Disturbance of substantial organic carbon stocks downstream (e.g. in downstream peatlands).
Potential asbestos contamination in mineral amendments, and exposure during mining, processing, transport, and feedstock application.
Air quality impacts from silicate application and dust exposure.
Health risks to workers and communities due to airborne particulates.
Hazardous mineral waste generation along the supply chain.
Heavy metal accumulation in soils and water systems.
Altered soil chemistry affecting crop yield and agrochemical use.
Altered soil physical properties affecting e.g. water drainage.
Water contamination from silicate application, impacting drinking water.
Harm to soil, water, air quality, biodiversity, and organisms from feedstock use.
Exceeding national and local pollutant thresholds.
Presence of radioactive materials or hazardous elements in feedstock.
Fossil energy use for mining, grinding, and transport of rocks and minerals.
Project Developers shall assign a likelihood and severity score of each risk, and provide an explanation of their choices. The VVB and Rainbow’s Certification team shall evaluate the assessment and may recommend changes to the assigned scores.
All risks with a high or very high risk score are subject to a Risk Mitigation Plan, which outlines how Project Developers will mitigate, monitor, report, and if necessary, compensate for any environmental and/or social harms.
Additional proof may be required for certain high risk environmental and social problems.
The Project Developer, the Rainbow Certification Team, or the VVB may suggest additional risks to be considered for a specific project.
Additionally, Project Developers shall:
meet national and local regulations for pollutant levels and fertilizer limits, and shall measure and report the elements listed in the Feedstock Characterization section related to chemical composition, mineralogy, radioactivity, and particle size distribution.
If no regulations set thresholds for feedstock metal content, Project Developers shall the potential metal accumulation in soils as a result of feedstock application and assess the risk of deployment.
If deploying on soils where heavy metal levels already exceed regulatory limits, prove that the project activity will not significantly elevate pollutant levels and/or bio-available pollutants (e.g. if heavy metals are taken up and exported in harvested biomass).
provide safety protocols required for feedstock application, to minimize adverse impacts to farmer health, local air or water quality, upon project validation.
measure heavy metal content in soils and biomass grown where rock was spread, in addition to the feedstock measurements described in the Feedstock characterization section.
measure soil organic carbon in treatment and control plots, at least once after rock spreading during the crediting period (strongly recommended to measure more frequently)
model heavy metal dissolution in the environment, based on Feedstock characterization measurements.
notify local stakeholders if adverse local environmental impacts are expected following application.
describe how project revenue benefits farmers and local communities.
describe any potential downstream sensitive ecosystems, and plans to monitor for negative impacts resulting from rock spreading (e.g. pH shifts, contamination...).
disclose the nature and impact of mining activities to source feedstock.
Leakage
The project activity should not cause GHG emissions to be indirectly transferred elsewhere.
Project Developers shall transparently evaluate the potential leakage risks from activity shifting and from upstream/downstream emissions in the PDD. Note that due to the LCA approach for GHG reduction quantification, most relevant upstream and downstream emissions are likely already included in the quantification.
Any material sources of leakage that cannot be mitigated shall be conservatively included in the GHG reduction calculations or the discount factor.
Project Developers shall evaluate the following activity shifting risks:
Diversion of rare earth elements and critical minerals from other applications, such as renewable energy supply chains.
Potential misallocation of mineral waste that could have lower-emission alternative uses.
Land use changes from project infrastructure impacting undisturbed or high-value land.
Quantify the impact of spreading feedstock on crop yields. If statistically significant and material yield declines are measured compared to the baseline, replacement emissions shall be included for the project to deduct for this impact.
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