MethodologyMineralization of Alkaline Materials (Ex Situ)RBW-CDR-MINV1.0Last updated - 12 October 2025Go to projects (0)Overall Available Credits0tCO2eqOverall forecasted delivery0tCO2eqUsed mechanism—)
About the methodologyCement, concrete, and other alkaline materials are significant sources of greenhouse gas emissions, releasing CO₂ during production and generating large volumes of mineral residues. Industrial by-products are commonly reused, but often in low-value applications that neutralize their impact rather than fully harness their carbon storage potential.Mineralization provides a scalable alternative by leveraging the natural reactivity of these materials: captured CO₂ combines with a wide range of alkaline feedstocks to form stable carbonates that store carbon permanently. The Rainbow methodology offers a framework to measure and certify carbon removal and avoidance across diverse industrial residues, beyond cement and concrete alone.Read documentationTechnologyEx situ mineralization stores carbon by reacting captured CO₂ with alkaline residues in controlled conditions, forming stable carbonates. A wide range of industrial by-products — from concrete and slags to ashes or other mineral wastes — can serve as feedstocks.The mineralized products can be reused in construction, for example as aggregates, concrete blocks, or supplementary cementitious materials. In some cases, carbonated residues may also be safely landfilled while retaining their stored CO₂.This pathway offers flexibility in CO₂ sourcing. The process can use biogenic or atmospheric CO₂ to generate removal credits, as well as fossil or calcination CO₂ to generate avoidance credits. In addition, some projects may issue avoidance credits when mineralization improves binder strength and reduces cement use. This versatility ensures that mineralization projects contribute both to permanent removals and to significant emission reductions across industrial processes.QuantificationThe methodology quantifies avoided and removed emissions in line with ISO 14064-2.The baseline accounts for carbon storage that would have occurred without the project, such as natural carbonation of concrete in use or alternative management of alkaline feedstocks. Where applicable, it also accounts for emission reductions from avoided cement use.The project scenario covers all activities and emissions linked to ex situ mineralization. This includes sourcing and transporting alkaline feedstocks, capturing and supplying CO₂, operating the carbonation process, and managing the mineralized products.The calculations compare the emissions from the baseline and project scenarios, while quantifying the amount of CO₂ permanently stored through mineralization. The methodology allows project developers to choose between two validated approaches to measure carbonate formation: continuous monitoring of gaseous CO₂ inflows and outflows, or solid sampling of carbonated materials with laboratory analysis to directly quantify carbon content. This flexibility ensures robust results across diverse technologies and operational contexts.Compliance)
GHG emissions calculationWe adhere to the ISO14064-2 standard to accurately quantify GHG emissions reductions and sequestration.Read more)
Project reportingAll projects comply with the General Standard Rules in accordance with ICVCM and ICROA requirementsRead more)
Audit and verificationAll projects undergo validation and recurring monitoring audits by accredited Validation and Verification Bodies (VVBs).Read more)
Credit traceabilityOur registry offers end-to-end traceability for the lifecycle of our credits, preventing double-counting and double-claiming.Read moreStatusProjects using this methodology0projects ↗Overall Available Credits0tCO2eqOverall forecasted delivery0tCO2eq
SDG Co-benefits most found in the projects)
Achieve the sustainable management and efficient use of natural resources.)
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Upgrade infrastructure and retrofit industries to make them sustainable.)
Improve global resource efficiency in consumption and production.)
Improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials.