Eligible technologies

Eligible activities

All projects certified under this methodology must cause carbon removals via accelerated and/or enhanced carbonation of alkaline minerals by CO₂.

Many different technological setups are eligible under the present methodology and widely described in the . Eligible project setups may include but are not limited to the following technological processes, final products, CO₂ sources, and alkaline materials:

Eligible technologies

• carbonation curing of cementitious materials

• carbonation during fresh concrete mixing/hydration

• carbonation of solid materials, to add to e.g. concrete or asphalt

Eligible products

• Ready mix concrete, mixed and installed

• Pre-cast concrete blocks

• and concrete aggregate, destined for use in concrete, asphalt, road subbase or construction fill

Eligible CO₂ sources

• atmospheric CO₂ from direct air capture (DAC)

• biogenic CO₂ from point-source capture (e.g. bioenergy production)

• fossil CO₂ from point-source capture (e.g. coal plants)

• , or other non-fossil CO₂ from heavy industries

• mixed CO₂ from waste incineration

• pure or mixed CO₂ streams of any type listed above

Eligible alkaline sources

• Coal fly ash

• Cement residues (e.g. cement kiln dust)

• Concrete production waste (e.g. concrete wastewater)

• Recycled concrete

• Paper mill residues

• Municipal incineration by-products (e.g., bottom ash, APC residues)

• Steel manufacturing waste

• Nickel tailings

• Red mud from aluminum processing

• Natural rock, mining waste

Projects that contain components not listed above, but that meet the requirements of the present methodology and the Riverse Standard Rules, shall be considered on a case-by-case basis.

Projects under this methodology are eligible for

• removal Riverse Carbon Credits (RCCs) related to carbonation with biogenic, ambient and atmospheric CO₂,

• avoidance RCCs related to carbonation with fossil and CO₂, and

• avoidance RCCs related to reduction of cement use.

Carbon removals under this methodology are estimated to have a permanence horizon of at least 1000 years. Reversal risks and baseline removals are assessed according to this duration.

Credits are issued on the basis of carbonated materials sale to the next actor in the supply chain.

Carbonation with fossil and calcination CO₂ counts as Carbon Capture and Storage (CCS) and is issued avoidance credits. These do not count for carbon dioxide removal (CDR), but for simplicity and readability, this pathway may be referred to as removal throughout the methodology.

Project scope

One project is defined as the operation of one or more reactors within a single country, using the same technology and monitoring approach, and operated at sites that are under the oversight or data access of a single Project Developer—regardless of whether the developer directly owns or manages each site.

The project scope covers all additional removals and induced emissions, caused by the project activity, that would not have occurred in the baseline scenario/in the absence of the project.

For example, if the project is co-located with a concrete manufacturing site, the emissions from concrete production (i.e. energy use emissions, infrastructure embodied emissions...) that would have occurred anyway are not counted towards the project induced emissions.

Removals from carbonation during the use phase of concrete are excluded by default from this methodology, due to 1) the requirements that the carbonated material have similar removals to the baseline scenario material and 2) difficulty in accurately measuring and monitoring use phase removals. This may be reassessed on a case by case basis.

For example, any removals that would have occurred anyway (e.g. due to natural carbonation in concrete), are not counted towards project removals.

Project Developers shall categorize the project's carbon capture and carbonation sites as retrofits on top of existing sites, or the installation of new sites. This helps distinguish between the project scope and the . Project Developers shall prove the extent of existing operations of any connected activities using historical proof of operations of the existing site/s.

Project developers shall summarize the following key descriptive meta-information for the project:

• Carbonation reaction type, type of metal/s contributing to mineral formation, and expected carbonate compound type

• Expected carbonation timeline after reactor exit, based on the kinetics of the specific technology (e.g. full carbonation occurs within 24 hours, 1 week, etc.)

• Temperature and pressure of the reactor

Carbonation batch

A carbonation batch is the quantity of carbonated material produced using the same input materials (alkaline feedstock and CO₂) and operating conditions. It is assumed that all carbonated material from the same carbonation batch has similar characteristics relevant to carbonation performance and measurement accuracy (i.e. carbonation rate, bulk density…). This facilitates carbonated material solid sampling and measurements, where a representative sample may taken for each carbonation batch.

A change in alkaline feedstock triggers a new carbonation batch when any of the following occur:

• A change in material category, based on recognized standards (e.g. ASTM, EN),

• A substantial change in material properties, even within the same product category,

• A change in supplier or geographic source of the feedstock.

A change in the CO₂ input triggers a new carbonation batch if:

• The CO₂ supplier or source changes, or

• The composition of the CO₂ stream changes significantly (e.g. shift in biogenic vs. fossil fraction).

This definition represents the recommended approach, but may be adapted on a case-by-case basis depending on the project's operating conditions. It is in the Project Developer's best interest to define carbonation batches at a granular level, and resample and remeasure accordingly. Doing so helps reduce measurement variability and improves confidence that reported CO₂ storage variability falls within the eligible range.

Measurements and reporting are performed at the carbonation batch level. Verification and credit issuance may be done per carbonation batch, or annually on the cumulative carbonation batches from that year.

A carbonation batch has a maximum validity of 365 days. After this period, a new batch must be defined and monitored, even if feedstock and CO₂ conditions remain unchanged.