The Puro Standard published the first carbon crediting methodology for enhanced rock weathering (ERW) in the carbon removal markets in 2022. Developed in collaboration with a working group of experts, project developers and scientific researchers, it was approved by Puro.earth’s Advisory Board following a period of public consultation. 

In 2024, we published a minor update to the ERW methodology, integrating key learnings from advancements in science and technology. This update also improved transparency and operational usability by incorporating supplementary guidelines directly into the methodology.

We are proud that our Enhanced Rock Weathering methodology has facilitated the development of innovative carbon removal projects, helping to scale ERW as a viable climate solution. As part of the Puro Standard’s regular review cycle, we are now initiating work on the 2025 methodology update, which will further refine verification processes, integrate the latest scientific insights, and enhance the scalability of ERW certification. 

Projects currently undergoing audit or verification under the existing methodology will continue through the certification process as usual, maintaining the same rigorous standards that uphold market confidence and scientific integrity. The update will build upon the current framework, incorporating refinements that further strengthen the robustness and credibility of ERW certification.

Background to the update

The 2025 update of the Puro Standard Enhanced Rock Weathering methodology will build on the foundation laid out by the previous minor update, and consider:

• Advancements in carbon quantification: Incorporating the latest scientific and technological developments to improve the robustness of CO2 removal quantification. This includes refining carbon storage calculation approaches, addressing uncertainty and ensuring the representativeness of field measurement data. 
• Additionality and baseline additions: Reviewing and refining criteria for additionality and baseline carbon sequestration scenarios.
• Alignment with Puro Standard: Ensuring alignment with the Puro General Rules 4.1 and other updates to Puro Standard documents. 
• Operational learnings and stakeholder feedback: Implementing improvements based on real-world application of the ERW methodology and input from our suppliers and working group collaborators).

This update is a standard evolution of our methodology, ensuring it remains at the forefront of best practices while maintaining stability for ongoing and future projects.

Timeline and consultation period

The update process is scheduled to happen between late Q1 and Q2 2025. Given the significance of the changes, a three-week-long public consultation period will be organized, and tentatively planned for June 2025. This consultation will include a public and recorded webinar.
 
Initial feedback on current version & constitution of a working group

To leverage the expertise of our network, we invite all relevant stakeholders to submit feedback on the current methodology. 

Submit feedback & apply to participate in the working group

Additionally, a working group will also be established., Organizations with relevant ERW expertise can apply via the same form (applications are accepted until March 28 2025 ). The working group will:

• Review the draft update as it is being written by the Puro team. 
• Participate in three-four dedicated sessions in May 2025, focusing on specific methodological topics. 

To ensure efficiency, the working group size may be limited and restricted to entities with significant ERW expertise.

Approval and deployment

After incorporating the feedback received during the public consultation, the updated methodology will be presented to Puro’s independent scientific Advisory Board for approval. Pending approval, deployment of the updated ERW methodology is expected to begin in H2 2025, with specific transition dates to be determined. 

Kind regards, 
The Puro Team