We are pleased to announce the launch of the updated Puro Enhanced Rock Weathering (ERW) methodology (Edition 2025). 

This update reflects the rapidly evolving science and technology behind ERW, ensuring that our methodology remains both scientifically rigorous and practical for carbon removal suppliers and project developers worldwide. It also aligns the ERW methodology with the latest Puro General Rules and the ICVCM CCP. 

For this update, we have collaborated with a diverse group of experts from academia, industry, and the non-profit sector, held three workshops, and interviewed other relevant stakeholders. The final published version was approved by Puro’s scientific advisory board after being subjected to public consultation, which resulted in 91 minor and 4 major modifications in response to 144 public comments. We thank everyone involved for their invaluable contribution to the methodology development process. 

Major changes introduced in this update 

• Enhanced quantification approaches: A detailed description of eligible CDR measurement approaches has been added to ensure reliable quantification of carbon removed. Seven different eligible approaches are described in this update. To ensure robustness, the methodology requires the combination of two approaches: one to quantify stored CO2, and one to validate this quantification. 
• Detailed sampling requirements: Clear sampling guidelines ensure scientifically sound and statistically representative measurement of CDR through careful characterization of soil chemistry with an emphasis on measurement precision and accuracy and the rigorous use of control plots for carbon accounting. 
• Clarified role of modeling: Quantification of CDR always requires site-specific field measurements; modeling is recognized as an optional tool to extrapolate data from these measurements. 
• Updated accounting for loss terms: Losses are explicitly addressed with clear instructions for their quantification and accounting. They include secondary carbonate and silicate mineral formation, cation adsorption, plant loss, non-carbonic acid weathering, as well as river and ocean losses. 
• Uncertainty management: The update introduces an uncertainty discount and requires robust quantification of uncertainty by frequentist or Bayesian approaches for the different components of the carbon removal calculation (“CORC equation”).