Isometric today released a protocol for carbon dioxide removal (CDR) via River Alkalinity Enhancement (RAE) for public consultation. The protocol details requirements and procedures for carbon removal that occurs via rivers.
Rivers are the main way carbon moves across the Earth’s continents and into oceans. As a result, rivers generally have a higher concentration of carbon dioxide than the atmosphere and release up to 2.5 billion tonnes of carbon dioxide into the air every year. In RAE, powdered alkaline rocks—such as finely crushed limestone—are carefully added to river water. These materials react with the carbon dioxide in the rivers and convert it into stable carbonate and bicarbonate ions. This conversion prevents carbon dioxide from being released into the atmosphere. The carbonate and bicarbonate ions are ultimately transported by rivers to the ocean, where the carbon dioxide is stored for tens of thousands of years.
Rivers have strong potential for carbon removal as they naturally collect and transport carbon dioxide.
RAE for the purposes of carbon dioxide removal is a recent innovation, but the process behind it is safe and well understood. It is also known as river liming and it has been practiced for decades to manage river acidification and protect pH-sensitive species—such as trout and salmon.
This industry-first protocol takes a scientifically rigorous approach to monitoring, reporting and verification (MRV) for RAE. Three key elements of the protocol ensure that buyers and suppliers can have confidence that any credit issued under Isometric’s RAE protocol represents a tonne of carbon dioxide durably removed from the atmosphere.
Flexible quantification framework
No two rivers are the same. To account for this inherent variability and complexity, the protocol employs a flexible quantification framework. This framework adjusts to the site-specific conditions of each RAE project—capturing the full dynamics of RAE over time and space from the point of the alkalinity addition to ocean storage. This comprehensive framework enables robust tracking of carbon removal while accommodating the diverse nature of river environments.
Direct measurement of alkaline feedstock weathering
Direct measurements can be taken at multiple points in a river, after the introduction of alkaline materials. This helps confirm how much of the added alkalinity dissolves and reacts to capture carbon dioxide—providing a high level of confidence in the quantification of carbon removal.
Dynamic baseline
The protocol quantifies the dynamic baseline state of each river—including a range of variables such as water flow, temperature, pH levels—using statistical and process models, to accurately account for the changes that result from RAE. These models—which include short-range chemistry prediction and river transport modeling—are specific to the conditions of each site and have stringent requirements for validation.
CarbonRun, a leading RAE supplier, provided extensive feedback during the development of this protocol.
Shannon Sterling, CarbonRun, Founder and COO / CSO, said:
“Rivers are the critical link in the global carbon cycle between the terrestrial sources and ocean sinks. For over four years, the CarbonRun team has worked with Dalhousie University and the Nova Scotia Salmon Association on the question of how alkalinity additions for river restoration can also remove carbon dioxide. It’s so exciting to see this work come to fruition.
“The Isometric team has developed a River Alkalinity Enhancement protocol that leverages the unique strengths of rivers, including the ability to observe CDR in real time. We’ve tested the protocol in the field and are excited about its ability to support MRV that is efficient, affordable, practical and builds trust. We are excited about the potential for River Alkalinity Enhancement to help mitigate the worst effects of climate change while restoring our rivers and estuaries.”
This protocol was developed in line with the Isometric Standard and was created in collaboration between Isometric’s in-house Science Team and reviewers from Isometric’s independent Science Network of over 300 scientific experts. Comments on this protocol are welcome from interested buyers, suppliers and scientists during the 30-day public consultation period which ends on April 26, 2025.
