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Isometric today released a protocol for carbon dioxide removal (CDR) via wastewater alkalinity enhancement (WAE) for public consultation. The protocol details requirements and procedures for carbon removal that occurs in wastewater treatment.
In wastewater treatment, microbes are used to break down organic waste. This biological treatment produces carbon dioxide (known as biogenic carbon dioxide) that would be released into the atmosphere under the normal operating conditions of a wastewater treatment plant.
This existing process is a perfect candidate for carbon removal. In WAE, alkaline materials, such as finely crushed limestone, are added to the biological treatment process. These alkaline materials react with the carbon dioxide produced by the microbes and convert it into bicarbonate ions, which do not enter the atmosphere. The bicarbonate ions remain in the wastewater stream, continue through the remaining treatment steps and are discharged to a river or other body of water. The reacted carbon dioxide does not get released during the wastewater treatment process and is instead transported to the ocean, where it is sequestered for tens of thousands of years.
Wastewater treatment processing and discharge is safe, regulated and highly monitored. Multiple treatment steps clean and disinfect water before it reaches rivers and oceans. WAE has high scaling potential because it leverages existing infrastructure, is relatively low cost and is a straightforward addition to this well established process.
This industry-first protocol takes a scientifically rigorous approach to monitoring, reporting and verification (MRV) for WAE. Three key elements of the protocol ensure that buyers and suppliers can have confidence that any credit issued under Isometric’s WAE protocol represents a tonne of carbon dioxide durably removed from the atmosphere.
Precise direct measurements
The WAE process takes place within the controlled environment of a wastewater treatment facility, where inputs and outputs of alkaline materials and carbon can be directly measured. This allows for accurate calculation and validation of the amount of alkaline materials added and how much of this feedstock dissolves and reacts to capture carbon dioxide. This provides high confidence in the quantification of gross carbon removal.
Strict accounting for downstream losses
After treated water is discharged into rivers or oceans, some of the captured carbon dioxide may still enter the atmosphere. The amount of carbon dioxide that is released this way is known as a downstream loss. Under the Isometric protocol, downstream losses are conservatively accounted for through the use of riverine and ocean models. These well established models are specific to the river or ocean chemistry of each WAE site and based on existing public datasets and peer-reviewed studies.
Rigorous definition of baseline emissions
WAE is particularly scalable because it adds on to an existing process that has a low operational footprint. This means the lifecycle analysis only needs to account for emissions that are additional beyond the business-as-usual operations of an existing wastewater treatment plant. The Isometric protocol accounts for rigorous and realistic baseline scenarios.
Carbon removal supplier CREW Carbon, a leading WAE supplier, has provided extensive feedback during the development of this protocol. CREW utilizes a proprietary approach developed at Yale University, which combines precise mineral dosing, inline monitoring and downstream tracking to measure and remove biogenic carbon dioxide produced during the wastewater treatment process. CREW's monitoring platform quantifies the amount of carbon entering the plant and the amount removed by their process for highly measurable and durable CDR. CREW is the first supplier signed up to issue credits under the Isometric protocol.
Dr. Joachim Katchinoff, CREW Carbon Co-Founder and CEO, said:
"Alkalinity-based carbon dioxide removal, like enhanced weathering, has a massive potential for climate impact and being able to deliver tons of measurable CDR today is key. The wastewater treatment process produces significant amounts of biogenic carbon dioxide in closed, existing infrastructure which offers a significant opportunity to apply alkalinity-based CDR to these systems. Isometric's release of this protocol represents the necessary scientific standards, providing the community with confidence in transparency and rigor, while ensuring CREW's carbon dioxide removal meet the most stringent industry criteria."
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 ending on 15 Dec 2024.
