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Isometric recently released a module on the storage of carbon dioxide via carbonation in the built environment. This module details the monitoring and modeling requirements for durable carbon dioxide storage in concrete.
Carbon dioxide can be stored in concrete through several methods. This module specifically focuses on methods that use carbonation, in which a stream of concentrated carbon dioxide (typically from a Direct Air Capture or Biogenic Carbon Capture and Sequestration (BCCS) project) is reacted with rock to form carbonate minerals. Under the module, projects may use direct carbonation methods—in which carbon dioxide reacts with concrete during the mixing or curing process—or may incorporate carbonated materials (such as mine tailings or recycled concrete) into concrete.
Carbonate minerals store carbon for thousands of years under the typical conditions on the Earth’s surface. However, under certain conditions, carbon dioxide from carbonate minerals can be released. While these conditions are uncommon, there is considerable uncertainty in the storage environment of carbonated concrete through its lifetime. For example, concrete may be used in one or more types of structure throughout its functional life, depending on regional policies and trends surrounding concrete use after structure demolition. Across long timescales, the process of construction, demolition and concrete reuse may occur several times.
Consequently, the uncertainty in the volume of carbon dioxide stored within a given amount of concrete increases with each subsequent construction-demolition-reuse cycle as the storage conditions cannot be directly observed.
To account for this uncertainty, Isometric has developed a reversal risk model that accounts for potential re-release of carbon dioxide across potential life cycles and storage environments. The model can be tailored to incorporate data from specific regions and projects and is used to determine an uncertainty discount. If no data is available, the most conservative uncertainty discount is applied.
This module allows for credits to be certified with a durability of 1000 years.
In carbonation of concrete, carbon removal can be quantified and measured directly-on site. This provides high confidence in credit generation for both buyers and suppliers.
The built environment module requires suppliers to comply with two key points to ensure the process is rigorous:
- System requirements: suppliers must provide comprehensive documentation on reactor design and maintenance to ensure optimal functionality
- Direct measurement of inputs and outputs from the reactor system
Additionally, suppliers are encouraged to submit additional data on regional operations. This allows calculation of project-specific uncertainty discounts through the reversal risk model.
This module was created in collaboration between Isometric’s in-house Science Team, external consultants from academia and industry—including Arup’s built environment material specialists—and reviewers from Isometric’s independent Science Network of over 200 scientists and climate experts.
Comments during the consultation period are welcome from interested buyers, suppliers and scientists and will be considered before the module is finalized.
