CDR Verification Framework Documentation
Docs: Component
Mineral weathering (alkalinity release)
Uncertainty
The effects of enhanced weathering should be understood as an overall shift in CO₂ fluxes as a result of introducing alkalinity to the system through rock weathering. While most applied minerals will ultimately weather, enhanced weathering approaches should only be credited when the impact on atmospheric CO₂ actually occurs. The rate of rock weathering, and therefore alkalinity introduction, depends on many factors including rock type, particle size, soil type, ambient temperature, precipitation, and irrigation. At a given point in time, it may be possible to measure how much rock has weathered via elemental analysis or by tracking changes in the concentration of tracer elements that originate in the applied rocks and persist in the soil after rock weathering. Rock weathering may be facilitated by different sources of acid (carbonic or non-carbonic) and result in different weathering products, which can each have unique impacts on system CO₂ fluxes. If rock is weathered by carbonic acid, a potential product is dissolved inorganic carbon (DIC). To inform a lower bound on rock weathering and characterize how much additional DIC is leaving the site because of the weathering, effluent from the weathering site can be continuously monitored to detect changes in the carbonic acid system. These changes can be constrained by monitoring any two components of the carbonic acid system: pH, total alkalinity (TA), partial pressure of CO₂ (pCO₂), or dissolved inorganic carbon (DIC). Both approaches — monitoring of the rock in the weathering site and monitoring the effluent leaving the weathering site — are areas of active innovation.
Applicable pathways
Pathway
VCL
Enhanced Weathering
3
Revision history

Dec 19 2022
Second release. Tweaked the equation for total carbon removal to begin with Mineral weathering rather than Mineral application. Changed the Mineral weathering component to represent the additive factor 'quantity of released alkalinity' rather than the subtractive factor 'non-weathered portion of rock'. These edits occured as part of a broader update of the Enhanced Weathering pathway.

Sep 20 2022
Moving this quantification target ('quantity of released alkalinity') to modify 'Mineral weathering' rather than 'Alkalinity run-off'. Estimating the non-weathered potion of rock can be done either by trying to measure how much rock is left, or by tracking the alkalinity and pH of the run-off, and therefore could therefore be associated with either 'Mineral weathering' or 'Alkalinity run-off' in the pathway diagram. We are moving it based on initial feedback that associating it with 'Mineral weathering' would be a more intuitive relationship.

Sep 19 2022
First release.
Mineral weathering (alkalinity release)
Uncertainty
The effects of enhanced weathering should be understood as an overall shift in CO₂ fluxes as a result of introducing alkalinity to the system through rock weathering. While most applied minerals will ultimately weather, enhanced weathering approaches should only be credited when the impact on atmospheric CO₂ actually occurs. The rate of rock weathering, and therefore alkalinity introduction, depends on many factors including rock type, particle size, soil type, ambient temperature, precipitation, and irrigation. At a given point in time, it may be possible to measure how much rock has weathered via elemental analysis or by tracking changes in the concentration of tracer elements that originate in the applied rocks and persist in the soil after rock weathering. Rock weathering may be facilitated by different sources of acid (carbonic or non-carbonic) and result in different weathering products, which can each have unique impacts on system CO₂ fluxes. If rock is weathered by carbonic acid, a potential product is dissolved inorganic carbon (DIC). To inform a lower bound on rock weathering and characterize how much additional DIC is leaving the site because of the weathering, effluent from the weathering site can be continuously monitored to detect changes in the carbonic acid system. These changes can be constrained by monitoring any two components of the carbonic acid system: pH, total alkalinity (TA), partial pressure of CO₂ (pCO₂), or dissolved inorganic carbon (DIC). Both approaches — monitoring of the rock in the weathering site and monitoring the effluent leaving the weathering site — are areas of active innovation.
Applicable pathways
Pathway
VCL
Revision history

Dec 19 2022
Second release. Tweaked the equation for total carbon removal to begin with Mineral weathering rather than Mineral application. Changed the Mineral weathering component to represent the additive factor 'quantity of released alkalinity' rather than the subtractive factor 'non-weathered portion of rock'. These edits occured as part of a broader update of the Enhanced Weathering pathway.

Sep 20 2022
Moving this quantification target ('quantity of released alkalinity') to modify 'Mineral weathering' rather than 'Alkalinity run-off'. Estimating the non-weathered potion of rock can be done either by trying to measure how much rock is left, or by tracking the alkalinity and pH of the run-off, and therefore could therefore be associated with either 'Mineral weathering' or 'Alkalinity run-off' in the pathway diagram. We are moving it based on initial feedback that associating it with 'Mineral weathering' would be a more intuitive relationship.

Sep 19 2022
First release.