Inorganic-Organic Carbon coupling in models for enhanced weathering.

Although enhanced weathering is a promising CDR technology, experimental evidence from the past years have tempered expectations and call for caution. These experiments show two major things: first the impact on soil organic matter (SOM) can be large and, particularly in the short term, can lead to enhanced carbon dioxide emissions rather than the hoped for carbon dioxide removal. Second, very limited (or no) leaching of alkalinity to deeper ground water is observed, and instead the cations released from weathering end up locally in different soil pools.

 

Advancing our understanding of this inorganic-organic (IC-OC) coupling requires the development of numerical models that couple inorganic and organic carbon cycles. Here we present the implementation of several established SOM models in the geochemical software platform PhreeqC. This well established platform has a strong track record in simulating soil water chemistry and allows for a flexible selection of a broad range of geochemical processes. We show how different models and different ways of coupling affect simulated behavior of CO2 exchange with the atmosphere and alkalinity fluxes towards ground-water, how they compare to observed data from selected experiments and elaborate on the challenges involved.