A Novel Soil Porewater Extraction Technique for Enhanced Rock Weathering Products: SATuration - Centrifugation

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Abstract
Enhanced Rock Weathering (ERW) involves the application of crushed silicate-rich minerals to agricultural soils as a promising Carbon Dioxide Removal (CDR) strategy, with potential benefits for soil health and crop productivity. Effective Monitoring, Reporting, and Verification (MRV) techniques are essential for carbon credit validation and scalability of ERW. Current MRV methods, such as in-field soil porewater extraction, represent a potential barrier for scaling-up ERW because the accuracy, sensitivity, and consistency of this technique is limited by soil moisture availability. Here we test a new technique for quantifying ERW called the SATuration Centrifugation (SAT-C) technique, which could prove to be a more accurate, sensitive, and consistent means of quantifying ERW. This novel method combines soil core saturation using deionized water and centrifugation to extract porewater from a defined soil volume, independent of initial moisture conditions. Comparative analyses show strong concordance between SAT-C and conventional rhizon sampling for key elemental concentrations. Furthermore, bicarbonate concentrations inferred from charge balance correlate with measured alkalinity across distinct soil types from two grassland ERW trials. SAT-C provides a robust, consistent tool for soil porewater extraction in ERW MRV, improving sampling accuracy regardless of soil moisture and thereby supporting more reliable carbon accounting and verification frameworks.
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