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Initial Validation of a Soil-Based Mass-Balance Approach for Empirical Monitoring of Enhanced Rock Weathering Rates

2023; American Chemical Society; Volume: 57; Issue: 48 Linguagem: Inglês

10.1021/acs.est.3c03609

1520-5851

Tom Reershemius, Mike Kelland, Jacob S. Jordan, Isabelle R. Davis, Rocco D’Ascanio, Boriana Kalderon-Asael, Dan Asael, Tim Jesper Suhrhoff, Dimitar Z. Epihov, David J. Beerling, Christopher T. Reinhard, Noah J. Planavsky,

Rock Mechanics and Modeling

Enhanced rock weathering (ERW) is a promising scalable and cost-effective carbon dioxide removal (CDR) strategy with significant environmental and agronomic co-benefits. A major barrier to large-scale implementation of ERW is a robust monitoring, reporting, and verification (MRV) framework. To successfully quantify the amount of carbon dioxide removed by ERW, MRV must be accurate, precise, and cost-effective. Here, we outline a mass-balance-based method in which analysis of the chemical composition of soil samples is used to track in situ silicate rock weathering. We show that signal-to-noise issues of in situ soil analysis can be mitigated by using isotope-dilution mass spectrometry to reduce analytical error. We implement a proof-of-concept experiment demonstrating the method in controlled mesocosms. In our experiment, a basalt rock feedstock is added to soil columns containing the cereal crop Sorghum bicolor at a rate equivalent to 50 t ha-1. Using our approach, we calculate rock weathering corresponding to an average initial CDR value of 1.44 ± 0.27 tCO2eq ha-1 from our experiments after 235 days, within error of an independent estimate calculated using conventional elemental budgeting of reaction products. Our method provides a robust time-integrated estimate of initial CDR, to feed into models that track and validate large-scale carbon removal through ERW.