A new soil-based approach for empirical monitoring of enhanced rock weathering rates

Tom Reershemius, Mike E. Kelland, Isabelle R. Davis, Rocco D’Ascanio, Boriana Kalderon Asael, Dan Asael, Dimitar E. Epihov , David J. Beerling, Christopher T. Reinhard , Noah J. Planavsky

Abstract

Enhanced rock weathering (ERW) has been touted as a scalable and cost-effective
potential carbon dioxide removal (CDR) strategy with significant environmental and agronomic co-benefits. However, a major barrier to implementation of ERW at scale is a robust monitoring, reporting, and verification (MRV) framework that can accurately, precisely, and cost-effectively measure the amount of carbon dioxide being removed by ERW in the field. Here we outline a new method based on mass balance in which metal analysis in soil samples is used to accurately track the extent of in-situ alkaline mineral weathering. We show that signal-to-noise issues can be overcome by using isotope-dilution mass spectrometry to reduce analytical error. We provide an
example of implementation of this method in a controlled mesocosm experiment. Using this approach, we calculate an average initial CDR value of 1.06 ± 0.50 tCO2eq ha-1
from our experiments after 235 days, within error of an independent estimate calculated using a conventional reaction product-based approach. Our method provides a robust time-integrated estimate of CDR potential that avoids the need to trace and measure soluble ERW reaction products and is designed to integrate seamlessly with existing agronomic practices. We suggest that these features render the approach less likely to encounter prohibitive barriers to scale than alternative techniques, providing the potential to confidently track and validate carbon removal through ERW.

A new soil-based approach for empirical monitoring of enhanced rock weathering rates