Quantifying CO2 removal at enhanced weathering sites : a multiproxy approach
Abstract
Enhanced weathering is a carbon dioxide (CO2) mitigation strategy that promises large scale atmospheric CO2 removal. The main challenge associated with enhanced weathering is monitoring, reporting, and verifying (MRV) the amount of carbon removed as a result of enhanced weathering reactions. Here, we study a CO2 mineralization site in Consett, Co. Durham, UK, where steel slags have been weathered in a landscaped deposit for over 40 years. We provide new radiocarbon, δ13C, 87Sr/86Sr, and major element data in waters, calcite precipitates, and soils to quantify the rate of carbon removal. We demonstrate that measuring the radiocarbon activity of CaCO3 deposited in waters draining the slag deposit provides a robust constraint on the carbon source being sequestered (80% from the atmosphere, 2σ = 8%) and use downstream alkalinity measurements to determine the proportion of carbon exported to the ocean. The main phases dissolving in the slag are hydroxide minerals (e.g., portlandite) with minor contributions (<3%) from sillicate minerals. We propose a new method for quantifying carbon removal rates at enhanced weathering sites, which is a function of the radiocarbon-apportioned sources of carbon being sequestered, and the proportion of carbon being exported from the catchment of the oceans.
Citation
Knapp , W J , Stevenson , E I , Renforth , P , Ascough , P L , Knight , A C G , Bridgestock , L , Bickle , M J , Lin , Y , Riley , A L , Mayes , W M & Tipper , E T 2023 , ' Quantifying CO 2 removal at enhanced weathering sites : a multiproxy approach ' , Environmental Science and Technology , vol. 57 , no. 26 , pp. 9854-9864 . https://doi.org/10.1021/acs.est.3c03757
Publication
Environmental Science and Technology
Status
Peer reviewed
ISSN
0013-936XType
Journal article
Description
Funding: W.J.K. acknowledges funding from NERC studentship NE/S007164/1. The radiocarbon analyses were supported by the National Environmental Isotope Facility (NEIF) under grant NE/S011587/1 (allocation number 2442.1021). E.T.T. acknowledges funding from NERC grants NE/T007214/1, NE/P011659/1, and NE/M001865/1. P.R. and W.M.M. acknowledge funding from UKRI greenhouse gas removal research programme (NE/P019943/1), and P.R. acknowledges funding from the Industrial Decarbonisation Research and Innovation Centre (EP/V027050/1).Collections
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.