Dataset Information

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 silicate minerals. We propose a novel 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 to the oceans.

SUBMITTER: Knapp WJ

PROVIDER: S-EPMC10324310 | biostudies-literature | 2023 Jul

REPOSITORIES: biostudies-literature

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Quantifying CO2 Removal at Enhanced Weathering Sites: a Multiproxy Approach.

Knapp William J WJ Stevenson Emily I EI Renforth Phil P Ascough Philippa L PL Knight Alasdair C G ACG Bridgestock Luke L Bickle Michael J MJ Lin Yongjie Y Riley Alex L AL Mayes William M WM Tipper Edward T ET

Environmental science & technology 20230621 26

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 radiocarb ...[more]

PMID: 37340979

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Project description:Coastal enhanced weathering (CEW) is a carbon dioxide removal (CDR) approach whereby crushed silicate minerals are spread in coastal zones to be naturally weathered by waves and tidal currents, releasing alkalinity and removing atmospheric carbon dioxide (CO2). Olivine has been proposed as a candidate mineral due to its abundance and high CO2 uptake potential. A life cycle assessment (LCA) of silt-sized (10 μm) olivine revealed that CEW's life-cycle carbon emissions and total environmental footprint, i.e., carbon and environmental penalty, amount to around 51 kg CO2eq and 3.2 Ecopoint (Pt) units per tonne of captured atmospheric CO2, respectively, and these will be recaptured within a few months. Smaller particle sizes dissolve and uptake atmospheric CO2 even faster; however, their high carbon and environmental footprints (e.g., 223 kg CO2eq and 10.6 Pt tCO2-1, respectively, for 1 μm olivine), engineering challenges in comminution and transportation, and possible environmental stresses (e.g., airborne and/or silt pollution) might restrict their applicability. Alternatively, larger particle sizes exhibit lower footprints (e.g., 14.2 kg CO2eq tCO2-1 and 1.6 Pt tCO2-1, respectively, for 1000 μm olivine) and could be incorporated in coastal zone management schemes, thus possibly crediting CEW with avoided emissions. However, they dissolve much slower, requiring 5 and 37 years before the 1000 μm olivine becomes carbon and environmental net negative, respectively. The differences between the carbon and environmental penalties highlight the need for using multi-issue life cycle impact assessment methods rather than focusing on carbon balances alone. When CEW's full environmental profile was considered, it was identified that fossil fuel-dependent electricity for olivine comminution is the main environmental hotspot, followed by nickel releases, which may have a large impact on marine ecotoxicity. Results were also sensitive to transportation means and distance. Renewable energy and low-nickel olivine can minimize CEW's carbon and environmental profile.

Dataset Information

Quantifying CO₂ Removal at Enhanced Weathering Sites: a Multiproxy Approach.

Publications

Quantifying CO<sub>2</sub> Removal at Enhanced Weathering Sites: a Multiproxy Approach.

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