skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Carbon dioxide removal during dissolution of granular basalt: A mass balance test of enhanced rock weathering at the hillslope scale
Title: Carbon dioxide removal during dissolution of granular basalt: A mass balance test of enhanced rock weathering at the hillslope scale
Enhanced rock weathering (ERW) is proposed as a carbon dioxide removal (CDR) strategy that sequesters carbon through the carbonic acid-promoted dissolution of ground silicate rocks. Studies have explored the efficacy of ERW through geochemical models and bench-scale reactors, but field-scale experimentation is limited. A year- long, replicated study was conducted at the Landscape Evolution Observatory (LEO) at Biosphere 2 to quantify basaltic CDR at the hillslope scale. LEO comprises three mesoscale surfaces (each 330 m2) with 1 m depth of granular basalt. We subjected these structures to three 30 d irrigation events followed by progressively lengthened dry periods. Aqueous discharge was collected bihourly for major and trace chemistry, and subsurface interactions were observed at 15 min intervals through distributed sensors enabling continuous monitoring of PCO2, volumetric water content, and total hillslope mass. This approach enabled closing of the carbon and water mass balance of the system for the duration of the experiment. CDR was quantified through direct monitoring of bicarbonate (HCO3) concentrations as validated through the charge balance of non-hydrolyzing cations and strong-acid anions. Concentration-discharge relations for HCO3 showed dilution trends with clockwise hysteresis, while a decrease in CO2 uptake occurred with increased hillslope water saturation (Shydro). The CDR rate, normalized to the specific surface area of the basalt, was -13.45 log10 moles C m 2 s 1, while other studies report CDR rates from -14 to -10 log10 moles m 2 s 1. We found that basalt CDR rates were impacted by depletions of PCO2 upon hydrologic infiltration, variable Shydro, and incongruent dissolution.  more » « less
Award ID(s):
2135405 2134453
PAR ID:
10668038
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Publisher / Repository:
Earth & Planetary Science Letters
Date Published:
Journal Name:
Earth and Planetary Science Letters
Volume:
671
Issue:
C
ISSN:
0012-821X
Page Range / eLocation ID:
119662
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, Biogeosciences)
    null (Ed.)
    Abstract. Meeting internationally agreed-upon climate targets requirescarbon dioxide removal (CDR) strategies coupled with an urgent phase-down offossil fuel emissions. However, the efficacy and wider impacts of CDR arepoorly understood. Enhanced rock weathering (ERW) is a land-based CDRstrategy requiring large-scale field trials. Here we show that a low 3.44 t ha−1 wollastonite treatment in an 11.8 ha acid-rain-impacted forested watershed in New Hampshire, USA, led to cumulative carbon capture by carbonic acid weathering of 0.025–0.13 t CO2 ha−1 over 15 years. Despite a 0.8–2.4 t CO2 ha−1 logistical carbon penalty from mining,grinding, transportation, and spreading, by 2015 weathering together withincreased forest productivity led to net CDR of 8.5–11.5 t CO2 ha−1. Our results demonstrate that ERW may be an effective, scalableCDR strategy for acid-impacted forests but at large scales requiressustainable sources of silicate rock dust. 
    more » « less
  2. ; ; ; ; ; ; (, Environmental Research: Energy)
    Abstract To achieve net zero carbon emissions by mid-century, the United States may need to rely on carbon dioxide removal (CDR) to offset emissions from difficult-to-decarbonize sectors and/or shortfalls in near-term mitigation efforts. CDR can be delivered using many approaches with different requirements for land, water, geologic carbon storage capacity, energy, and other resources. The availability of these resources varies by region in the U.S. suggesting that CDR deployment will be uneven across the country. Using the global change analysis model for the United States (GCAM-USA), we modeled six classes of CDR and explored their potential using four scenarios: a scenario where all the CDR pathways are available (Full Portfolio), a scenario with restricted carbon capture and storage (Low CCS), a scenario where the availability of bio-based CDR options is limited (Low Bio), and a scenario with constraints on enhanced rock weathering (ERW) capabilities (Low ERW). We find that by employing a diverse set of CDR approaches, the U.S. could remove between 1 and 1.9 GtCO2/yr by midcentury. In the Full Portfolio scenario, direct air carbon capture and storage (DACCS) predominates, delivering approximately 50% of CO2removal, with bioenergy with carbon capture and storage contributing 25%, and ERW delivering 11.5%. Texas and the agricultural Midwest lead in CDR deployment due to their abundant agricultural land and geological storage availability. In the Low CCS scenario, reliance on DACCS decreases, easing pressure on energy systems but increasing pressure on the land. In all cases CDR deployment was found to drive important impacts on energy, land, or materials supply chains (to supply ERW, for example) and these effects were generally more pronounced when fewer CDR technologies were available. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; (, Hydroshare)
    This resource provides accompanying discharge and hydrologic data (silicon, sodium, silicon stable isotopes, and discharge and irrigation fluxes) presented in 'Stable Silicon Isotope Fractionation Reflects the Routing of Water Through a Mesoscale Hillslope', Earth and Planetary Letters, https://doi.org/10.1016/j.epsl.2024.119098 This dataset was collected at the Landscape Evolution Observatory (LEO) in Tucson, Arizona from 2022-2023. Discharge chemistry and flux are reported for each of the three LEO hillslopes. Files are provided in ".csv" format. 
    more » « less
  4. ; ; ; ; (, Journal of Geophysical Research: Biogeosciences)
    Abstract The quantity and preservation of carbon‐rich organic matter (OM) underlying permafrost uplands, and the evolution of carbon accumulation with millennial climate change, are large sources of uncertainty in carbon cycle feedbacks on climate change. We investigated permafrost OM accumulation and degradation over the Holocene using a transect of sediment cores dating back to at least c. 6 ka, from a hillslope in the Eight Mile Lake watershed, central Alaska. We find decimeter‐scale organic‐rich (111 ± 45 kg C m−3) and organic‐poor (49 ± 30 kg C m−3) layers below an upper peat, which store 35% ± 11% and 41% ± 20% of the carbon in the upper 1 m, respectively. In organic‐poor layers, scattered14C ages of plant macrofossils and higher percentages of degradedAlnusandBetulapollen indicate reworking by cryoturbation and hillslope processes. Whereas organic carbon to nitrogen ratios generally indicate OM freshening up‐core, amino acid bacterial biomarkers, includingd‐enantiomers and gamma‐aminobutyric acid, suggest enhanced degradation prior to 5 ka. Carbon accumulation rates increased from ∼4 to 14 g C m−2 year−1from c. 8 to 0.2 ka, coinciding with decreasing temperatures and increasing moisture regionally, which may have promoted OM accumulation. Carbon stocks within the upper 1 m average 66 ± 13 kg C m−2, varying from 77 kg C m−2in a buried depression on the upper slope to 48 kg C m−2downslope. We conclude that heterogeneity in preserved OM reflects a combination of hillslope geomorphic processes, cryoturbation, and climatic variations over the Holocene. 
    more » « less
  5. ; (, Nature)
    Most current strategies for carbon management require CO2 removal (CDR) from the atmosphere on the multi-hundred gigatonne (Gt) scale by 2100. Mg-rich silicate minerals can remove >105 Gt CO2 and sequester it as stable and innocuous carbonate minerals or dissolved bicarbonate ions. However, the reaction rates of these minerals under ambient conditions are far too slow for practical use. Here we show that CaCO3 and CaSO4 react quantitatively with diverse Mg-rich silicates (for example, olivine, serpentine and augite) under thermochemical conditions to form Ca2SiO4 and MgO. On exposure to ambient air under wet conditions, Ca2SiO4 is converted to CaCO3 and silicic acid, and MgO is partially converted into a Mg carbonate within weeks, whereas the input Mg silicate shows no reactivity over 6 months. Alternatively, Ca2SiO4 and MgO can be completely carbonated to CaCO3 and Mg(HCO3)2 under 1 atm CO2 at ambient temperature within hours. Using CaCO3 as the Ca source, this chemistry enables a CDR process in which the output Ca2SiO4/MgO material is used to remove CO2 from air or soil and the CO2 process emissions are sequestered. Analysis of the energy requirements indicates that this process could require less than 1 MWh per tonne CO2 removed, approximately half the energy of CO2 capture with leading direct air capture technologies. The chemistry described here could unlock Mg-rich silicates as a vast resource for safe and permanent CDR. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email