Potential for large-scale CO2 removal via enhanced rock weathering with croplands

Anthropogenic CO2 of High Emission Scenario Compensated After 3500 Years of Ocean Alkalinization With an Annually Constant Dissolution of 5 Pg of Olivine

“…Within the suite of proposed CDR experiments exists the "ocean alkalinization in a high CO 2 world" scenario (CDR-ocean-alk). While most recent studies on negative emission technologiesand most contributions to CDRMIP-focus on centennial time scales (e.g., Keller et al, 2014;González and Ilyina, 2016;Lenton et al, 2018;Beerling et al, 2020), I here concentrate on long-term effects (thousands to millions of years) by analyzing simulations of CDR-ocean-alk performed with only one simple model, the carbon cycle box model BICYCLE.…”

Enhancing Natural Cycles in Agro-Ecosystems to Boost Plant Carbon Capture and Soil Storage

“…Actual basalt weathering rates and hence carbon drawdown potential remain uncertain, depending strongly on particle size (limited by grinding cost), climatic and soil conditions, and biological activity 8,47,48 . Water flow is critical because mineral surfaces have to be in contact with water for the dissolution reaction to take place, and disturbed for the reaction to continue 49 .…”

“…According to the rather limited body of existing studies, enhanced basalt weathering rates might be too low under realistic field conditions (range of 0.01 t C ha -1 yr -1 ) to sequester significant amounts of carbon dioxide on a societally relevant time scale (~100 years). Yet, modelling studies predict significant carbon capture potential in areas where hydrological and climate conditions are suitable 8 . This highlights an urgent need for more studies that assess mineral weathering in the field under realistic conditions, and strategies to increase the weathering rate (some of which are discussed in this article).…”

“…At such proposed application rates, the pH in soils of most textures and CECs will likely increase to 5.5-6.5, the ideal pH for most plants 108,109 . Yet, the response of soil pH to biochar and basalt application is slower than that to conventional lime addition because of a lower solubility 8,110 . Still, silicate rocks can be a sustainable lime replacement that avoid the CO2 emissions associated with lime production and application 111 .…”

“…One family of methods centres on enhancing natural biogeochemical processes. These techniques also have positive environmental impacts 3,4,[7][8][9] , and could (partly) pay for themselves by increasing natural capital and agricultural productivity 6 . Examples include (1) boosting the growth and standing carbon stock in plants in cropping and pasture systems through cover-and inter-cropping (e.g., agroforestry); (2) reestablishing and/or enhancing soil organic carbon (SOC) stocks 10 ; (3) production of biochar, which is plant biomass transformed at elevated temperatures under oxygen-limited conditions (pyrolysis) into a recalcitrant form that withstands decomposition for many decades/centuries to possibly even millennia 11 ; and (4) increasing the inorganic carbon sink in soils via Mg and Ca silicate weathering by working finely ground rock (basalt) into soils 12 .…”