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

In the paper

“Rock grinding to reduce particle size and maximise CDR is the primary energy consuming operation in ERW 22,23,73 .”

What the sources say

• Supported

  The Techno-economic assessment (section 4) says mining and crushing have negligibly small energy demands compared with grinding, whose electricity demand rises sharply as target grain size falls. The Introduction (section 1) also links grain-size reduction to greater weathering and CDR potential. Our copy does not provide page numbers for these passages. (LLM, conf=0.89)

  cites [22] Strefler, J. et al. Potential and costs of carbon dioxide removal by enhanced weathering of rocks. Environ. Res. Lett. 13, 034010 (2018). source
• Supported

  Section 3.4 says enhanced weathering grinds rock to increase reactive surface area and reports that the energy demand of rock grinding creates the largest CO₂ penalty and costs. Together, these support the claim that grinding for improved carbon removal is the primary energy-consuming operation. (LLM, conf=0.94)

  cites [23] Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018). source
• Supported

  The Material comminution section (lines 145–154) says that reducing rock to finer particles requires grinding and estimates its energy use at 0.6–2.0 GJ per tonne. It describes crushing as requiring minimal energy; the Material extraction section (lines 140–143) likewise describes extraction and application as requiring minimal energy. This supports grinding as the primary energy-consuming processing operation discussed. (LLM, conf=0.88)

  cites [73] Moosdorf, N., Renforth, P. & Hartmann, J. Carbon dioxide efficiency of terrestrial weathering. Environ. Sci. Technol. 48, 4809–4816 (2014). source

In the paper

“China, India, the United States and Brazil have large potential to help achieve average global CDR targets of 0.5 to 2 Gt CO2 yr -1 with extraction costs of ~$80-180 t -1 CO2.”

In the paper

“China, India, the United States and Brazil have large potential to help achieve average global CDR targets of 0.5 to 2 Gt CO2 yr -1 with extraction costs of ~$80-180 t -1 CO2.”

In the paper

“Overall, we find the three top ranked countries with the highest CDR potential are coincidentally the highest fossil fuel CO2 emitters (China, USA and India) 6 (Figure 1).”

What the sources say

• Not checked yetcites [6] Le Quéré, C. et al. Global carbon budget 2018. Earth Syst. Sci. Data 10, 2141–2194 (2018).

In the paper

“In Europe, ERW could aid significant decarbonisation of France and Spain (up to approximately 40%), and to a lesser extent Poland, Italy and Germany (all ~10%) (Figure 2).”

In the paper

“In the context of our CDR targets, ERW has a similar potential to that of other CDR strategies 23 estimated for 2050, including bio-energy with carbon capture and storage (BECCS), widely adopted in IPCC future scenarios (0.5-5 Gt CO2 yr -1 ), direct air carbon capture and storage (DAC) (0.5-5 Gt CO2 yr -1 ), biochar (0.5 to 2 Gt CO2 yr -1 ), soil organic carbon (SOC) sequestration (0.5-5 Gt CO2 yr”

What the sources say

• Not checked yetcites [23] Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018). source

In the paper

“For example, our ERW CDR range is comparable with large-scale implementation of BECCS in USA by 2040 (0.3-0.6 Gt CO2 yr -1 ), as constrained by biomass productivity, location and capacity of CO2 storage sites 24 .”

What the sources say

• Not checked yetcites [24] Baik, E. et al. Geospatial analysis of near-term potential for carbon-negative bioenergy in the United States. Proc. Natl Acad. Sci. USA 115, 3290–3295 (2018). source

In the paper

“Results show that China may be able to augment its pledged 2030 NDCs by ~5-10%, with similar gains for the USA, which has opted-out of the Paris agreement.”

In the paper

“the top three European countries with highest CDR potential are also the largest European emitters of CO2 from fossil fuels (Germany, Spain and Poland) 6 .”

What the sources say

• Not checked yetcites [6] Le Quéré, C. et al. Global carbon budget 2018. Earth Syst. Sci. Data 10, 2141–2194 (2018).

In the paper

“Results show that China may be able to augment its pledged 2030 NDCs by ~5-10%, with similar gains for the USA, which has opted-out of the Paris agreement.”

In the paper

“For India, the gain rises to 40% of its current pledged emissions, and Brazil may be able to offset 100% of its pledged 2030 CO2 emissions plus some fraction of those from other countries (Figure 2).”

In the paper

“Other countries outside Europe considered in our analysis (Indonesia, Canada, Mexico) may be able to augment their NDCs by up to 30% (Figure 2).”

In the paper

“Our geospatial analyses define a new technical potential CDR range for those nations with high capacity for ERW deployment on cropland (Figure 1; SI figs.S13-S15).”

In the paper

“China is the exception because its large increase in low carbon energy usage projected under the 2°C scenario 5 allows net CDR to rise by substantially reducing secondary CO2 emissions from logistical operations (Figure 1).”

What the sources say

• Not checked yetcites [5] Mercure, J.-F. et al. Macroeconomic impact of stranded fossil fuel assests. Nat. Clim. Chang. 8, 588–593 (2018). source

In the paper

“Overall trends in national CDR curves are relatively insensitive to the choice of energy scenario.”

In the paper

“These targets and costs are robust regardless of future energy policies.”

In the paper

“Our ERW scenarios (Table 1) correspond to an aggregate CDR of 25-100 Gt CO2 if sustained over 5 decades.”

In the paper

“The top five European nations with the highest net CDR potential could offset 30% of the EU27's current emissions”

What the sources say

• Not checked yetcites [6] Le Quéré, C. et al. Global carbon budget 2018. Earth Syst. Sci. Data 10, 2141–2194 (2018).

In the paper

“Costs per t CO2 removed are generally within this projected carbon price range in all nations, but unit costs increase when cropland area exceeds the optimal fraction, because the efficiency of weathering and CDR falls (Figure 3; Table 1).”

In the paper

“In Europe, ERW could aid significant decarbonisation of France and Spain (up to approximately 40%), and to a lesser extent Poland, Italy and Germany (all ~10%) (Figure 2).”

In the paper

“Average costs in USA ($160-180 t -1 CO2), Canada and European nations ($160-190 t -1 CO2) are almost 50% higher than those in China, India, Mexico, Indonesia, and Brazil ($55-120 t -1 CO2).”

In the paper

“Costs per t CO2 removed are generally within this projected carbon price range in all nations, but unit costs increase when cropland area exceeds the optimal fraction, because the efficiency of weathering and CDR falls (Figure 3; Table 1).”

In the paper

“Costs fall substantially for citizens in Brazil ($300), Indonesia ($103) and India ($135) (Table 1).”

In the paper

“National demand for crushed silicate rock is contingent on extent of ERW deployment (Extended Data Fig. 5).”

In the paper

“Our analysis identifies engineering challenges if ERW were to be scaled-up to help meet ambitious CDR targets as part of a wider portfolio of options 1,7,11,12 .”

What the sources say

• Not checked yetcites [1] Intergovernmental Panel on Climate Change (IPCC). Global Warming Of 1.5 °C. An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways (World Meteorological Organization, 2018).
• Not checked yetcites [7] United Nations Environment Programme The Emissions Gap Report 2018 (United Nations Environment Programme, 2018).
• Not checked yetcites [11] The Royal Society Greenhouse Gas Removal Technologies (The Royal Society, 2018).
• Not checked yetcites [12] Pacala, S. et al. Negative Emissions Technologies And Reliable Sequestration (National Academy of Sciences, 2018).

In the paper

“We calculate ƞ for average ocean temperature (17 °C), salinity (35%) and an RCP8.5 2050 dissolved pCO2 of 600 µatm, giving ƞ = 0.86, i.e., 0.86 mole of CO2 removal per mole of monovalent cation and 1.72 mol of CO2 removed per mol of divalent cation added to the oceans 20 .”

• Also stated in: § 2.1 Carbon dioxide removal. · plain

  “We calculate ƞ for average ocean temperature (17 °C), salinity (35%) and an RCP8.5 2050 dissolved pCO2 of 600 µatm, giving ƞ = 0.86, i.e., 0.86 mole of CO2 removal per mole of monovalent cation and 1.72 mol of CO2 removed per mol of divalent cation added to the oceans 23 .”

What the sources say

• Not checked yetcites [20] Smith, P. et al. Land-based options for greenhouse gas removal and their impacts on ecosystem services and the sustainable development goals. Annu. Rev. Environ. Res. 44, 255–286 (2019). source
• Not checked yetcites [23] Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018). source

In the paper

“We demonstrate with this approach that the simplified mass transfer inhibition term in equations 1-3 successfully described the same kinetic behaviour calculated by the RTM (Figs.S10-S12).”

In the paper

“For the basalts we considered, and under the soil conditions simulated, labradorite was the only mineral constituent that exhibited notable chemical inhibition.”

In the paper

“Allowing formation of either secondary clay mineral accelerated dissolution of basaltic minerals through suppression of Al ion activity in solution resulting in less kinetic inhibition of the dissolution reactions (Fig. S8, S9).”

In the paper

“These results show that when affinity effects for primary minerals are neglected, that secondary mineral accumulation is more rapid.”

• Also stated in: § Capital · plain

  “These results show that when affinity effects for primary minerals are neglected, that secondary mineral accumulation is more rapid.”

In the paper

“Uncertainty in net CDR increases as ERW deploys onto croplands occupying a wider range of environmental conditions.”

In the paper

“This is greatest during the first 100 days, especially under a low flow rate (200 mm yr -1 top panels) because there is little dilution of the weathered products, resulting in higher pore water concentrations exerting a stronger affinity effect.”

In the paper

“Under the 2°C energy policy scenario, (c) and (d), secondary CO2 emisssion generally drop for most nations as they transition to low carbon energy sources in 2050 and implement negative emissions.”

In the paper

“Comparison shows the close similarities between the simulated changes in pH, alkalinity flux (Ca 2+ + Mg 2+ + Na + + K + ), formation of pedogenic carbonate (CaCO3) and efficiency of CO2 removal (RCO2) for the reactive transport model ('RTM') and the performance model ('simple').”

In the paper

“Curves are the same irrespective of energy policy scenario.”

In the paper

“The results show close correspondence between models across all three flow regimes.”

In the paper

“Agreement between modelling approaches holds across a wide range of flows.”

In the paper

“Under the 2°C scenario, low carbon energy production used for rock ginding allows a simulated reduction in p80s for the same cropland fractional area.”

In the paper

“Only labradorite (green line) in these basalts exhibits noticeable effects.”

In the paper

“We show close correspondence between the results of the RTM with full chemical speciation and our simplified performance model for the weathering of either type of basalt (tholeiitic and alkaline) being considered (Figs S10, S11).”

In the paper

“As a result, the two approaches (RTM and performance model), give similar patterns of alkalinity release, pedogenic carbonate formation and CO2 removal (Fig. S12) to underpin our modelling approach.”

In the paper

“Kfeldspar also exerts a minor affinity effect but is present in such low concentrations that its influence on the basalt-porewater system can be considered to be negligible.”

In the paper

“Even the most ambitious emission phase-outs 9,10 fail to achieve the United Nations Framework Convention on Climate Change Paris Agreement targets for limiting global warming without the help of massive atmospheric Carbon Dioxide Removal (CDR).”

What the sources say

• Not checked yetcites [9] Hansen, J. et al. Young people’s burden: requirement of negative CO2 emissions. Earth Syst. Dyn 8, 577–616 (2017). source
• Not checked yetcites [10] Rockström, J. et al. A roadmap for rapid decarbonisation. Science 355, 1269–1271 (2017). source

In the paper

“Depending on soil type, atmospheric CO2-derived dissolved inorganic carbon may also be sequestered through the formation of soil carbonate minerals, which reduces the efficiency of carbon sequestration by ~50% 19 .”

What the sources say

• Not checked yetcites [19] Renforth, P. & Henderson, G. Assessing ocean alkalinity for carbon sequestration. Rev. Geophys. 55, 636–674 (2017). source

In the paper

“Co-deployment of ERW and SOC sequestration at large-scale might, therefore, contribute substantially to the 5 Gt CO2 yr -1 carbon removal target suggested in decarbonization scenarios 10 for 2050.”

What the sources say

• Not checked yetcites [10] Rockström, J. et al. A roadmap for rapid decarbonisation. Science 355, 1269–1271 (2017). source

In the paper

“This would save up to 10% of the remaining cumulative carbon emission budget (~900 Gt CO2) that gives a likely chance of limiting global warming to less than 2°C above the pre-industrial average surface temperature 10 .”

What the sources say

• Not checked yetcites [10] Rockström, J. et al. A roadmap for rapid decarbonisation. Science 355, 1269–1271 (2017). source

In the paper

“Compatibility of ERW and SOC sequestration may be realistic given that amendment of acidic organic-rich soils with silicate minerals, and resultant pH increase, had no effect on respiratory CO2 fluxes 28,29 , contrary to concerns that increased soil pH may accelerate organic matter decomposition 30 .”

What the sources say

• Not checked yetcites [28] Groffman, P. M. et al. Calcium additions and microbial nitrogen cycle processes in a northern hardwood forest. Ecosystems 9, 1289–1305 (2006). source
• Not checked yetcites [29] Dietzen, C., Harrison, R. & Michelsen-Correa, S. Effectiveness of enhanced mineral weathering as a carbon sequestration tool and alternative to agricultural lime: an incubation experiment. Int. J. Greenhouse Gas Control 74, 251–258 (2018). source
• Not checked yetcites [30] Smith, P., Haszeldine, R. S. & Smith, S. M. Preliminary assessment of the potential for, and limitations to, terrestrial negative emissions technologies in the UK. Environ. Sci. Process. Impacts 18, 1400–1405 (2016). source

In the paper

“These weathering products are transported via land surface runoff to the oceans with a storage lifetime exceeding 100,000 years 19 .”

What the sources say

• Not checked yetcites [19] Renforth, P. & Henderson, G. Assessing ocean alkalinity for carbon sequestration. Rev. Geophys. 55, 636–674 (2017). source

In the paper

“Extraction goals 1,7,9,10 later this century in most studies are on the order of at least 10 Gt CO2 yr -1”

What the sources say

• Not checked yetcites [1] Intergovernmental Panel on Climate Change (IPCC). Global Warming Of 1.5 °C. An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways (World Meteorological Organization, 2018).
• Not checked yetcites [7] United Nations Environment Programme The Emissions Gap Report 2018 (United Nations Environment Programme, 2018).
• Not checked yetcites [9] Hansen, J. et al. Young people’s burden: requirement of negative CO2 emissions. Earth Syst. Dyn 8, 577–616 (2017). source
• Not checked yetcites [10] Rockström, J. et al. A roadmap for rapid decarbonisation. Science 355, 1269–1271 (2017). source

In the paper

“Co-deployment of ERW with feedstock crops for BECCS and biochar could enhance the feasibility and carbon sequestration potential of these strategies 4,26 .”

What the sources say

• Not checked yetcites [4] Beerling, D. J. et al. Farming with crops and rocks to address global climate, food and soil security. Nat. Plants 4, 138–147 (2018). source
• Not checked yetcites [26] Amann, T. & Hartmann, J. Ideas and perspectives: synergies from co-deployment of negative emissions technologies. Biogeosciences 16, 2949–2960 (2019). source

In the paper

“Logistical infrastructure to apply basaltic rock dust to managed croplands already exists due to the common need to apply crushed limestone to reverse soil acidification from intensive cropping [2][3][4] .”

What the sources say

• Not checked yetcites [2][3][4]

In the paper

“More broadly, innovative ERW practices via soil amendments with targeted silicate minerals could help rebuild rapidly deteriorating agricultural soils on which over six billion people depend directly for food 48 .”

What the sources say

• Not checked yetcites [48] United Nations Global Land Outlook 1st edn (United Nations Convention to Combat Desertification, 2017).

In the paper

“Intensification of food production across 24 million hectares of productive agricultural land in South Asia and China, for example, is creating acidified, desilicated soils exhausted in plant nutrients (potassium, zinc and available phosphorus) that limit yields 45 .”

What the sources say

• Not checked yetcites [45] Savant, N. K., Datnoff, L. E. & Snyder, G. H. Depletion of plant-available silicon in soils: a possible cause of declining rice yields. Commun. Soil Sci. Plant Anal. 28, 1245–1252 (1997). source

In the paper

“ERW cannot offset all fossil fuel emissions, but using its cost as a guide, the per capita annual cost of achieving zero net emissions, a goal for decarbonisation, would be highest for Canada ($3004), the USA ($2780), China ($832) and EU28 nations ($1288).”

In the paper

“It would make ERW an economically attractive option for fastgrowing nations, such as India, China, Indonesia, Brazil and Mexico given their estimated CO2 extraction costs of ~ $75-100 t -1 CO2 (Figure 3).”

In the paper

“A carbon price of $100-150 t -1 CO2 would cover most of the ERW costs for the key nations reported here.”

In the paper

“Requirement for mining may be further reduced by utilizing artificial silicate by-products from industrial processes 37,38 , including calcium-rich silicates produced by iron and steel manufacturing (slags) with a long history of agricultural usage 4,39 .”

What the sources say

• Not checked yetcites [37] Renforth, P. et al. Silicate production and availability for mineral carbonation. Environ. Sci. Technol. 45, 2035–2041 (2011). source
• Not checked yetcites [38] Renforth, P. The negative emission potential of alkaline materials. Nat. Commun. 10, 1401 (2019). source
• Not checked yetcites [4] Beerling, D. J. et al. Farming with crops and rocks to address global climate, food and soil security. Nat. Plants 4, 138–147 (2018). source
• Not checked yetcites [39] Tubana, B. S., Babu, T. & Datnoff, L. E. A review of silicon in soils and plants and its role in US agriculture: history and future perspectives. Soil Sci. 181, 393–411 (2016). source

In the paper

“ERW may therefore also have a role in remediation of toxic metal contaminated soils and sediments across 20 million hectares of cultivated land in southern China and elsewhere 47 .”

What the sources say

• Not checked yetcites [47] Chen, J. Rapid urbanization in China: a real challenge to soil protection and food security. Catena 69, 1–15 (2007). source

In the paper

“Undertaking ERW practices with these materials addresses a critical need to fertilise soils with silica and other nutrients lost by harvesting that gradually depletes plant-available pools 39 .”

What the sources say

• Not checked yetcites [39] Tubana, B. S., Babu, T. & Datnoff, L. E. A review of silicon in soils and plants and its role in US agriculture: history and future perspectives. Soil Sci. 181, 393–411 (2016). source

In the paper

“ERW, therefore, has a role to play in compensating for residual carbon emissions from sectors recognized as being difficult to decarbonize, e.g., transportation by aviation, shipping, and agriculture 1,11 .”

What the sources say

• Not checked yetcites [1] Intergovernmental Panel on Climate Change (IPCC). Global Warming Of 1.5 °C. An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways (World Meteorological Organization, 2018).
• Not checked yetcites [11] The Royal Society Greenhouse Gas Removal Technologies (The Royal Society, 2018).

In the paper

“Net cost of ERW may be lower if rock dust is used as a fertilizer in organic agriculture, which currently occupies 57.8 million hectares, because it adds economic value by improving soil health, fertility and ecosystem services 35 .”

What the sources say

• Not checked yetcites [35] Crowder, D. W. & Reganold, J. P. Financial competitiveness of organic agriculture on a global scale. Proc. Natl Acad. Sci. USA 112, 7611–7616 (2015). source

In the paper

“Afforestation/reforestation and practices that increase soil carbon in natural ecosystems, including wetland restoration, have lower estimated costs (<$100 t -1 CO2) 23 .”

What the sources say

• Not checked yetcites [23] Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018). source

In the paper

“Carbon price is forecast by the World Bank 11 to reach $100-150 t -1 CO2 by 2050.”

What the sources say

• Not checked yetcites [11] The Royal Society Greenhouse Gas Removal Technologies (The Royal Society, 2018).

In the paper

“The difference largely reflects labour, diesel and electricity costs.”

In the paper

“Costs per t CO2 removed are generally within this projected carbon price range in all nations, but unit costs increase when cropland area exceeds the optimal fraction, because the efficiency of weathering and CDR falls (Figure 3; Table 1).”

In the paper

“Thus, bulk silicate production of these two nations could meet the demand for ERW with large CDR potential (Table 1).”

In the paper

“The reaction rate of a mineral undergoing dissolution in soil is governed by the law of kinetic mass action and is proportional to the moles of reactive sites on the mineral surface in contact with the reacting aqueous solution 14 .”

What the sources say

• Not checked yetcites [14] Schuiling, R. D. & Krijgsman, P. Enhanced weathering: an effective and cheap tool to sequester CO2. Clim. Change 74, 349–354 (2006). source

In the paper

“Monovalent and divalent base cations are released from basaltic minerals by dissolution based on stoichiometry (SI Table S2).”

• Also stated in: § 2.1 Carbon dioxide removal. · plain

  “Monovalent and divalent base cations are released from basaltic minerals by dissolution based on stoichiometry (Table S2).”

What the sources say

• Not checked yetcites SI Table S2
• Not checked yetcites Table S2

In the paper

“Together with the chemical affinity effects accounted for in our model, we constrain some of the systematic errors embedded in prior ERW assessments [15][16][17]21,22 .”

What the sources say

• Not checked yetcites [15][16][17]21,22

In the paper

“This version of the model (equation 7) is well-validated against flask-dissolution experiments (Fig. S3).”

In the paper

“SSP2 potentially represents the largest material production pathway, as other SSPs forecast lower consumption or economic growth producing 30-50% less material globally.”

• Also stated in: § 2.4 Forecasting bulk silicate waste production. · hedged

  “SSP2 potentially represents the largest material production pathway, as other SSPs forecast lower consumption or economic growth producing 30-50% less material globally.”

What the sources say

• Not checked yetcites [40] Washbourne, C.-L. et al. Rapid removal of atmospheric CO2 in urban soils. Environ. Sci. Technol. 49, 5434–5440 (2015). source

In the paper

“Deployment of any CDR strategy is inhibited by concern that it may erode society's perception of the climate threat and the urgency of mitigation measures 54 .”

What the sources say

• Not checked yetcites [54] Cox, E., Pidgeon, N. F., Spence, E. M. & Thomas, G. Blurred lines: the ethics and policy of greenhouse gas removal at scale. Front. Environ. Sci. https://doi.org/10.3389/fenvs.2018.00038 (2018). source

In the paper

“However, ocean carbonate chemistry reduces the efficiency of CO2 removal (ƞ) to an extent depending on ocean temperature, salinity and the surface ocean dissolved CO2 concentration.”

• Also stated in: § 2.1 Carbon dioxide removal. · plain

  “However, ocean carbonate chemistry reduces the efficiency of CO2 removal (ƞ) to an extent depending on ocean temperature, salinity and the surface ocean dissolved CO2 concentration.”

What the sources say

• Not checked yetcites [23] Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018). source

In the paper

“Our approach improves on prior analyses, which assumed a fixed radius between rock dust source and site of application 73 .”

What the sources say

• Not checked yetcites [73] Moosdorf, N., Renforth, P. & Hartmann, J. Carbon dioxide efficiency of terrestrial weathering. Environ. Sci. Technol. 48, 4809–4816 (2014). source

In the paper

“Extrapolation of laboratory weathering rates to the field scale is a recognized potential source of uncertainty in calculated CDR rates by ERW [2][3][4][22][23][24] .”

What the sources say

• Not checked yetcites [2][3][4][22][23][24]

In the paper

“Our analysis thus represents the first technoeconomic assessment in which detailed ERW carbon and economic costs vary within and between nations and account for socio-technical uncertainties in energy production.”

In the paper

“The measured SSA of a granular material is typically much higher than estimates of the surface area by geometric models of particle shapes, due to surface topography and porosity effects 15 .”

What the sources say

• Not checked yetcites [15] Kohler, P., Hartmann, J. & Wolf-Gladrow, D. A. Geoengineering potential of artificially enhanced silicate weathering of olivine. Proc. Natl Acad. Sci. USA 107, 20228–20233 (2010). source

In the paper

“This conceptualisation improves on the simplified case of a single mean particle diameter, previously used in ERW calculations [16][17][18]22,23 .”

What the sources say

• Not checked yetcites [16][17][18]22,23

In the paper

“Using this modelling framework, we analysed a baseline application rate of 40 t ha -1 yr -1 (equivalent to a <2 mm layer of rock powder distributed on croplands), which falls within the range of basalt amendments shown to improve crop production in field trials 4 .”

What the sources say

• Not checked yetcites [4] Beerling, D. J. et al. Farming with crops and rocks to address global climate, food and soil security. Nat. Plants 4, 138–147 (2018). source

In the paper

“CDR, via pathway 1, potentially sequesters two moles of CO2 from the atmosphere per mole of divalent cation.”

• Also stated in: § 2.1 Carbon dioxide removal. · hedged

  “CDR, via pathway 1, potentially sequesters two moles of CO2 from the atmosphere per mole of divalent cation.”

In the paper

“Industrialized nations (e.g., Canada) consume up to ~2% of their total energy production on rock comminution (crushing and grinding) processes 77 .”

What the sources say

• Not checked yetcites [77] Tromans, D. Mineral comminution: energy efficiency considerations. Min. Eng. 21, 613–620 (2008). source

In the paper

“Between 2006-2014, 185 kg of blast furnace slag and 117 kg of steel slag was produced for every tonne of crude steel 87 .”

• Also stated in: § 2.4 Forecasting bulk silicate waste production. · plain

  “Between 2006-2014, 185 kg of blast furnace slag and 117 kg of steel slag was produced for every tonne of crude steel 42 .”

What the sources say

• Not checked yetcites [87] U.S. Geological Survey. Mineral Commodity Summaries 2006 (US Geological Survey, 2006).
• Not checked yetcites [42] Haynes, R. J., Belyaeva, O. N. & Kingston, G. Evaluation of industrial waste sources of fertilizer silicon using chemical extractions and plant uptake. J. Plant Nutr. Soil Sci. 176, 238–248 (2013). source

In the paper

“Current state-of-knowledge 52 precludes a detailed treatment of the role of surface passivation by formation of amorphous silica-rich surfaces for basalt grains added to agricultural soils.”

What the sources say

• Not checked yetcites [52] Daval, D., Calvarusa, C., Guyut, F. & Turpault, M.-P. Time-dependent feldspar dissolution rates resulting from surface passivation: experimental evidence and geochemical implications. Earth Planet. Sci. Lett. 498, 226–236 (2018). source

In the paper

“However, mechanical comminution produces an approximately log-normal psd 16 that varies with different grinding and milling technologies.”

What the sources say

• Not checked yetcites [16] Hartmann, J. et al. Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification. Rev. Geophys. 51, 113–149 (2013). source

In the paper

“Even without separating out cement waste from other materials 59 , very little of the leachate contained elemental concentrations above typical water quality standard ranges [60][61][62] .”

What the sources say

• Not checked yetcites [59] Siebert, S. & Doll, P. Quantifying blue and green virtual water contents in global crop production as well as potential production losses without irrigation. J. Hydrol. 384, 198–217 (2010). source
• Not checked yetcites [60][61][62]

In the paper

“For the USA, mining cost is 6.99 $ t -1 as obtained from prior analysis 22 .”

What the sources say

• Not checked yetcites [22] Strefler, J. et al. Potential and costs of carbon dioxide removal by enhanced weathering of rocks. Environ. Res. Lett. 13, 034010 (2018). source

In the paper

“Industrialized nations (e.g., Canada) consume up to ~2% of their total energy production on rock comminution (crushing and grinding) processes 36 .”

What the sources say

• Not checked yetcites [36] Bebbington, A. J. & Bury, J. T. Institutional challenges for mining and sustainability in Peru. Proc. Natl Acad. Sci. USA 106, 17296–17301 (2009). source

In the paper

“These results suggest that our approach, which does not explicitly account for the effects of secondary clay minerals on acceleration of primary mineral dissolution, is conservative with respect to calculating basalt dissolution.”

In the paper

“Results indicate allowing kaolinite formation accelerates dissolution of labradorite (dashed vs solid green lines) and augite (dashed vs solid red lines) through suppression of Al ion activity in solution resulting in less kinetic inhibition of the dissolution reactions.”

In the paper

“Results indicate allowing montmorillonite formation accelerates dissolution of labradorite (dashed vs solid green lines) and augite (dashed vs solid red lines) through suppression of Al ion activity in solution resulting in less kinetic inhibition of the dissolution reactions.”

In the paper

“Although the number of grid cells to be optimized is reduced by orders of magnitude during the classification, the approximation proved robust with small error and bias when tested at low resolution due to small intra-class variability.”