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Fisher, J. (2023) Can ‘enhanced rock weathering’ help combat climate change? [Illustration]. Available at: https://www.bbc.com/news/science-environment-65648361 (Accessed: 05 April 2024)

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Enhanced weathering (EW) involves the acceleration of the natural carbon sequestration process through the chemical weathering of silicate rocks (Lewis et al., 2021).

Click here for a project on enhanced weathering in the UK

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Tropical zones are seen in dark blue along the Equator. Source: https://www.metoffice.gov.uk/weather/climate/climate-explained/climate-zones (Accessed: 11 April 2024)

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This study has explored the rate of EW in temperate climate zones like the United Kingdom. However, I hope to compare the carbon sink potential ranges of EW in the UK to CDR data from tropical regions such as Brazil.

Silicate weathering rates depend on:

temperature

run-off

rate of physical erosion

Though silicate rock weathering should theoretically be accelerated by warm, humid tropical circumstances, lowland tropical habitats are typically characterized by thick, mature soils that experience minimal physical disturbance, meaning that natural rates are frequently quite low.

As a result, in contrast to other temperate zones where kinetics largely determine the speed of silicate weathering, the availability of new mineral surfaces in the tropics limits the rate of natural rock weathering.

(Edwards et al., 2017)

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Map of the United Kingdom (UK) Source: https://ontheworldmap.com/uk/ (Accessed: 29 March 2024)

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"An Act to set a target for the year 2050 for the reduction of targeted greenhouse gas emissions; to provide for a system of carbon budgeting; to establish a Committee on Climate Change; to confer powers to establish trading schemes for the purpose of limiting greenhouse gas emissions or encouraging activities that reduce such emissions or remove greenhouse gas from the atmosphere; to make provision about adaptation to climate change; to confer powers to make schemes for providing financial incentives to produce less domestic waste and to recycle more of what is produced; to make provision about the collection of household waste; to confer powers to make provision about charging for single use carrier bags; to amend the provisions of the Energy Act 2004 about renewable transport fuel obligations; to make provision about carbon emissions reduction targets; to make other provision about climate change; and for connected purposes."

Click here

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Legislation is available in different versions:

Latest Available (revised): The latest available updated version of the legislation incorporating changes made by subsequent legislation and applied by our editorial team. Changes we have not yet applied to the text, can be found in the 'Changes to Legislation' area.

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An Act to set a target for the year 2050 for the reduction of targeted greenhouse gas emissions; to provide for a system of carbon budgeting; to establish a Committee on Climate Change; to confer powers to establish trading schemes for the purpose of limiting greenhouse gas emissions or encouraging

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Abdalqadir et al. (2024) A state of the art of review on factors affecting the enhanced weathering in agricultural soil: strategies for carbon sequestration and climate mitigation [Figure]. Available at: https://link.springer.com/article/10.1007/s11356-024-32498-5#Sec3 (Accessed: 04 April 2024)

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Methodology for quantification and verification of carbon dioxide removal (MRV)

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Methodology for quantification and verification of carbon dioxide removal (MRV)

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Link to the full paper here

The MRV process flowchart, which encompasses all phases from planning to acknowledgment, was developed based on previous articles to provide a thorough framework for assessing EW as a CDR technique.

Sites are chosen for EW application based on a comprehensive study of geological, climatic and soil conditions combined with a baseline evaluation of carbon stocks and soil characteristics in the initial “Pre-implementation” phase.

The "Implementation" phase comprises applying EW materials precisely to specific places and carefully documenting the application rates, procedures, and timing.

The “Monitoring” phase is crucial, involving analysis of soil and water for changes in alkalinity, electrical conductivity, and other indicators of carbon sequestration. It also includes measuring greenhouse gas flux and utilizing remote sensing to assess broader impacts. Innovative and cost-effective monitoring proxies, such as electrical conductivity and volumetric water content, are utilized as well.

After gathering data, the "Reporting" stage compiles information into thorough reports that analyse environmental effects and sequestration rates. These reports are subsequently distributed to stakeholders. To ensure environmental integrity, verification is needed for confirmation of the reported data against that of established MRV protocols and validation of carbon sequestration claims.

To continue to improve EW practices, the MRV process concludes with “Feedback and Adjustment”. In “Certification and Recognition”, a successful CDR is recognised by issuing carbon credits or certifications that justify the contribution made to mitigate climate change.

This systematic approach to MRV emphasises the precision and detail required in the documentation and verification of effectiveness of EW as a CDR technique. The creation of effective MRV frameworks for EW require the integration of policy, scientific methodologies and innovative measurement techniques. Significant challenges include the need for scalable and fair verification procedures, methodological uncertainties, and variability in carbon sequestration efficacy. On-going research and cutting-edge methodologies aim to address these challenges which demonstrate MRV's potential to accurately assess EW project outcomes and guarantee transparency, comparability, and credibility in CDR claims associated with EW endeavours (Abdalqadir et al., 2024).

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Enhanced Rock Weathering for Carbon Capture | CO2 removal

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Climate Science (2024) Enhanced Weathering: Making Rocks Weather Faster to Undo Climate Change [Illustration]. Available at: https://climatescience.org/advanced-enhanced-weathering (Accessed: 04 April 2024)

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In the process of chemical weathering, atmospheric carbon dioxide (CO2) dissolves in rainfall to produce weak carbonic acid (H2CO3), which dissolves the finely ground basalt and releases bicarbonate ions and other solutes like calcium and magnesium.

Water from precipitation runoff or groundwater finally transports the dissolved calcium and bicarbonate ions into rivers and the ocean. Due to the higher pH and lower CO2 content in seawater, the bicarbonate ion is permanently locked up in solid calcium carbonate (CaCO3), which is formed by the interaction of the bicarbonate ion with calcium ions already present in seawater. On the ocean floor, these freshly created calcium carbonate minerals precipitate and settle as sediments.

Sedimentary rocks, such as chalk, limestone, and dolomite, can be created when these sediments are compressed and cemented over time (Lewis et al., 2021).

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This project investigates enhanced weathering (EW) as a potential carbon dioxide removal (CDR) strategy and illustrate its effects on land management, agriculture approaches and soil carbon sequestration.

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McDermott, F. (2024) 'Weathering' [Lecture], GEOL30340: Weathering. University College Dublin. 11 April.

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Improved productivity and reduced agricultural CO2 emissions

Silicate rocks contain phosphorous (P), magnesium (Mg), potassium (K) and calcium (Ca) which are limiting nutrients for plant growth, thus their release due to the dissolution of silicate rocks via EW can lead to the fertilisation of crops. Regions with heavily weathered tropical soils such as Brazil or Africa have a history of using ground silicate rocks to enhance soil quality and boost crop productivity. For example, the addition of basalt to cocoa plants has led to an increased level of nutrients such as K, Mg, Ca compared to untreated plants. This application of basalt often lead to the treated plants being 50 percent taller and 60 percent thicker-stemmed than untreated plants after 2 years. In some regions such as Mauritius, the application of basalt was often used in combination with standard nitrogen (N), P, K fertiliser treatments which results in a yield increase of 29 percent over five successive crops and only 17 percent over three successive crops in separate replicated trials compared to plots receiving only basalt, indicating a positive correlation between basalt and fertiliser.

EW allows for the absorption of silica in the form of silicic acid for major tropical crops such as rice, oil palm, sugar cane, maize and sorghum. Through the mechanical strengthening of cell walls (via silicon deposition in tissues) and the priming of defence systems, silica absorption in these crops boosts resistance to important pests and diseases. By lowering leaf transpiration rates, silicon can increase water-use efficiency and possibly increase crop resistance to drought. Consequently, employing silicate rocks for EW might lower the need for pesticides and their related expenses while also enhancing food security in areas vulnerable to drought.

The application of crushed basalt can raise pH levels in highly weathered tropical soils, aiding in mitigating soil acidification in agricultural areas more broadly and addressing production challenges in crops grown on acidic soils (e.g., heavy metal toxicity in plants, as seen in oil palm cultivation on drained peatlands in Southeast Asia). The impact of EW on soil pH aligns with that of liming agricultural soils to counter acidification. Substituting silicate EW for lime application helps reduce CO2 emissions associated with lime's reaction with soil water and its production.

Land sparing

Deforestation is causing tropical agricultural areas to continue expanding rapidly. Silicate rock application, however, may lessen the need for new agricultural land if crop yields rise. This might lead to reduced deforestation and/or greater natural forest recovery on abandoned marginal farms. Land and greenhouse gas emissions were reduced during the Green Revolution in Asia and Latin America, indicating that higher yields brought about by EW may allow for even more land savings. Absence of effective market regulation and land planning, however, may cause perverse outcomes of higher-yielding, cheap tropical crops, including further deforestation.

Reduced risk of phytoplankton blooms in rivers and reefs

The ratios of silicon (Si) to nitrogen (N) and silicon (Si) to phosphorus (P) in runoff water determine the threat of eutrophication. When algal blooms are caused by high N and P but low Si, cultural eutrophication takes place. High Si: P and Si: N ratios in runoff from the erosion of silicate rocks are expected to result from their EW. This will raise the amount of diatoms in the water, limiting cultural eutrophication and promoting a variety of productive food webs. Along with the potential advantage of increased diatom production contributing to an increase in CO2 drawdown in the seas, this might also have a positive impact on heavily polluted riverine, reef, and marine ecosystems downstream of large tropical agricultural producing regions.

(Edwards et al., 2017)

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Strekeisen, A. (n.d.) Dunite (Dun Mountain) [Illustration]. Available at: https://www.alexstrekeisen.it/english/pluto/dun.php (Accessed: 05 April 2023)

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Past literature recommended the use of the fast-weathering dunite rock, which is mostly composed of the silicate mineral olivine. Dunite gets its distinctive green color from the mineral olivine. The mineral is most appropriate for weathering, but it also contains dangerous trace elements, nickel (Ni) and chromium (Cr), which may be released into the environment as it dissolves (Strefler et al., 2018).

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Dangers of Chromium (Cr) on human health

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Dangers of Chromium (Cr) on human health

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Humans need Cr(III), which is essential for the metabolism of fat, protein, and glucose.

Furthermore, it was found that the Cr(VI) form poses a health risk to humans, especially through acute and long-term inhalation exposures that exacerbate respiratory tract issues, the major target organ for toxicity.

(Prasad et al., 2021)

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Begum et al. (2022) A comprehensive review on the sources, essentiality and toxicological profile of nickel [Figure]. Available at: https://pubs.rsc.org/en/content/articlehtml/2022/ra/d2ra00378c (Accessed: 12 April 2024)

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Chronic exposure to nickel and nickel compounds can build up in the body and cause a number of harmful health effects in people, including lung fibrosis, renal, cardiovascular, and respiratory tract cancer.

(Genchi et al., 2020)

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The distinctive hexagonal rock formation of the Giant's Causeway seen above consists of basalt rock.

Mafic igneous rocks such as basalt are composed of abundant calcium and magnesium-rich silicate minerals widely proposed to be suitable for scalable carbon dioxide removal (CDR) by EW (Lewis et al., 2021).

Basalt is viewed as an alternative to dunite since it contains fewer harmful elements and may even function as fertilizer by supplying nutrients (such as calcium and magnesium) which are lacking in many tropical regions. Although it has a poorer weathering efficiency, the increase in plant biomass carbon caused by nutrient release can offset this (Strefler et al., 2018).

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Renforth, P. (2012) The potential of enhanced weathering in the UK [Figure]. Available at: https://www.sciencedirect.com/science/article/pii/S1750583612001466?via%3Dihub (Accessed: 04 April 2024)

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The distribution of natural silicate rock formations across the UK

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The distribution of natural silicate rock formations across the UK

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The economic viability of enhanced weathering hinges on the abundance of nearby basalt resources (Renforth, 2012).

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Beerling et al. (2018) Farming with crops and rocks to address global climate, food and soil security [Figure.]. Available at: https://www.nature.com/articles/s41477-018-0108-y (Accessed: 06 April 2024) 

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Enhanced weathering has been tested in laboratory settings and small-scale field trials (TRL 3-4); however, its scalability has not been proven yet (Beerling et al., 2018; Amann et al., 2020).

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Carbon Dioxide Removal (CDR) Strategies 

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Carbon Dioxide Removal (CDR) Strategies 

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A fact sheet from the IPCC's sixth assessment report in relation to land and ocean CDR strategies.

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Tropical rainforests are found near the Equator in a band between the Tropics of Capricorn and Cancer, which are shown on the map as dotted lines. Source: Encyclopædia Britannica, Inc. (Accessed 10 April 2024)

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Greenhouse gas emissions from grinding and transport

Depending on grain size, global analyses show that the energy expenditures (i.e., CO2 emissions) related to extracting, processing, and dispersing rock dust may reduce the effectiveness of EW's CO2 sequestration by 10 percent to 25 percent. However, as the globe moves toward more decarbonized energy sources, this cost should go down. NOx emissions would rise with more crushed rock being transported. This might cause ground-level ozone (O3) to rise to dangerous levels for plant and human health in 16 Mha of oil palm plantations, which are known to be major emitters of isoprene.

Yield quality

EW suggests the possibility that harmful substances found in certain silicate minerals might become accessible and reduce yields, or they could build up in the food chain and cause problems for human health. As was previously indicated, the breakdown of olivine may release nickel (Ni) and chromium (Cr), which might be troublesome in significant mines and in agriculture when these elements are present in minerals associated to asbestos. To prevent these unintentional negative effects, EW with basalt is favored instead; nevertheless, basalt is less efficient than olivine in capturing CO2 (around 0.3 tCO2 t−1 vs 0.8 tCO2 t−1 olivine). The lack of heavy metal toxicity and ancillary advantages of basalt for crop productivity, soil enhancement, and greenhouse gas emission reduction that are less likely to result from olivine would reduce the practical hurdles to adoption by farmers in tropical agroecosystems.

Biodiversity impacts within plantations and adjacent forest

Wildlife in tropical farmland provide essential ecosystem services such as pollination and pest control. The effect of the application of silicate is still unknown. In particular, increasing pH could negatively impact species adapted to low pH soils which are widespread, especially peatland. Forest edges are first affected by environmental changes (e.g. increased wind, higher nutrient loads). The effect of crushed silicates on forest from farmland is still uncertain. If the consequences are negative, this would be a pressing issue given that 25% of the Amazon and Congo and 91% Brazilian Atlantic forest is within 1 km of farmland edge.

Reduced water quality in rivers and reefs

Reduced reproduction and recruitment in river fish populations may occur if unweathered silicates are carried into rivers, possibly during strong tropical rainstorms. This might lead to increased inorganic turbidity and sedimentation. Reef diversity and depth limit are reduced, coral death is caused by increased sediment loads, and inorganic turbidity. Therefore, there might be very detrimental effects on nearby fisheries and conservation efforts; however, these losses would have to be balanced against any advantages from less organic turbidity (i.e., lower eutrophication). Riverine plants and animals may also suffer from elevated pH levels in the water, particularly in naturally acidic drainage systems like peatlands.

Mining and infrastructural expansion

Although silicates are considered a waste product from mining and steel and iron production, the increase in demand of silicates for EW may require larger mines. For example, rock application to 670 Mha of tropical cropland at 10 t ha−1 yr−1 would require 6.7 Pg of rock per year, and at 50 t ha−1 yr−1 would need 33.5 Pg annually [5]. By comparison, global silicate production is 7-17 Pg [46] and global aggregate production is 40 Pg [47,48]. Mine creation is environmentally harmful, driving deforestation across the tropics and often occurring within or near to areas of high biodiversity value. Development and expansion of road and rail infrastructure for mining can increase access to biodiverse and remote ecosystems, which combined with employment opportunities, encourage population immigration, land clearing for agriculture and hunting.

(Edwards et al., 2017)

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Buckingham, F.L. and Henderson, G.M. (2024) The enhanced weathering potential of a range of silicate and carbonate additions in a UK agricultural soil [Table]. Available at: https://www.sciencedirect.com/science/article/pii/S0048969723063283 (Accessed: 10 April 2024)

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Carbon dioxide removal (CDR) potential of enhanced weathering in the UK

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Carbon dioxide removal (CDR) potential of enhanced weathering in the UK

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The table presents the carbon sequestration potential of six treatments (Agricultural Lime - AGL, Basalt, Cement Kiln Dust - CKD, Olivine, Steel slag, Volcanic ash). Among these, steel slag and CKD showed the highest effectiveness in capturing CO2 after a single application. This efficacy is attributed to the rapid dissolution of industrial silicates, leading to a high influx of Ca into the solution. Among the naturally occurring silicates studied, basalt exhibited the greatest efficiency in carbon consumption.

After taking into consideration the hydrological changes across the country and scaling up the CDR potential of basalt over UK agriculture, it is estimated that applying 50 t ha−1 of basalt for ten years may consume 1.8 ± 0.9 MtCO2 yr−1.

Buckingham, F.L. and Henderson, G.M. (2024)

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Kantzas et al. (2022) Substantial carbon drawdown potential from enhanced rock weathering in the United Kingdom [Figure]. Available at: https://www.nature.com/articles/s41561-022-00925-2#Abs1 (Accessed: 02 April 2024) 

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Net CDR by ERW deployed on UK arable croplands

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Net CDR by ERW deployed on UK arable croplands

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Simulating ERW implementation on arable lands across different basalt supply scenarios (S1 to S3) projected a removal of 6–30 MtCO2 yr−1 by 2050 (Fig. 1a–c). This accounts for up to 45% of the CO2 emissions removal necessary for achieving UK net-zero emissions, which requires approximately 58 MtCO2 yr−1 (balanced net-zero pathway engineered carbon removal requirement ~58 MtCO2 yr−1; range 45–112 MtCO2 yr−1).

The maximum CDR rates predicted by the model were primarily influenced by the geographic scope of ERW application, expanding with increased resource availability (Fig. 1a–c). Additionally, ongoing effects from previous years also played a significant role. CDR rates per unit area showed a continual increase over time due to successive annual applications of rock dust, even if the deployment land area remained constant.

(Kantzas et al., 2022)

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Buckingham et al. (2022) Soil core study indicates limited CO2 removal by enhanced weathering in dry croplands in the UK [Table]. Available at: https://www.sciencedirect.com/science/article/pii/S0883292722002864 (Accessed: 03 April 2024)

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Soil core study indicates limited CO2 removal by enhanced weathering in dry croplands in the UK

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Soil core study indicates limited CO2 removal by enhanced weathering in dry croplands in the UK

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The CDR rate determined from this observational study is 5 to 25 times slower than the rate estimated in Kantzas et al.'s detailed modeling study above (6–30 MtCO2 yr−1). Kantzas et al. (2022) considered lower basalt application rates (40 t ha−1 yr-1) but projected continuous addition over multiple years to achieve a stable annual CDR rate.

One significant factor contributing to the higher CDR potential in Kantzas et al. (2022) is likely the use of elevated water fluxes in their UK model (461–849 mm yr−1), which far exceed actual net water fluxes observed from river flow in agricultural regions.

Assuming a linear relationship between water flux and CDR potential, and increasing the flux above for all arable land accordingly, suggests 1.3 ± 0.1 MtCO2 yr−1 as a best estimate for the drawdown potential of EW in the UK when accounting for variation in hydrology.

(Buckingham et al., 2022)

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Abdalqadir et al. (2024) A state of the art of review on factors affecting the enhanced weathering in agricultural soil: strategies for carbon sequestration and climate mitigation [Figure]. Available at: https://link.springer.com/article/10.1007/s11356-024-32498-5#Sec3 (Accessed: 04 April 2024)

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Factors affecting EW rate in agricultural soil

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Factors affecting EW rate in agricultural soil

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The efficiency of EW in soil depends on several factors, including:

EW materials

particle size

application rate

soil properties

land management

weather and climate.

EW materials

EW materials, derived from natural silicate formations and industrial byproducts, are crucial for enhanced weathering (EW) strategies aimed at CO2 sequestration. These materials, ranging from acidic to basic compositions, are chosen based on cation richness, mineralogy, dissolution rates, trace elements, life cycle assessments, availability, and cost-effectiveness. Basalt, dunite, olivine, and wollastonite are notable EW materials due to their chemical compositions and mineralogical characteristics, influencing their effectiveness in capturing CO2.

Particle size

Smaller particles have larger surface areas, which accelerate weathering and CO₂ absorption rates. Research suggests that particles measuring between 10 to 20 µm in diameter work best for efficient weathering, with smaller particles demonstrating notably improved CO2 absorption rates. However, reducing particle sizes through comminution processes requires substantial energy.

Application rate

This rate varies based on the EW material used, CO2 removal goals, and the land area. Although the optimal application rates are still debated, higher rates generally lead to more significant CO2 sequestration per hectare due to increased reactive surface areas. However, this relationship is complex, as seen in studies where factors like mineral composition and particle size also influence sequestration rates. For example, different application rates of olivine, wollastonite, and basalt in various experiments demonstrate varying CO2 sequestration efficiencies, highlighting the need for nuanced considerations beyond just the application rate.

Soil properties

Factors like pH, texture, organic matter, microbial activity, CEC, porosity, temperature, and moisture content all influence the effectiveness of EW processes. For instance, soil pH affects mineral solubility and CO₂ availability, while organic matter and microbial activity can accelerate weathering. Soils with higher CEC and porosity tend to facilitate more efficient weathering reactions, leading to increased CO₂ removal. Understanding these soil properties helps optimize EW strategies for effective CO₂ sequestration, although maintaining appropriate moisture levels and considering other soil characteristics are vital for long-term success.

Weather and climate

Warmer temperatures generally accelerate mineral dissolution, potentially enhancing CO2 sequestration rates, whereas colder climates can impede this process. Regional variations in humidity, precipitation, and seasonal changes further modulate weathering rates; high rainfall and wetter soils typically promote faster weathering, while dry climates slow down the process. Extreme weather events and microclimate variations from agricultural activities also play roles in altering local weathering environments

Land management

Incorporating EW materials can alter soil pH and nutrient availability, impacting weathering rates significantly. Practices that enhance soil organic matter and moisture retention, coupled with erosion control and proper irrigation management, contribute to optimal conditions for efficient weathering reactions. Additionally, reforestation and afforestation efforts indirectly support EW by improving soil health and biological processes, showcasing the interconnectedness of land management and carbon sequestration through EW.

(Abdalqadir et al., 2024)

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Buckingham and Henderson (2024) found that based on their findings, the estimated financial benefit of enhanced basalt weathering on agricultural land (£0.41/ha) is equivalent to £34 per field per year for the UK (assuming an average UK farm size of 81 ha).

The monetary value of EW application may be an insignificant incentive but an additional financial return for the work carried out.

Buckingham, F.L. and Henderson, G.M. (2024)

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Renforth, P. (2012) The potential of enhanced weathering in the UK [Figure]. Available at: https://www.sciencedirect.com/science/article/pii/S1750583612001466#aep-abstract-id14 (Accessed: 11 April 2024)

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The primary energy consumption in enhanced weathering is size reduction of rocks. As depicted in the figure above, comminution involves a number of steps including blasting/drilling, primary, secondary and tertiary crushing, and grinding.

It is estimated it takes up to 180 kWh t−1 to produce 10 μm particles. (Renforth, 2012)

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Strefler et al. (2018) Potential and costs of carbon dioxide removal by enhanced weathering of rocks [Figure]. Available at: https://iopscience.iop.org/article/10.1088/1748-9326/aaa9c4/meta (Accessed: 10 April 2024)

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Carbon sink potential of basalt and dunite in tropical areas

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Carbon sink potential of basalt and dunite in tropical areas

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The estimated carbon capture on agricultural land could reach up to 95 Gt CO2 a−1 per year for dunite and 4.9 Gt CO2 a−1 per year for basalt (Strefler et al., 2018).

This is clearly a greater carbon sink potential than that observed in the studies for the UK.

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McDermott, F. (2024) 'Weathering' [Lecture], GEOL30340: Low Temperature Geochemistry. University College Dublin. 11 April.

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Factors affecting weathering:

Rock Type

Basalt can be classified as a mafic rock depending on its mineral content.

Weathering of mafic rocks produces concentrated waters with higher Ca2+/Na2+ and Mg2+/Ca2+ ratios than felsic rocks such as granite, rhyolite

weathering rates are significantly higher than at lower pH values

Climate

Temperature

Chemical reactions proceed more rapidly

at higher temperatures

Precipitation

More water allows

more chemical reactions and therefore more

weathering.

Chemical weathering is moisture-limited in

arid and semi-arid regions.

Relief

Weathering limited regime

Weathering rate limited by chemical

processes where erosion is active.

Transport limited regime

Weathering products accumulate where

erosion is minimal.

In high-relief and mountainous areas,

landsliding and other erosion processes

remove weathering products.

In low-relief areas, these weathering

products build up and inhibit further

weathering

Vegetation

Vegetation also stabilises the soil which

prevents physical erosion → decreases weathering

increases contact time of initial weathering products and incoming precipitation → increases weathering

Deforestation → high TDS in runoff waters → colonisation of plants of a previous un-vegetated area

Time

Contact time between rock and water is an important

variable that control water chemistry.

High rainfall usually results in shorter contact times but

depends on how rainfall is distributed in time.

In arid areas soil/weathering zone may dry out for part of year – salts precipitate in soils.

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McDermott, F. (2024) 'Weathering' [Lecture], GEOL30340: Low Temperature Geochemistry. University College Dublin. 11 April.

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How does silicate weathering interact with atmospheric CO2?

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How does silicate weathering interact with atmospheric CO2?

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Weathering removes atmospheric CO2 and locks it up. The idea is to scale up the natural process of silicate weathering.

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McDermott, F. (2024) 'Carbonate dissolution' [Lecture], GEOL30340: Low Temperature Geochemistry. University College Dublin. 10 April.

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Nutrient Enrichment

Silicate rocks (like basalt) are rich in essential nutrients and micronutrients.

When these rocks undergo weathering, they release minerals such as calcium, magnesium, potassium, phosphorus, sulfur, and micronutrients like copper, iron, manganese, molybdenum, and zinc.

These nutrients are crucial for plant growth and soil health.

This may reduce the reliance of N-rich fertilisers.

Addressing Soil Deficiencies

Crushed silicate rocks can help address deficiencies in potassium and micronutrients in agricultural soils.

Depletion of these nutrients is often due to continuous farming practices and soil nutrient stripping.

Improved Crop Yields

EW has been linked to increased crop yields, especially in areas with highly weathered, acidic soils.

Faster weathering minerals applied in temperate climates have also shown positive results, leading to improvements in yields for crops like maize and potatoes.

Controlled Nutrient Release

Silicate rock amendments release nutrients slowly, reducing the risk of nutrient leaching and surface run-off.

This controlled release is beneficial for sustained plant nutrition without harming water sources.

pH Neutralization

Silicate rocks can neutralize acidic soils, raising pH levels to more optimal ranges for plant growth.

Improved pH levels also enhance nutrient availability in the soil, further contributing to increased crop yields.

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This mitigation measure might create a false sense of hope for the public, letting them to continue their current lifestyles without any real change. Although Enhanced Weathering (EW) can contribute to combating climate change, it represents only a minor advancement in the right direction.

This mitigation measure while scalable, should be used in combination with a number of other measures such as reforestation, rewetting peatlands, direct air capture with carbon storage (DACCS), etc.