Enhanced Rock Weathering

Rock weathering is a natural process where minerals in rocks break down and release charged particles called cations (like calcium and magnesium). These cannot exist alone, so they combine with negatively charged ions—most commonly bicarbonate, (formed from atmospheric CO₂ ± aerobic respiration of plants and microbes in soil and rainwater ± soil porewater).

While the silicate part of the rock forms neutral compounds, the dissolved cations and bicarbonates can either precipitate into the soil, move into groundwater, or travel to rivers and oceans.

Fig1: Overview of the process of enhanced rock weathering (shown in this case for basalt). Also shown are the basic chemical reactions that lead to the weathering process (reproduced from Beerling et al. 2025)

• Mineralogy – The type of minerals in the rock determines how quickly it reacts and how much CO₂ it can capture—some dissolve rapidly (like forsterite), while others are much slower (like K-feldspar).
• Grain Size – Smaller rock particles provide more surface area, allowing reactions to happen faster and increasing the overall rate of weathering.
• Soil pH – Weathering generally happens faster in acidic soils (pH < 6), slows near neutral pH, and can increase again under very alkaline conditions (pH > 9).
• Plants & Soil Enzymes – Plant roots create conditions that promote mineral breakdown, while also releasing organic compounds, enzymes, and proteins—especially under nutrient stress—that accelerate weathering; enzymes like carbonic anhydrase play an important role in enhancing these processes.
• Temperature – Higher temperatures usually speed up weathering reactions, but they can also reduce soil moisture and CO₂ solubility, which may limit the overall effect.
• Other Factors – Additional factors like climate conditions, water availability, and soil saturation also influence how effectively ERW works.

• Improved soil pH – ERW releases base cations into the soil, which helps raise soil pH in acidic soils and makes land more suitable for agriculture.
• Replenishment of soil nutrients – Different silicate rocks supply essential nutrients—mafic and ultramafic rocks are especially rich, while felsic rocks also add potassium, calcium, and iron.
• Increased crop yield – Soils treated with basalt and other silicate rocks show improved nutrient availability, which supports better plant growth and higher crop yields.
• Greater crop resilience – Silicon released during weathering strengthens plants, helping them better withstand drought, heat stress, salinity, and strong winds.

• Large agricultural base – India has extensive croplands, providing a strong foundation for large-scale ERW implementation.
• Availability of suitable rocks – India has abundant basalt and other suitable silicate rocks, which are ideal for weathering-based carbon removal.
• Favorable tropical climate – Warm and humid conditions in many regions of India support faster weathering rates, improving ERW effectiveness.
• Low operational costs – Existing agricultural systems and local resource availability can help keep implementation costs relatively low, supporting scalability.

Fig. 6: Top Left – Map of India showing the location of major basalt source regions. Top Right – Map of India showing the distribution of croplands. Bottom (left to right) – Map showing the source to cropland rail distances, costs and CO2 emissions, respectively, for India (modified after Beerling et al. 2020)

Fig. 7: Area Integrated Sustainability index and carbon dioxide removal potential of the ERW supply chain for India, China and USA (left) and 9 other countries (right). Bright flags show the results for business-as-usual scenario, while the shaded flag represent results for 2°C energy policy scenarios. Size of circles represent higher index values (modified after Eufrasio et al. 2022)

• Dust and Respiratory Health Risks – Crushing and spreading rocks can release fine silica dust, which may affect lung health if inhaled over long periods and in high amounts.
  • Safeguard: Use protective equipment, dust suppression methods, and regular health monitoring for workers involved in handling rock material.
• Risk of Toxic Element Leaching – Some rocks may contain trace amounts of potentially harmful elements that could enter soil or water if not properly managed.
  • Safeguard: Careful selection of safe rock sources, regular testing of soil and water, regulated application practices, and continued scientific research.
• Fairness and Farmer Protection – Large-scale ERW projects may raise concerns about land use, ownership, and fair compensation for farmers.
  • Safeguard: Ensure strong land rights, transparent agreements, fair compensation, and involve farmers in decision-making processes.
• Soil and Ecosystem Balance – Changing soil chemistry can affect soil organisms that play a key role in nutrient cycling and soil health.
  • Safeguard: Long-term ecological studies to understand impacts and ensure soil ecosystems remain healthy and balanced.
• Uncertainty Around Crop Uptake – It is not fully known how trace elements from weathered rocks may accumulate in crops over time.
  • Safeguard: Continuous research and monitoring of crop safety and food chain impacts.
• Impacts on Water Bodies – Runoff from treated soils may change water chemistry, including increasing alkalinity, which could affect aquatic life.
  • Safeguard: Monitor nearby water bodies and apply ERW carefully near sensitive aquatic ecosystems.
• Regional Knowledge Gaps – Most studies are limited to specific regions, so outcomes may vary across different climates and soil types.
  • Safeguard: Conduct region-specific field trials and adaptive monitoring to ensure locally suitable practices.

Technical Report 

Policy Brief

Executive Summary

IISER Bhopal CCS Workshop: Grounding Policy in Science: Developing a Policy Framework for Enhance Rock Weathering in India

American Geophysical Union – 2025: Towards Developing an Evidence-driven Policy Framework to Leverage Enhanced Rock Weathering in India