Assessing global potential for enhanced weathering

A Rock-Based Removal Approach

Removing carbon dioxide from the atmosphere is considered necessary alongside emissions reductions, but proposed removal approaches differ in their storage duration, energy requirements, cost and potential scale. Enhanced weathering applies finely ground silicate rock to soils, increasing the mineral surface available to react with carbon dioxide and form dissolved carbon compounds. The approach could store carbon over long timescales, but its performance depends on rock chemistry, weather, soil conditions and the emissions generated by mining, grinding, transport and spreading. Assessing these factors together is important because a large theoretical capacity does not by itself establish how much carbon a deployment would remove net of its own emissions.

Authors Li Ruan, Jianwu Li, Zhaoliang Song, and colleagues from the Zhejiang Academy of Agricultural Sciences, Zhejiang A & F University, and Tianjin University assessed enhanced-weathering potential using a global silicate-rock dataset of 9,088 records. The study compared basalt, peridotite and granitoid using theoretical carbon-sequestration potential and weathering indices, then evaluated basalt’s distribution and life-cycle carbon footprint. The authors modeled 50-year outcomes for particles of 10, 37, 100 and 1,000 μm across different pH conditions, incorporating estimates of process energy and emissions. They also assessed cropland suitability globally using temperature, precipitation and soil-pH data.

Comparing Silicate Materials

Peridotite had the highest estimated maximum carbon-sequestration potential, at 0.72 ± 0.16 tonnes of CO₂ per tonne of rock, compared with 0.30 ± 0.08 for basalt and 0.09 ± 0.05 for granitoid. The researchers also compared chemical weathering intensity using the chemical index of alteration, or CIA. Average basalt CIA was 61.48 ± 13.16, and the authors reported that basalt samples spanned weak, moderate and strong weathering categories. Peridotite generally had higher CIA values than basalt, while granitoid values were mostly below 60.

The authors identify basalt as the more suitable material for cropland applications, despite peridotite’s higher theoretical capacity. They note that peridotite can contain substantial nickel and chromium, raising potential environmental concerns, while basalt’s main metal components are described as relatively harmless. Basalt also contains nutrient elements including phosphorus, potassium, magnesium and calcium, and the paper reports that it covers about 5.2% of the world’s land area. The theoretical rock-capacity figures assume that all released cations result in permanent carbon storage and do not account for downstream carbon dioxide outgassing; the authors therefore describe these estimates as an upper bound before such losses.

Footprints and Particle Size

The life-cycle assessment estimated carbon dioxide emissions from mining, crushing, grinding, transport and spreading basalt. For particles of 10 μm, estimated process emissions ranged from 81.18 to 182.95 kg CO₂ per tonne of basalt; for 37 μm, from 27.48 to 63.68 kg CO₂ per tonne. Estimates were 21.40–50.16 kg CO₂ per tonne for 100 μm particles and 16.40–39.07 kg CO₂ per tonne for 1,000 μm particles. The range reflects the study’s assessment of different energy sources, and grinding and transportation were identified as major contributors to process emissions.

Over the modeled 50-year period, lower soil pH increased basalt dissolution and the modeled carbon-sequestration efficiency. At pH 4, particles of 10, 37 and 100 μm sequestered enough carbon in the assessment to offset application-process emissions, whereas 1,000 μm particles did not offset those emissions within 50 years. The study also notes that coarse particles may continue weathering beyond that period, so their longer-term effects should not be dismissed. Because finer grinding can improve weathering while increasing energy use and emissions, the authors identify 10–100 μm as an optimal grain-size range in their assessment, and describe acidic cropland soils with initial pH 4.5–6.0 as the most suitable agricultural context.

Global Potential and Limits

The global assessment combined temperature, precipitation and soil pH with cropland cover to map where basalt weathering may be more favorable. At an application rate of 40 tonnes per hectare, the study estimates that applying basalt across 1.57 billion hectares of suitable cropland could yield approximately 18.84 Gt CO₂ of theoretical sequestration after complete weathering. That scenario would require approximately 62.8 Gt of basalt. The authors identify stronger potential in Southern Asia, Southeast Asia, Latin America and West-Central Africa, with particularly favorable modeled conditions in parts of Brazil and Myanmar; they also identify India, Ethiopia, Russia, Iceland and Brazil among areas with extensive basalt distribution.

The authors frame the 18.84 Gt CO₂ estimate as theoretical, conditional on complete weathering, and not as a prediction of realized removal. Deployment would need to account for material availability and transport distances, grinding requirements, energy sources and local environmental conditions. The study concludes that basalt selection, local sourcing, suitable particle sizes and locations with favorable weathering conditions can help balance carbon uptake against implementation emissions. It also states that potential adverse effects and safety concerns require interdisciplinary research, and that enhanced weathering cannot replace emissions reductions; the assessment provides a theoretical basis for considering it as one possible contribution to global net-zero targets by 2050.

Corresponding Author: Jianwu Li or Zhaoliang Song

Original Source: https://doi.org/10.1007/s44246-026-00282-4

Contributions: Jianwu Li and Zhaoliang Song contributed to the conception, design and funding acquisition of the study. Li Ruan contributed to the data collection and analysis. The first draft of the manuscript was written by Li Ruan and edited and commented on by Cong-Qiang Liu, Changxun Yu, Guilin Han, Zimin Li, Xiaole Sun, Bo Peng, Hui Henry Teng, Nanthi S. Bolan, and Bhupinder Pal Singh. All authors read and approved the final manuscript.