Enhanced Rock Weathering for Improved Smallholder Farmer Welfare: An At-Scale Case Study for Rice Agriculture in India

Abstract:

Enhanced rock weathering (ERW) is a carbon dioxide removal (CDR) technique that accelerates natural geologic processes by spreading crushed silicate rocks, such as basalt, on agricultural lands. When minerals in basalt react with atmospheric carbon dioxide dissolved in water (CO₂ + H₂O ⇌ H₂CO₃), carbon is durably converted to bicarbonate (HCO₃^–). For example, in the case of the silicate mineral wollastonite (CaSiO₃), this process follows:

                                                 CO₂(aq) + H₂O ⇌ H₂CO₃                                                                                                                   (1)

                                                 CaSiO₃ + 2H₂CO₃ ⟶ Ca²⁺ + 2HCO₃^– + SiO₂ + H₂O.                                                                    (2)

During these reactions, the newly formed bicarbonate replaces dissolved CO₂ and carbonic acid, sequestering atmospheric carbon in a form that is ultimately transported to the ocean and stored on geological timescales.

Smallholder farmers produce approximately one-third of the world’s food yet face persistent challenges from soil degradation, limited access to affordable inputs, and growing climate variability. ERW offers a pathway to address these constraints while generating durable CDR. During a commercial-scale deployment in the 2024 monsoon rice season in Chhattisgarh, India, we applied basalt across over 2,000 acres farmed by more than 600 smallholders. Paired field measurements indicate a median yield increase of 22.9%, corresponding to estimated revenue gains of $310 per farmer—approximately 20% of baseline household income. A simplified mass balance model applied to soil geochemical data constrains first-year weathering extent at τ = 0.27 (68% CI: 0.14–0.39), yielding initial CDR potential of 1.6 tonnes CO₂ per acre. Together, these results demonstrate that ERW can simultaneously deliver measurable livelihood benefits and climate mitigation under real-world smallholder conditions. Because CDR generates verifiable and monetizable outcomes that are economically separate from on-farm productivity gains, climate finance can underwrite the costs of soil restoration without requiring farmer co-investment. Combined measurement of CDR potential and yield response provides the empirical foundation for scaling ERW in smallholder systems. Establishing these outcomes jointly, we demonstrate a replicable pathway for climate-financed agricultural development.