CO₂ removal with enhanced wollastonite weathering in acidic and calcareous soils

Wollastonite powder removed CO₂ in soils with pH values of 4.4, and 7.7, at 1.0 and 1.1 g C kg⁻¹ soil, respectively.

The application of silicate rock powder to agricultural soils is a promising strategy for atmospheric CO₂ removal. However, most research focuses on inorganic carbon sequestration via enhanced rock weathering, overlooking its impact on soil organic carbon (SOC) decomposition, which is essential for quantifying net CO₂ removal. To address this gap, we conducted a 233-day incubation experiment to investigate the impact of wollastonite powder on soil CO₂ emissions, SOC decomposition, pH, and cation concentrations across three agricultural soils with pH levels of 4.4, 5.6, and 7.7. Results showed 89.0% and 74.4% rock powder weathering in the most acidic and alkaline soils, respectively. In acidic soils, wollastonite powder addition increased CO₂ emissions due to the release of intrinsic CaCO₃ containing in wollastonite or/and SOC. However, these CO₂ emissions accounted for less than 20% of the total CO₂ removal by wollastonite weathering. In contrast, alkaline soils experienced a reduction in CO₂ emissions with wollastonite powder amendment. Net CO₂ removal for soils with pH 4.4 and 7.7 were 1.0 and 1.1 g C kg⁻¹ soil, respectively. This study confirms that wollastonite weathering is effective for CO₂ mitigation regardless of soil pH.