14 ERW - Enhanced Rock Weathering
Ho
Enhanced rock weathering (#ERW) seems like a promising way to remove CO₂ from the atmosphere. However, this paper says that to remove 1 billion tonne of CO₂ per year requires land area larger than the entire United States.
Linke Abstract
The ability of engineered enhanced rock weathering to impact atmospheric CO2 has been challenging to demonstrate due to the many processes occurring in soils and the short time span of current projects. Here we report the carbon balance in an Icelandic Histic/Gleyic Andosol that has received large quantities of basaltic dust over 3,300 years, providing opportunity to quantify the rates and long-term consequences of enhanced rock weathering. The added basaltic dust has dissolved continuously since its deposition. The alkalinity of the soil waters is more than 10-times higher than in equivalent basalt-dust-free soils. After accounting for oxidation and degassing when the soil waters are exposed to the atmosphere, the annual CO2 drawdown due to alkalinity generation is 0.17 tC ha-1 yr-1. This study validates the ability of fine grained mafic mineral addition to soils to attenuate increasing atmospheric CO2 by alkalinity export. Induced changes in soil organic carbon storage, however, likely dominate the net CO2 drawdown of enhanced weathering efforts.
Linke Conclusions
The results of this study confirm the ability of the addition of fine-grained basaltic rock to soils to enhance CO2 drawdown directly from the atmosphere due to alkalinity production. In total it is estimated that 17 ± 3.6 g C m− 2 yr− 1 is currently drawn down and added to rivers by alkalinity production from our South Iceland field site. The enhanced alkalinity production of our soils was produced by the addition of approximately 1.7–2.6 t m− 2 of basaltic dust to this soil over 3,300 years. Upscaling of this process to address even a small fraction of the mass of anthropogenic CO2 emissions to the atmosphere, however, may be challenging for two reasons: 1) this enhanced weathering process is slow and would require more land than what is available for a sizeable drawdown of anthropogenic CO2 through alkalinity production and 2) the here to date unquantified effect of adding basalt powder to soils on soil organic matter. So, although this study serves as a proof of concept of the potential of enhanced weathering efforts to contribute to attenuating atmospheric CO2 concentrations, the degree to which this approach will prove successful at a larger scale remains unclear.
Linke (2023) Direct evidence of CO2 drawdown through enhanced weathering in soils