RUI: CAS-Climate: Carbon sequestration through enhanced weathering in agricultural soils with co-benefits to soil quality and crop yield

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Carbon dioxide removal at the gigaton scale will be necessary to meet international goals for limiting future warming. Enhanced weathering is an exciting carbon dioxide removal technology that could be applied in agriculture using existing infrastructure while providing added benefits to farmers through improved soil quality and crop yields. In place of more traditional materials used in agriculture (like carbonate rocks used for liming), silicate rocks rich in Ca and Mg (e.g., basalts) are attractive because their dissolution consumes carbon dioxide and ultimately stores that carbon as alkalinity in the oceans. Spreading crushed silicate rocks increases the rate of weathering (and carbon removal) by increasing the available mineral surface area for weathering. However, field experiments evaluating enhanced weathering are rare and realized rates of carbon removal and co-benefits are poorly understood. This award supports research that will conduct a three-year field trial testing the carbon removal efficiency and co-benefits to crops and soils of annual applications of crushed silicate minerals. The investigator will monitor a three-year field trial through collaboration with local farming partners in southeastern Minnesota. Experimental treatments of enhanced weathering include a locally occurring crushed basalt and a silicate industrial waste product (slag). The project will prioritize direct tracking of carbon sequestration through measurements of alkalinity in soil water, total carbon content of soils (both organic and inorganic carbon), and soil respiration rates. Careful monitoring of soil organic carbon and microbial communities in the soil will help to determine the impacts that crushed silicates have on the soil microbiome and the organic component of soil carbon, both of which are the main focus of many efforts in conservation agriculture. All phases of this research will be conducted with undergraduate students from Carleton College. Results from this work will provide important real-world constraints on enhanced weathering and will be shared broadly with both the scientific and agricultural communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.