Climate Change Mitigation through Enhanced Weathering in Bioenergy Crops
Kantola, I. B., Masters, M. D., Wolz, K. J., DeLucia, E. H.
Bioenergy crops are a renewable alternative to fossil fuels that reduce the net flux of CO2 to the atmosphere through carbon sequestration in plant tissues and soil. A portion of the remaining atmospheric CO2 is naturally mitigated by the chemical weathering of silica minerals, which sequester carbon as carbonates. The process of mineral weathering can be enhanced by crushing the minerals to increase surface area and applying them to agricultural soils, where warm temperatures, moisture, and plant roots and root exudates accelerate the weathering process. The carbonate byproducts of enhanced weathering are expected accumulate in soil water and reduce soil acidity, reduce nitrogen loss as N2O, and increase availability of certain soil nutrients. To determine the potential of enhanced weathering to alter the greenhouse gas balance in both annual (high disturbance, high fertilizer) and perennial (low disturbance, low fertilizer) bioenergy crops, finely ground basalt was applied to fields of maize, soybeans, and miscanthus at the University of Illinois Energy Farm. All plots showed an immediate soil temperature response at 10 cm depth, with increases of 1- 4 °C at midday. Early season CO2 and N2O fluxes mirrored soil temperature prior to canopy closure in all crops, while total N2O fluxes from miscanthus were lower than corn and soybeans in both basalt treatment and control plots. Mid-season N2O production was reduced in basalt-treated corn compared to controls. Given the increasing footprint of bioenergy crops, the ability to reduce GHG emissions in basalt-treated fields has the potential to mitigate atmospheric warming while benefitting soil fertility with the byproducts of weathering.