EVALUATING THE BIOGEOCHEMICAL EFFECTS OF CARBON SEQUESTRATION THROUGH ENHANCED ROCK WEATHERING OF CRUSHED BASALT ON URBAN AND FORESTED SOILS IN APPLETON AND BAILEYS HARBOR, WI

On geologic timescales, the weathering of silicate rocks is among the most powerful negative feedbacks controlling atmospheric CO₂. However, this process is too slow to meaningfully impact our current climate crisis. Enhanced rock weathering (ERW) is one of the most promising carbon capture strategies to remove anthropogenic carbon from the atmosphere. Models suggest that by milling mafic minerals to increase surface area, the process of silicate weathering can be accelerated to sequester enough carbon to be significant on human timescales. Our project is designed as part of a ground-proofing effort to determine the accuracy of these ERW models. We aim to (1) field test the actual efficacy of the geochemical models that predict promising results for ERW, and to (2) test how the model responds to different soil and climatic conditions. Our sampling sites include a small organic farm located in Appleton, WI, as well as a variety of forested areas in Baileys Harbor, WI. Carbon capture rates through ERW may be heavily dependent on local weather conditions, existing soil chemistry, and application rates. At Lawrence University, we are testing the biogeochemical effects of these variables through quantitative XRD (qXRD), DNA, and pH analyses. We will use qXRD analysis to track temporal mineralogical changes in the soil as the basalt weathers. DNA analysis will be used to track changes in microbial communities, while pH will be used as a proxy for carbon sequestration and soil health. We predict that pH measurements of our soils will become more basic as basalt weathers to form carbonate minerals and carbon is captured. Our work at Lawrence will contribute to improving the biogeochemical models of ERW and provide a framework for the feasibility of ERW as a long-term carbon storage mechanism in the Midwest.