Aggregated monitoring of enhanced weathering on agricultural lands

Terrestrial enhanced weathering (EW) on agricultural land is a promising carbon dioxide removal (CDR) pathway with high potential to scale. Enhanced weathering also has the potential to provide significant agronomic co-benefits to farmers and producers. Today, most EW field trials are funded through the voluntary carbon market (VCM) with the purpose of generating carbon removal credits for corporate sustainability goals. As a result, monitoring, reporting, and verification (MRV) frameworks for EW are designed for attribution of tons of removal via weathering to individual fields. Here, we describe approaches for aggregation of weathering indicators across multiple fields using aqueous, solid, and gas phase measurements. First, we demonstrate that larger agricultural catchments are at least as suitable as smaller ones for detecting weathering signals in river chemistry, and in some cases may even offer advantages due to lower variability and background weathering fluxes. Second, we assess quantification uncertainty from in-field solid phase soil measurements at increasing scales and show that errors in CDR quantification can be reduced by aggregating signals over many fields. Third, we expand our in-field analysis to consider the cost-uncertainty trade-offs of in-soil gas flux monitoring at scale. Critically, we also highlight that aggregation sets must be defined in advance and all plots included, as biased selection of fields can generate apparent removal signals out of statistical noise. Taken together, we find that aggregated monitoring of EW—quantifying CDR over multiple fields at once—can both improve existing MRV frameworks and support integration of EW practices with a broader array of government policies, unlocking funding and public support to achieve climate-relevant scale.