Christina Larkin

Terrestrial enhanced weathering (EW) is a promising emerging carbon dioxide removal technique which involves the acceleration of natural weathering processes via the deployment of crushed rock feedstocks, typically Ca- and Mg-rich silicates, in soils. While models predict this has the potential to remove multiple gigatonnes of CO2 annually, as an open-system pathway, the measurement (monitoring), reporting, and verification (MRV) of carbon removal and storage is challenging. We will review the current literature showing the state-of-play of different methods for monitoring EW, as well as outlining links between industry, regulation and academia. Additionally we outline a set of enhanced weathering carbon definitions in order to align academic studies and emergent industry in this area with the established voluntary carbon offset market. We will discuss two main pathways for measuring EW, one focused on solid phase measurements and the other on the aqueous phase. Additionally, gas phase measurements have been deployed to understand CO2 fluxes, but are dominated by short-term organic carbon cycling. We emphasise that, although there is complexity in tracing EW CDR in the natural field environment, established literature validates existing approaches, and each measurement approach has strengths and limitations. The complexity inherent in EW is navigable through redundant measurement strategies and well designed experiments, which we highlight are crucial in the nascent stages of the EW industry.