Measurements in Geochemical Carbon Dioxide Removal

Geochemical carbon dioxide removal (CDR) technologies capture and store carbon dioxide (CO2) from the atmosphere using alkaline materials that are rich in calcium (Ca) and magnesium (Mg). Alkaline materials include natural rocks such as basalt, industrial by-products such as steel slag, or artificially generated and industrially produced materials such as lime. Geochemical CDR technologies speed up the reactions of such materials with air or other CO2-bearing gases, and convert the CO2 into solid carbonate minerals or dissolved inorganic carbon in the ocean. Gigatonne (Gt) scale removal is potentially possible with geochemical CDR owing to the abundant quantities of alkaline materials, in addition to durable carbon storage over thousands of years.

Interest in geochemical CDR has expanded considerably over the past 5 years, as researchers and practitioners explore its feasibility. However, further research, development, and deployment of geochemical CDR may be limited by a lack of robust and standardised approaches to measurement. In this work, aspects of measurement in geochemical CDR are considered with the objectives of i) accounting for carbon accumulation in a material or solution, ii) assessing the capacity of the material to react with CO2, iii) understanding how material properties may impact the speed of reaction with CO2, iv) collecting sufficient information on a material to aid in the design of a reaction process, and v) collecting sufficient information such that risks associated with a mineral can be assessed. In order to help meet these objectives, materials properties must be collected via analytical techniques.

Here we present guidance for the application of these analytical techniques in the form of standard operating procedures (SOPs), tailored to meet the needs of geochemical CDR projects. The collection of accurate data obtained through standardised methods could facilitate project feasibility, design and operation, carbon accounting, and foster regulatory confidence in the industry. Given the often-heterogeneous nature of alkaline materials and the range of technologies that might facilitate their reaction with CO2, this document is for guidance only and the protocols should be adapted to suit the needs of the user. As the field innovates, we anticipate updating this report with additional operating procedures, and welcome such contributions to future editions.