Atmospheric monitoring of carbon capture and storage leakage using radiocarbon

We outline the methodology for detection of carbon dioxide (CO2) leaks to the atmosphere from carbon capture and storage (CCS) using measurements of radiocarbon in CO2. The radiocarbon method can unambiguously identify recently added fossil-derived CO2 such as CCS leaks due to the very large isotopic difference between radiocarbon-free fossil derived CO2 and natural CO2 sources with ambient radiocarbon levels. The detection threshold of 1 ppm of fossil-derived CO2 is comparable to other proposed atmospheric detection methods for CCS leakage. We demonstrate that this method will allow detection of a 1000 ton C yr−1 leak 200-300 m from the source during the day and more than 600 m away at night. Using time-integrated sampling techniques, long time periods can be covered with few measurements, making the method feasible with existing laboratory-based radiocarbon measurement methods We examine the method using previously published observations and new model simulations for a case study in Taranaki, New Zealand. Plant material faithfully records the radiocarbon content of assimilated CO2 and we show that short-lived grass leaves and cellulose from tree rings provide effective time-integrated collection methods, allowing dense spatial sampling at low cost. A CO2 absorption sampler allows collection at controlled times, including nighttime, and gives similar results.