The opinion article published in the Proceedings of the National Academy of Sciences of the United States (PNAS) seeks to cast doubt on the safety of CO₂ storage. The authors highlight the importance of considering seismic activity for siting, permitting and managing CO₂ storage sites and arrive at a very pessimistic conclusion about the achievable safety. As pointed out by Hill in his rebuttal, the researchers fail to fully account for the multiple geologic storage options that when taken together indicate a much more optimistic outlook of long-term safety of CO₂ storage.

Over 1 billion tonne of CO₂ has already been safely injected into depleted oil fields for enhanced oil recovery in the United States since the 1970’s. According to the National Energy Technology Laboratory, at least 20 billion additional tonnes of CO₂ could be injected into such fields. These projects, along with other CO₂ injection projects globally, are closely monitored for any resulting seismic activity. To date, none has been reported.

At Bellona we fully recognise the importance of seismicity and careful selection of suitable sites for CO₂ storage. We appreciate the Stanford researchers bringing attention to this issue, but strongly disagree with their conclusions about the pessimistic outlook of geologic CO₂ storage.

Even more research is needed in this topic, but the evidence is already there. We are convinced by the potential of CCS to be a safe and sustainable solution for dramatically reducing CO₂ emissions globally.