Facing the uncertainty of CO2 storage capacity in China by developing different storage scenarios by Samuel Höller and Peter Viebahn Energy Policy

Höller and Viebahn (2016) aim to “provide a systematic overview of the potential for the geological sequestration of CO2 assessed to date for China”. They describe the purpose of their paper to be “the calculation of the effective capacity as this capacity is the basis for further estimation of matched or practical capacity” and one of the results is named a “China-specific efficiency factor”. Although they “do not undertake basic geological research”, they “provide an overview of existing results by reviewing published studies, and apply the scenario methodology to storage capacities in order to identify the different sources of uncertainty in a transparent manner.”
One of their conclusions is that “the efficiency values are the most important aspect when calculating effective storage capacities”. They were “surprised about the wide range of assumptions and parameter settings (…). However, it was out of the scope of this work to get to the bottom of the considered studies and to verify and improve each assumption, method and parameter involving the authors of the studies.” For the S2 (mid case) CO2 capacity estimation for saline aquifers in China, they use an efficiency factor of 0.13 (“weighted mean of all efficiency values [based on the analysis of 13 studies] is 13 per cent”).
We consider that an average efficiency factor for saline aquifers in China of 0.13 is based on a misunderstanding of efficiency factors in CO2 storage and on questionable methodology. We appreciate the author's openness about the limits of their study but a published “China-specific efficiency factor” factor of 0.13 for saline aquifers based on incomplete understanding of the topic in a peer reviewed journal requires a critical response. In the following we will show that the methodology of the paper is not based on current best practise. We will start with our main point of criticism, the use of both regional scale and single structure (local) storage efficiency factors.