A systematic assessment, based on an extensive literature review, of the impact of gaps and uncertainties on the results of quantitative risk assessments (QRAs) for CO₂ pipelines is presented. Sources of uncertainties that have been assessed are: failure rates, pipeline pressure, temperature, section length, diameter, orifice size, type and direction of release, meteorological conditions, jet diameter, vapour mass fraction in the release and the dose-effect relationship for CO₂. A sensitivity analysis with these parameters is performed using release, dispersion and impact models. The results show that the knowledge gaps and uncertainties have a large effect on the accuracy of the assessed risks of CO₂ pipelines. In this study it is found that the individual risk contour can vary between 0 and 204m from the pipeline depending on assumptions made. In existing studies this range is found to be between <1m and 7.2km. Mitigating the relevant risks is part of current practice, making them controllable. It is concluded that QRA for CO₂ pipelines can be improved by validation of release and dispersion models for high-pressure CO₂ releases, definition and adoption of a universal dose-effect relationship and development of a good practice guide for QRAs for CO₂ pipelines.

The main goal of this study is to identify knowledge gaps and uncertainties in Quantitative Risk Assessments (QRA) for CO₂ pipelines and to assess to what extent those gaps and uncertainties affect the final outcome of the QRA. The impact of methodological choices and uncertain values for input parameters on the results of QRA's have been assessed through an extensive literature review and by using commercially available release, dispersion and effect models. It is made apparent that over the full life cycle of a QRA knowledge gaps and uncertainties are present that may have large scale impact on the accuracy of assessing risks of CO₂ pipelines. These encompass the invalidated release and dispersion models, the currently used failure rates, choosing the type of release to be modeled and the dose-effect relationships assumed. Also recommendations are presented for the improvement of QRA's for CO₂ pipelines.