With the global ambition of CO₂ reduction, existing oil & gas pipeline networks are often re-assessed for future use in a de-carbonised world. Currently the majority of existing pipelines is still transporting hydrocarbons. However, several studies are carried out regarding conversion of gas pipelines to future hydrogen use and some are already converted and transporting hydrogen.

To meet the UN climate goals the question of re-use and storage (CCU/CCS) of CO₂ is getting more important. This presentation focuses on pipeline transportation of CO_2.. New standards e.g. by ISO are currently developed for a safe operation of pipelines under changed transported media.

As it can be seen in the phase diagram of CO₂, the triple point (pure CO₂, 31°C and 73,9bar) is situated in the typical operating range of pipelines. Therefore several challenges arise, starting from dependences of the triple point on impurity and possible multi-phase conditions. Latest developments of how to deal with phase changes and design criteria for CO₂ transportation pipelines are presented here.