SINTEF, one of Europe’s largest research organisations, has published a blog post about the impurities found in concentrated CO₂ streams captured from pre- and post-combustion gas mixtures. Under the assumptions that SINTEF researchers used when predicting impurities, the least pure CO₂ stream would come from natural gas processing with amine-based absorption, with the most pure coming from a coal-fired power plant with either ammonia or amine-based absorption. The types of impurities varies depending on the case, with N₂ always being present, CO and O₂ usually being present, and NO_x and SO_x often being present, and H₂S, hydrogen, methane, ammonia and amines, as well as carbon radicals sometimes being present. Such findings are important, as they will inform decisions not only about the choice of combustion and capture systems, but also of transport systems.