Hydrogen is an environmentally cleaner resource of energy to end users without the release of pollutants, such as particulate matter or carbon dioxide at the point of end use. Significant development of renewable energy enables the production of pure hydrogen by water electrolysis (instead of reforming natural gas) without environmental impact, although substantial work (e.g. cost, storage, distribution infrastructure) needs to be done to overcome the challenges for H2 to be a major economy factor. The production of direct reduced iron (DRI) by using renewable energy (electricity)-generated hydrogen will be an ultra-low or even zero CO2 emissions alternative ironmaking technology. This PhD research will start from the critical literature review of the state-of-the-art with regards to hydrogen application in the steel industry, and focus on some of the challenging and unsolved areas such as product qualities from DRI processes and the hydrogen utilisation efficiency, aided by thermodynamic and kinetic simulations. The research will study the behaviour of impurities in iron ores during H2 reduction (e.g. its own behaviour and its effect on iron oxide reduction) and the behaviour of impurities (elements and compounds) in DRI during steelmaking.