This work studies large-scale hydrogen-based decarbonisation pathways for blast furnace basic oxygen furnaces (BF-BOF) used in steel sector with the conventional fossil configuration as the benchmark. Direct use of hydrogen gas and hydrogen carrier options, namely ammonia and methanol, were assessed using customised techno-economic frameworks that incorporate storage and dehydrogenation requirements. The results show distinct energy demand patterns: direct hydrogen integration imposes a substantial electrical load due to compression and cryogenic cooling, without increasing thermal demand relative to the benchmark. In contrast, while carrier-based systems pose a lower electrical burden, additional thermal input of up to 0.85 GJ/tonne crude steel is required for cracking or reforming. Further analyses of sensitivity, stochastic, and profitability collectively indicate that hydrogen carriers represent the most commercially robust pathway, with median levelised costs around USD 513/tonne crude steel. Moreover, ammonia and methanol in BF-BOF steelmaking can yield investment returns that approach those of conventional BF-BOF under realistic steel price conditions. From an environmental perspective, hydrogen and ammonia pathways enable significant reductions in emissions. Nevertheless, ammonia offers a balanced combination of emissions abatement and techno-economic viability. The findings highlight the role of hydrogen carriers as a practical, and economically viable technology for reducing emissions by steel industry.