Climate change requires transforming the production processes of high-emission industries toward low-carbon technologies. One of the main emitters of greenhouse gases is the steel industry. Therefore, steel manufacturers are planning to substitute the blast furnace-basic oxygen furnace route with hydrogen-based direct reduction and electric arc furnaces. Thus, direct greenhouse gas emissions can be avoided almost entirely. This involves changes in the materials and energies used. Besides hydrogen, natural gas is becoming more important for the direct reduction of iron ores. Therefore, future greenhouse gas emissions associated with low-carbon steelmaking are deeply intertwined with the developments of the system environment. Upon potential transformation pathways of the system environment, future greenhouse gas emissions from natural gas and hydrogen-based direct reduction coupled with electric arc furnaces are investigated. To this end, a prospective cradle-to-gate life cycle assessment approach is used. The results indicate that greenhouse gas emissions highly depend on the electricity mix if hydrogen is produced by electrolysis. Using natural gas for direct reduction is a viable short-term option until the decarbonization of the energy sector is further advanced.