Comparing the decarbonization benefit provided by waste-based hydrogen routes to green steel production process: an analytical model

In the present context of global decarbonization, the steelmaking sector plays a key role. It is indeed one of the so-called hard-to-abate sectors. The high emissions from steelmaking depend on the use of the Blast Furnace-Basic Oxygen Furnace (BF-BOF) route, which generates 1.8 tCO2eq per ton of Liquid Steel (LS). The production of direct reduced iron (DRI) to power an electric arc furnace is currently the most adopted solution to achieve the decarbonization goals. This alternative, based on the use of natural gas, offers a decarbonization potential of about 34% compared to the BF-BOF route. The most promising alternative, however, consists of using electrolysis-based hydrogen (H2) to produce DRI. This solution would drastically reduce direct and indirect process emissions but requires a radical energy transition. In the current transition phase, waste-based H2 production routes could be attractive, but their potential need to be evaluated with respect to the steelmaking process. To this concern, the objective of the present work is to assess the decarbonization potential of three waste-based H2 production routes (i.e., gasification, incineration and anaerobic digestion-based) with respect to the electrolysis-based steelmaking route. An environmental analytical model was therefore developed to evaluate the total (i.e., direct, indirect, and avoided) greenhouse gases emissions associated with the production of 1 ton of LS by employing the different routes. A sensitivity analysis was also carried out to understand the benefit provided by each waste-based H2 alternative in the current energy transition phase. The results obtained confirmed the need for radical emission reductions from electricity generation to make electrolysis-based H2 production environmentally favorable and revealed a high decarbonization potential for waste-based routes in the current energy transition phase.