Fact and Fake on Steelmaking Routes Decarbonization

Abstract

The pressure to reduce greenhouse gas (GHG) emissions in the steel industry is resulting in a massive transformation in the traditional way steel is produced. Many steel players are paving the road to large investments for shifting from the blast furnace (BF) and basic oxygen furnace (BF-BOF) route towards the direct reduction (DR) with electric furnaces (DR-EAF) for primary steel production. The implementation of this route shifting assumes that direct reduction reactors can be adapted to operate with increasingly hydrogen enriched natural gas, as low-carbon hydrogen becomes available. Another key assumption most steelmakers are using to support their decisions is that, prior to using green hydrogen, they will be able to use blue hydrogen produced from steam methane reforming with carbon capture and storage, the so-called blue hydrogen. This assumption is supported by the allegation that blue hydrogen is a lower CO2 equivalent emitter than the traditional natural gas used in the direct reduction processes. However, life cycle assessments of blue hydrogen production have shown that blue hydrogen may only be about 10% less polluting than natural gas, due to the inefficiencies associated with the carbon capture systems, and upstream and downstream methane leakage. In this paper, the GHG footprints of different decarbonization alternatives for the steel industry are evaluated. One important conclusion is that the generally accepted reduction claim of 43% in CO2eq emission from the migration of BF-BOF route to natural gas-based DR-EAF (NG-DRI-EAF) may be reduced to only 22%, when methane leakage is considered. Hence, only DR-EAF with green hydrogen and renewable energy supply could lead to the production of truly low GHG footprint steel, with less than 600kg of CO2eq emission per ton of crude steel.