Can bioenergy with carbon capture and storage result in carbon negative steel?

This paper explores the potential of achieving negative emissions in steelmaking by introducing bioenergy with carbon capture and storage (BECCS) in multiple steelmaking routes, including blast furnace and HIsarna smelt reduction, and Midrex and ULCORED direct reduction. Process modelling and life cycle assessment were used to estimate CO2 balances for 45 cases. Without bioenergy or CCS, the estimated life cycle CO2 emissions for steelmaking were 1.3-2.4 t CO2/t steel. In our model, aggressive BECCS deployment decreased net CO2 to the order of -0.5 t to 0.1 t CO2/t steel. CCS showed a larger mitigation potential than bioenergy, but combined deployment was most effective. As BECCS use increased, CO2 from background supply chains became more relevant. In the high BECCS cases, if decarbonized electricity is assumed, net CO2 estimates decreased by 400-600 kg CO2/t steel. Conversely, at 700 g CO2/kWh, all cases appeared to be net CO2-positive. Accounting for the carbon debt of biomass, beyond biomass supply chain emissions, increased net CO2 estimates by approximately 300 kg CO(2)eq/t steel. We conclude that CO2-negative steel is possible, but will require significant interventions throughout the production chain, including sustainable biomass cultivation; efficient steel production; CO2 capture throughout steel and bioenergy production; permanent storage of captured CO2; and rigorous monitoring.