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

Abstract

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 CO₂eq/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.