From symbiosis to scarcity: evaluating disruption associated with decarbonisation to circular waste materials between the UK cement and steel sectors

• Decarbonisation pathways will disrupt UK cement-steel industrial symbiosis. • UK steel sector is expected to reach decarbonisation targets through transition to secondary steelmaking. • Shortages in ground granulated blast furnace slag supply due to domestic and global steelmaking shifts could limit the availability of low carbon cement. • Low carbon supplementary cementitious materials threatened by reliance on imports. The UK cement and steel industries are decarbonising rapidly to meet net-zero targets. This study explores the unintended consequences of these efforts, particularly the potential disruption of industrial symbiosis between sectors. Cement production in the UK increasingly relies on ground granulated blast furnace slag (GGBS), a low carbon supplementary cementitious material (SCM). However, the shift from primary to secondary steelmaking threatens domestic GGBS supply. This research uses material flow analysis, life cycle assessment, and economic modelling to evaluate future GGBS availability, carbon intensities, and supply chain vulnerabilities. Findings indicate that although the steel sector is expected to reduce its environmental impact, this will cause the cement sector to face a potential shortfall in domestic SCMs, increasing reliance on imports through cross-sector decoupling and stagnation of decarbonisation. Addressing these challenges is vital to ensure a sustainable cross-sector supply chain and support future UK and global infrastructure resilience.