Life Cycle Assessment of Structural Steel Use in Commercial Building Construction in Lagos: A Materials Engineering Approach

This study applies life cycle assessment (LCA) methodology to quantify the environmental impacts of structural steel use in commercial building construction in Lagos, South West Nigeria, covering the material extraction, production, fabrication, use, and end-of-life phases. The construction sector is a major contributor to Nigeria's greenhouse gas emissions and resource consumption, and systematic LCA data for Nigerian construction materials remain sparse, limiting the evidence base for sustainable material selection decisions. The study follows ISO 14040 and 14044 LCA methodology, with system boundaries defined from steel ore extraction through building demolition and scrap recycling. Primary data are collected from three commercial building projects in Lagos through material quantity surveys, fabrication shop records, and interviews with project teams. Background data for steel production are adapted from the World Steel Association LCI dataset, calibrated for the Nigerian induction furnace production route. Impact categories assessed include global warming potential, cumulative energy demand, acidification, and end-of-life recycled content credit. Findings indicate that the steel production phase accounts for 72 percent of the total global warming potential across the life cycle, while the high scrap recyclability of structural steel generates a significant credit at the end-of-life stage. Induction furnace production in Nigeria has 35 percent lower GWP per tonne than the integrated blast furnace route at equivalent scrap input levels. Keywords: life cycle assessment, structural steel, commercial building, Lagos, environmental impact.