Waste Reduction and Material Efficiency in Nigerian Iron Foundries: A Lean Manufacturing Assessment

This study evaluates waste reduction opportunities and material efficiency improvements in selected iron foundries in Nnewi, Anambra State, South East Nigeria, applying lean manufacturing principles to foundry process analysis. The Nnewi foundry cluster is one of West Africa's most significant secondary casting centres, producing automotive components and industrial castings, yet systematic assessment of material waste and process inefficiency in this sector has not been conducted in recent years. The study adopts a mixed-methods action research approach, combining process observation, material flow mapping, scrap rate data collection, and structured interviews with production managers at eight foundry enterprises. Lean waste categories are mapped onto foundry-specific process stages including charge preparation, melting, pouring, shakeout, and finishing. Key performance indicators including metal yield, energy consumption per tonne of casting, and customer rejection rate are baseline-measured and benchmarked against published foundry industry standards. Findings reveal an average metal yield of 72 percent compared to a best-practice benchmark of 82 percent, with the largest material losses attributable to excessive gate and riser systems and avoidable mould erosion defects. Energy consumption per tonne is 25 percent above the benchmark, linked to suboptimal charge preparation and excessive holding time. The study proposes a prioritised lean improvement roadmap for Nnewi foundries. Keywords: lean manufacturing, iron foundry, material efficiency, waste reduction, Nnewi.