Aggregate Production Planning for a Cement Plant in Ebonyi State to Minimize Cost Over a Seasonal Demand Cycle

Cement demand in Nigeria exhibits strong seasonal variation driven by construction activity cycles, with peak demand coinciding with the dry season building period from November to April. This study develops an aggregate production plan for a cement manufacturing plant in Ebonyi State, South East Nigeria, to minimize total production, inventory holding, and workforce adjustment costs over a 12-month planning horizon. Monthly demand forecasts are derived from three years of historical sales data using the Holt-Winters seasonal model. Three aggregate planning strategies, pure chase, level production, and a mixed strategy, are evaluated and compared on total cost. A linear programming formulation of the mixed strategy is solved to determine the optimal combination of regular production, overtime production, inventory build-up, and workforce adjustments across all 12 months. Results indicate that the LP-optimized mixed strategy reduces total planning period costs by 19 percent relative to the pure chase strategy and 12 percent relative to the level production approach, achieving savings primarily through strategic inventory pre-build during low-demand months to avoid costly overtime during the peak season. The model incorporates hiring and layoff cost parameters calibrated from plant HR records. Recommendations include adopting the mixed strategy as the annual production plan template and updating demand forecasts quarterly. This research demonstrates how aggregate planning optimization can improve cost performance in Nigeria's construction materials sector. Keywords: aggregate production planning, cement manufacturing, seasonal demand, Ebonyi State, cost minimization