Energy Efficiency Audit and Waste Heat Recovery Opportunities in a Cement Plant in Benue State

Cement manufacturing is one of the most energy-intensive industrial activities in Nigeria, and plants in Benue State, North Central Nigeria, face mounting pressure to reduce energy costs and carbon dioxide emissions in alignment with the National Renewable Energy and Energy Efficiency Policy. This study conducts a comprehensive energy audit of a medium-scale cement plant in Gboko covering the raw mill, kiln system, cement mill, and auxiliary systems. Energy data including fuel consumption, electrical power, steam usage, and production rates were collected over a six-week monitoring period and analysed in accordance with ISO 50001:2018 principles. Specific energy consumption was calculated for each production unit and benchmarked against International Energy Agency best available technology reference values. Specific heat consumption of the kiln system was 4.2 GJ per tonne of clinker, compared to the global best practice of 2.9 GJ per tonne, indicating a 45% efficiency gap. Waste heat from the kiln preheater exit gases and clinker cooler exhaust accounted for an estimated 34% of total input energy. Techno-economic analysis of organic Rankine cycle power generation using kiln exit gas waste heat indicated a projected payback period of 4.1 years at current electricity tariffs, with potential annual power generation of 3.2 GWh. The study provides actionable waste heat recovery and energy management recommendations for the Gboko facility and the broader Nigerian cement sector. Keywords: energy audit, cement plant, waste heat recovery, organic Rankine cycle, Benue State