ENERGY BENCHMARKING AND CARBON FOOTPRINT REDUCTION OPPORTUNITIES IN PORTLAND CEMENT MANUFACTURING PROCESSES IN NIGERIA.
ABSTRACT
Energy benchmarking and carbon footprint reduction opportunities in Portland cement manufacturing processes in Nigeria are presented. Life Cycle Assessment (LCA) is used to estimate the environmental impact of three cement manufacturing processes in Nigeria. The energy consumption of the cement manufacturing processes are evaluated using energy Benchmarking and Energy Savings Tool for cement (BEST-Cement). BEST-Cement evaluates and compares the energy consumption of the cement manufacturing processes in Nigeria to China (world largest producer of cement) and International energy benchmark practices. Energy Conservation Supply Curves (ECSC) were used to evaluate energy and emission reduction mitigations measures through the application of energy efficient measures/technological changes. A list of 34 energy efficiency measures/technologies were applied as per the technological requirement of each cement manufacturing process technology in constructing an Energy Conservation Supply Curve (ECSC). The carbon footprint of 1 tonne of Portland cement produced by the wet, semi-wet and dry cement manufacturing processes in Nigeria estimated using the 100 years Global Warming Potential (GWP) value are 871 kg of CO2 Eq, 694.45 kg CO2 Eq and 621 kg of CO2 Eq respectively per tonne. The average technical potential for thermal and electrical energy savings for the three cement manufacturing processes when compared to International cement manufacturing energy benchmarks were 35% and 39.27%. When compared to Chinese cement manufacturing energy benchmarks, the average technical potential for thermal and electrical energy savings were 29% and 25.56% respectively. Results from the Energy Conservation Supply Curve model, indicates that the cost-effective energy efficiency potential for the wet cement plant in 2010 is 235,038 GJ/year, which accounts for 6.87% of primary energy, for the semi-wet process it is estimated at 237,913GJ/year which accounts for 8.89% of primary energy and the dry cement plant estimated to be 374,055GJ/year which accounts for 14% of primary energy. The reduction in carbon footprint emissions due to use of selected energy efficiency measures/technological changes applied to the Conservation Supply Curves estimates that a total of 12,362 tCO2Eq per year, 12,694 tCO2Eq per year and 20,502 tCO2Eq per year are achieved for the wet, semi-wet and dry cement manufacturing processes in Nigeria respectively.