ENERGY ANALYSIS AND ESTIMATION OF CO2 EMISSION OF SELECTED PLASTIC RECYCLING PLANTS IN NIGERIA

Energy management is a technical and management function which is to monitor, record, analyse, critically examine, alter and control energy flows through systems so that energy is utilized with maximum efficiency.  In line with this, a study was conducted in 4 randomly selected plastic recycling plants located in Osun and Oyo States in South West Nigeria.  The plants referred to as 1, 2, 3 and 4 in the study were investigated to determine the energy utilization patterns, estimate the CO2 emission and carry out exergy analysis.  The process analysis method of energy accounting was adopted to evaluate the energy requirement for each of the unit operations involved in the selected plants.  Investigation revealed that the types of energy used in the recycling plants were electrical, thermal and human labour with percent contribution of 7.14, 92.83 and 0.03% of the total energy in plant 1.  The corresponding values in the other plants were 87.81, 0, 11.9%; 22.44, 77.53, 0.03% and 8.12, 91.81, 0.06% respectively.  The total energy requirements for the four plants per tons of raw plastic wastes were 16.9, 0.5, 49.3 and 11.5 GJ respectively.  The amount of CO2 emitted in all the four plastic plants, which were mainly from the use of liquid fuels, were 76.8, 77.2, 74.5 and 90.6 tons of CO2 for 2005, 2006, 2007 and 2008 production years respectively.  The exergy analysis revealed that melting operation accounted for the highest exergy (available energy) in all the four selected plants. The results of this study have provided baseline data needed for monitoring energy utilization and policy making decision in the selected plastic recycling plants which could also find useful application in other similar plants in Nigeria