Abstract
As global warming is an urgent global issue, cement industry is promoting policies including waste utilization to reduce the emission of greenhouse gases. Various types of plastic wastes are used as alternatives to coal in the cement burning process, including automobile shredder residues, and other difficult-to-recycle plastic wastes which were otherwise usually incinerated and/or disposed of in a landfill. This study aimed to develop a material flow model incorporating both the cement production and plastic waste treatment processes for the estimation of CO2 emissions based on a life-cycle analysis. CO2 emissions were compared between two systems: the recovery system, wherein the coal used for firing the cement clinker was partly replaced with plastic waste, and the baseline system, wherein the cement clinker was fired with coal only and plastic waste incinerated separately. Based on actual plant data, the use of 23kg of plastic waste per ton of cement produced was estimated to result in a reduction in CO2 emissions of 76kg compared with the baseline system. Most of the reduced CO2 emissions were those accounted for the combustion of coal and plastic waste. Sensitivity analyses showed that the use of plastic waste contributed to calculated emissions reduction, whereas the alternate scenarios of electricity and transportation did not cause much change. These results support continued development of technologies for plastic waste utilizations aiming at CO2 emissions in the cement industry.
