# Characterization and Use of Char Produced from Pyrolysis of Post-Consumer Mixed Plastic Waste
## 3 Results and Discussion
[39] study to valorize the plastic film fraction from a recycling plant located in Italy. This fraction was characterized, obtaining a composition of 92-95% PE film, 5% PP, >1% PS, >1% PET and traces of other materials. It should be noted that the differences observed between the results of the different researchers are mainly due to the fact that not all studies refer to the same rejection fraction and nor all municipal solid waste treatment plants use the same sorting system. In furthermore, the studies belong to different countries, where customs and lifestyles are different. In addition, samples may vary depending on the time of year, so it is difficult to make comparative studies in this case. Considering the results obtained in the characterization of the mixed plastic bales obtained in this work (Table 1), only PP, HIPS, EPS and film fractions were considered to be used in the pyrolysis tests. The PET fraction, although it is presented in high proportion, is of interest to recycling companies and can therefore be sold on the market, so its use by pyrolysis would not be of interest. Therefore, the following composition has been selected for the mixture to be used in the pyrolysis tests: 55.7% PP, 8.6% PS-HIPS, 10.1% PS-EPS and 25.7% film. 1.2 Elemental and Immediate Analysis of the Main Polymers Existing in the Non-Recyclable Mixed Plastics Bales from Municipal Solid Waste  
Table 2 presents the results of the immediate and elemental analysis of each of the polymers contained in the non-recyclable mixed plastics bales from municipal solid waste. The main polymers existing in the bales are composed almost totally of volatile matter, with a very low fixed carbon and ashes content. It should be observed that PS-HIPS is the material that shows the greatest differences, especially in ash content. This may be due to the fact that this material is accompanied by additives such as flame retardants that would remain in the ashes [40]. Almost all of the plastic wastes have high carbon content, the lowest being that of PS-HIPS with 66.47%, while its oxygen content is the highest, which may be related to the above. The results are in agreement with those obtained by [PERSON] et al. [41]. In the case of PP, almost identical results are obtained in both immediate and elemental analysis, with a fixed carbon content of 0%, volatile matter content of 99.4% and ash content of 0.67%. Elemental analysis shows a carbon content between 77.5-86.1%, hydrogen content between 14.2-13.7%, oxygen content between 7.4-0.2% and nitrogen content of 0.1%. However, the results obtained for PS differ from those obtained in the present study, although it should be noted that the type of PS used by the researchers is not specified. The research performed by [PERSON] et al. [42] also shows similar results to those of this work. Again, results for PP are the most similar, with 0% moisture, fixed carbon and ashes content, and C of 85.1%, H of 13.38% and O of 1.52%. Finally, [PERSON] et al. [43] performed immediate and elemental analysis of post-consumer plastic film waste samples, obtaining similar results, 69.3-81.8% C, 11.1-13.2% H, 0.1-2.4% H and 0.1-6.1% O.  
Pyrolysis of the Main Polymers Existing in the Non-Recyclable Mixed Plastics Bales from Municipal Solid Waste  
The yields to products (solid, liquid and gas) have been calculated by means of the following equations,  
\[\eta_{\text{solid}}=\frac{m_{\text{s}}}{m_{0}}\times 100 \tag{9}\]  
\[\eta_{\text{liquid}}=\frac{m_{\text{l}}}{m_{0}}\times 100 \tag{10}\]  
\[\eta_{\text{gas}}=100-\eta_{\text{solid}}-\eta_{\text{liquid}} \tag{11}\]  
where \(m_{0}\) = initial mass of the sample to be pyrolyzed; \(m_{\text{s}}\) = mass of the solid obtained in the pyrolysis process; \(m_{\text{l}}\) = mass of liquid obtained in the pyrolysis process. Table 3 presents the yields to products at different temperatures and using different types of polymers in the pyrolysis process.