# Management of Plastic Wastes through Recent Advanced Pyrolysis Processes
## 1 Introduction
All plastic wastes have higher volatile-matter content, implying that they are easy to burn and good candidates for pyrolysis. Also, the low ash content suggests that the primary products of pyrolysis of these plastics are plastic oil and gases, with a low char content. The low moisture content of the plastic wastes indicates that there is no need for thermal processing to remove the water content before processing them by pyrolysis [13; 14]. The ultimate analysis provides more comprehensive data by obtaining the elemental composition of plastic waste. Alternatively, plastics with more carbon and hydrogen components instead of oxygen or chlorine result in higher-quality petroleum-based products. HDPE, LDPE, PS, and PP are composed of mainly carbon and hydrogen with low levels of  
Figure 3: Plastic wastes affect marine life, forests, and wildlife, and consume landfills. oxygen and chlorine. Therefore, they can potentially produce pyrolysis oil with a higher heating value (HHV). However, the presence of chlorine in these wastes is undesirable because pyrolysis of this waste will produce hydrogen chloride (HCl) gas, and chlorinated organics, which are harmful. PET and PVC have lower carbon and hydrogen content, higher chlorine content for PVC, and higher oxygen content for PET waste. The low carbon and hydrogen contents would result in a low percentage of pyrolysis oil with a low HHV. Also, pyrolysis of PET would generate significant amounts of CO and CO\({}_{2}\), and pyrolysis of PVC would generate high amounts of HCl and chlorinated organic compounds [15; 16; 17]. The pyrolysis process (refer to Figure 4) is an endothermic reaction occurring in an oxygen-free atmosphere at temperatures ranging from 200 to 1300 \({}^{\circ}\)C, depending on the feedstock characteristics [30]. Heat must be provided into the reactor to drive the thermal decomposition of the waste into products. This process is carried out in an inert gas environment, usually at atmospheric or slightly high pressure, although vacuum conditions are sometimes employed [16]. During pyrolysis, long-chain polymers (plastic waste) are broken into smaller segments, resulting in wax solid (char), pyrolysis oil, and non-condensable gasses. Pyrolysis oil consists of several oxygenated organic compounds such as carboxylic acids, aldehydes, ketones, and water [31]. Nevertheless, the exact composition of the pyrolysis oil depends on the feedstock of the process. The non-condensable gases, consisting of CH\({}_{4}\), H\({}_{2}\), CO, and CO\({}_{2}\), can be recycled into the process as an energy source to make the pyrolysis process self-sustaining. Lastly, the char is usually carbon-rich and can be used to make activated carbon and adsorbents, and graphene and its derivatives [32]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**Type of Plastic**} & \multirow{2}{*}{**Chemical Structure**} & \multicolumn{4}{c}{**Proximate Analysis**} & \multicolumn{4}{c}{**Ultimate Analysis**} & \multirow{2}{*}{**Reference**} \\ \cline{3-3} \cline{5-10}  & & **Fixed** & **Volatile** & & & & & & & \\  & **Carbon** & **Matter** & & & & & & & & \\ \hline PET & 9.37 & 88.54 & 2.09 & 61.87 & 4.35 & 33.78 & 0.00 & 23.40 & [18; 19] \\ \hline PP & 0.030 & 99.97 & 0.00 & 84.61 &  
The major product of pyrolysis of waste is dependent mainly on the reaction temperature, process residence time, and the heating rate used. The main product of the pyrolysis of biomass according to [PERSON] et al. [33], with low temperatures, less than 450 \({}^{\circ}\)C, is biochar. At higher temperatures of more than 800 \({}^{\circ}\)C, larger amounts of gases and ash are produced. Pyrolysis oil is primarily produced at an intermediate temperature range. The pyrolysis process can also be classified into slow, intermediate, and fast, based on the temperature, heating rate, feedstock residence time, and vapor residence time. In slow pyrolysis, the major product is char, while intermediate pyrolysis produces fractions of liquid, solid, and gases.