# Management of Plastic Wastes through Recent Advanced Pyrolysis Processes
## 3 Recent Advances in Fuel Production from Plastic Pyrolysis  
Currently, research is focusing on utilizing the pyrolysis process to convert plastic wastes into fuels and alternatives to petroleum-based products. Recent advances in the use of pyrolysis to treat plastic waste are discussed below. Figure 4: A schematic of a typical pyrolysis process of plastic waste to produce liquid oil. **Microwave-assisted catalytic pyrolysis:** [PERSON] et al. [35] investigated the feasibility of producing fuel from the catalytic pyrolysis of plastic waste. The pyrolysis process was conducted in a novel continuous microwave-assisted pyrolysis (CMAP) system constructed in the lab. The details of the CMAP unit are illustrated in Figure 5a. In their study, the effect of plastic composition, temperature, and catalysis on the yield and composition of the products were investigated. The main types of plastic used for the pyrolysis process were HDPE, PP, and PP pellets. The catalyst utilized in this study was ZSM-5 (Zeolite Socony Mobil-5). The temperature inside the ball bed reactor was maintained at set levels between a range of 500 \({}^{\circ}\)C and 740 \({}^{\circ}\)C, using a PLC control system. It was found that the highest plastic liquid yield of HDPE 47.4 wt%, was found at 560 \({}^{\circ}\)C. Also, as the temperature increased from 500 to 740 \({}^{\circ}\)C, more non-condensable gas was produced, increasing their yield from 17.6 to 74.7 wt%, while decreasing the wax yield from 40.5 wt% to 1.3 wt%. The higher heating values (HHVs) of the gas products were also calculated to be in the range of 45.3 to 46.9 MJ/kg, compared to that of common gas fuels such as propane (50 MJ/kg) and natural gas (45 MJ/kg). Moreover, the effect of plastic composition was investigated for three different feedstocks at 600 \({}^{\circ}\)C. It is observed that pyrolysis of pure PP chip produced higher yields of gases (48.6%) and liquid (44.8%), and less wax (5.2%) compared to HDPE pyrolysis. The yields of gas, liquid, and wax products of HDPE pyrolysis were 37.6%, 40.2%, and 15.7%, respectively. The results suggested that PP is more prone to thermal degradation than HDPE. This finding was also reflected in the composition difference of the liquid products. The liquid product from the pyrolysis of PP had more aromatic content and a larger C5-C12 fraction, and less n-alkene content. Finally, the effect of catalysis on the process was studied, by packing 200 g of ZSM-5 pellets into a catalyst bed and heating to 620 \({}^{\circ}\)C. It was found that in feedstocks the catalytic activity of ZSM-5 was diminished after 30 min of the pyrolysis process. However, the catalytic pyrolysis for 30 min resulted in higher liquid yield and minimal wax yield in comparison to the thermal pyrolysis process. Also, the liquid product has considerably higher aromatic content, higher gasoline fraction, higher isomerized aliphatic content, and lower n-alkene content. The energy balance analysis indicated that 5 MJ of electrical energy was needed to process 1 kg of HDPE with this system, with energy efficiency as high as 89.6%. Moreover, 6.1 MJ of electrical energy can be generated from the gas products, making this pyrolysis process self-sufficient in terms of energy. Figure 5: _Cont._Figure 5: Schematic diagrams of different pyrolysis reactor systems (**a**–**d**). The figures are reproduced with the copyright permissions from References [35; 36; 37; 38]. (**a**) A schematic diagram of the continuous microwave-assisted pyrolysis (CMAP) system [35]. (**b**) A schematic diagram of the pyrolysis of plastic using an auger reactor [36]. (**c**) A schematic diagram of the MAP experimental setup with the quartz reactor [37]. (1) Temperature reading device, (2) K-thermocouple, (3) microwave oven, (4) quartz reactor, (5) condensed unit, (6) bracket, (7) vacuum pump, (8) switch valve. (**d**) A schematic diagram of the pyrolysis of plastic using a novel plasma reactor [38]. **Fast-pyrolysis in auger reactor:** [PERSON] et al.