A Study on Pyrolysis of Plastic Wastes for Product Recovery and Analysis

Abstract

In this twenty-first century, industrialization, urbanization and modernization have led to rapid generation of waste plastics causing a global concern for safe disposal. Owing to the current trend in plastic waste generation, there is a need to utilize the huge amount of high calorific plastic trash into a valuable source of energy as a solution to the waste disposal cum energy crisis issues. In this context, pyrolysis has been acknowledged as an efficient waste to energy technology degrading waste plastics under anaerobic conditions into oil, gas and char products. The current initiative deals with the study of thermal pyrolysis of waste plastic polyethylene in a batch pyrolyser at an inert environment to recover value-added products followed by their characterization. The plastic waste pyro-feedstock of 100 g shredded low-density polyethylene (LDPE) bags, a significant part of plastic waste stream, was used per batch experiment. Thermo-gravimetric analysis (TGA) was done at different heating rates of 10, 20 and 40 °C/min to evaluate the waste degradation profile based on temperature. Pyrolysis experiments were carried out in the temperature range of 450–600 °C at a heating rate 20 °C/min producing 74–84% oil, 11–20% gas and 2–15% char as by-products. The highest oil yield was observed at 550 °C with maximized gas and solid char formation at 600 and 450 °C, respectively. The FTIR data infers that the derived pyro-oil comprises mainly alkanes, alkenes and aromatic groups indicating fuel quality. The gas product was analysed using gas chromatography which highlights the presence of H2, CO and C1–C6 hydrocarbons without any trace of CO2 after the process. The residual char was also characterized using BET and FESEM. Thus, LDPE plastic wastes offer a potential energy value after pyrolysis through the sustainable recovery of value-added products. Further research on process scale-up and product applications is anticipated.